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SPOCS 6.0 User Guide

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1. 70 PSD dBm Hz via ETSI noise model FA 80 ech 90 D 100 110 120 130 4 SPOCS Freq Hz A L L L L li fi ji L L L ji f ji f L L 500k 1M 1 5M 2M Figure 31 Shape of the generated noise profile at the LT side of the loop for upstream performance testing Ge ETSI Noise profile on NT side generated via noise model FA PSD dBm Hz via ETSI noise model FA 80 sch 90 Z 100 4 110 120 130 4 SPOCS Freq Hz 1 40 L L L L il li L L L li fi li L L L 0 500k 1M 1 5M 2M Figure 32 Shape of the generated noise profile at the NT side of the loop for downstream performance testing 2 5M a TRO WARNING The above mentioned noise profile generated by SPOCS will be a slightly different from what is defined by ETSI in TS 101 388 This is because ETSI has updated its preferred way to incorporate length dependencies in the evaluation of crosstalk coupling TS 101 388 ADSL requires that the evaluation of the involved transmission function named Sto f L is to be normalized against an average 135 ohm knowing that ADSL is a 100 ohm system while the more recent TR 101 830 2 Spectral Management recommends to normalize it against the characteristic impedance of the loop SPOCS follows the latter because it provides consistent results among different scenarios but it will result in a minor difference with TS 101 388 However if this difference is relevant for compliance testing we recomme
2. This button allows the user to inspect what scenario has been created Show Topology This button allows the user to generate a graphic representation of the topology being defined If you right click the mouse above each node it will tell you how many systems are attached to that node Button Description PBO Power Back Off This button allows the setting of power control parameters This button appears at the LT NT and disturbers LT and NT side See section 6 2 for further details and section 4 2 3 as well Parameters When this button is pushed the properties of the receiver model are displayed See section 6 3 for further details Count Scale Allows to choose between applying a number of disturbers COUNT or the dB s SCALE contributed by a specific disturber This lets the user to apply conditions like those one specified at the standard See section 4 2 3 for further details B Branching Branching define for each disturber group of interest its own Page 69 81 D TNO 2009 SPOCS 6 0 User Guide TRO loop length that branches away from the main loop It colors red when non zero Hit the Show Topology button to check what topology you are defining See section 4 2 3 for further details More Allows adding more disturbers Another screen is popped up to continue adding disturbers This feature can be done at the LT and NT side 8 2 2
3. but focusing only on the disturbers When multiples choices can be selected a warning appears showing this to the user Synchronize Once silent When Keep xx Paired is disabled then the user could want to automatically find the counterpart This feature allows the user doing this by taking the LT side as the master side and the NT as the slave side NT following the configuration established at the LT side Here there is no information about the matching that have been found and configured Synchronize Once with change Proceeds exactly as Synchronize Once silent but by selecting info this option the user will get information about the matching that have been found and configured Page 67 81 D TNO 2009 SPOCS 6 0 User Guide TRO Menu Items Menu Description All the tuneable models at the LT and NT side are hidden to the user In addition properties of the receiver models are disabled as well as other parameters like FEXT NEXT values k2 and k3 Advanced All the models are shown for both LT and NT sides In addition Properties of the receiver models are shown All the models are shown at both LT and NT side to enable on purpose a downstream modem to transmit into the upstream direction Basic Expert Menu Items Menu Description None No logging information is visible Screen The logging information is sent to the screen File The logging information is se
4. 1000 000 1250 000 1500 000 1750 000 2000 000 2250 000 2500 000 2750 000 3000 000 3250 000 3500 000 3750 000 4000 000 4250 000 4500 000 4750 000 5000 000 DataRateGLT 1234095 047 1195736 170 1157011 534 1119850 865 1083825 964 1047007 938 1010431 238 973912 489 937050 793 99898 163 862426 765 824589 484 786447 576 748038 446 709403 318 670613 177 631734 656 92842 657 54028 460 calculation time dT DataRateGNT 9638860 219 9121966 019 8744156 900 8441755 748 8185782 026 7960472 987 7756187 413 7566336 573 7385476 692 7207294 979 7021512 248 6809022 803 6539706 913 6183951 985 733312 823 194551 835 4565255 854 3991349 275 3463863 922 Figure 9 Output Text File Performance Table SPOCS can also show you the spectra that are evaluated as intermediate result This option is disabled by default since it slows down the performance evaluations significantly Enable this first via the View menu where you can also modify what kind of spectra you would like to see VIEW Select Spectra Here you can choose the signals you want to plot and analyze VIEW Show Spectra select it if the check marker is absent Hit the RUN button and the plots in figure 10 and 11 will be shown Figure 10 shows e The upstream signal transmitted from the NT side e The received upstream signal LT side being attenuated by the loop and modem im
5. 9 2 Receiver Model SPOCS full only The list of the receiver models can be retrieved from the GUI of SPOCS Menu Library Receiver library Some of them are e ADSL POTS up FDD SpM 2 ADSL POTS dn FDD SpM 2 ADSL ISDN up FDD SpM 2 ADSL ISDN dn FDD SpM 2 ADSL POTS up EC SpM 2 ADSL POTS dn EC SpM 2 ADSL ISDN up EC SpM 2 ADSL ISDN dn EC SpM 2 Two examples illustrate how these names can be broken down into smaller fragments ADSL POTS up EC SpM 2 ADSL POTS Up EC SpM2 Base name of the Intended intended for use in a Obtained from ETSI model for frequency SpM 2 standard upstream overlapping mode Echo Cancelling Page 72 81 D TNO 2009 SPOCS 6 0 User Guide TRO VDSL2 A up B8 expert guess VDSL2 A Up B8 expert guess Base name of the Intended B8 refers to bandplan Parameters are based model for 998 on an educated guess upstream on what could be realistic values 9 3 Loop Model The list of the Loop models can be retrieved from the GUI of SPOCS Menu Library Loop library Some of them are e KPN_LI underground cable L1 50x4x0 5mm 0 5km e KPN_L2 underground cable L2 150x4x0 5mm Ikm e KPN_L3 underground cable L3 48x4x0 8mm 1 1km e KPN_L4 underground cable L4 150x4x0 5mm 1 5km e KPN_HI indoor cable HI 30x4x0 5mm 0 36km An example illustrates how these names can be broken down into small
6. MyLicenses DirProfiles DirScenarios DirLicenses oil BRAR IE S only sla dp dp Adding user defined libraries usually with extention sla Protected libraries of type slb cannot be loaded in this way and will always be rejected ale d dp dp Some Predefined variables ProgDir contains the program directory where spocs exe is CurrDir contains the current directory dp dp d dp You can load multiple libraries as follows LibFile_Tra end 1 ProgDir Libs MyTransmitters_Partl sla LibFile_Tra end 1 ProgDir Libs MyTransmitters_Part2 sla LibFile_Tra end 1 ProgDir Libs MyTransmitters_Part3 sla dp d dp de dp Uncomment the lines below if you want to load the example libraries on start up and keep them after a library reset dp d SLibFile_Tra end 1 ProgDir Examples examples_UserLibs Example_transmitterlib sla SLibFile_Rec end 1 ProgDir Examples examples_UserLibs Example_receiverlib sla SLibFile_Loop end 1 ProgDir Examples examples_UserLibs Example_cablelib sla SLibFile_PBO end 1 ProgDir Examples examples_UserLibs Example_PBOlib sla dp dp Adding warnings when generating noise profiles that exceed the capabilities of your noise generator dp de dp WARNINGLEVEL_MAXNOISEPOWER The maximum noise level in a testloop is a combination of a the maximum output power of the noise generator b the injection loss and
7. S parameters impedance etc Transmit Viewer Call the Transmit Viewer tool which allows the user to observe the spectra characteristics of the modems at both sides of the link 8 1 8 WINDOW Menu In this option it is possible to observe all the windows opened by SPOCS including plots output text box etc and switch among those windows 8 1 9 HELP Menu Currently it contains 2 options HTML Help and About The HTML Help has already lots of useful information about SPOCS libraries the use of its models capabilities like macros and release notes However it is still considered as under development The About options provides the current version of SPOCS contact information and disclaimers 8 2 Buttons In this section each button of the GUI interface will be described 8 2 1 On SPOCS full only Button Description Run Start a performance simulation to find margin or bitrate See 4 6 2 and 4 6 1 for further details Find k1 In order to run the simulation looking for the suitable length that achieves the Bit Rate or Margin parameters previously established at the LT side as well as at the NT side See section 4 6 3 for further details Generate LT noise profile DSLAM This feature will allow the user to export the PSD profile of the LT side to a suitable noise generator Generate NT noise profile CPE The same as above for the NT side Show Scenario
8. 100 ohm 7 40 D s 2 Received Signal 100 ohm 60 Uz l 3 Received Noise 100 ohm 80 rt 7 100 4 120 4 140 F 8 160 1 a 180 i i 4 200 L 1 1 SPOCS Freq Hz 1 220 L L L L i fi i L L L L 1 i fi L L 0 500k 1M 1 5M 2M 2 5M Figure 6 Spectra at the LT side of the loop as specified in figure 4 3 3 Generating my first performance prediction SPOCS full only This second example quickstart_2 ssf represents again a noisy loop 0 5mm cable where an ADSL modem pair the victim shares a cable with 15 similar modem pairs the self disturbers and 3 SDSL modem pairs the alien disturbers on other wire pairs Figure 7 shows the definition of such a scenario which can be loaded via quickstart_2 ssf from the directory lt InstallDir gt Examples Examples_manual It is very similar to the one in quickstart_1 ssf but with the difference that it now sweeps the loop length in steps of 250 meter from 500m up to 5000m To change this sweep redefine the sweep parameter k1 as lt start value gt lt step value gt lt stop value gt as explained in more detail on section 4 2 5 If you prefer feet over meter see section 4 2 6 for further details Page 11 81 TNO 2009 SPOCS 6 0 User Guide SPOCS quickstart_2 ssf File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL O07 255 SpM 2 POTS
9. 130 i 8 SPOCS Freq Hz Zi L L L L li fi li L L L li fi li f L L 500k 1M 1 5M 2M 2 5M Figure 34 Shape of a noise profile generated from a disturber mix at the NT side of the loop for downstream performance testing s ETSI Noise profile on NT side approximated via a disturber mix PSD dBm Hz via ETSI noise model FA 80 J T J a 1 90 100 4 110 120 130 4 SPOCS Freq Hz 140 L L L L li fi i L L L li L li fi L L 0 500k 1M 1 5M 2M 2 5M Figure 35 Shape of a noise profile generated from a disturber mix at the NT side of the loop for downstream performance testing Page 35 81 TNO 2009 SPOCS 6 0 User Guide TRO 5 2 Example 2 Performance calculation of ADSL over POTS SPOCS full only The profile of the previous example enables performance testing for a single loop length and repeating that for various lengths can by quite time consuming SPOCS enables you to calculate this quickly for a range of loop length and this example explain how 5 2 1 Case 2a Margin calculation of ADSL over POTS Figure 36 shows how to change the scenario from the previous example see figure 33 with a fixed loop length into a scenario with variable loop length that can be swept in length The circles and arrows illustrate what has been added the loop length is replaced by the sweep parameter k1 that is instructed to sweep from 250 meter to 4000 meter in steps of 250 meter see section 4 2 5 for further d
10. 4 3 Inspecting the characteristics Of a scenario 23 EEN E ee Re Ee UE 24 4 5 Defining a DSL system under study SPOCS full only 25 d Selecting victim MOIS sineira espi SASSEL Sdt ee Et 25 4 5 2 Selecting simulation forgelg 26 4 6 Running performance calculations SPOCS full only 27 4 6 1 Running bit rate colecnloattons 27 4 6 2 Running margin ealenlontone 28 4 6 3 Running reach calculations cccccccsccceeeescceesenseeeeenseeeeseceeesenseeeeseaeeeeseaeeeeeseaeeeeeenneeeenas 29 5 APPLICATION EXAMPLES cscssssssssssrsssssscsesssssssssesssesssssssssssesssesessssssssesssesssesseesseees 31 5 1 Example 1 Building noise profiles for ETSI teste 31 5 1 1 Case la Noise profiles via a predefined ETSI model 31 5 1 2 Case Ib Noise profiles via a disturber mix 34 5 2 Example 2 Performance calculation of ADSL over POTS SPOCS full only eeeeeeeeeeeeeees 36 5 2 1 Case 2a Margin calculation of ADSL over POTS 36 5 2 2 Case 2b Bitrate calculation of ADSL over POTS 38 5 2 3 Case 2c Inspecting intermediate specthrg 40 5 3 Example 3 Impact Analysis of VDSL2 on ADSL2plus SPOCS full only 42 5 4 Example 4 Branching ADSL and VDSL SPOCS full only 45 6 USING ADVANCED FEATURES scssssssssssssssssssssesssesssessscsssesssesssesssesssesssesssesssesssessoess 48 6 1 Selecting different levels of expertise eee eeseeesseecsseeeeseeeesceeesaeecsseecseeceeeeesaeeesaeecsaeesseeesee 48 Page 2 81 TNO 2009 SPOCS 6
11. Rounded a Th Frequency MHz L L L L L L L D PPOCS i 1 h i i 1 1 1 i 0 0 2 0 4 0 6 0 8 1 1 2 1 4 Figure 63 The bitloading can be visualized via the receiver inspector 6 4 Adding user definable models SPOCS full only SPOCS offers the functionality to add your own models to the libraries This is a powerful mechanism to enable you to keep the list of SPOCS models up to date with the developments in standardization and to allow you to add country specific models or other models of your special interest to the libraries Further details can be found in the Library Guide 6 5 Calculating Equivalent Disturber Levels SPOCS full only The crosstalk is a combination of NEXT and FEXT from many disturbers where each disturber may be located at different locations It is possible for several topologies to represent all these disturbers by only two equivalent disturbers assumed to be co located with the modems under test and producing exactly the same crosstalk This is obvious for a simple scenario with exactly two nodes but not for scenarios with multiple nodes Therefore such a representation does not exist for all possible scenarios The purpose of calculating equivalent disturber levels is an analytical one It may be helpful to understand how crosstalk values will change when changing parameters in complex scenarios The ETSI noise models are examples of disturbers
12. o la lo la la lo lo lo le l la la DA Waaa Th spocs6o D Figure 24 Selecting what performance parameter is to be simulated The options are Margin Signal or Noise and achievable Bit Rate Line or Data e Noise Margin Ratio Pa2 Pn1 by which the received noise power Du may increase to power Da until the recovered signal no longer meets the predefined quality criteria This ratio is commonly expressed in dB e Signal Margin Ratio P P by which the received signal power P may decrease to power Ba until the recovered signal no longer meets the predefined quality criteria This ratio is commonly expressed in dB In most practical situations the signal margin is very close to the noise margin e Line Rate The raw bitrate transported over the line and includes all overhead needed for error correction Line Rate is always a few percent higher then the Data Rate Page 26 81 D TNO 2009 SPOCS 6 0 User Guide TRO e Data Rate The payload bitrate transported over the line without any overhead needed for error correction Data Rate is always a few percent lower then the Line Rate You will find 2 options for each Margin alternative no matter if we are dealing with Noise or Signal These 2 options are Line Rate and Data Rate In turn if you prefer using Data Rate or Line Rate you will also have 2 options All the possibilities are summarized below TARGET PARAMETER Data Rate Noise Margin Calcula
13. 0 User Guide 6 2 Using Power back off models i 4 i 73 daycedishs Seadasentislasealiane tials resets deeded 48 6 2 1 Selecting a PBO Model Seis euents wlnti ent data Seed 48 6 2 2 Available PBO models and its parameters ccceecccceeeseceeeeeeeeeeesceeeeeeaeeceeenseeetenneeeeenaees 49 632 3 Inspecting a PBO MOdel EE 49 6 3 Using Receiver models SPOCS full only eee eeseceeseeceseeesneeeeeeeseecsseecsseeeesaeessaeessaeesseeesee 50 6 3 1 Selecting an alternative Receiver Model 50 6 3 2 Selecting tuneable receiver modele 52 6 3 3 Selecting a generic receiver model 53 6 3 4 Inspecting a receiver model bitlooding 53 6 4 Adding user definable models SPOCS full only 54 6 5 Calculating Equivalent Disturber Levels SPOCS full only 54 6 6 Running repetitive tasks via macros SPOCS full only 55 7 USING PLUG INS SPOCS FULL ONLY ccssssssssssssssesssesssesssessscssscsssesssessscsssesssssoess 56 GEM Loop UE 56 GEERT 56 71 2 Loop Builder Description aeniea anna an enn ann oe 57 E Tempest 62 Pod Transmit VIC WED a iima a a RE A E A a a E ENEE 63 8 SUMMARY OF MENUS BUTTONS AND FIELDS sseesesseeseeseeseeseeseeseseeeseseeeseesesseseeeseseeeee 65 CN e d RE 65 cord WE EE 65 8 1 2 VIEW Menn SPOCS UII Only cniinn anite aeoaea aoaient 65 8 1 3 VIEW Menu SPOCS light on 66 8 1 4 LIBRARY EEN 66 OPED CONFIG MEN EE 67 8 1 6 MACROS Menu SPOCS full ob 68 8 1 7 TOOLS Menu SPOCS full Only cscccs
14. Frequency Show Noise plot at LT side Shows in one plot the above selected noises at LT side DSLAM Show Noise plot at NT side Shows in another plot the above selected noises at NT side CPE Show Legend Provides information about the sources of the plots Show Grid Allows the use of grid on the plot By default it uses dashes Show Grid as solid lines This allows the use of grid on the plot but the grid is forced to be solid lines instead of dashes Hold plots when recalculated Useful for comparison among different simulations The old plots remain in the performance plot while the new ones are processed 8 1 4 LIBRARY Menu Po UDRAR Menu Items Menu Description Transmitter Disturber Library Contains the transmitter models for different xDSL systems Receiver Library Contains the receiver models for different xDSL systems See also section 6 3 Loop Library Contains different cable models American European etc Power back off library Contains the PBO models See also section 6 2 NOTE The receiver library has been disabled in the light version Each of these items has the same sub menu items which are Sub Menu Items Menu Description Append In order to append models to the library Reset To reset the current library to default set of models Page 66 81 D TNO 2009 SPOCS 6 0 User Guide TRO List All In order to observe the models that are currently being loaded i
15. Guide TRO 7 2 Loop Viewer The loop viewer allows the user exploring the cable characteristics parameters like S parameters Gu S12 S21 S22 transmission properties such as attenuation impedance etc Besides the built in cable models that come with SPOCS the models created by the user can also be explored in the tool The tool is straightforward to use Therefore further details are omitted 2 toop viewer s view Clipboard Units Help lossless cable S Characteristic Transmission S_T hd Characteristic Transmission 57 Amplitude S dB 1 Frequency kHz Figure 71 Loop Viewer GUI Tool Page 62 81 TNO 2009 SPOCS 6 0 User Guide TRO 7 3 Transmit Viewer The transmit viewer allows the user exploring the spectra of the built in transmitter models that come with SPOCS or created by the user through user definable libraries BEE View Clipboard Help Transmit Spectrum GE E E E E dee WAAT A E del Lee 93 0 dBm 8 1000 kHz 167 807 dBmHz PEPE E EE EE PSD dBm Hz O OA E E ee eee E E docses cscs dee EE mice EE EE E E E E EE TE e E i 1 5 2 Frequency kHz x 107 Figure 72 Transmit Viewer GUI tool Area Description A It contains all the transmitter models B It draws the spectra corresponding to the selected transmitter model C Options that are self descriptive View Counterpart transmitter Shows the spec
16. INP the mechanism to protect the system against Impulse Noise effect Changing Delay will change the amount of overhead difference between the LineRate and the DataRate EOCOH Embedded Operational Channel OverHead This parameter has a range from 8 to 64 Kbps and is used for exchanging messages between the modems Figure 58 Understanding the parameter of the receiver models Page 51 81 TNO 2009 SPOCS 6 0 User Guide TRO 6 3 2 Selecting tuneable receiver models Most of the receiver models have fixed parameter values meaning that you cannot change their values This protects you from unattended changes In special cases you may want to tweak one or more of these parameters for instance to account for a better noise gap or another amount of impulse noise protection This is only possible for the receiver models that are specifically intended to be tuneable To get access to one of the tuneable receiver models you have to bring the level of expertise at least to the Advanced level Additionally the auto completion mode should be switched off for victims so that you can overrule the default receiver model by a tuneable model of your choice You can change them both via the CONFIG menu CONFIG AUTOR COMPLETION MODE KEEP VICTIMS PAIRED disabled CONFIG LEVEL OF EXPERTISE ADVANCED Now the listbox of the receiver will contain tuneable models as well To warn you that you have selected a
17. It is however more convenient to calculate multiple performance values for a range of stress conditions and to present it as a plot For instance the attainable bitrates as a function of the loop length or the noise margins as function of the number of disturbers To facilitate that SPOCS has a powerful feature on board to do that in a highly flexible manner the sweep parameter k1 Examples of its use for a range of loop lengths have been discussed in section 4 2 1 and shown in figure 21 indow Help lt Only for unprotected use within TNO the Netherlands gt indow Help lt Only for unprotected use within TNO the Netherlands gt E H eg age mg E LG be E Figure 21 The length of sections in a loop can be made flexible by replacing a constant by the loop parameter k1 to sweep the loop length from short to long This sweep parameter k1 is a fundamental concept within SPOCS and gives you inlimited possibilities to evaluate the performance as a function of something Its definition is essentially a comma separated list of values As soon as the parameter k1 is used anywhere on the front page of the GUI the simulator evaluates the performance for each value within that list It does not matter where k1 is used it can be to define the loop length a single section of a loop the number of disturbers crosstalk coupling etc You can use it on multiple places at the same time both as a single value or as an expression
18. KPN_L1 underground cable L1 50x4x0 5mm TP up ADSL O07 031 SpM 2 POTS C 6 E 6 enges 48 onge w sell L Generate LT noise profile DSLAM Generate NT noise profile CPE TPL dn ADSL 007 255 SpM 2 POTS TPL SDSL 1024 s SpM 2 TPL up ADSL 007 031 SpM 2 POTS PBO TPL SDSL 1024 s SpM 2 AU THE Id SPOCS 6 0 Figure 7 Scenario definition for my first performance simulation Hit the RUN button and the performance plot in figure 8 and performance table in figure 9 will be shown They represent the bitrate that a victim modem pair under test is expected to achieve at 6 dB noise margin when it is impaired by the disturbers of the above scenario If the loop length equals 3km you can read from the plot and table that it will be 862 kb s in upstream and 7 02Mb s in downstream Performance Plot 10M T T F F F b s 1 DataRate Up 2 DataRate Dn 9M F 2 8M F 7M 6M DM 4M 3M b i i _ 2M AM DI d SPOCS Sweep Parameter k1 gt y A cole E E SAE T ace E S S S A A EE E 0 500 1k 1 5k 2k 2 5k 3k 3 5k 4k 4 5k 5k Figure 8 Predicted data Rate Mb s as a function of the loop length m Performance Plot Page 12 81 TNO 2009 SPOCS 6 0 User Guide SPOCS 15 Jan 2009 15 55 48 gt seconds evaluated performance kl ResultData 500 000 750 000
19. Loop Builder Fie Clipboard View Units Help Custom loop type Bi AWG26 26 Gauge AWG Twisted Pair 11 417 yor ANS gy 4L 1 TP2 testloop i AWG24 T1424 j m m AWG24 24 Gauge AWG Twisted Pair 11 417 ke 3 CC e Ska 2 TS 2000 3000 Length meter Figure 67 Layout of the Loop Builder Tool Section Name Description A Loop Library Type of cable to be used Alternatives are Pre defined cables User definable cables the string Custom loop type appears when a new cable is being created Composition of Loop Type of cable selected per section Options There are the following fields Cable type Cable to be used from the SPOCS loop library Tap Indicates that the section is a bridge tap If not selected then it is assumed to be a cascade straight i e a cable followed by another type of cable section Length This field contains 2 boxes Quantity Box This box indicates for instance the number of units of the selected cable or the percentage related to the total loop length Type of unit This box indicates the metrics used in the quantity box that is meters feet etc or if it is related in some percentage to the total loop length auto option Length distribution It shows the absolute lengths of all the cascade straight sections Total Loop Length Total distance and the units in which it is given meter feet km etc Notice that the sum
20. Noise Vyhite 140dBm HZz LAJI LE SPOCS 6 0 Figure 39 A scenario for calculating the margin of ADSL over POTS as a function of the loop length Figure 40 shows the results in a plot and figure 41 shows the same in a tabular format The plot shows the attainable bitrates as a function of the loop length if the modem has to operate with at least 6 dB noise margin These bitrates drop with the loop length but on a distance of 3 km it is still possible to offer 3 05 Mb s in downstream and 528 kb s in upstream under the assumed stress conditions Page 38 81 TNO 2009 SPOCS 6 0 User Guide Performance Plot b s 8M MI 6M 5M AM 3M 2M IM 11 SPOCS L L 1 it 0 T li 1 E Ke e T T 1 DataRate Up 2 DataRate Dn Sweep Parameter L 1 I T k1 gt 5 0 500 1k 1 5k 2k 2 5k 3k 3 5k 4k Figure 40 The attainable bitrate of ADSL over POTS as a function of the loop length when it operates under the stress conditions of the scenario defined in figure 39 lt SPocs seconds 15 Jan 2009 16 31 35 evaluated performance EL ResultData 250 000 500 000 750 000 1000 000 1250 000 1500 000 1750 000 2000 000 2250 000 2500 000 2750 000 3000 000 3250 000 3500 000 3750 000 4000 000 DataRateGLT 1126613 368 1034381 177 971876 692 918687 985 869300 997 820942 600 772879 449 724
21. On SPOCS light only Button Description Show spectra Calculates a noise profile and shows the results Generate LT noise profile Calculates a noise profile and exports the LT profile to file DSLAM Generate NT noise profile CPE Calculates a noise profile and exports the NT profile to file Show Scenario This button allows the user to inspect what scenario has been created Show Topology This button allows the user to generate a graphic representation of the topology being defined If you right click the mouse above each node it will tell you how many systems are attached to that node Button Description PBO Power Back Off This button allows the setting of power control parameters This button appears at the LT NT and disturbers LT and NT side See section 6 2 for further details and section 4 2 3 as well Count Scale Allows choosing between applying a number of disturbers COUNT or the dB s SCALE contributed by an specific disturber This lets the user to apply conditions like those one specified at the standard See section 4 2 3 for further details B Branching Branching define for each disturber group of interest its own loop length that branches away from the main loop It colors red when non zero Hit the Show Topology button to check what topology you are defining See section 4 2 3 for further details More Allows adding more disturbers Another screen is p
22. Sub Menu Items Menu Description Transmitted Signal Adds curves of the transmitter signal at the other side of the loop See the example in section 5 2 case C Received Signal Adds curves of what signal arrives at the input of the receiver Received Noise Adds curves of what signal arrives at the input of the receiver Page 65 81 D TNO 2009 SPOCS 6 0 User Guide TRO Received NEXT contribution Adds curves of the NEXT portion at the input of the receiver Received FEXT contribution Adds curves of the NEXT portion at the input of the receiver Received Direct noise Adds curves of the direct noise at the input of the receiver contribution Equivalent Disturber Levels Extracts the equivalent disturber levels from the received noise See section 6 5 for further details Highlight Usable Spectrum Corresponds to the area between the received signal and the received noise See the example in section 5 2 case C 8 1 3 VIEW Menu SPOCS ight only VIEW ISELECT SPECTRA OOOO Sub Menu Items Menu Description Crosstalk noise Allows seeing all noise received by the modem under test in the plot of PSD vs Frequency NEXT contribution Allows seeing the NEXT portion in the plot of PSD vs Frequency FEXT contribution Allows seeing the FEXT portion in the plot of PSD vs Frequency Direct noise contribution Allows seeing the direct Noise in the plot of PSD vs
23. applied and the reduced power that is injected into the loop Receiver inspector Right click your mouse when it is above the select box of the receiver models It opens a context menu and one of its menu items is named Receiver inspector It shows the bitloading of a DMT modem under the stress conditions of your scenario 4 4 Exporting noise profiles A noise profile is a PSD description of the noise that the receiver of a modem observes within a given scenario It is the cumulation of all contributions from the involved disturbers mainly what disturbers on other lines couple into the wire pair under study crosstalk noise plus some residual out of band noise of a disturber pair that share the same wire pair direct noise If you specify all stress conditions of a scenario SPOCS can evaluate the cumulated noise spectrum for each end of the loop This noise level can be exported to file by hitting the lt Generate LT noise profile DSLAM gt or lt Generate NT noise profile CPE gt button By forwarding the noise profile to a noise generator that support the synthesis of user definable noise your test setup can emulate the noise for any flavour of DSL operating within arbitrary scenarios NOTE 1 In order to avoid problems in compatibility among different noise generators SPOCS will give a warning message if the noise level exceeds a predefined maximum power or the frequency exceeds a predefined upper frequency Thes
24. at the same time As soon k1 has been used somewhere SPOCS will sweep it and produce a performance plot otherwise SPOCS evaluates only a fixed performance value More details on the sweep parameter can be found in section 4 2 5 4 6 3 Running reach calculations The reach of a modem pair under study victim is a number that is specified for a given bit rate and noise margin It tells the longest loop length on which the modem pair can be deployed if it has to operated for a given bit rate and at least 6 dB noise margin The reach is fixed number that holds for a link and not for an individual modem If downstream operates for a certain loop length at 6 dB margin and upstream at 2 dB margin then the loop length is beyond the reach Therefore reach means that both modems have to operate under at least 6 dB margin Reach has to be evaluated in an iterative manner and has to take the margin of the modems at both ends of the loop under consideration This makes that we have to tell SPOCS to do an iterative search to find beyond what length the margin condition does not hold anymore for one of the two This iteration is constrained between a minimum and maximum value and that a solution may not exist between these limits Figure 28 highlights the relevant steps to enable such a reach calculation Page 29 81 TNO 2009 SPOCS 6 0 User Guide SPOCS File View Library Config Macros Tools Window Help lt Only for unprotected use within
25. c a small adjustment to account for crest factors and warning margins As a rule of thumb different crest factors might require an adjustment of about 0 1 to 0 3 dB lower or higher Some example values estimated for commercially available noise generators are summarized below AP dp d d d dp dp d dp WarningLevel_dBm Output Level d m InjectionLoss_dB Adjustment_dB Spirent DLS 5402DC dBm 22 5d8 0 0dB 9 5 dBm Spirent DLS 5403D i3dEm 19 5dB gt 0 0dB 625 dem Spirent DLS 5404 Jet 17 5dc8 0 00cB 4 5 dBm Spirent DLS 5405 13dBm 15 3dB 0 0dB 2 3 dBm Spirent DLS 5406 ldem 5 iJidB 0 0dB T79 dBm WarningLevel_MaxNoisePower 7 SdaBm WarningLevel_MaxNoiseFreq 30E6 Hz S NETWORK SETTINGS H TTE PROXTY dp dp These settings are only required if you are using a time limited version for evaluation purposes that requests permission to a Licence Server via dp Page 79 81 D TNO 2009 SPOCS 6 0 User Guide TRO the public internet AND if your local network grants you only an internet connection if traffic is re routed via a local proxy server Leave it undefined in all other cases Ask you local administrator what the host name and port numbers are of your local proxy server a sProxyName mylocalproxyname mycompany com sProxyPort 8080 Figure 75 Typical content of a configuration file of SPOCS
26. lt Generate LT noise profile gt button A context menu pops up and one of its menu items is named Noise inspector This will show the spectrum that will be written to file after hitting lt Generate LT noise profile gt An alternative is to enable the show of spectra as shown below Each time you hit the lt run gt button the spectra will be shown FILE VIEW SHOW SPECTRA gt activated Furthermore you may consider disabling the drawing of all curves in the plot except to one for noise This is shown in figure 30 When you hit the lt RUN gt button SPOCS will draw the curves in figure 31 and 32 SPOCS Example1 caseA ssf File We Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt v Show Spectra Transmitted Signal TPL up ADSL 007 031 SpM 2 POTS BR v Show Upstream in performance plots 10 Show Downstream in performance plots si v Show Legend Show Markers in curves Received FEXT contribution DSLIPOTS dnfEC SpM 2 M N 4 Show Grid Received DIRECT noise contribution i E Show Grid as solid lines Equivalent Disturber Levels i Parameters Hold plots when recalculated Highlight Usable Spectrum Figure 30 Selecting what curves are to be drawn in a spectral plot Page 32 81 TNO 2009 SPOCS 6 0 User Guide ETSI Noise profile on LT side generated via noise model FA 2 5M
27. restart of the package However the dynamic library will be lost if kept in the same program directory after a re installation Therefore it is strongly recommended to store the user definable libraries in other directory rather than the program directory The loop builder tool comes with an option in the File menu to clear on purpose the content of the dynamic library If the information regarding the new models defined by the user has not been exported to an user definable library file all the information will be lost NOTE The new cable models created via the Loop Builder tool are directly available from the GUI in SPOCS However if there are fixed lengths in the construction of the cable the minimum length to be used for simulation of a specific DSL study via k1 parameter should be equal or greater than the fixed length configured in the Loop Builder 7 1 2 3 Example Creating a composite loop with one bridge tap We show here how to create a composite loop via the Loop Builder tool Page 59 81 TNO 2009 SPOCS 6 0 User Guide TRO Loop Builder File Clipboard View Units Help Information on Loop custom Toop type __ Constructed by Loop Builder 1 Composition of Loop Section Cable type Tap Length Length Distribution 1 AWG26 26 Gauge AWG Twisted Pair 11 417 aj F Tap 70 fauto gt 3220 2 AWG24 24 Gauge AWG Twisted Pair 11 417 I Tap 30 fau
28. side received noise at NT side and downstream signal transmitted at the other side of the line Page 14 81 TNO 2009 SPOCS 6 0 User Guide TRO 4 Defining and running scenarios 4 1 Overview of the GUI The main panel of the Graphic User Interface GUI of SPOCS is shown in figure 12 From here you can define and run all your scenarios of interest e Defining the stress environment loops crosstalk disturbers frequency range e Defining a sweep for instance to calculate performance as a function of the loop length e Defining the modem pair under study victims For performance predictions you have to define them all but if only a noise profile is to be defined you can leave the system under study undefined the E blocks are simplified in SPOCS light This section discusses how to define an arbitrary scenario and how to export the associated noise or to run a performance simulation Terminology A loop is a connection between two modems via a single wire pair A loop has two sides or ports LT and NT and therefore also two transmission directions downstream and upstream e LT Line Termination a neutral name of the loop side that is closest to the core network In many cases it is located at the central office CO where the modem is part of the DSLAM but it could also be in a street cabinet in a distribution point or in a repeater at the customer side The LT is always on the left side in the GUI of SPOCS e NT N
29. you the attainable bitrate for such a scenario e A Instruct the LT receiver to evaluate margin by selecting noise margin or signal margin as simulation target The difference between these options is explained in section 4 5 2 e B Once the simulation target is set to margin the GUI will automatically switch to the associated bitrate parameter data rate or line rate Initially you will get a default value but you can overrule it with your value of interest e JCT Do exactly the same for the receiver at the other side of the loop e D Specify the loop length as a value that has to be swept Simply define the length as the result of sweep parameter k1 and subsequently define a proper sweep In the example of figure 27 we have defined the sweep as 100 100 5000 meaning a sweep starting with 100 ending with 5000 in steps of 100 The result is that the loop length sweeps from 100 meter to 5 km e E Hit the lt RUN gt button and SPOCS will evaluate and show you the margin as function of the loop length Mark that the performance is presented as a function of the sweep parameter k1 In this example it represents the loop length but SPOCS is not restricted to that SPOCS has generalized this concept and you can use the sweep parameter k1 in any field of the frontpage of the GUI For instance at a field that defines the number of disturbers or the crosstalk coupling You can even use k1 at different places
30. 1 However most of them may go beyond what is needed for defining realistic scenarios It uses the same syntax as within the third party tool Matlab from the Mathworks 4 2 2 Defining crosstalk coupling in the loop The default values for NEXT and EL FEXT coupling in the cable are visible via the GUI as shown in figure 18 The NEXT value represents the normalized near end crosstalk coupling at 1MHz and the EL FEXT value represents the normalized equal level far end crosstalk of 1 km cable at 1 MHz The values used in figure 18 are pragmatic values that have been used in many DSL standards Page 18 81 TNO 2009 SPOCS 6 0 User Guide TRO indow Help lt Only for unprotected use within TNO the Netherlands gt Loop model KENT underground cable L1 5040 5mm lf r 3000 m eee 1000 500 1500 m s na 50 BIM CS i RE mme Figure 18 The crosstalk coupling values for NEXT and equal level FEXT can be modified The values hold for all loop sections The default values for NEXT and EL FEXT can be modified via the configuration file of SPOCS see annex C These values are also tuneable via the GUI but this is disabled on default If it is grayed out and you would like to change them you must switch the level of expertise from basic mode to advanced mode via the config menu See section 6 1 for further details Since all loop sections are assumed to have equal properties per unit length the valu
31. 2 testloop 2 11 424 ANSI VDSL 3 testloop 3 11 424 ANSI VDSL 4 testloop 4 Bridgetaps 11 424 Coun 4NSI VDSL 5 testloop 5 Bridgetaps T1424 Tj ANSI VDSL 6 testloop 6 Bridgetaps T1 424 ANSI YDSL 7 testloop 7 Bridgetaps 11 424 DYNAMIC LIBRARY Find k1 s Bien a spocseo W Figure 70 Selection of the new cable model from the main menu of the simulator Notice that it is under the dynamic library label Generate NT noise profile CPE i Oe i ee Di kk After the user has created one or more new cable models these can be saved to one user definable library file by using the export library option All these new models will be grouped in this library file When exporting the library the user is asked to choose the directory where this file will be saved and the name of the file e g lib_loop_user_1 sla Once this is done the user might use this library by loading the user definable library file in the main menu of the simulator Library Loop Library Append and then choosing the file he has created Afterwards he will have access to the models available in this library file from the main menu of the simulator Notice that if the dynamic library has not been cleared FilelClear Dynamic library from the Loop Builder tool the models that reside in the dynamic library are still available from the GUI of SPOCS Page 61 81 TNO 2009 SPOCS 6 0 User
32. 611 326 675995 085 627049 253 577832 983 28499 001 479237 393 430300 184 382012 285 334780 601 calculation time dT 4 016 DataRateGNT 8426763 495 7516565 363 6942917 711 6489606 295 6088231 984 708109 076 332772 854 4951711 116 4555628 592 4131882 450 3660105 454 3048227 893 2350246 437 1681253 682 832394 371 419272 445 Figure 41 The same bitrates of ADSL over POTS as shown in figure 40 but now in a tabular format Page 39 81 D TNO 2009 SPOCS 6 0 User Guide TRO 5 2 3 Case 2c Inspecting intermediate spectra When SPOCS calculates performance various intermediate results are evaluated such as signal and noise spectra On default these results are not shown so you must enable this first via the following menu item FILE VIEW SHOW SPECTRA activated If you reload and run the example scenario 1b in figure 33 or replace the loop length by a fixed number of 3250m then SPOCS will show the spectra in figure 42 and 43 as well On default 3 curves will be shown e 1 The transmit signal as transmitted on the other side of the loop e 2 The receive signal as observed at the input of the receiver under test e 3 The noise as observed at the input of the receiver under test The distance between receive and transmit curves is the cable loss in dB The distance between the received signal and noise curve is the signal to noise ratio This area is highlighted by the green lines be
33. For instance k1 k1 275 3 812 k1 26 k2 The syntax of defining the list of values for k1 is similar to the syntax being used by the third party program Matlab for defining a row matrix The format of this parameter is Min step Max or vall val2 val3 or a mix of them i e 100 100 1500 which means that the first value is 100 it will continue in steps of 100 and the last value will be 1500 Other examples are summarized below Format Example Output Min Max 100 400 k1 contains values from 100 to 400 in steps of one unit Min step Max 100 100 400 k1 contains 100 200 300 400 values val1 val2 val3 100 400 1000 k1 contains values 100 400 and 1000 val1 500 k1 contains only one value 500 vall min step max 200 400 50 700 k1 contains 200 400 450 500 550 600 650 and 700 When k1 is not used anywhere in the scenario or has only one single value then a single result will occur single performance value and or single PSD at LT and NT side Page 22 81 D TNO 2009 SPOCS 6 0 User Guide TRO Constants The fixed parameters k2 and k3 are single values constants no list of values that you can use anywhere in the definition of the scenario This can keep the specification readable especially when k2 or k3 is used at different places at the same time A typical application occurs for scenarios with sub loops e Example 1 We can set up k1 k3 0 50 k3 k2 4000 k3 1500 and Leng
34. Help lt Only for unprotected use within TNO the Netherlands gt Cl KPN_L1 underground cable L1 50x4x0 5mm E Cl KPN_L1 underground cable L1 50x4x0 5mm f A bb 1000 500 1500 50 Figure 15 Connecting the NT modem to different nodes of a loop Sweeping section lengths Many performance calculations are presented as a function of the loop length meaning that such a length sweeps between a minimum and maximum values in predefined steps A section length can be made flexible by defining its length as an expression that involves the sweep parameter k1 This is a fundamental concept within SPOCS which is explained in more detail in section 4 2 5 When the sweep parameter k1 is used to define a section length SPOCS will analyze the scenario for all the values being allocated to k1 Figure 16 illustrates how to define this On the left picture it is used only once in one section but on the right picture it is used in two sections at the same time by means of an expression This gives you virtually unlimited means to specify topologies with an arbitrary dependency of the sweep parameter k1 In both cases the sweep parameter k1 is specified as a list of values starting in this example with k1 500 ending with k1 5000 and in steps of 250 Mark that when El is used in a section length the total loop length is not a fixed value anymore The GUI responds to that by showing the shortest and th
35. It can be obtained via nsis sourceforge net 1 4 Support Support sales and licenses inquiries on SPOCS can be obtained via www spocs nl Page 5 81 TNO 2009 SPOCS 6 0 User Guide TRO 2 Overview of the capabilities of the tool 2 1 What is SPOCS about SPOCS is equipped to assist you in two kinds of applications e Predicting DSL performance gt Performance simulator e Creating custom noise profiles gt Noise profiler Predicting DSL performance SPOCS can be used to predict the performance of DSL modems under noisy stress conditions loops and crosstalk from other DSL modems Performance can be evaluated as maximum bit rate as margin or as reach both as plot or in a tabular format Plots of the spectral results PSD s of noise and signals being received by the modems under test can be generated as well All these plots can be copied via the clipboard to other applications Creating custom noise profiles SPOCS can be used to define complicated noise profiles to control the noise generators in a DSL test setup This allows users to tests the performance of DSL modems in a lab environment testloop noise generator under user defined noise conditions Define in SPOCS an arbitrary scenario of loops and systems calculate the noise spectrum that will result from that system mix on a wire line and save it to file The resulting profile in a tabular ASCII format can serve as input for noise generators that allow the generation o
36. L2 models has been reduced This is because SPOCS starts in a Basic level of expertise which is intended only during a learning period We recommend switching to the Advanced level of expertise via the config menu and do not give in to the temptation of selecting the Expert mode See section 6 1 for further details You can overrule this default via the configuration file as explained in annex C More models will come available if you switch to the Expert mode and it will disable protection against selecting invalid models However it gives you additionally access to e Models representing PSD masks specifying peak values instead of nominal values e Models intended for the other side to study the transmission of downstream signal in upstream direction Page 25 81 TNO 2009 SPOCS 6 0 User Guide TRO Extending the list of receiver models tuneable models On default a receiver model is selected automatically for you But even when you disable this feature the list of receivers is restricted to those models that cannot be modified This prevents an accidental change of these parameter However sometime you may prefer to change this by hand at your own responsibility SPOCS allows you to do that when you have selected a so called tuneable model More details can be found in section 6 3 Disabling the autocompletion modes On default when you select a transmitter on one side SPOCS will automatically select t
37. Line x Digital Subscriber Line term to encompass all DSL technologies Crosstalk Page 4 81 D TNO 2009 SPOCS 6 0 User Guide TRO 1 Disclaimer and copyrights 1 1 Copyrights of SPOCS and associated libraries c 1996 2009 The Netherlands Organisation for Applied Scientific Research TNO Delft the Netherlands All rights reserved No part of this publication may be reproduced and or published by print photo print microfilm or any other means without the previous written consent of TNO 1 2 Disclaimer The origin of this software tool is branded as SPOCS by TNO Simulator for Performance of Copper Systems but is also distributed as 5D10 and 5C60 by Spirent Although SPOCS was created with the utmost care the end user license rights are granted on a strict AS IS basis TNO does not accept any liability for damage that the owner or user of SPOCS might incur due to the use of this software Reverse engineering of SPOCS and associated libraries is strictly prohibited unless and to the extent explicitly permitted by relevant law The use of SPOCS is subject to specific end user license conditions as integrated in the software as amended from time to time 1 3 Third party rights SPOCS has been compiled using the MATLAB compiler and associated MCR libraries The MCR runtime libraries are licensed components of MATLAB c 1984 2007 The Mathworks Inc The installer has been compiled using an open source scripting language NSIS
38. Multiple configuration files may exist when SPOCS starts SPOCS will first read the configuration file in the program directory where the program resides Secondly it checks if a spocs cfg file does also exist in the current directory If this is the case it will overrule all settings being specified This feature enables a dedicated configuration file for different studies for instance to load user defined libraries that are only meaningful for that particular study Page 80 81 D TNO 2009 SPOCS 6 0 User Guide TRO ANNEX D References 1 Transmission and Multiplexing TM Access Networks Spectral Management on metallic access networks Part 2 Technical methods for performance evaluations draft ETSI TR 101 830 2 v1 1 1 2005 09 Sept 22 2005 2 Rob Van den Brink KPN Research Realistic ADSL noise models contribution to ETSI STC TM6 Meeting 29 Nov 3 Dec 1999 3 ETSI TS 101 388 v1 3 1 2002 05 Technical Specification Transmission and Multiplexing TM Access Transmission systems on metallic access cables Asymmetric Digital Subscriber Line ADSL European specific requirements 4 970p02r3 Cable reference models for simulating metallic access networks ETSI STC TM6 meeting 22 26 June 1998 Lulea Sweden Page 81 81
39. O al LOOP KPN_L1 underground cable L1 50x4x0 5mm 0 5km V Victim D Disturber 1 4 NodeNumber NEXT 50 dB 1Mhz EL FEXT 45 dB 1Mhz 1km Vit Vit Mrs V r Figure 17 Graphic representation of the topology being created More examples of section lengths It may be clear that SPOCS allows for a lot of flexibility in defining the section lengths of a loop topology The means for specifying section lengths are virtually unlimited It allows numbers the sweep parameter k1 constants k2 and k3 and all kinds of expressions from these The examples below give a view on the different possibilities Case A k1 Case B k1 2 400 Case C k1 2 k2 k3 one section swept via k1 one section swept via an expression with k1 one section swept via an expression with k1 and two constants k2 k3 one section of constant length via an expression with k2 and k3 Two sections of constant lengths Five sections of constant lengths Four sections of constant lengths Two sections the second one is swept Case D k2 3 k3 Case E 2000 1500 Case F 500 500 500 250 250 Case G 100 100 250 2 250 4 250 Case H 500 k1 HHHH HE HE Case I 100 k2 k3 k1 Four sections all constant except for the last one In principle you can even use more advance expression including all kinds of mathematical functions like min k1 5000 max 100 k1 abs k1 exp k1 and sin k
40. S Used in SDSL and HDSL This is related to the use of capacity For example if the total capacity were 5 Mbps and Lines is set to 2 this would mean that the real capacity treated in SPOCS for calculations is equal to 2 5 Mbps BITPERSYM Number of Bits per symbol BITLOADRANGE These two values represent the minimum as well as the maximum number of bits per tone per symbol SYMBOLRATE Used in DMT systems ADSL VDSL2 A common choice used in ADSL and VDSL systems is to set to 4000 baud s FREQBANDS Frequency Bands to be used Used in the generic Shannon model CARRIERFREQ The frequency carrier Mostly used when working with CAP systems i e HDSL CAP FREQTONES Used when working with DMT corresponding to the set of sub carriers The use and location of the freq tones varies according to each product supporting DMT DF The delta frequency is the spacing between DMT carriers Common value is 4 3125KHz though in VDSL2 systems it may change to 8 625 KHz when high frequencies are used INP Impulse Noise Protection This is a parameter used in ADSL2 in order to deploy a protection mechanism for the effect of impulse noise There are several tables on ref 3 4 from which the user can choose the symbols to be used in conjunction with the delay Changing INP will change the amount of overhead difference between the LineRate and the DataRate DELAY This is a parameter used in ADSL2 and provides in conjunction with
41. S are to predict the noise levels associated with the 99 worst case limits because that criteria is commonly used The modeling follows the FSAN sum to cumulate all crosstalk see ETSI SpM 2 1 As a result you are to provide values for the normalized NEXT and EL FEXT of a cable as a whole and not the NEXT and EL FEXT between individual wire pairs When SPOCS evaluates the performance under a noise power that equals the 99 probability limit you should realize that in most cases the actual performance will be better then predicted The use of 100 worst case limits is commonly avoided to prevent for over pessimistic analyses NOTE The noise levels in xDSL product standards that are specified for testing purposes are all defined by using that 99 worst case rationale It means more or less If the modem can survive from this noise level it will work in almost all cases of a scenario 4 2 3 Selecting disturbers A disturber is a source that impairs the performance of the victim modem under study Like victims disturbers come also in pairs Crosstalk disturbers These disturbers are representing modems in other wire pair that couple into the wire pair of the victim modem On default when you select a disturber on one side SPOCS will automatically select the associated one at the other side The naming convention uses the following prefixes e TPL denotes that a model represents a template PSD of an individual modem e MIX deno
42. TNO the Netherlands gt ee re a NT tranamitter upstream CPE S TPL dn ADSL OO7 255 SpM 2 POTS B KPN_L1 underground cable L1 50x4x0 5mm TPL up ADSL 007 031 SpM 2 POTS B DataRate DataRate LineRate 7 d Show Tgp l Show Scenario Generate NT noise profile CPE esp parameter ap b 2 TPL ISDN 2610 SpM 2 TPL HDSL 261 2 SpM 2 TPL up ADSL O07 031 SpM 2 POTS PBO TPL SDSL 2304 s SpM 2 see PBO H Le TET dee l le le lo o ale la o la lo lo e lo o a lo lo Ja ja Figure 28 Relevant settings for a reach calculation om Start defining a scenario of interest with a victim modem pair under study a disturber mix and associated loops The following steps bring you the attainable bitrate for such a scenario e A Instruct the LT receiver to evaluate margin by selecting noise margin or signal margin as simulation target The difference between these options is explained in section 4 5 2 e B Once the simulation target is set to margin the GUI will automatically switch to the associated bitrate parameter data rate or line rate Initially you will get a default value but you can overrule it with your value of interest e JCT Do exactly the same for the receiver at the other side of the loop e D Specify the loop length as a value that has to be swept during the iteration Simply define the length as the result of sweep parameter k1 and subseque
43. TNO Information and Communication Technology TNO Report SPOCS 6 0 User Guide Date January 21 2009 Title User Guide version for SPOCS 6 0 Authors Rob F M van den Brink Hernan C rdova Status Released All rights reserved No part of this publication may be reproduced and or published by print photoprint microfilm or any other means without the previous written consent of TNO In case this report was drafted on instructions the rights and obligations of contracting parties are subject to either the Standard Conditions for Research Instructions given to TNO or the relevant agreement concluded between the contracting parties Submitting the report for inspection to parties who have a direct interest is permitted 2009 TNO s TRO Delft Brassersplein 2 P O Box 5050 2600 GB Delft The Nederlands www tno nl www spocs nl eng 81Pages TNO 2009 SPOCS 6 0 User Guide Table of Contents TABLE OF CONTENTS cscssssssssscssscsssessscssscssscssscssscssscssscssscsssesssessscssscsssesssesssesssessscsssesssessossoess 2 LIST OF ABBREVIATIONG cscsssssssssssssssssesssesssesssesssessscsssssssesssesssesssessscsssesssesssesssesssesssessoess 4 1 DISCLAIMER AND COPYRIGHT sccsccsssossscssccssecssecseeseesscessessceesseescesseesseeeseesseesoeees 5 1 1 Copyrights of SPOCS and associated libraries 1 0 0 0 eeeeeseeeseessseecsseeeeseecesneeesaeecsaeesseeeenaeeesaee 5 UE age DIE E 5 1 3 Thitd p
44. ance SDSL and HDSL since the concept of attainable bitrate is meaningless for a fixed bitrate modem e B Once the simulation target is set to bitrate the GUI will automatically switch to the associated margin parameter noise margin or signal margin A commonly used value for margin is 6 dB but you can overrule it with other values e JCT Do exactly the same for the receiver at the other side of the loop e D Specify the loop length as a value that has to be swept Simply define the length as the result of sweep parameter k1 and subsequently define a proper sweep In the example of figure 26 we have defined the sweep as 100 100 5000 meaning a sweep starting with 100 ending with 5000 in steps of 100 The result is that the loop length sweeps from 100 meter to 5 km e E Hit the lt RUN gt button and SPOCS will evaluate and show you the attainable bitrate as function of the loop length Mark that the performance is presented as a function of the sweep parameter k1 In this example it represents the loop length but SPOCS is not restricted to that SPOCS has generalized this concept and you can use the sweep parameter k1 in any field of the frontpage of the GUI For instance at a field that defines the number of disturbers or the crosstalk coupling You can even use k1 at different places at the same time As soon k1 has been used somewhere SPOCS will sweep it and produce a performance plot otherwi
45. annon capacity limit Roughly the amount of dB that the noise can increase before the link quality gets too low It is often represented by the symbol TdB NOISE Corresponds to the receiver noise known as Prno_ ap see clause 5 1 of 1 ECHOSUP The fragment of the transmit signal that echoes into the receiver is usually suppressed by an echo canceller Some residual echo will always remain after echo cancellation adds like noise to the received signal and reduces the performance EchoSup is a parameter of a simple model to express what fraction of the received echo has left and will behave like noise If set to Inf it becomes infinite as if the echo cancellation were ideal DISTSUP The received signal is distorted by cable loss and the signal that was transmitted is recovered from the received signal by means of an equalizer Usually these equalizers are very effective but not perfect The restored signal will always differ slightly from the transmitted signal and this will also add noise to the received signal thus reducing the performance DistSup is a parameter of a simple model to express what fraction of the transmitted signal is not recovered and will behave like noise If set to Inf it becomes infinite as if the equalization were ideal RN The impedance of the modem and in use for both the transmitter and the receiver Changing the impedance changes the signal loss in a cable and the echo LINE
46. aper EE EE EE Oe ee elon ee 5 UE E 10 0 0 0 EE 5 2 OVERVIEW OF THE CAPABILITIES OF THE TOOL csccssssssssssssssevsseeseesseeeseesseees 6 SN EIERE e 6 2 2 Using SPOCS as DSL Performance simulator 00 cee cesecesseeceseceesseeesseeceseeeseesesaeeesaeessaeesseeenes 7 2 2 1 Example 2 Spectral Management SpM Spscltes 7 2 2 2 Example 1 DSL deployment Srrdiee 8 2 3 Using SPOCS to create custom noise profiles for DSL testing eeeseeeseeereeerresrrerrrerrrerrrsrerereeeres 8 2 3 1 Example 1 DSL performance festge 8 2 3 2 Example 2 Product Selection ssnin a asiaa aai eiai in aE 8 3 QUICK START EXAMPLES cccsccssssssssssssssecssecsseesseessecsseesseesseessesssessseescesseessesssesesessoeees 9 3 1 Loading afirst example SCM aro ess 2 05204 tune eis eE eS SE a inna NEEN 9 3 2 Generating my first noise profile ouckestart 1 sel 9 3 3 Generating my first performance prediction SPOCS full only 11 4 DEFINING AND RUNNING SCENARIDOG csccssssssssssssssssssssesssssssesesssesescesscesscesseseeees 15 Al Overview Of the BI 15 4 2 Defining a stress environmen tirio eesecsseeesseeeessecesseecsaeecssceceseecesaeecsaeecsaeecseesenaeessaeeesaeers 16 GR 16 4 2 2 Defining crosstalk coupling in the Joen 18 4 2 3 Selecting distur bers EE 20 4 2 4 Defining frequency range and com 21 4 2 5 Defining sweeps k1 and constants k2 and K l 22 4 2 6 Using metric or imperial wmits ia e Ei Eaa ER REEE 23
47. as extreme as the first one Note that this is only Page 43 81 TRO TNO 2009 SPOCS 6 0 User Guide true in a statistical sense In 99 of the cases the impact will not be so severe as shown in figure 49 but this severity can happen in practice The second figure 50 shows that when the cabinet location is changed that the severity in impact will change as well but it remains significant and probably unacceptable in most operational cases 16M Impact ofVDSL2 on ADSL2plus downstream performance T b s 14M F 1 12MH 10M aM 6M 4M 2M 1 reference ADSL2plus Only 2 1 VDSL2 disturber at 2000m 3 50 VDSL2 disturbers at 2000m SPOCS Sweep Parameter k1 ay f b l b l i i l L i 0 500 1k 1 5k 2k 2 5k 3k 3 5k 4k 4 5k 5k Figure 49 Deploying only one VDSL2 system from a cabinet without proper measures can have a severe negative impact on ADSL2plus deployments from the exchange 0 Impact of VDSL2 on ADSL2plus downstream performance 16M l b s 1 reference ADSL2plus Only J 14M 2 50 VDSL2 disturbers at 2000m 4 3 50 VDSL2 disturbers at 1500m 12ML m 4 50 VDSL2 disturbers at 1000m 10M 8M J 6M d 4MH SPOCS Sweep Parameter k1 gt 0 1 1 i 1 i i i i 1 1 1 1 0 500 1k 1 5k 2k 2 5k 3k 3 5k 4k 4 5k 5k Figure 50 Changing the location of the cabinet will chang
48. bled in Basic Mode See section 4 2 5 for further details k3 This is a general purpose constant that is disabled in Basic Mode See section 4 2 5 for further details Page 71 81 D TNO 2009 SPOCS 6 0 User Guide TRO 9 Nomenclature followed for the models This section deals with the nomenclature used in SPOCS for the different models used in the built in libraries The objective of this section is to show to the user the meaning of the name of the models with a few examples 9 1 Transmitter Model The list of the transmitter disturber models can be retrieved from the GUI of SPOCS Menu Library Transmitter disturber library Some of them are e TPL up ADSL 007 031 SpM 2 POTS TPL dn ADSL 007 255 SpM 2 POTS TPL up ADSL 007 030 SpM 2 POTS FDD GB7 TPL dn ADSL 038 255 SpM 2 POTS FDD GB7 TPL up ADSL 007 03 1 SpM 2 POTS FDD ADJ TPL dn ADSL 033 255 SpM 2 POTS FDD ADJ Two examples illustrate how these names can be broken down into smaller fragments TPL ISDN 2B1Q SpM 2 TPL ISDN 2B1Q SpM2 The model Base name of the model Obtained from ETSI produces a SpM 2 standard template MSK dn ADSL2 A 033 511 G992 5 FDD MSK dn ADSL2 A 033 511 G992 5 FDD The model Base name of DMT tone 33 Obtained from ITU produces a mask the model to 511 are used G992 5 and intended for downstream in this model for use in a frequency non overlapping mode
49. cable model You can select a cable model from a list with many predefined models including predefined models for composite cables being defined in various DSL standards ETSI ITU DSLF In the example below we have selected cable model KPN_L1 which represents a cable with 0 5 mm wire pairs commonly used in the Netherlands Sections A loop can be subdivided in multiple sections to enable loop topologies where modems are deployed from different locations A two section topology can be adequate to represent a central office from where ADSL is deployed a street cabinet from where VDSL2 is deployed and a few customer locations that are all approximated as co located Figure 14 illustrates how to subdivide a single loop of 3km into multiple sections The more comma separated numbers you add to the field where the loop length is defined the more sections will occur If you change the number of sections the GUI will immediate respond to that by a symbolic drawing above the length field In SPOCS all cable sections must have equal properties per unit length so a cascade of a 0 5 mm cable with a 0 8mm cable is not possible from the GUI This requires the use of a composite loop model as explained in section 7 1 indow Help lt Only for unprotected use within TNO the Netherlands gt findow Help lt Only for unprotected use within TNO the Netherlands gt Cl Ia e underground cable L1 50x4x0 E x f Cl KPN_L1 undergr
50. cause it is a fair measure for the maximum bitrate If you use some imagination and increase the noise by 6 dB then the remaining area reduces This will be a fair measure for the attainable bitrate at 6 dB noise margin You can make more curves visible or disable most of them by selecting the curves of interest via the menu item FILE VIEW SELECT SPECTRA activate deactivate what is needed NT spectra Downstream signal received noise T T PSD dBm Hz 1 Transmitted Signal 100 ohm 40 m 1 2 Received Signal 100 ohm i 3 Received Noise 100 ohm 7 60 80 Se 3 E 7 100 120 L 140 i i i 160 i l E 180 SPOCS 0 500k 1M 1 5M 2M 2 5M Figure 42 The downstream receiver will observe these spectra at the NT side of the loop if it is part of the scenario shown in figure 33 Freq Hz li 1 L i li 1 li 1 1 200 Page 40 81 D TNO 2009 SPOCS 6 0 User Guide TRO LT spectra Upstream signal received noise T T Ser dBm Hz 1 Transmitted Signal 100 ohm 7 40 j i 2 Received Signal 100 ohm 3 Received Noise 100 ohm 60 gt 80 H 100 120 140 160 180 L 200 SPOCS Freq Hz 7 1 L 1 li fi fi 500k 1M 1 5M 2M 2 5M Figure 43 The downstream receiver will observe these spectra at the NT side of the loop if it is
51. ced via the CONFIG menu See section 6 1 for further details You can load this example scenario from disk FILE LOAD select lt InstallDir gt Examples examples_manual Example4 CaseA ssf FILE LOAD select lt InstallDir gt Examples examples_manual Example4 CaseB ssf FILE LOAD select lt InstallDir gt Examples examples_manual Example4 CaseC ssf FILE LOAD select lt InstallDir gt Examples examples_manual Example4 CaseD ssf You can inspect these scenarios one for one to see how branching and power back off have been applied When the PBO button colours red you can inspect the amount of PBO for that disturber transmitter by right clicking its PBO button A context menu will then pop up and one of its menu items is the PBO inspector Figure 53 illustrates the ADSL bitrates as evaluated for case A B and C e Curve A is below B since the topology without branching is too pessimistic Ignoring branching for ADSL studies can easily result in predictions that are 10 15 too pessimistic e Curve C is above B since the PBO settings has shaped VDSL2 too deep It would require an adjustment of the PBO settings to make curve C and B similar but this is out of scope of this example Figure 54 illustrates the VDSL bitrates for street cabinets positioned at 2km distance from the central office e ADSL2plus downstream performance from exchange b s L 1 classic predictio
52. cros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL O07 255 SpM 2 POTS KPN_L1 underground cable L1 50x4x0 5mm TP up ADSL O07 031 SpM 2 POTS i bh E Te ze Show Topology TPL up ADSL 007 031 SpM 2 POTS gt TPL SDSL 1024 s SpM 2 WE o le le Le le o o lo Id spocs6o W Figure 4 Scenario definition for my first noise profile For SPOCS full only SPOCS can show you the generated spectra in advance but this is disabled by default Enable this first via the View menu VIEW Show Spectra select it if the check marker is absent Hit the RUN button and the plots in figure 5 and 6 will be shown For SPOCS light only SPOCS can show you the generated spectra in advance Hit the Show Spectra button and the plots in figure 5 and 6 will be shown Page 10 81 D TNO 2009 SPOCS 6 0 User Guide TRO LT spectra Upstream signal received noise T T PSD dBm Hz 1 Transmitted Signal 100 ohm 7 40 H DI 2 Received Signal 100 ohm 3 Received Noise 100 ohm SPOCS Freq Hz 7 220 L L L L fi i L L L li fi i fi L L 500k 1M 1 5M 2M 2 5M Figure 5 Spectra at the LT side of the loop as specified in figure 4 NT spectra Downstream signal received noise PSD dBm Hz 1 Transmitted Signal
53. ct our self to noise model FA test loop 2 and the bitrates 2 048 kb s downstream and 512 kb s upstream The reach requirements for these combinations are almost the same 3225 down 3275 up and in this example it is approximated by 3250 meter 5 1 1 Case 1a Noise profiles via a predefined ETSI model SPOCS has all these ETSI noise models and test loops in its libraries and we assume for this example that you have access to them e The library model TPL dn ADSL 007 255 SpM 2 POTS refers to downstream ADSL over POTS All DMT carriers between 7 and 255 are used for downstream transmission and the model is specified in SpM 2 the ETSI spectral management standard TR 101 830 2 e The library model TPL up ADSL 007 031 SpM 2 POTS refers to upstream ADSL over POTS All DMT carriers between 7 and 31 are used for upstream transmission and the model is specified in SpM 2 the ETSI spectral management standard TR 101 830 2 e The library model ETSILADSL 2 standard test loop 0 5 mm refers to test loop 2 as specified by ETSI in TS 101 388 e The library model MIX dn X LT FA refers to ETSI noise model FA for ADSL over POTS and models the equivalent of multiple disturbers Figure 29 illustrates how to define the scenario The loop length is fixed at 3250 m for the selected bitrates You can load this example scenario via FILE LOAD select lt InstallDir gt Examples examples_manual Example1 caseA ssf Pag
54. dies and gives access to tuneable models The recommended level to work with is the Advanced level but beginners can take advantage from starting SPOCS in the Basic level The default choice on start up is the Basic level but this default can easily be changed by customizing the configuration file as explained in the annex C The difference between the levels are roughly as follows e Basic level recommended only for beginners o transmitter disturber models are limited to the most relevant once o model parameters cannot be changed o values for NEXT and FEXT cannot be changed o parameter k2 and or k3 cannot be used e Advanced level recommended for common use o Access to all relevant transmitter disturber models PSD templates o Access to tuneable models if you want to change some model parameters o NEXT and FEXT can be changed from the GUI o Parameters k2 and k3 can be used on top of the sweep parameter k1 e Expert level discouraged unless you know exactly what you are doing o Access to all transmitter disturber models defined in the library overwhelming B Not only for PSD templates but also for PSD masks B Using transmitters in the wrong direction downstream modems in upstream NOTE If you read a scenario that contains models that are only available for higher levels of expertise SPOCS will raise an error Simply increase the current level of expertise and read it again 6 2 Using Power back off models DSL modems can be equi
55. e 31 81 TNO 2009 SPOCS 6 0 User Guide TRO SPOCS Example1 caseA ssf File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL OO7 255 SpM 2 POTS g ETSI ADSL 2 standard testloop 0 5 mm a TPL up ADSL 007031 SpM 2 POTS wo mol i Jz i _PBO_ ADSLIPOTS dn EC SpM 2 S IN_Margin hd s f d Show Topology Show Scenario Generate NT noise profile CPE Mores 2 MIX up X NT FA gt ADSLPOTS E E BR la Le e Lo Te Le Lo e Le le le le gt lo a o la le e Noise Vyhite 140dBm Hz 7 Figure 29 Relevant settings for generating an ETSI noise profile ise White 140dBm Hz TE LE spocsso W On SPOCS light only The noise profile is calculated and written to file after hitting the button lt Generate LT noise profile gt To inspect what spectra will be written you should hit the button lt Show Spectra gt An alternative is right clicking your mouse when it is above the lt Generate LT noise profile gt button A context menu pops up and one of its menu items is named Noise inspector This will also provide the spectrum that will be written to file after hitting lt Generate LT noise profile gt On SPOCS full only The noise profile is calculated and written to file after hitting the button lt Generate LT noise profile gt To inspect what will be written right click your mouse when it is above the
56. e longest length of the loop that can be achieved with the current definitions It adapts immediately to changes in the definitions of section lengths or sweep range lindow Help lt Only for unprotected use within TNO the Netherlands gt lindow Help lt Only for unprotected use within TNO the Netherlands gt KPN_L1 underground cable L1 50x4x0 5mm Figure 16 The l length of sections in a loop can be made flexible by replacing a constant by the loop parameter k1 to sweep the loop length from short to long Page 17 81 D TNO 2009 SPOCS 6 0 User Guide TRO Inspecting section lengths The symbolic drawing of the sections above the length field is not to scale For your convenience SPOCS can make a graphic representation of the loop topology that you have defined Push the lt Show gt button to draw the topology on scale Figure 17 shows it for the fixed length examples in figure14 When the length of one or more sections is specified by means of the sweep parameter k1 the highest value for the sweep parameter k1 is used to draw the topology The red line marked with V illustrates what loop section s are being used by the victim modem pair under test in this example between node 1 and 2 Loop range 1000 500 1500 3000 m Only the maximum values are drawn below SPOCS 1000 500 1500 DSLAM S CPE LT DI 2 3 4 NT e lt upstream gt lt downstream gt v O
57. e the amount of eploying only one VDSL2 system from a cabinet will have a significant negative impact on ADSL2plus deployments from the exchange unless proper measures are taken Page 44 81 D TNO 2009 SPOCS 6 0 User Guide TRO 5 4 Example 4 Branching ADSL and VDSL SPOCS full only It is a common approach in performance studies to keep the involved topology as simple as possible Many VDSL2 studies assumed a straight loop where all customers are at the end of the line or distributed along the line as shown in figure 51 streat Customers Central office cabinet 1 2 3 S VDSL Figure 51 An over simplified topology assuming all customers distributed along the same loop Real life topologies however are not like straight loops they are branched It is common in the Netherlands that a 900 wire pair distribution cable leaves the central office to arrive in a street cabinet From thereon the cable fans out into nine 100 wire pair cables SPOCS has the capability to include branching in your scenario and the example below show why you need it and cannot make good simulations without it Figure 52 illustrate a few topologies where 360 broadband systems are deployed to a single distribution area e Case A is a simple straight topology assuming that all customers are virtually collocated at the end of the loop It represents the classic approach of describing a topology e Case B is a branched topology that rep
58. e values are fixed and can be modified by means of the configuration file of SPOCS see the annex Changing default settings NOTE 2 A noise profile is evaluated and specified in terms of powers and is as such independent from the involved termination impedances Your noise generator however has to inject the noise into a test loop that is terminated with physical impedances Since the actual noise power that is dissipated by these termination impedances will change with their impedance values the noise power being aimed the target noise and what is being dissipated the actual noise may be different in practice You should calibrate your setup to compensate for this difference and some noise generators are equipped with convenient compensation means for this NOTE 3 The file format of a noise profile is essentially a table with two columns the first one contains the frequency in Hz and the second on the power in dBm Hz Some versions of SPOCS are tailored to a specific noise generator and will therefore generate a file format that is more dedicated to that generator In such a case an additional dialog box pops up to set and or overrule various settings for that particular noise generator Page 24 81 D TNO 2009 SPOCS 6 0 User Guide TRO 4 5 Defining a DSL system under study SPOCS full only SPOCS is a program with the capability to predict the performance of a pair of victim modems under specifi
59. ed stress conditions This could mean the Bit Rate the Margin or the Reach of these modems A victim modem is the modem under study for which the performance is to be predicted under noisy stress conditions There are two of these modems one identified as the LT modem LT Line Termination usually the DSLAM located in the central office and another one identified as the NT modem NT Network Termination usually a CPE located at the customer premises A victim modem is a combination of a transmitter and a receiver and each modem has its own impedance 4 5 1 Selecting victim models Transmitter models A suitable transmitter model can be selected from a list of predefined models Many models are taken from the ETSI SpM 2 standard 1 or are in line with a product standard Each model of that list has its own design impedance which is 100 Q for many systems but some models are based on 135 Q or 150 Q The actual value is indicated on the screen as Rv This impedance is relevant since SPOCS takes it fully into account when evaluating the insertion loss of the transmitted signal by the cable Receiver models A suitable Receiver model can also be selected from a list of predefined models For special purposes you can even select receiver models that are more generic for line codes like PAM CAP QAM and DMT or even a pure Shannon modelling approach On default when the auto completion mode is enabled the receiver model is au
60. ed in the ETSI Spectral Management standard TR 101 830 2 Figure 34 and 35 show the resulting noise profile as well as the one obtained via the ETSI noise model FA These profiles are not the same but close so the use of a disturber mix is not suitable for compliance testing However the noise profiles generated via a disturber mix are not only closer to what can be expected in reality their definition is also closer to what they actually represent SPOCS Example1 caseB ssf sl x File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt f T A TPL dn ADSL 007 255 SpM 2 POTS BR ETSI ADSL 2 standard testloop 0 5 mm a TPL up DSL 007 031 SpM 2 POTS A gi el SI Show Topology Generate LT noise profile costa Show Scenario Generate NT noise profile CPE eC isn 261 0 lt SpM 2 PBO BI f TPL ISDN 2610 SpM 2 a IPLHDSL2B102 SpM 2 zl TPL up ADSL 007 031 SpM 2 POTS gt PBO IPL SDSL 2304 s SpM 2 Z P PBO d Boao INTE EEE aa De Le E a INoise VVhite 140dBmsHz s r fc INoise White 1 40dBm Hz ES Figure 33 Generating a noise profile via a disturber mix Page 34 81 TNO 2009 SPOCS 6 0 User Guide a TRO ETSI Noise profile on LT side approximated via a disturber mix 70 7 PSD dBm Hz via ETSI noise model FA 80 J J 90 M 100 110 120
61. element contributes to the scenario Page 23 81 D TNO 2009 SPOCS 6 0 User Guide TRO Scenario inspector Hit the button lt Show Scenario gt and it will show a compact description of most settings of your scenario Topology inspector Hit the button lt Show Topology gt and it will show a graphic representation of the length of all loop sections main sections and branched sections Noise inspector Right click your mouse when it is above the lt Generate LT noise profile gt button A context menu pops up and one of its menu items is named Noise inspector This will show the spectrum that will be observed by the receiver under test Loop inspector Right click your mouse when it is above the select box of the loop models It opens a context menu and one of its menu items is named Loop inspector It shows the transfer function of the total loop all sections in cascade as you have defined it in your scenario PSD inspector Right click your mouse when it is above the select box of a disturber or transmitter models It opens a context menu and one of its menu items is named PSD inspector It shows the PSD of that particular transmitter before any power back off is applied if any PBO inspector Right click your mouse when it is above the lt PBO gt button of a disturber It opens a context menu and one of its menu items is named PBO inspector It shows the transmit power before PBO is
62. ent modifications Save as Save the current modifications with another name Clear Scenario Delete Clear the scenario on the GUI and bring it back to a status as if SPOCS was just started Change Directory Select another directory as the default for reading scenarios Follow Directory Set the directory of the current scenario as default Exit Terminates SPOCS 8 1 2 VIEW Menu SPOCS full only EW Menu Items Menu Description Show Spectra Instructs SPOCS show intermediate spectral results in a separated window during a performance calculation See the example in section 5 2 case C Select Spectra Only Available when Show Spectra is enabled See table below and the example in section 5 2 case C Show Upstream in performance It shows only the upstream performance curve plots Show Downstream in It shows only the downstream performance curve performance plots Show Legend Provides information about the sources of the plots Show Markers in curves It shows by means of circles the points where performance has been evaluated Show Grid Allows the use of grid on the plot By default it uses dashes Show Grid as solid lines This allows the use of grid on the plot but the grid is forced to be solid lines instead of dashes Hold plots when recalculated Useful for comparison among different simulations The old plots remain in the performance plot while the new ones are processed
63. er fragments KPN_L1 underground cable L1 50x4x0 5mm 0 5km KPN_L1 underground cable L1 50x4x0 5mm 0 5km Unique name of Descriptive text Info on dimensions the model Note 0 5 km might be misnomer Actually it means that the model was extracted from measurements taken from a 0 5 loop Nevertheless the model can be used for any length 9 4 PBO Model The list of the PBO models can be retrieved from the GUI of SPOCS Menu Library Power back off library Some of them are e PBO dn ADSL POTS G992 1 annex A e PBO dn ADSL ISDN G992 1 annex B e PBO dn ADSL POTS e PBO dn ADSL ISDN An example illustrates how these names can be broken down into smaller fragments PBO dn ADSL POTS G992 1 annex A PBO dn ADSL POTS G992 1 annex A The model Intended Base name of the Obtained from ITU provides power for down model standard G992 5 back off stream Page 73 81 Rep TNO 2009 SPOCS 6 0 User Guide TRO ANNEX A Terminology Access Port is the physical location appointed by the loop provider where signals for transmission purposes are injected into the local loop wiring Access Rule mandatory rule for achieving access to the local loop wiring equal for all network operators who are making use of the same network cable that bounds the crosstalk in that network cable Cable Fill or Degree of Penetration number and mixture of transmission techniques connected t
64. erbose UnitsLen meter Smust be one of meter km inch feet yard kft mile Z DEFAULT SCENARIO VA VUES NEXT and Equal Level FEXT are a measure for the frequency dependent crosstalk coupling between the wire pairs A universal or standardized value does not exist since the values are cable dependent Commonly used values are predefined below Uncomment the lines that matches your preferences or add other defaults Common values for European studies Cable_NEXT 50 0 in dB at 1MHz Cable_ELFEXT 45 0 S in dB at 1MHz and 1 km Common values for North American studies T1 417 Annex A 3 2 1 2 and A 3 2 2 SCable_NEXT 10 1lo0g10 8 536e 15 1le6 3 2 50 6875 dB 1MHZ Cable_ELFEXT 10 log10 7 74e 21 le6 2 le3 feet 45 9527 dB 1MHz 1km Define the directories where SPOCS writes its output files like scenarios or noise profiles It will be ignored if the specified directory could not be found Page 78 81 TNO 2009 SPOCS 6 0 User Guide TRO dp de dp predefined variables S ProgDir contains the program directory where spocs exe is S CurrDir contains the current directory examples S DirScenarios Suse current directories DirScenarios C User MyScenarios DirScenarios ProgDir MyScenarios DirProfiles ProgDir Output MyProfiles DirLicenses C User Secrets MySpocsLicenses DirLicenses ProgDir
65. es 6 3 1 Selecting an alternative Receiver Model To select an alternative receiver model different from the default choice you have to disable the auto completion mode for victim modems You can deactivate it from the Config menu via CONFIG AUTO COMPLETION MODES Keep victims paired Now the listbox of the receiver becomes selectable and you can select an appropriated one The list of specific receiver models is long enough to find a matching one for most modems that are conform some DSL standard If you are analyzing a non standard but good quality modem using a line code that is unknown to you then the Generic DEFAULT model may give fair simulation results To find out what each model means select one and right click on it with your mouse This opens a context menu with an info entry to provide you with basic information about the model For more details please check the SpM 2 1 standards of the model you are interested in Additional information can be found by pushing the lt Parameters gt button on the receiver box It shows the values of parameters being used Each model has its own list of parameters being a subset of the list shown below Parameters of Receiver models GAP It corresponds to the effective Gap in Signal To Noise Ratio NR Gap SNR Page 50 81 D TNO 2009 SPOCS 6 0 User Guide TRO Gap is a performance parameter that indicates how close the detection approaches the Sh
66. es for NEXT and EL FEXT hold for all sections So NEXT is always to be specified by a single value and the same applies for EL FEXT If needed you may specify that value by a number by the sweep parameter k1 by the constants k2 or k3 or even by an expression Some background information on the interpretation of crosstalk power The models for crosstalk coupling are used to evaluate the crosstalk power in the wire pair under study which originates from all disturbers in other wire pairs The meaning of the crosstalk power is not obvious and some physical background is needed to understand why Figure 19 illustrates what happens in a real cable Each loop has multiple wire pairs and the electromagnetic coupling between these wires causes that systems in other wire pairs induce crosstalk noise in the wire pair that interconnects the victim modem pair In practice however there is a significant spread in coupling values between individual wire pairs Even when all these coupling factors are exactly known the overall crosstalk will not be deterministic if there is no information to what wire pairs a set of disturbers are connected So how to deal with that Local Exchange downstream Customer Premises upstream Figure 19 Crosstalk Coupling in the Loop To understand the answer assume a hypothetical experiment with many modems and a cable When that cable with N wire pairs is filled up completely with similar disturbers the res
67. etails By hitting the lt RUN gt button SPOCS will calculate the noise margin for all values of the sweep parameter in both transmission directions You can load this example scenario via FILE LOAD select lt InstallDir gt Examples examples_manual Example2 caseA ssf To speed up the calculation process it is recommended to de activate the presentation of intermediate spectra FILE VIEW SHOW SPECTRA de activate SPOCS Example2 caseA ssf 15 x File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL O07 255 SpM 2 POTS ETSI ADSL 2 standard testloop 0 5 mm n E TPL up ADSL 007 031 SpM 2 POTS a o ADSLPOTS up EC SpM 2 ae athe n ADSLIPOTS dn EC SpM 2 BE N_Margin 2048 J j Show Topology Show Scenario Generate NT noise profile CPE It Mo J Mh 2 fTPL ISDN 2610 SpM 2 IPLHDSL2B102 SpM 2 Sw TPL up ADSL 007 031 SpM 2 POTS gt TPLSDSL 2304s SpM2 z SR d 5000 e e mam SE z TRO 2 _ Noise White 140dBmHz Noise White 1 40dBmiHz 5 rs S z SPOCS 6 0 Figure 36 A scenario for calculating the margin of ADSL over POTS as a function of the loop length L IUIIUIUAI Io Le Je le Io Je lo lo leie le bibibisbbisisisiksb zbRbRISbEI JAIL dt Figure 37 shows the results in a plot and figure 38 shows the same in a tabular format The plot shows that
68. etwork Termination a neutral name of the loop side that is opposite to the LT side In many cases it is located at the customers premises where the modem is called CPE customers premises equipment but it could also be in a repeater at the central office side The customer is always right in the GUI of SPOCS e Downstream transmission from LT to NT e Upstream transmission from NT to LT SPOCS File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt NIV bisisiskskiksisisbis Figure 12 Overview of the GUI Page 15 81 TNO 2009 SPOCS 6 0 User Guide TRO Stress environment Section for both SPOCS full and SPOCS light Loops and crosstalk 4 2 1 A Loop model cable and length between these modems 4 2 2 and crosstalk coupling parameters Disturbers 4 2 3 Bl Crosstalk disturbers for LT and NT B2 Other disturbers for LT and NT Frequency range 4 2 4 C Frequency range and count Sweeps Constants 4 2 5 D Sweep parameter k1 and constants k2 and k3 DSL system under study only for SPOCS full Victim modem 4 5 1 El LT Side of modem link under study E2 NT Side of modem link under study Figure 13 Overview of the main blocks in the GUI of SPOCS 4 2 Defining a stress environment 4 2 1 Defining a loop topology Loops The definition of a loop topology starts with selecting a suitable
69. f custom specified noise such as the Spirent DLS5204 series of noise generators These functionalities are to serve different applications as shown below Software tool Figure 1 SPOCS Functionality NOTE This software tool is available in different versions When branded as SPOCS or 5D10 it can do both performance predictions but the 5C60 has disabled prediction functionalities noise profiles only tailored to DSL testing The GUI graphic user interface of the light version is a slightly different from the full version For reasons of simplicity both versions are described in the same manual showing the GUI of the full versions in most cases Page 6 81 D TNO 2009 SPOCS 6 0 User Guide TRO 2 2 Using SPOCS as DSL Performance simulator A primary functionality of SPOCS is the ability to predict the performance of a DSL system under various operational stress conditions This stress includes the impairment of a large number of different xDSL disturbing neighbouring systems at arbitrary locations and the loss and crosstalk coupling of different cable types at arbitrary lengths Performance is a generic term that can be represented in different ways SPOCS can represent this performance as a maximum bit rate as b noise or signal margin and c as reach Bit rates and margins are usually presented as a function of the loop length but other parameters may also be used for that e g as a function of the number of d
70. feet AwG26 IT i 7 Commands H mn 1380 feet AWG24 300 feet AWG26 o mie Gees Delete Section 100 Save oop 0 ee 1000 it 1000 2000 3000 4000 5000 6000 Length feet Figure 69 GUI interface for Example 1 after save loop The constructed loop model has been saved to the dynamic library under the name Example1 LoopBuilder Now it is possible to export the dynamic library containing the newly constructed model to a file This library file can be loaded afterwards into the GUI of SPOCS by Library Loop LibrarylAppend Page 60 81 TNO 2009 SPOCS 6 0 User Guide a TRO Now this loop is available from the main menu of SPOCS as shown in Figure 70 Notice that the newly created model has not been exported to an user definable library file but still is available in the dynamic library SPOCS File view Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt 1 USER 2 Defined by user ETSI VDSL 4 standard testloop 100 180 ohm NORTH AMERICAN CABLES AWG26 26 Gauge AWG Twisted Pair 11 417 AWG24 24 Gauge AWG Twisted Pair 11 417 ANSWYDSL TP1 TP1 AWG26 11 424 ANSIVDSL TP2 TP2 AWG24 T1424 ANSWYDSL TP3 TP3 DAMO 71 424 ANSIVDSL FP FP Flat Untwisted Pair 11 424 ANSIVDSL 1 TESTLOOPS ANSI VDSL 1 Til testloop 1 AVVG26 T1424 ANSI VDSL 1 TP2 testloop 1 AVVG24 T1424 ANSI VDSL
71. friendly graphical interface that allows creating new models for composite loops e g bridge taps in a relatively easy way 500 m 500 m 0 4 mm PE 0 4 mm PE Sect 1 tap Sect 3 tap LT NT Sect 2 casc Sect 4 casc Figure 65 Composite cable for ETSI HSDL 6 NOTE Please notice that composite loops can be simulated in SPOCS but no nodes can be located in these intermediate cascade straight positions A composite loop is formed by cable sections and by junctions A junction is simply where 2 types of cables are merged No nodes are supported in the junctions in the current version of SPOCS A node as is considered by SPOCS contains active DSL equipment DSLAM s CPE modems etc Page 56 81 TNO 2009 SPOCS 6 0 User Guide TRO Composite Loop KPN_L1 KPN_L2 7 1 2 Loop Builder Description 7 1 2 1 The Graphical User Interface GUI This section will help to get used to the GUI of the Loop Builder tool Figure 66 shows the Loop Builder interface when this is called from the GUI of SPOCS Notice that there are no cable sections yet sl Fie Clipboard View Units Help KPN_L1 underground cable L1 50x4x0 5mm 0 5km be Topology of Loop Figure 66 Loop builder GUI tool We will use the following example cable sections have been added see Figure 67 to describe the different areas of this tool Page 57 81 s TNO 2009 SPOCS 6 0 User Guide TRO
72. g compliance to standard requirements while templates are intended for modelling purposes 1 SPOCS differentiates one from the other by prefixing the string TLP for Template and MSK for Mask and these masks are only visibly if you work in the expert mode see section 6 1 for further details The formal definitions are reproduced below More details can be found on 1 e PSD Mask The absolute upper bound of a PSD measured within a specified resolution band NOTE The purpose of PSD masks is usually to specify maximum PSD levels for stationary signals e PSD Template The expected average PSD of a stationary signal NOTE The purpose of PSD templates is usually to perform simulations The levels are usually below or equal to the associated PSD masks For comparative purposes a graphic showing roughly the difference between masks and template is presented below The ADSL2 L G 992 3 FDD Downstream mask and template have been used to clarify these concepts PSD dBmy Hz vs Frequency KHz TPL gt Template e smmem MSK gt Mask PSD dBm H d d DN Ze Frequency Hz L 10 10 Figure 74 Difference between Masks and Templates Page 77 81 D TNO 2009 SPOCS 6 0 User Guide TRO ANNEX C Changing default settings Once SPOCS is installed you can customize the way SPOCS initializes if the default settings are not good enough for you You may skip t
73. he associated one at the other side as well as the associated receiver models In case your study requires another combination you can disable this behavior via the following menu setting CONFIG AUTO COMPLETION MODES gt deselect Keep victims paired To enable it only once for all disturber and victim modems select CONFIG AUTO COMPLETION MODES gt select Synchronize once 4 5 2 Selecting simulation targets A simulation target specifies what performance parameter should be predicted after hitting the lt Run gt or lt Find gt button This can be noise margin or system margin and when the modem is rate adaptive like for ADSL you can also select datarate or linerate The simulation target can be set individually for each receiver model Figure 24 illustrates how to select the different simulation targets for an LT receiver from the GUI BER File View Library Config Macros Tools Window Help lt Only For unprotected use within TNO the Netherlands gt TDL dn ADSL GO7 255 SpM 2 POTS KPN_L1 underground cable L1 50x4x0 5mm th DSLPOTS dn EC SpM 2 x d DataRate var TPL up ADSL 007 031 SpM 2 POTS e N Margin Ol S_Margin GET S j De D EES Liner ineRatg profile DSLAM Generate HT noise profile CPE TPL dn ADSL 007 255 SpM 2 POTS TPL SDSL 1024 s SpM 2 2 TPL up ADSL 007 031 SpM 2 POTS gt PBO e le OO e e le le ls le le o
74. he same margin of ADSL over POTS as shown in figure 37 but now in a tabular format Page 37 81 TNO 2009 SPOCS 6 0 User Guide TRO 5 2 2 Case 2b Bitrate calculation of ADSL over POTS The observation that the downstream margin is a few dB above the upstream margin means that the downstream bitrate can be increased without reducing the reach Additionally on shorter loops the bitrate can increase for both directions if 6 dB margin is considered as adequate Figure 39 illustrates how to change the scenario of figure 36 for calculating the attainable bitrate as a function of the loop length The definition of the sweep parameter k1 remains unchanged compared to figure 36 The only things that are to be changed are the simulation targets at the receivers they change from margin to bitrate see section 4 5 2 for further details You can load this example scenario via FILE LOAD select lt InstallDir gt Examples examples_manual Example2 caseB ssf SPOCS Example2 caseB ssf ll x File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL 007 255 SpM 2 POTS a ETSI ADSL 2 standard testloop 0 5 mm e TPL up ADSL 007 031 SpM 2 POTS i Show Topology Show Scenario Generate NT noise profile CPE B TPL ISDN 2B1 Q SpM 2 a PBO 0 2 fP up ADSL007 031 lt SpM 2POTS l Le e Lo Te Lo e Le le le le le e lo la a la le le o a
75. his for the first time to change it later If you want to customize the initialization process open the configuration file lt InstallDir gt spocs cfg in any plain text editor e g NotePad WordPad etc as long as it is saved in a plain ASCII text format Then when opened the user will find some text similar to the one described in Figure 75 All the lines that start with the symbol represent a comment The user can customize the initialization of SPOCS by modifying this configuration file according to his needs focusing on e Expertise level at start up Logging output if desired This will help the user to see what is happening during the simulation Name of the logging file Gf the Logging option has been set to File Extra user defined Libraries that are desired to be loaded Default Values for Crosstalk Coupling FEXT and NEXT Defining Directories for Profiles Scenarios and Licenses Defining max levels when using profiles features Maximum Noise Power and Maximum Noise Frequency e Defining proxy settings only relevant for evaluation versions that are enabled via an internet connection to the TNO license server CONTENTS OF lt INSTALLDIR gt SPOCS CFG Level Advanced S must be one of Basic Advanced Expert Logging Screen Smust be one of None Screen File LogFile spocs log must be a valid filename LogLevel Minimal must be one of Minimal Limited V
76. his via the Config menu Config Level of expertise Advanced Now the listbox of the receiver will contain generic receiver models as well The parameters of these models are all tuneable and the following parameters apply to each model PROPERTIES SHANNON PAM CAP DMT Gap Noise EchoSup DistSup Rn impedance Lines BitPerSym BitLoadRange SymbolRate FreqBands x mM o x Le gt RER gt gt xo a a a a xo o a a a a CarrierFreq x FreqTones dF INP Delay EOCOH Figure 62 General and Specific Properties of the Generic Models mM LT gt Le gt 6 3 4 Inspecting a receiver model bitloading To find out what bitloading a DMT model does with a transmit signal right click on the receiver list box with your mouse This opens a context menu and one of its menu items is named Receiver inspector Figure 63 illustrates the result of hitting that menu item The dotted curve rounded is close to what bitloading an actual Page 53 81 D TNO 2009 SPOCS 6 0 User Guide TRO modem would report under the stress conditions of your scenario The solid curve fractional is the one being used during calculations DMT Bit Loading diagram Receiver Model ADSL POTS dn EC SpM 2 N_Margin 5 38 DataRate 2048 00 kb s Gap 7 50 dB NT side I I I T T Bit Loading bits carrier Fractional Linerate 2350 kb s J 7
77. io Pn2 Pn1 by which the received noise power Pn1 may increase to power Pn2 until the recovered signal no longer meets the predefined quality criteria NOTE This ratio is commonly expressed in dB NT access port or NT port for short is an access port for injecting signals designated as NT port NOTE Such a port is commonly located at the customer premises and intended for injecting upstream signals Performance is a measure of how well a transmission system fulfils defined criteria under specified conditions NOTE Such criteria include reach bit rate and noise margin Power Back off is a generic mechanism to reduce the transmitter s output power NOTE It has many purposes including the reduction of power consumption receiver dynamic range crosstalk etc Power Cut Back a specific variant of power back off used to reduce the dynamic range of the receiver that is characterized by a frequency independent reduction of the in band PSD NOTE It is used for instance in ADSL and SDSL PSD Mask The absolute upper bound of a PSD measured within a specified resolution band NOTE The purpose of PSD masks is usually to specify maximum PSD levels for stationary signals PSD Template The expected average PSD of a stationary signal NOTE The purpose of PSD templates is usually to perform simulations The levels are usually below or equal to the associated PSD masks Signal Category is a class of signals meeting the
78. iring for transmission purposes Transmission Equipment equipment connected to the local loop wiring that uses a transmission technique to transport information Transmission System set of transmission equipment that enables information to be transmitted over some distance between two or more points Page 75 81 D TNO 2009 SPOCS 6 0 User Guide TRO Transmission Technique electrical technique used for the transportation of information over electrical wiring Upstream Transmission transmission direction from a port labelled as NT port to a port labelled as LT port NOTE This direction is usually from the customer premises via the local loop wiring to the central office side Victim Modem modem subjected to interference such as crosstalk from all other modems connected to other wire pairs in the same cable that is being studied in a spectral management analysis NOTE This term is intended solely as a technical term defined within the context of these studies and is not intended to imply any negative judgement Page 76 81 D TNO 2009 SPOCS 6 0 User Guide TRO ANNEX B The difference between PSD Templates and Mask Standards speak about PSD masks and sometimes about PSD templates and these two are very different A mask is roughly a set of peak values that should not be exceeded A template is roughly a nominal value of a PSD or an expected value averaged within a small frequency band Masks are intended for provin
79. isturbers SPOCS can evaluate bit rates and margin in a direct way and evaluates reach in an iterative way They can all be evaluated for a range of operational stress conditions signal loss in loops and noise due to other disturbers and crosstalk coupling and for a range of modems like ISDN SDSL HDSL ADSL ADSL2plus VDSL VDSL2 etc SPOCS can present this predicted performance in both a graphic way plot and a tabular way in a textbox SPOCS can also provide the end user with intermediate calculation results such as for instance the power spectral density PSD as function of the frequency of signals transmitted received etc and noises total crosstalk NEXT only FEXT only etc Max bitrate specified margin all for various loop lengths Reach fixed bitrate Noise margin fixed bitrate Signal margin fixed bitrate all for various loop lengths at 6 dB noise margin Figure 2 Different ways to express the performance of a system 2 2 1 Example 2 Spectral Management SpM Studies Once a technology is identified as attractive it still may have a negative impact on the integrity of deployed services A well known example is the deployment of VDSL2 from a street cabinet while ADSL2plus systems are deployed in the same cable from the local exchange Without proper measures shaping VDSL2 transmit power the impact on ADSL2plus will be very negative With SPOCS you can perform impact analyses and quantify h
80. k1 k2 2000m 5000 m Only the maximum values are drawn below SPOCS 2000 3000 DSLAM ee CPE LT DI 2 3 INT lt upstream gt lt downstream gt x e All D1 Io Bea G LOOP KPN_L1 underground cable L1 50x4x0 5mm 0 5km V Victim D Disturber 1 3 NodeNumber NEXT 50 dB 1Mhz EL FEXT 45 dB 1Mhz 1km V t TPL dn ADSL2 A 033 511 G992 5 FDD V t TPL up ADSL2 A 007 031 G992 5 V r ADSL2 A up FDD expert guess V r ADSL2 A dn FDD expert guess D1 TPL dn ADSL2 A 033 511 G992 5 FDD 200 k3 D1 TPL up ADSL2 A 007 031 G992 5 200 k3 D2 TPL dn VDSL2 B7 5 8a 997 M2x A k3 D2 TPL up VDSL2 B7 5 8a 997 M2x A k3 D3 Noise White 140dBm Hz 1 D3 Noise White 140dBm Hz 1 Figure 48 Graphic representation of the scenario in figure 46 obtained via the lt SHOW gt button Figure 49 and 50 shows the results from sequential simulations Results from sequential runs can be kept in a single plot if the plots are hold in between This behaviour can be toggled via the menu item VIEW HOLD PLOTS WHEN RECALCULATED The first figure 49 shows a significant impact if the first VDSL2 modem is deployed from a cabinet you have to shape the PSD of VDSL2 to prevent this but that is beyond the scope of this example Adding more and more VDSL2 modems will have an additional impact but not
81. l You can define plenty of them via a text editor load them in SPOCS and run them with one mouse click Further details can be found in the Programming Guide Page 55 81 D TNO 2009 SPOCS 6 0 User Guide TRO 7 Using plug ins SPOCS full only A plug in is a utility that accompanies SPOCS The Tools menu item in the menu bar of SPOCS contains all the current plug ins enabled in SPOCS Future plug ins will be also placed under this option The current list of available plug in is e Loop Builder e Loop Viewer e Transmit Viewer We will describe each in the sequel 7 1 Loop Builder This section explains the relevance of the Loop Builder tool its graphical interface how to create composite loops and how to use them in specific DSL studies 7 1 1 Why is this tool relevant SPOCS supports already a big amount of cable models for both European and North American regions However in order to provide flexibility to the user and adjust its simulation scenario as much as possible to reality an extension has been added to allow the insertion of new cable models In particular composite loop models such as bridge taps topologies can be added In the original method to include new models it was necessary to create manually library files in ASCII In order to create the composite loop shown in 65 or any other loop in the general sense the loop builder feature is added to SPOCS providing several advantages e g a user
82. lustrates the result of hitting that menu item The upper curve represents the downstream transmit signal of a VDSL2 system deployed from a street cabinet before any PBO is applied The lower curve represent what signal level is injected into the loop after being shaped by the PBO model Page 49 81 TNO 2009 SPOCS 6 0 User Guide TRO PBO model PBO dn PSD_Shaping_ITU_EXPERIMENTAL Transmit model TPL dn VDSL2 B8 4 8a 998 M2x A Loop model KPN_L1 underground cable L1 50x4x0 5mm 0 5km P Loop length 500 m t i i I I i i P J j aneen into eee rr Source Spectrum before PBO Transmit Spectrum after PBO 40 L 7 7 d 80 L H J 100 120 L S 1 40 SPOCS fi i L fi i Freq Hz 7 l l l l 0 500k 1M 1 5M 2M 2 5M 3M 3 5M 4M 4 5M 5M Figure 57 The amount of power back off can be visualized via the PBO inspector 6 3 Using Receiver models SPOCS full only On default the receiver model of a modem is auto selected by SPOCS as soon as you select its transmitter This choice is often a good choice and therefore again on default the GUI prevents you from changing this choice However in some cases there is a need to overrule the selection for instance to a select another receiver model or b to change its parameter valu
83. minimum set of specifications identified in TR 101 830 1 NOTE Some signal categories may distinct between different sub classes and may label them for instance as signals for downstream or for upstream purposes Signal Margin ratio Ps1 Ps2 by which the received signal power Ps1 may decrease to power Ps2 until the recovered signal no longer meets the predefined quality criteria NOTE This ratio is commonly expressed in dB Spectral Compatibility generic term for the capability of transmission systems to operate in the same cable NOTE The precise definition is application dependent and has to be defined for each group of applications Spectral Management art of making optimal use of limited capacity in metallic access networks NOTE This is for the purpose of achieving the highest reliable transmission performance and includes Designing of deployment rules and their application Designing of effective access rules Optimized allocation of resources in the access network e g access ports diversity of systems between cable bundles etc Forecasting of noise levels for fine tuning the deployment Spectral policing to enforce compliance with access rules Making a balance between conservative and aggressive deployment low or high failure risk Spectral Management Rule generic term incorporating voluntary deployment rules mandatory access rules and all other voluntary measures to maximize the use of local loop w
84. n 4 12M l l 2 branched without VDSL 8 3 branched with shaped VDSL 10M 8M 6M 4M OML l l 0 SPOCS Sweep Parameter k1 gt li li L li 0 500 1k 1 5k 2k 2 5k 3k 3 5k 4k 4 5k 5k Figure 53 ADSL performance as predicted from the scenarios A B and C of example 4 Page 46 81 TNO 2009 SPOCS 6 0 User Guide TRO VDSL2 downstream performance from cabinet 50M T T T b s 1 branched prediction I 45M A 1 40M 35M 30M 25M F 20M 15M 10MH i 5ML d SPOCS fi li fi L i li L L li fi L L li fi 0 200 400 600 800 1k 1 2k Figure 54 VDSL performance as predicted from scenario D of example 4 Sweep Parameter k1 gt 0 Page 47 81 D TNO 2009 SPOCS 6 0 User Guide TRO 6 Using Advanced Features 6 1 Selecting different levels of expertise The list of possible models can be overwhelming and this is not always favourable SPOCS enables the use of different expertise modes namely Basic Advanced and Expert to reduce the list of models on a user request You can easily switch between these modes via the Config menu as shown in figure 55 SPOCS File view Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt Logging destination UPS Logging level Figure 55 Working in the advanced level of expertise is the recommended level for many stu
85. n the directory lt InstallDir gt Examples examples_manual Once SPOCS is started you can load your first example scenario via the menu FILE LOAD select lt InstallDir gt Examples examples_manual xxx ssf To make that directory the current directory for easy loading other scenarios in the same directory you use the menu FILE FOLLOW DIRECTORY 5 1 Example 1 Building noise profiles for ETSI tests ETSI has defined various performance tests for ADSL to prove that the performance of a modem can meet their minimum performance objectives as specified in ETSI TS 101 388 It has to be verified for a range of stress scenarios 4 different noise models to be applied to 8 different test loops and a range of payload bitrates Each combination of noise loop and bitrate has its own reach requirements specified as the electrical length of the loop Upstream and downstream are tested separately and have different reach requirements The noise models are assumed to represent near worst case scenarios where the modems share the cable with many other disturbing modems To perform such a test in a lab environment a noise profile is required to instruct a noise generator what noise it should inject in test loop with a given length In this example we will generate a noise profile that is dedicated for ADSL over POTS systems using overlapping spectra this is called ADSL annex A in the associated ITU standard We will restri
86. n the libraries A text box appears showing the libraries that can be used Status A textbox shows the date when the libraries were created and the current status 8 1 5 CONFIG Menu Menu Items Menu Descripon Auto completion Modes See below and select one of e Keep victims paired e Keep disturbers paired e Synchronize Once silent e Synchronize Once with change info Level of Expertise See below and select one of e Basic e Advanced e Expert See section 6 1 for further details Units for displaying values only Allows the user to choose the unit metrics for displaying purposes into the different plot windows Options are Km m inch feet yard kft mile See also section 4 2 6 Logging Destination Catch all kinds of message and status information See below and select one of e None e Screen e File Logging Level Control the amount of information being logged See below and select one of e Minimal e Limited e Verbose The sub options have also some alternatives explained below Menu Items Menu Description Keep Victims Paired Once a transmitter is chosen either at the NT or LT side then disabled on SPOCS light automatically sets the proper transmitter model for the other side and the receiver models for both sides When multiples choices can be selected a warning appears showing this fact to the user Keep Disturbers Paired Does the same than Keep victims Paired
87. nces when new technology is introduced in an access network For instance introducing the deployment of VDSL2 from a cabinet the new technology in a network where all deployments are from the central office the legacy The impact analysis should answer the question whether the legacy will be disturbed by the new technology in a disproportional manner or not and if yes how much Such a study compares the performance result under different scenarios that are considered as equivalent This means that all scenarios serve the same number of customers and one of them the reference scenario represents the legacy situation This example 3 illustrates how to do that assuming ADSL2plus from the central office as legacy and VDSL2 from street cabinets as new technology It requires some advanced features of SPOCS which become available when you increase the level of expertise to advanced via the CONFIG menu See section 6 1 for further details At first we need to define a loop topology with multiple sections as explained before in section 4 2 1 Secondly we need a way to modify that scenario in such a way that the location of the street cabinet and the number of VDSL2 systems can be varies in a convenient manner All these scenarios have to be equivalent meaning that the number of systems remains the same for all those scenarios This is where the use of the constants k2 and k becomes convenient a
88. nd the use of expressions becomes powerful see section 4 2 5 and 4 2 1 Figure 46 shows how we can define all scenarios by varying only the values of constant k2 and k3 Figure 47 illustrates a few values of interest being used in this example If you push the lt SHOW gt button SPOCS will provide you with a graphic summary of the scenario as shown in figure 48 You can load this example scenario from disk and to modify k2 and k3 FILE LOAD select lt InstallDir gt Examples examples_manual Example3 ssf Page 42 81 TNO 2009 SPOCS 6 0 User Guide SPOCS Example3 ssf File View Library ADSL2 A an FDD expert guess 3 BW Generate LT noise profile osLam Generate NT noise profile CPE Find k1 s THO spocs6o W BI a B B B E DI DI B E DI D Ct tt tt Noise VVhite 1 40cBmHz S Figure 46 Defining a range of scenarios by using k2 for the cabinet position and k3 for the number of VDSL2 systems The total number of disturbers is always kept at 200 JI Scenario l ref 2 3 4 5 Loop sections k2 k1 k2 k1 Sweep parameter max 100 k2 50 5000 k2 Location of the cabinet 0 2000 2000 1500 1000 k3 Number of VDSL2 systems 0 1 50 50 50 Figure 47 By changing the values for k2 and k3 we can easily analyze different variants of the scenario in figure 46 Loop range k2
89. nd to use noise profiles that are fully dedicated to a particular standard of interest They can account for all these inconsistencies between different standards Page 33 81 TNO 2009 SPOCS 6 0 User Guide TRO 5 1 2 Case 1b Noise profiles via a disturber mix SPOCS brings you that ability to generate noise profiles form arbitrary scenario s and not only for a limited number of noise models and test loops of a standard The ETSI noise models are to represent a mix of disturbers and noise model FA originates from a high penetration scenario It was modelled for a mix using 400 wire pairs in a 900 wire pair cable 90xISDN 40xHDSL 2 180xADSL 90xSDSL as described in e Brink FSAN Realistic ADSL noise models ETSI contribution 994t37a0 dec 1999 e Brink Heuvel FSAN Update of SDSL noise models as requested by ETSI TM6 ETSI contribution 993t22a0 sept 1999 Figure 33 illustrates how to configuration the scenario if equivalent noise model ETSI FA is replaced by 400 individual disturbers You can load this example scenario via FILE LOAD select lt InstallDir gt Examples examples_manual Example1 caseB ssf The resulting noise profile will not be exactly the same as for the ETSI noise model since it depends also on the assumptions being made about the PSD s of these individual disturbers These assumptions have been changed over the years and the models used in figure 33 are the most recent ones and defin
90. nits are selected for displaying results To enable a convenient way to specify loop length in units like yards and kft various conversion constants are predefined Entering the expression 3 kft reads like imperial units and still produce a length in meter These kinds of expressions can be used in any field on the GUI front panel including the fields for loop length sweep parameter k1 constants k2 and k2 etc Figure 22 summarizes the predefined conversion constants and figure 23 provides a few examples on how to use them There names are case sensitive Conversion constant Remark inch 1 inch 0 0254 m feet 1 feet 12 inch 0 3048 m yard l yard 3 feet 0 9144 m kft 1 kft 1000 feet 304 8 m mile 1 mile 1760 yard 5280 feet 1609 3 m Figure 22 Predefine conversion constants to convert length into meters Expressions to Remark convert into meters Example 1 k1 0 0 1 10 mile Meaning k1 units are in miles Example 2 Len k1 kft Meaning Len units are in kilofeet Example 3 Len 300 feet 700 Meaning 300 feet and 700 meters Example 4 Len 300 700 feet Meaning that all the lengths of the scenario under study are in feet Example 5 Lenz 3 kft Meaning that the length field is equal to 3 kilofeet Figure 23 Various example on how to use the constants in figure 22 4 3 Inspecting the characteristics of a scenario SPOCS has several inspectors on board to find out what each
91. nt to a file which can be renamed by the user and also contains the output information that corresponds to the output textbox as a result of the simulation Menu Items Menu Description Minimal If logging is enabled send only the most relevant information to the log screen or log file Limited If logging is enabled send a moderate amount of information to the log screen or log file Verbose If logging is enabled dump as much as possible to the log screen or log file This is usually only needed for debugging purposes 8 1 6 MACROS Menu SPOCS full only Menu Items Menu Description Run from file Load and run immediately the selected macro script file In order to work properly the selected file should contain execution commands Load Load the selected macro script file When the macro is loaded the macros enabled by the file appear on the MACROS Menu field Stop Stops the current macro that is being executed See the Programming Guide for further details 8 1 7 TOOLS Menu SPOCS full only Menu Items plug ins Menu Description Loop Builder Call the Loop Builder tool which allows the user the creation of new composite loops which can include bridge taps Page 68 81 TNO 2009 SPOCS 6 0 User Guide gt TRO Loop Viewer Call the Loop Viewer tool which allows the user exploring the loop characteristics such as transmission characteristics
92. ntly define a proper sweep interval In the example of figure 28 we have defined the sweep as 100 100 5000 meaning an iterative search between min k1 100 and max k1 5000 The value for step is irrelevant and will be ignored e E Hit the lt FIND gt button and SPOCS will iterate k1 within the specified interval and returns the maximum length for which both modems can operate under at least 6 dB margin SPOCS warns you if no solution can be found In that case extend the interval and try again Mark that the reach is iterated for the sweep parameter k1 In this example it represents the loop length but SPOCS is not restricted to that SPOCS has generalized this concept and you can use the sweep parameter k1 in any field of the front page of the GUI For instance at a field that defines the number of disturbers or the crosstalk coupling You can even use k1 at different places at the same time More details on the sweep parameter can be found in section 4 2 5 NOTE Reach When calculating the Reach the user has to choose Margin Signal or Noise as TARGET parameter at a fixed Bit Rate Line or Data Page 30 81 D TNO 2009 SPOCS 6 0 User Guide TRO 5 Application examples This section describes SPOCS functionalities and user interface by going step by step through some basic to more advanced examples They are additionally to the quick start examples discussed in section 3 These and other examples can be found i
93. o the ports of a binder or cable bundle that are injecting signals into the access ports Cable Management Plan CMP list of selected access rules dedicated to a specific network NOTE This list may include associated descriptions and explanations Deployment Rule voluntary rule irrelevant for achieving access to the local loop wiring and proprietary to each individual network operator NOTE A deployment rule reflects a network operator s own view about what the maximum length or maximum bit rate may be for offering a specific transmission service to ensure a chosen minimum quality of service Disturber source of interference in spectral management studies coupled to the wire pair connecting victim modems NOTE This term is intended solely as a technical term defined within the context of these studies and is not intended to imply any negative judgement Downstream Transmission transmission direction from port labelled as LT port to a port labelled as NT port NOTE This direction is usually from the central office side via the local loop wiring to the customer premises Echo Cancelled EC term used within the context of ADSL to designate ADSL systems with spectral overlap of downstream and upstream signals NOTE In this context the usage of the abbreviation EC was only kept for historical reasons The usage of the echo cancelling technology is not only limited to spectrally overlapped systems but can also be used by FDD s
94. odels A PBO model forces some amount of power back off of the transmit power before it is injected into the loop For instance ADSL is required to reduce its downstream when the loop is short to prevent that the modem at the customer side gets overloaded Hit the PBO button and select an appropriated model for it The amount of power reduction is not fixed but may depend from different factors like the insertion loss of the loop or the signal power being received Extending the list of disturbers On default the list of disturbers is restricted to prevent that you get lost in an overwhelming number of models Especially the large number of VDSL2 models has been reduced This is because SPOCS starts in a Basic level of expertise which is intended only during a learning period We recommend switching to the Advanced level of expertise via the config menu and do not give in to the temptation of selecting the Expert mode See section 6 1 for further details You can overrule this default via the configuration file as explained in annex C More models will come available if you switch to the Expert mode and it will disable protection against selecting invalid models However it gives you additionally access to e Models representing PSD masks specifying peak values instead of nominal values e Models intended for the other side to study the transmission of downstream signal in upstream direction Disabling the autocompleti
95. of the absolute lengths selected in the Section cable construction should not exceed the total loop length B2 Position of the Allows the user to select the position of the DSLAM DSLAM Composite loops are defined in a left to right fashion just as in various standards The user should Page 58 81 D TNO 2009 SPOCS 6 0 User Guide TRO explicitly choose whether the LT DSLAM is positioned at the left hand side or a the right hand side of the drawing C Plot Section It draws a picture of the topology of the constructed model D Control Buttons It has six buttons Add Section It adds a new section in the composite loop being created by the user Delete Section It deletes the last section Delete Loop It deletes the loop from the dynamic library Save Loop It saves the loop to the dynamic library It asks for a name and brief description the latter is for information purposes only Export Library It copies the content of the dynamic library to a file defined by the user Exit Ends the builder application tool 7 1 2 2 The Dynamic Library concept You can save constructed models to the dynamic library If you want to group these models in a file you can do it by using the option export library After adding models to the dynamic library these models are directly available in the simulator These models are also available after a
96. on modes On default when you select a disturber on one side SPOCS will automatically select the associated one at the other side In case your study requires another combination you can disable this behavior via the following menu setting CONFIG AUTO COMPLETION MODES gt deselect Keep disturbers paired To enable it only once for all disturber and victim modems select CONFIG AUTO COMPLETION MODES gt select Synchronize once 4 2 4 Defining frequency range and count Impairment and performance is only calculated with the selected frequency range at the specified resolution The frequency range is set from 0 to Fmax This frequency range should at least cover the full transmission band of the victim modem plus a bit extra otherwise it cannot calculate performance in a correct way ADSL uses frequencies up to at least 1 1 MHz ADSL2plus up to 2 2 MHz and VDSL2 uses frequencies in the up to 8 5 12 17 and 30 MHz Fmin is always forced to zero Page 21 81 TNO 2009 SPOCS 6 0 User Guide TRO Count provides the linear resolution that SPOCS will use when evaluating the system under study i e if Fmin 0 and Fmax 1200 KHz then a count value of 5000 indicates that the resolution is approximately equal to 1200 0 5000 0 24 KHz 4 2 5 Defining sweeps k1 and constants k2 and k3 Sweeps The performance of a system under specific stress conditions is a single value margin or bitrate
97. opped up to continue adding disturbers This feature can be done at the LT and NT side 8 3 Fields Field Description Length If only k1 or a fixed value is introduced in this field SPOCS will treat the scenario as a 2node scenario If a list of comma separated values surrounded by brackets is written in this field i e vall val2 val3 then SPOCS will treat the scenario as a multi node scenario See section 4 2 1 for further details This field requires that length is specified in meters See section 4 2 6 on how to use it with imperial units NEXT By default the near end crosstalk coupling it is configured as 45 dB 1 MHz See section 4 2 2 for further details Page 70 81 D TNO 2009 SPOCS 6 0 User Guide TRO EL FEXT By default the equal level far end crosstalk coupling it is configured as 50 dB 1 MHz 1 km See section 4 2 2 for further details Field Description Fmax It corresponds to the maximum frequency that will be taken into account when using the transmitter models selected by the user See section 4 2 4 for further details Count This is used to specify the resolution that will be used when calculating the spectra See section 4 2 4 for further details Field Description k1 This is the sweep parameter used for instance to evaluate performance as a function of the loop length See section 4 2 5 for further details k2 This is a general purpose constant that is disa
98. ound P L1 50x4x0 Sai hd L Cl KPN_L1 underground cable L1 Ca Sai bd f 11000 500 1500 dow Help lt Only for unprotected use within TNO the Netherlands gt 3000 SI E Lengt m no 2000 2000 Figure 14 Defining loops of 3km length but with a different number of sections Page 16 81 TNO 2009 SPOCS 6 0 User Guide TRO Nodes The end of each section is demarcated by a unique sequential node number so a loop has two or more nodes This enables you to define the location of modems in the loop topology Figure 15 illustrates how to specify the node of the modem at the NT side of the loop customer premises If you change the node number of a victim modem the GUI will immediate respond to that by changing the node color in the symbolic drawing above the length field e Red is used for nodes connected to a victim node e Green is used for all other nodes e Black is used for the zero node to show that it is not connected e Blue is used when a node number is out of range and no part of the topology Node numbers are to be sequential and to be specified by a single character so 0 1 2 3 8 9 A B C D Y Z This means a maximum of 35 nodes or 34 sections A modem link uses two nodes and by convention the node number at the NT side of the link left central office is always lower than at the LT side right customer premises indow Help lt Only for unprotected use within TNO the Netherlands gt findow
99. ow much impact a specific amount of PSD shaping will have on both ADSL2plus as well on VDSL2 itself If zero impact on ADSL2plus means a high associated bit rate reduction of VDSL2 a compromise may be considered Page 7 81 D TNO 2009 SPOCS 6 0 User Guide TRO 2 2 2 Example 1 DSL deployment Studies The DSL noise environment is country specific Some systems are not allowed or not deployed in some countries while the number of wire pairs per cable and the characteristics of these cables are country specific When new and promising xDSL technologies come available it is not obvious how it will perform in a particular noise environment However this is essential information for making strategic decisions on deploying such systems With SPOCS you can make performance predictions that are tailored to the noise environments of your preference Not only for strategic decisions but also to develop deployment guidelines to identify what bit rate be promised at what quality margin to a certain loop length 2 3 Using SPOCS to create custom noise profiles for DSL testing Another functionality of SPOCS is the ability to evaluate the PSD power spectral density of crosstalk noise as it will be observed by the receiver of a victim modem This is an intermediate result of a full performance prediction but a target result for performance testing in the lab The profiler functionality of SPOCS enables the user to export this PSD as a noise p
100. parameters but such a capability is intended for a next revision of SPOCS Page 52 81 D TNO 2009 SPOCS 6 0 User Guide TRO 6 3 3 Selecting a generic receiver model The list of specific receiver models is long enough to find a matching one for most modems that are conform some DSL standard However in some cases this is not good enough and you may need to access one of the generic receiver models that are beneath these specific models The ETSI SpM 2 standard 1 identifies several generic models for receiver performance dedicated to different line code principles SPOCS supports the following generic models e Shifted Shannon which is line code independent and therefore the most generic one e PAM dedicated to line codes using Pulse Amplitude Modulation e CAP QAM dedicated to line codes using Quadrature modulation e DMT dedicated to line codes using multiple discrete tones These generic models are the basis for all specific models in the library where each specific model has its own set of parameter values These generic models are used in the following specific receiver models PAM ISDN SDSL HDSL 2B1Q CAP HDSL CAP and VDSL1 CAP now obsolete DMT ADSL VDSL2 Figure 61 Examples of DSL systems working based on the different generic models To get access to one of the generic receiver models you have to bring the level of expertise to at least the Advanced level You can change t
101. part of the scenario shown in figure 33 L 220 0 If you make a sweep through various loop lengths as used in example 2b shown in figure 39 then you will see multiple spectra as well This will slow down the calculation speed significantly and therefore these plots are disabled by default Figure 44 and 45 show the spectra in case the loop length is swept e NT spectra Downstream signal received noise PSD dBm Hz 1 Transmitted Signal 100 ohm 40 ps 1 2 Received Signal 100 ohm 60 3 Received Noise 100 ohm 80 100 120 140 160 180 200 SPOCS Freq Hz 220 500k 1M 1 5M 2M 2 5M Figure 44 The downstream receiver will observe these spectra at the NT side of the loop if the loop length is swept see figure 39 Page 41 81 D TNO 2009 SPOCS 6 0 User Guide TRO LT spectra Upstream signal received noise T T PSD dBm Hz 1 Transmitted Signal 100 ohm 2 Received Signal 100 ohm 3 Received Noise 100 ohm 150 200 SPOCS Freq Hz ae ee ee E tt 500k 1M 1 5M 2M 2 5M Figure 45 The downstream receiver will observe these spectra at the NT side of the loop if the loop length is swept see figure 39 250 0 5 3 Example 3 Impact Analysis of VDSL2 on ADSL2plus SPOCS full only An impact analysis is a study of the conseque
102. pedances e The received noise spectra LT side for each length of the loop which is a combination of FEXT from upstream disturbers NEXT from downstream disturbers and other disturbers Line shared noise background noise Figure 11 shows e The downstream signal transmitted from the LT side e The received downstream signal NT side being attenuated by the loop and modem impedances e The received noise spectra NT side for each length of the loop which is a combination of FEXT from downstream disturbers NEXT from upstream disturber and other disturbers Line shared noise background noise Page 13 81 D TNO 2009 SPOCS 6 0 User Guide TRO LT spectra Upstream signal received noise T T de dBm Hz 1 Transmitted Signal 100 ohm 7 2 Received Signal 100 ohm 3 Received Noise 100 ohm Ei A Les T E Q CH j SPOCS L 220 0 500k 1M 1 5M 2M 2 5M Figure 10 Upstream signal transmitted at the other side of the line received upstream signal LT side and received noise at LT side NT spectra Downstream signal received noise PSD dBm Hz 1 Transmitted Signal 100 ohm 40 CDI 2 Received Signal 100 ohm 60 3 Received Noise 100 ohm 80 100 120 140 160 180 200 SPOCS Freq Hz 220 0 500k 1M 1 5M 2M 2 5M Figure 11 Received downstream signal NT
103. pped with a mechanism called power back off that reduces their transmit power It has many purposes including the reduction of power consumption improving receiver dynamic range reducing crosstalk etc Power cut back is a specific simplified variant of power back off characterized by a frequency independent reduction of the in band PSD It is used for instance in ADSL and SDSL Detailed information on PBO is available via the Help menu of SPOCS 6 2 1 Selecting a PBO model On default PBO is not applied By hitting one of the PBO buttons a dialog box pops up to select a model of choice It is easy to verify if PBO is activated or not for a particular modem The PBO buttons highlight in red if any PBO model is selected This is shown in figure 56 Page 48 81 TNO 2009 SPOCS 6 0 User Guide TRO Show Topology Show Scenario de e N ut Figure 56 The PBO button colours red if PBO is activated for that Seen modem To find out in the dialogbox what each model means select one and right click on it with your mouse This opens a context menu with an info entry to provide you with basic information about the model More info is available via the overall Help menu of SPOCS Most of the PBO models have fixed parameter values meaning that you cannot change their values This protects you from unattended changes In special cases you may want to tweak one or more of these parameters Therefore some of the models are made t
104. ransported when the signal to noise ration deteriorates by a given value margin The usual way to present it is by means of a curve as a function of the loop length This makes that we have to sweep the value for the loop length and to fix the value for the margin Figure 26 highlights the relevant steps to enable such a bit rate calculation Page 27 81 TNO 2009 SPOCS 6 0 User Guide SPOCS File View Library Config Macros Tools Window Help lt Only For unprotected use within TNO the Netherlands gt iT trenamitter downetreem e AN TRL dn ADSL 007 255 SpM 2 POTS Generate NT noise profile CPE p More r TPL HDSL 261 2 SpM 2 BR TPL up ADSL 007 031 SpM 2 POTS gt TPL SDSL 2304 s SpM 2 PB TPL dn ADSL 007 255 SpM 2 POTS TPL SDSL 2304 s SpM 2 REES EE EE Aiii ii i a Tt tt ttt A Figure 26 Relevant settings for a bitrate calculation Start defining a scenario of interest with a victim modem pair under study a disturber mix and associated loops The following steps bring you the attainable bitrate for such a scenario e A Instruct the LT receiver to evaluate bitrates by selecting DataRate or LineRate as simulation target The difference between these options is explained in section 4 5 2 Mark that this is only possible for modems that are rate adaptive such as for instance ADSL and VDSL It is impossible to do that for fixed bitrate modems such as for inst
105. resents the same real world topology but in an improved manner The 360 ADSL systems fan out from the street cabinet into 9x40 branches Each branch transports 40 ADSL systems and does not couple any crosstalk into another branched As a result the predicted performance is somewhat higher then in case A since case A is too pessimistic e Case C is the same branched topology as in case B but now we have moved 180 systems from the central office ADSL to the street cabinet VDSL so that the same number of customers are being served VDSL however is branched as well into 9x20 branches so only 20 of them share the branch of the ADSL systems under study The rest does not contribute to the received crosstalk e Case D is almost the same as case C with the difference that case D is to study VDSL performance Mark that VDSL is disturbed by only 20 ADSL systems in the same branch and not by the 180 ADSL systems from the central office Street Customers Central office cabinet Case A p O O 360 ADSL 360 ADSL Street cabinet Central office B Case B 40 ADSL Street Central office cabinet Case C 20 ADSL Case D 20 VDSL 180 VDSL Figure 52 Topologies being analyzed in example 4 Page 45 81 D TNO 2009 SPOCS 6 0 User Guide TRO This example 4 illustrates how to instruct SPOCS to do these studies It requires some advanced features of SPOCS which become available when you increase the level of expertise to advan
106. rofile and to download it into a noise generator In other words SPOCS can specify the Noise Profile for a noise generator as part of a test setup to verify for instance modem performance Figure 3 shows a simplified scenario of a DSL setup with Near End Cross Talk NEXT and Far End Cross Talk FEXT contributions This oversimplified example is restricted to single disturbers at each side of the line When more disturbers are involved and or located at different positions SPOCS handles their combination DSL under test DSL under test LT transmitter DS NT receiver DS LT receiver US NT transmitter US Downstream Upstream disturber disturber systems systems Figure 3 A simplified scenario for a test setup that can be evaluated by SPOCS 2 3 1 Example 1 DSL performance testing If you are a vendor of xDSL technology designing new products you can optimize the modem design by testing its behaviour Your modem will be used in a wide range of very different operational conditions that are sometimes very different from the few standard stress conditions defined by bodies like ETSI and ITU Similar to the previous example SPOCS can generate all kinds of noise profiles for testing purposes which are valuable in improving products For example chipset manufacturers or academic users can apply their new algorithms for coding or spectral usage and evaluate how much performance gain it will really bring 2 3 2 Example 2 Prod
107. sccessccevecceseneesenesesneceseecessccenanesseneseaceseneeseneneenaes 68 OAS WINDOW Meni cesinccsvtasitascctin ches cars eo aa e beaut castceaveagcuates aea niais 69 dr DEEP ee ed ees ed ee Eed EE eege 69 8 2 Buttons ninae E a EA EE REENEN EE 69 E2 Om SPOCS UL only E 69 8 2 2 EE 70 B Fieldsin na a a a e a E a A ee 70 9 NOMENCLATURE FOLLOWED FOR THE MODELS eeeseesseerseesoeesoeesoeesoeesoeesoeesoeesoeeseeee 72 9 1 Transiitter Mod l isiin aia a a E A E a E E ea 72 9 2 Receiver Model SPOCS full only 72 9 32 Loop M del cds es sands eet EE dE EE a A E A N TEE AE EES 73 VE SE VR Be E EE 73 ANNEX A TERMINOLOGY scccssssssscssssssscsssssssesssessscsssessssesesssssesssessseseseesscssscssscsssesesesseees 74 ANNEX B THE DIFFERENCE BETWEEN PSD TEMPLATES AND MASK csscsssoossees 77 ANNEX C CHANGING DEFAULT SETTINGG cscccssssssssssssssssessesssesssesssesssesesessseessessseseseees 78 ANNEX D REFERENCES sessisssriisssereosiesirorisecorsritosrocosossosribesssiki pesse csbor osrisesors kibori tise sirosi esrti 81 Page 3 81 s TNO 2009 SPOCS 6 0 User Guide TRO List of Abbreviations 2B1Q ADSL BER CAP CMP CO CPE DFE DLC DMT DSLAM EC EL FEXT EPL ETSI FBL FDD FEXT FSAN GABL HDSL IMA INP ISDN ISDN BA LT LT port LTU MDF NEXT NT NT port NTU OLR PAM PBO POTS 2 Binary 1 Quaternary Use of 4 level PAM to carry two bits per pulse Asymmetric Digital Subscriber Line Bi
108. se SPOCS evaluates only a fixed performance value More details on the sweep parameter can be found in section 4 2 5 4 6 2 Running margin calculations The margin of a modem under study victim is a number that is specified for a given bit rate and loop length It tells the amount of dB the signal to noise ration can deteriorate before the modem link gets unreliable The usual way to present it is by means of a curve as a function of the loop length This makes that we have to sweep the value for the loop length and to fix the value for the bitrate Figure 27 highlights the relevant steps to enable such a margin calculation Page 28 81 TNO 2009 SPOCS 6 0 User Guide SPOCS File View Library Config Macros Tools Window Help lt Only For unprotected use within TNO the Netherlands gt TDL dn ADSL OO7 255 SpM 2 POTS os KPN_L1 underground cable L1 50x4x0 5mm TPL up ADSL O07 031 SpM 2 POTS DataRate DataRate LineRate if f il Generate NT noise profile CPE TPL ISDN 261 SpM 2 PBO TPL HDSL 261 2 SpM 2 PBO TPL dn ADSL O07 255 SpM 2 POTS TPL up ADSL 007 031 SpM 2 POTS PBO TPL SDSL 2304 s SpM 2 Io Le Je le foo Je joo foo fo jo le AAA AA TH TET iit Figure 27 Relevant settings for a margin calculation Start defining a scenario of interest with a victim modem pair under study a disturber mix and associated loops The following steps bring
109. t Error Rate Carrier less Amplitude Phase modulation Cable Management Plan Central Office Customer Premise Equipment Decision Feedback Equalizer Digital Loop Carrier Discrete Multi Tone modulation DSL Access Multiplexer Echo Cancelled Equal Level Far End Crosstalk Estimated Power Loss European Telecommunications Standards Institute Fractional Bit Loading Frequency Division Duplexing Duplexed Far End Cross Talk Full Service Access Networks Gain Adjusted Bit Loading High bit rate Digital Subscriber Line Inverse Multiplexer for ATM Impulse Noise Protection Integrated Services Digital Network ISDN Basic rate Access Line Termination Line Termination port commonly at central office side Line Termination Unit Main Distribution Frame Near End Cross Talk Network Termination Network Termination port commonly at customer side Network Termination Unit Online Reconfiguration Pulse Amplitude Modulation Power Back Off Plain Old Telephone Service Single sided Power Spectral Density Packet Mode Transmission Trans Convergence Layer Quadrature Amplitude Modulation Rounded Bit Loading Symmetric single pair high bit rate Digital Subscriber Line Signal to Noise Ratio ratio of powers Simulator for Performance Of Copper Systems Seamless rate adaptation Truncated Bit Loading Trellis Coded Modulation TRAnsmitter Ungerboeck Coded also known as trellis coded Very high bit rate Digital Subscriber
110. tes that a model represents the equivalent of a mix of disturbers as defined in standards Their contribution to the overall impairment depends on the NEXT and EL FEXT setting as well as the length and insertion loss of the coupled sections Direct disturbers These disturbers are representing modems using the same wire pair as the victim modem under test but in another frequency band It is typically used to add line shared noise like from ISDN systems or background noise from unidentified sources On default when you select a disturber on one side SPOCS will automatically select the associated one at the other side Its contribution to the overall impairment is independent from the NEXT and EL FEXT setting Node selection Disturbers inject their signal in the loop from a location that is named by a node number A node value 0 means that the disturber is inactive They can be co located with the two victim modems or be at different locations like in street cabinets or distributed along the line More details can be found in section 4 2 1 Note that the node number at the LT side has to be lower then the node number on the NT side Increasing disturber count or scale Increasing the count for one disturber pair is exactly the same as defining an equal amount of identical disturber links It is implemented by increasing the level of the disturber in a special way Leave the mouse pointer a few seconds above a field for specif
111. tes the Data Rate at the Noise Margin set by the user Data Rate Signal Margin Calculates the Data Rate at the Signal Margin set by the user Line Rate Noise Margin Calculates the Line Rate at the Noise Margin set by the user Line Rate Signal Margin Calculates the Line Rate at the Signal Margin set by the user Noise Margin Data Rate Calculates the Noise Margin at the Data Rate set by the user Noise Margin Line Rate Calculates the Noise Margin at the Line Rate set by the user Signal Margin Data Rate Calculates the Signal Margin at the Data Rate set by the user Signal Margin Line Rate Calculates the Signal Margin at the Line Rate set by the user REMARK Target Parameters the TARGET parameters are Margin Signal or Noise and Bit Rate Line or Data The others are considered PROPERTIES of the receiver model Figure 25 Target Parameters in SPOCS 4 6 Running performance calculations SPOCS full only To prepare SPOCS for a performance calculation start defining a scenario of interest with a victim modem pair under study a disturber mix and associated loops In this section we will concentrate on what has to be added to enable performance calculations like attainable bitrate noise margin and reach 4 6 1 Running bit rate calculations The attainable bit rate of a modem under study victim is a number that is specified for a given margin and loop length It tells the maximum bitrate that can still be t
112. th k2 2 k1 k3 leading to an analysis where node 2 is fixed 2000 m away from the first node and the distance between the second node CAB and the third one CPE is swept from 0 to 1500 m e Example 2 The sweep parameter k1 might be also set to k3 k3 50 0 k2 4000 k3 1500 and Length k2 2 k1 k3 leading to identical results You can use one constant in the other parameters if you account for the order of evaluation SPOCS evaluates k3 first then k2 and may use the result of k3 and finally k1 and may use the results of k3 and k2 The use of k2 and k3 is disabled when working in the basic mode You can increase the level of expertise via the CONFIG menu item See section 6 1 for further details 4 2 6 Using metric or imperial units SPOCS allows changing the units between metric an imperial units according to a user definable choice Units in displayed results All calculations are done in metric units whatever the unit settings are but results can be displayed in imperial units as well The available units in SPOCS are meter km inch feet yard kft and mile On default results are presented in meter but this default can be changed via a configuration file See annex C for further details You can also change it from the GUI via the menu CONFIG UNITS for displaying values only gt select unit of interest Units in input fields All fields require metric units independently from what u
113. that are the equivalent of tens or hundreds of modems If such equivalence does exists SPOCS can extract the PSD levels of these two equivalent disturbers from the crosstalk levels generated in a multi node multi disturber scenario It starts by simplifying the scenario into the one shown in figure 64 and solves a few equations to find what PSD levels of the two equivalent disturbers can produce exactly the same crosstalk level as the one in the complex scenario under study Page 54 81 D TNO 2009 SPOCS 6 0 User Guide TRO If such equivalence does not exist SPOCS will warn you about that It will produce PSD levels that are only a fair approximate of the crosstalk of the complex scenario TRANSFER INSERTION LOSS lt LT side Next t next NT side downstream upstream Figure 64 Modeling NEXT and FEXT The calculation of equivalent disturber levels can be activated from the VIEW menu VIEW Select Spectra Equivalent Disturber Levels If this option is enabled the plots with calculated spectra will include equivalent disturber levels as well 6 6 Running repetitive tasks via macros SPOCS full only You will run pretty soon into repetitive tasks such as for instance the creation of plots with multiple curves from sequential tasks Or to beautify the layout of a plot colours axis line widths labels plot size etc top make it publication ready This is where the use of macros becomes powerfu
114. the margin drops with the loop length and that the downstream margin is often a few dB better than for upstream When the length exceeds about 3 km then the upstream margin drops below 6 dB This is the reach for this bitrate combination Beyond that length the system will operate but upstream may become unreliable If you hit the lt FIND gt button SPOCS will evaluate that reach for you and returns a value of about 3084 m Page 36 81 TNO 2009 SPOCS 6 0 User Guide TRO Performance Plot dB 1 N_Margin Up ECH 2 N_ Mag a l Margin Dn _ SR Dip 20 15 10 F 5 Di SPOCS Sweep Parameter k1 gt i a pi pojasi Lig E ee E 0 500 1k 1 5k 2k 2 5k 3k 3 5k 4k Figure 37 The margin of ADSL over POTS as a function of the loop length when it operates under the stress conditions of the scenario defined in figure 36 lt SPOCS 15 Jan 2009 16 30 38 gt calculation time dT 4 606 seconds evaluated performance kl N_MarginGLT N_MarginG NT ResultData 250 000 26 981 28 534 500 000 23 842 25 432 750 000 21 716 23 506 1000 000 19 907 22 012 1250 000 18 226 20 754 1500 000 16 580 19 606 1750 000 14 943 18 284 2000 000 13 298 16 819 2250 000 11 638 15 153 2500 000 9 964 13 588 2750 000 8 274 11 873 3000 000 6 572 9 808 3250 000 4 859 7 299 3500 000 3 137 4 286 3750 000 1 409 0 927 4000 000 0 325 Z2 686 Figure 38 T
115. to 1380 3 AWG26 26 Gauge AWG Twisted Pair 11 417 z M Tap 300 ee z 4 24 i i AWG24 24 Gauge AWG Twisted Pair 11 417 I Tap 400 keet 400 Total Loop Length 5000 feet Position of DSLAM LT and CPE HT CG DSLAM left CPE right C CPE left DSLAM right Topology of Loop T T T T T T O M 2472822 gt 8 2527 ieme zm 3220 feet AwG26 IC i 7 Commands H zm 1390 feet ANG24 EN a ae ae fea nes Add Section Delete Section Delete oop Save Loop 0 1000 D 1000 2000 3000 4000 5000 Length feet Figure 68 GUI interface for Example 1 before save loop It is still under construction Custom loop type Loop Builder F joj x Fie Clipboard view Units Help Loop Library SE mea xample1 LoopBuilder Defined by user x Constructed by Loop Builder Composition of Loop Section Cable type Tap Length Length Distribution 1 AWG26 26 Gauge AWG Twisted Pair 11 417 gt T Tap 70 fauto 3220 2 AWG24 24 Gauge AWG Twisted Pair 11 417 I Tap 30 fauto H 1380 3 AWG26 26 Gauge AWG Twisted Pair T1 417 bd M Tap 300 Jieet E 4 24 1 i AWG24 24 Gauge AWG Twisted Pair 11 417 I Tap 400 keet 400 fe Total Loop Length 5000 feet Position of DSLAM LT and CPE HT CG DSLAM left CPE right C CPE left DSLAM right Topology of Loop T T T T T T O E Geesen we 5220
116. tomatically selected to match the transmitter model This auto completion mode can be disabled for victim modems via the CONFIG menu For advanced studies if your work in the advanced mode selectable via the CONFIG menu you can select a tuneable receiver model By hitting the lt parameter gt button you can change the parameters being used for that model For special cases when this is not enough you can also select one of the more generic models for line codes like PAM CAP QAM and DMT or even a pure Shannon modelling approach PBO models An optional power back off model can be selected to reduce the transmit power for instance to activate the upstream power back off for VDSL2 or to force downstream PSD shaping to VDSL2 modems The amount of power back off depends on the selected PBO model and is for some PBO models also dependent on the insertion loss of the loop and or the signal levels of the modem at the other side Node selection Modems inject their signal in the loop from a location that is named by a node number They can be at locations like a central office in street cabinets or distributed along the line More details can be found in section 4 2 1 Note that the node number at the LT side has to be lower then the node number on the NT side Extending the list of transmitters On default the list of transmitters is restricted to prevent that you get lost in an overwhelming number of models Especially the large number of VDS
117. tra transmitted at the other side of the link Logarithmic frequency axis Changes the frequency axis to logarithmic scale Hold plots Allows the user keeping the current plot and show new spectra it can be useful for spectra comparison Expert mode This corresponds to an experimental mode and is currently under development D Gives the pair information selected that is the corresponding x value frequency to the corresponding y value PSD Allows the user exploring a specific frequency range between fstart and fstop Buttons that allows the user going back lt lt and forward gt gt among transmitter models and also to clear Clear the current plot and leaves Exit this tool Figure 73 shows an example of the spectra visualized in the Transmit Viewer Page 63 81 TNO 2009 SPOCS 6 0 User Guide Transmit Viewer PL dn VDSL2 B8 4 12a 998 M2x A i i H TPL dn VDSL2 B8 4 12a 998 M2x A 14 5 dBm 1000 kHz 51 679 dBm Hz R 7 Figure 73 Transmit Viewer GUI tool Page 64 81 D TNO 2009 SPOCS 6 0 User Guide TRO 8 Summary of menus buttons and fields 8 1 Menu BAR The menu bar of SPOCS is on top showing File View Library Config 8 1 1 FILE Menu This contains the common options encountered in any program Menu Items Menu Description Load Loads a scenario from file Save Save the curr
118. tuneable model the GUI responds on it by highlighting the lt Parameters gt button from yellow to red Pili J9s File View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL O07 255 SpM 2 POTS BR KPN E underground cable L1 50x4x0 5mm CS up ADSL 007 031 SpM 2 POTS Peo Ca ADSL POTS up EC SpM 2 p aper Ze dn FDD expert guess 30 SHDSL Enhanced P PANT ADSL LIBRARY ADSLPOTS dn FOD SpM 2 ADSLASDN dn FDD SpM 2 ADSLIPOTS dn EC SpM 2 Show Topology ADSLASDN dnJEC SpM 2 Show Scenario f ADSLIPOTS dn FDD D ADSLASDN dn FDD TPL up ADSL ON ADSLPOTS an EC TPL up ADSL2 ADSL2 4 dn FDD expert guess ADSL2 6 dn FDD expert guess ADSL2 4 dn FDD expert guess a u S Lo a Io le ejo le leie is TRUITT Tj mm D O O a D Figure 59 Receiver Models in SPOCS Fixed and Tuneable SPOCS Fie View Library Config Macros Tools Window Help lt Only for unprotected use within TNO the Netherlands gt TPL dn ADSL O07 255 SpM 2 POTS BR KPN_L1 underground cable L1 50x4x0 5mm TPL up ADSL OO7 034 ou POTS _PBO_ ADSL POTS LECHEN D Ge M rr WI Figure 60 The lt PARAMETER gt button colours red if you have changed a parameter of a tuneable model The current version of SPOCS does not support that the sweep parameter k1 can be used in the tuneable
119. u can do that via the menu FILE FOLLOW DIRECTORY The scenario used for a simulation will be called henceforth a Simulation Scenario 3 2 Generating my first noise profile quickstart_1 ssf This first example quickstart_1 ssf represents a noisy loop 0 5mm cable of 3 km where an ADSL modem pair the victim shares a cable with 15 similar modem pairs the self disturbers and 3 SDSL modem pairs the alien disturbers on other wire pairs Figure 4 shows the definition of such a scenario that can be loaded via quickstart_1 ssf from the directory lt InstallDir gt Examples Examples_manual The victim modem pair is impaired by crosstalk being a cumulation of the contributions from all individual disturbers By hitting the button Generate LT noise profile SPOCS will calculate the spectrum of the cumulated crosstalk noise as it will be observed by the modem at the LT side of the loop commonly the location of a DSLAM in a central office It saves the result a noise profile into a file in a format that can be used by your noise generator for synthesizing noise with exactly the same spectrum The button Generate NT noise profile facilitates the same for the other side of the loop but with a different spectrum commonly the location of a CPE at the customer s premises Page 9 81 TNO 2009 SPOCS 6 0 User Guide SPOCS quickstart_1 ssf 15 x File View Library Config Ma
120. uct selection Similar xDSL solutions from different vendors perform differently They all may pass standardized tests but these tests are usually still under development when new technology becomes available In addition standard stress conditions are usually very different from operational noise environments With SPOCS you can make product assessments that are tailored to the noise environments of your preference SPOCS can predict a noise environment and create a noise profile of the spectra that can be observed by a modem under study When such a noise profile is fed to a noise generator that supports the creation of user definable noise you can test in your lab how a particular modem implementation will really perform under noisy stress conditions Page 8 81 Rep TNO 2009 SPOCS 6 0 User Guide TRO 3 Quick Start Examples This quick start provides you with two examples for using SPOCS One dedicated to performance testing profiler functionality and another to performance simulations predictor functionality 3 1 Loading a first example scenario SPOCS comes with several example scenarios These can be found on lt InstallDir gt Examples Examples_manual Once SPOCS is started you can load your first example scenario via the menu FILE LOAD gt select lt InstallDir gt Examples Examples_manual quickstart_1 ssf To make that directory the current directory for easy loading other scenarios in the same directory yo
121. ulting crosstalk power in each wire pair from N 1 disturbers connected to the other wire pairs is maximal and therefore unambiguous This upper limit is the saturated crosstalk power for that type of disturber for that particular wire pair However if the number M of disturbers is lower M lt N 1 this crosstalk power will commonly change when another combination of M wire pairs will be chosen So an exact expression for the resulting crosstalk as function of the number and type of disturbers does not exist if it remains unknown to which wire pairs they are connected What does exist are crosstalk powers that occur with a certain probability To illustrate that consider an experiment that connects 30 disturbers to a cable with 100 wire pairs in 100 000 different ways If the resulting noise is observed in one particular wire pair it is most likely that you will also observe 100 000 different Page 19 81 D TNO 2009 SPOCS 6 0 User Guide TRO crosstalk noise powers The result of such a probability experiment is therefore not a single power but a wide range of powers with a certain probability distribution Within this range a certain crosstalk noise power can be found that is not exceeded in X of the cases That power level is named a probability limit for a particular wire pair and the crosstalk models in SPOCS are to predict how such a limit behaves as a function of number and type of disturbers The crosstalk models in SPOC
122. uneable only visible when working in the advanced level or higher as explained in section 6 1 6 2 2 Available PBO models and its parameters The amount of power back off may depend on fixed settings on the insertion loss of the loop on the level of the received signal or a mix of these The model converts a source signal generated by a transmitter model into a transmit signal and that transmit signal is injected into the loop This conversion is controlled by one or more of the following values e the source signal spectrum as provided by the transmitter model e the source signal spectrum of the modem at the other side of the loop without PBO at the other side e the characteristic transfer of the loop being studied to account for attenuation Different DSL standards have produced different PBO mechanisms and therefore you can select a PBO model from a list with many options individually for each transmitter disturber A complete list of PBO models and a description of its parameters can be found via the Help menu via Power back off models index of all PBO models Selecting PBO models in downstream direction Selecting PBO models in upstream direction 6 2 3 Inspecting a PBO model To find out how much a selected PBO model modifies a transmit signal you can right click on the PBO button with your mouse This opens a context menu and one of its menu items is named PBO Inspector Figure 57 il
123. ying how much dB this increase will be Expert users may consider specifying this increase directly in dB s In such a case hit the count button so that its label changes to scale Now you can specify yourself how much dB is required to represent multiple disturbers Page 20 81 Rr TNO 2009 SPOCS 6 0 User Guide TRO Adding Branches Most topologies are branched in practice It is common that a distribution cable leaving a central office LT with 900 wire pairs fan out from a street cabinet into 9 independent cables of 100 wirepairs This is depicted below in figure 20 Branching is the mechanism to define such topologies It has an impact on the performance of a modem pair under study since most of the disturbers starting from the central office do not arrive at the same customer location Topologies without branching are often too pessimistic about the performance being predicted A detailed example of such a study is discussed in section 5 4 To add a branch to a topology hit the B button to specify the length of the branch for each individual group of disturbers Hit the Show Topology button to see a graphic representation of the topology you have defined nine cables 100 wire pairs each single cable 900 wire pairs Figure 20 Distribution cables usually fan out from street cabinets or underground splices into multiple cables with less wire pairs This is called branching Adding PBO m
124. ystems Electrical Length The electrical length of each loop is defined as the insertion loss at a given test frequency ft Local Loop Wiring part of a metallic access network terminated by well defined ports for transporting signals over a distance of interest NOTE This part includes mainly cables but may also include a Main Distribution Frame MDF street cabinets and other distribution elements The local loop wiring is usually passive only but may include active splitter filters as well Loop Provider organization facilitating access to the local loop wiring NOTE In several cases the loop provider is historically connected to the incumbent network operator but other companies may serve as loop provider as well LT access port or LT port for short is an access port for injecting signals designated as LT port NOTE Such a port is commonly located at the central office side and intended for injecting downstream signals Max Data Rate maximum data rate that can be recovered according to predefined quality criteria when the received noise is increased with a chosen noise margin or the received signal is decreased with a chosen signal margin Page 74 81 Rep TNO 2009 SPOCS 6 0 User Guide TRO Network Operator organization that makes use of a local loop wiring for transporting telecommunication services NOTE This definition covers incumbent as well as competitive network operators Noise Margin rat

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