WLAN Outdoor Guide - e
Contents
1. If the receiving antenna is outside of this ideal area however significant losses in performance will be the result The current signal quality over a P2P connection can be displayed on the de vice s LEDs or in the LANmonitor in order to help find the best possible align ment for the antennas The display of signal quality on the LEDs must be activated for the wireless LAN interface LANconfig Wireless LAN gt General gt Physical WLAN settings gt Operation The faster the LED blinks the better the connection a blinking frequency of 1 Hz represents a signal quality of 10 dB double the frequency indicates that the signal strength is twice as high WLAN Outdoor Guide Release 07 08 19 Point to point connections 3 2 Antenna alignment Physical WLAN settings WLAN interface 2 x Operation Radio Performance Point to Point Client mode IV WLAN interface enabled WLAN operation mode Access point x Link LED function Connection count 6 Tre ek LED funcion Cert A Chest sig gnal streng pe in Client mode operat ARMEE al EF P strength Gi enn the fs edere as In LANmonitor the connection quality display is opened with the context menu Right clicking with the mouse on Point to point activates the option Adjusting Point to Point WLAN Antennas leid File Device View Tools Help LANCOM Systens El y WAN connections None 5 EEN Wireless LAN SRE ont tnont S Firewall Ac GO2. trostatic discharge or reduce the surges to a level that is harmless for people and equipment Note Please refer to Chapter Lightning and surge protection WLAN Outdoor Guide 14 Release 07 08 Point to point connections 3 Point to point connections BAT Wireless access points can serve not only as central stations in a wire less network they can also operate in point to point mode to bridge longer distances For example they can provide a secure connection between two networks that are several kilometers apart without direct cabling or expen sive leased lines Fl a be ANTENNA ACCESS POINT NN l ANTENNA ACCESS POINT When using access points and appropriately polarized antennas in accor dance with IEEE 802 11n two wireless links can be established simultane ously between the end points of a point to point connection This allows higher data throughput to be achieved or greater distances to be covered than when using other standards H POLARIZATION POLARISATION H MIMO AP 802 11n DIVERSITY DIVERSITY MIMO AP 802 11n This chapter introduces the basic principles involved in designing point to point links and provides tips on aligning the antennas WLAN Outdoor Guide Release 07 08 15 Point to point connections 3 1 Geometric dimensioning Note Please refer to the appendix of WLAN Outdoor Guide for information on the frequency ranges used You can find information on configuring the a
3. 5 Installation 5 1 Safety advice WLAN Outdoor Guide Release 07 08 22 22 24 25 26 29 33 33 5 2 Mounting the access points 5 2 1 Selecting where to mount 5 2 2 Wall mounting 5 2 3 Pole mounting 5 3 Mounting antennas 5 3 1 Selecting where to mount 5 3 2 Wall mounting 5 3 3 Mast mounting 5 4 Mounting the lightning rods 5 4 1 Dimensioning of the lightning rod 5 4 2 Distance to the components at risk 5 4 3 Lightning charge conduction grounding 6 Appendix 6 1 Antenna gain EIRP and antenna radiation characteristics 6 2 Selecting the frequency band 6 2 1 2 4 or 5 GHz band 6 2 2 Special regulations for the 5 GHz band 7 Index WLAN Outdoor Guide Release 07 08 Preface 1 Preface The advantages of wireless LANsre are obvious they offer flexibility mobi lity and convenience at a lower cost than cabled networks WLANs can be quickly installed without any changes to the building s construction and they offer new applications not available with cabled LANs BAT wireless routers and BAT access points combine with appropriate antennas for establishing wireless LANs both indoors and outdoors BAT wireless routerBAT access pointThis document applies for all BAT wireless routers and BAT access points in combination with antennas of the BAT product line and it provides general information on the outdoor operation of wireless LAN systems Information on the installation and basic configura tion of the various wireless r
4. Pceeaee ee Te enaar g nA ci7 amp A i 6 i 1 2 Hirschmann Wireless LAN Distance Calculator p B HIRSCHMANN ce Go Country er p 7 Point A Frequency Band mnan E Point B 7 Emdeaamontat condition otter rn ret spec Zj u 4 t KE AccesspolntiCHent Adapter xtra barse sat z AccesspointiClient Adapter mmmn u 16 Cable 1 gn f w anmenm FE pe mastheight m 52 Surge Arrestor p EJ datarste Mbps 6 Surge Arrestor ne an N 2 a Cable 2 he can El Cable 2 he Cate E Fy 5 Antenna mma Antenna EE z C a a Antenna morsen Argens Infermation Tatenna Type Orresdrechons stenen Tar SONT Aamteama TypeJOrendeectionad antenna t range Kees an gna co a motse dences Not be mes in Tepiication li beat paced w contre hal w areas Or on motile dences Not be venen Interface Croptewresowce J Aton DOSAR gt LA SRRA IEEE E Positioning the antennas Antennas do not broadcast their signals linearly but within an angle that de pends on the model in question The spherical expansion of the signal waves results in amplification of or interference to the effective power output at cer tain intervals of the connection between the transmitter and receiver The areas where the waves amplify or cancel themselves out are known as Fres nel zones Fresnel zone 3 Radius R Fresnel zone 2 Distance d Fresnel zone 1 PRODUCTIO
5. Rh HIRSCHMANN A Belden Company WLAN Outdoor Guide WLAN Outdoor Guide Technical Support Release 07 08 HAC Support hirschmann de Windows Windows Vista Windows XP and Microsoft are registered trademarks of Mi crosoft Corp LCOS is registered trademarks of LANCOM Systems GmbH The naming of copyrighted trademarks in this manual even when not specially indicated should not be taken to mean that these names may be considered as free in the sense of the trademark and tradename protection law and hence that they may be freely used by anyone 2008 Hirschmann Automation and Control GmbH Manuals and software are protected by copyright All rights reserved The copying reproduction translation conversion into any electronic medium or machine scannable form is not permitted either in whole or in part An exception is the preparation of a backup copy of the software for your own use For devices with embedded software the end user license agreement on the en closed CD applies This product includes software developed by the OpenSSL Project for use in the OpenSSL Tool kit http www openssl org This product includes cryptographic software written by Eric Young eay cryptsoft com This product includes software developed by the NetBSD Foundation Inc and its contributors The performance features described here are binding only if they have been expressly guaran teed in the contract This publication has been created by H
6. TPC and DFS is not stipulated for all fields of application The following table provides information about the permitted use and corresponding transmission powers within the EU Transmissionpower ean mW dBm Use DFS TPC 5 15 5 25 30 13 Indoor 5 15 5 25 60 14 Indoor v 5 15 5 25 200 23 Indoor YU YU 5 25 5 35 200 23 Indoor Y Y 5 470 5 725 4000 36 Indoor Outdoor 4 YU Note Other regulations may apply for use in other countries Please refer to the current wireless network regulations for the country in which you wish to operate a wireless LAN device and ensure that you set the country of operation in the wireless LAN settings The USA and Asia use different frequency bands and maximum signal strengths that are different than the European standard In the USA three subbands each 100 MHz wide are used for wire less networks in the 5 GHz band The lower band ranges from 5150 5250 MHz the middle band ranges from 5250 5350 MHz and the upper band ranges from 5725 5825 MHZ In the lower band a maximum average EIRP of 50 mW is permitted in the middle band this is 250 mW and 1 W in the upper band In Japan the use of the 5 GHz band is possible to a limited extent only the lower band of 5150 5250 MHZ is approved for private use WLAN Outdoor Guide Release 07 08 49 Index 7 Index Numerics 2 4 GHz band Advantages 45 Disadvantages 45 5 GHz band 47 49 Advantages 45 Disadvant
7. point and antenna has a considerable influence on the attenuation in the wireless LAN system as a whole thus impacting for example the available range and possible data rates Locations where components are mounted outdoors should be as close as possible to the point where the coaxial or Ethernet cables enter the building Excessive stretches of outdoor cabling are exposed to increased danger from the effects of lightning In outdoor areas avoid locations that are close to exposed metallic con ductors such as guttering downpipes etc 5 3 2 Wall mounting Permanent mounting can take place directly on a wall or with the adjustable swivel fixture 5 3 3 Mast mounting An alternative is to mount the antenna directly on a mast or similar thus en suring that the antenna has a particularly high degree of exposure WLAN Outdoor Guide Release 07 08 37 Installation 5 4 Mounting the lightning rods 5 4 Mounting the lightning rods Lightning rods create a spatial shield that is designed to protect the compon ents in a wireless LAN such as antennas or access points from a direct light ning strike The following aspects should be considered when choosing where to mount them Dimensioning of the lightning rod Vertical and horizontal distance from the components at risk Lightning rod grounding Danger The dimensioning installation and grounding of the lightning rods should only be performed by trained electricians 5 4 1 Dimensioni
8. spaces To protect mi litary applications in the 5 GHz band the DFS Dynamic Frequency Selec tion and TPC Transmission Power Control procedures were prescribed However DFS and TPC allow significantly higher transmission powers ma ximum 1000 mW to be used than with other previously valid standards Dynamic Frequency Selection DFS Dynamic Frequency Selection DFS was stipulated to prioritize primary applications DFS initially assumes that no channel is available in the corresponding frequency band The wireless LAN device initially selects an arbitrary channel and performs what is known as a Channel Availabi lity Check CAC Before transmitting on a channel for 60 seconds Channel Observation Time COT a check is run to see if a different device is already working on this channel and the channel is therefore occupied If this is the case a different channel is checked by the CAC If not then the wireless LAN device can start transmitting Even during operation a check is run to see if a primary application such as a radar device is using this channel This exploits the fact that radars frequently work according to the rotation method whereby a tightly bundled directional transmission signal is transmitted by a rotating antenna A remote receiver perceives the radar signal as a short pulse radar peak If a device receives such a radar peak then it pauses the transmission operation and monitors the channel for further pulses If ad
9. the transmission of lightning current over the cables leading from exposed objects such as antennas directly into the building So called lightning ar resters type 1 offer protection from these lightning currents They are fit ted to the relevant cables directly where they enter the building This type of lightning protective device prevents lightning current from entering via the protected cabling however surges can still occur that must be pre vented through the use of further surge protection adapters e g BAT surge arrestor Power supply Surges can also find their way into the building via the po wer supply and thereby endanger electronic equipment Surge arresters type 2 can be used to protect against such surges They work by redu cing the voltage peaks to a sufficiently low level These type 2 adapters are fitted for example in the electrical cabinet Devices The final link in the surge protective chain is the protection of the devices themselves For this type 3 surge protective devices are used for example in the form of power socket adapters This type of SPD works by lowering any surges that may occur to a level that is not dangerous for highly sensitive equipment The assessment of risk and the resulting design of a suitable lightning pro tection system is always dependent on local conditions for example the fre quency with which lightning strikes are to be expected and ideally needs to be carried out by trained exper
10. AT surge arrestor ACCESS POINT Antenna in an unex je posed place Pen line PEL 16mm Cu The basic situation shows an application where the antenna is not mounted in an exposed place there is therefore no danger of a direct lightning strike gt Itis sufficient for lightning protection to have an adequately dimensioned potential equalization line for the antenna gt The access point must be protected with a BAT surge arrestor for internal protection in any case WLAN Outdoor Guide 30 Release 07 08 Lightning and surge protection 4 3 Internal lightning protection E Scenario 2 Antenna in an exposed place safety clearance to arresting device observed Safety clearance gt 100 cm _ _ _ _ _ _ gt gt Antenna in an exposed pla ce BAT surge arrestor ACCESS POINT Potential equalization line PEL 16mm Cu In this example the antenna is mounted in such a way that a direct lightning strike is possible A lightning rod with a sufficiently large safety clearance of more than 100 cm is installed as a protective measure gt As external lightning protection both the antenna and the lightning rod are separately grounded with their own potential equalization lines gt There are no other aspects to be considered for internal lightning protec tion WLAN Outdoor Guide Release 07 08 31 Lightning and surge protection 4 3 Internal lightning protection E Scenario 3 The ac
11. N ADMINISTRATION WLAN Router OBSTRUCTION ACCESS POINT WLAN Outdoor Guide Release 07 08 17 Point to point connections 3 1 Geometric dimensioning The Fresnel zone 1 must remain free from obstruction in order to ensure that the maximum level of output from the transmitting antenna reaches the recei ving antenna Any obstructing element protruding into this zone will signifi cantly impair the effective signal power The object not only screens off a portion of the Fresnel zone but the resulting reflections also lead to a signi ficant reduction in signal reception The radius R of Fresnel zone 1 is calculated with the following formula as suming that the signal wavelength A and the distance between transmitter and receiver d are known R 0 5 V A d The wavelength in the 2 4 GHz band is approx 0 125 m in the 5 GHz band approx 0 05 m Example With a separating distance of 4 km between the two antennae the radius of Fresnel zone 1 in the 2 4 GHz band is 11 m in the 5 GHz band 7 m To ensure that the Fresnel zone 1 remains unobstructed the height of the an tennas must exceed that of the highest obstruction by this radius The full height of the antenna mast M should be as depicted Safety 1m Obstruction height H l l OBSTRUCTION ADMINISTRATION PRODUCTION Earth s curvature E M R 1m H E earth s curvature The allowance for the curvature of the earth E can be calculated at a di stance d a
12. ages 46 A Access point 11 Angle of beam spread 41 Antenna Calculator 16 Antenna diversity 13 44 Antenna gain 40 Antenna power 18 C Campus coverage 7 D Data communication to mobile objects 8 DFS 16 46 49 Directional antenna 13 44 Download 6 Dynamic Frequency Selection 16 46 Dynamic frequency selection 16 E EIRP 40 47 Equivalent isotropic radiated power 40 F Firmware 6 Fresnel zone 18 G Gain 40 H Hotspot 8 WLAN Outdoor Guide 50 Release 07 08 Index IEEE 802 11a IEEE 802 11b IEEE 802 11g IEEE 802 11n Industrial applications Isotropic radiator L Lightning protection Designing the lightning protection system Internal lightning protection Surge protection adapter SA 5L 28 30 31 Lightning protector External lightning protection Lightning current arresters Lightning rods Lower band M Middle band Mounting access points Pole mounting Wall mounting Mounting antennas Pole mounting Wall mounting 0 Omnidirectional antenna 13 P PoE PoE Injector Point to multipoint Point to point Point to point mode Polarization diversity 14 Power hub Power over Ethernet Power supply Power switch WLAN Outdoor Guide Release 07 08 12 12 12 12 40 26 25 24 24 24 49 49 35 35 37 37 43 12 12 15 44 12 12 12 12 51 Index R Radiation characteristics Radio channels Indoor and outdoor operation Radio channels ETSI EU Radio channels FCC US Relay mo
13. antenna In practice the different antenna models have beams that are focused into sectors of varying size These geometrical radiation characteristics are ex pressed by the equivalent isotropic radiated power or EIRP To determine EIRP an antenna is viewed theoretically as an isotropic or spherical radiator that emits radiation of the same power in all directions The EIRP is the amount of power that would have to be emitted by an isotropic antenna to produce the peak power density observed in the direction of maximum an tenna gain emmen The power fed into the antenna is focused and thus amplified into a main beam direction This amplification is referred to as gain The greater the fo cussing the greater is the antenna gain WLAN Outdoor Guide Release 07 08 40 Appendix 6 1 Antenna gain EIRP and antenna radiation The geometrical beam pattern from an antenna is described by the angle of beam spread and by what is referred to as the radiation characteristics The radiation characteristics represent the spatial distribution of the radiated po wer ACCESS POINT To simplify the problems of representing three dimensional power distributi on two planes horizontal and vertical are taken and the emitted power is plotted as measured in various directions WLAN Outdoor Guide Release 07 08 41 Appendix 6 1 Antenna gain EIRP and antenna radiation The bold line indicates the power that was measured in a certai
14. area Support will help you with many answers to frequently asked questions FAQs Furthermore the knowledgebase offers you a large reserve of information The latest drivers firmware utilities and documentation are constantly available for download In addition BAT support is available For telephone numbers and contact addresses of BAT support please see the enclosed leaflet or the Hirsch mann website WLAN Outdoor Guide 6 Release 07 08 Introduction 2 1 Application scenarios 2 Introduction This chapter presents the basic application scenarios for wireless LAN out door systems These include for example campus coverage industrial appli cations and wireless links We also list the components required to set up a wireless LAN system outdoors 2 1 Application scenarios Wireless LAN systems can act as an extension to or even as a replacement for cabled networks In some cases wireless LANs even provide completely new application possibilities which can mean a major advance in the way work is organized or significant cost savings 2 1 1 Campus coverage Coverage for campuses is provided by wireless LAN system antennas moun ted on building facades or on special mountings or masts In this way radio cells cover the open areas and all wireless LAN clients with the appropriate rights have access to the network A common term used here is campus co verage because this solution is used by a large number of colleges and
15. ccess points Lightning rod height The lightning rod must be high enough to ensure that the equipment that is to be protected such as antennas are within the spa tial shield Besides the exact rolling sphere method used to determine the areas at risk there is the simpler protective angle method which can be used to approximate the spatial shield formed by a lightning rod This me thod assumes an area of 45 under the lightning rod to be safe from direct lightning strikes 5 4 3 Lightning charge conduction grounding Lightning rods must always be grounded with a separate adequately dimen sioned potential equalization line PEL with a cross section of at least 16 mm Cu The connection to the grounding system must be made using the shortest path Note If the lightning rod and antenna are mounted together on the same mast and the distance to the antenna is more than 100 cm the lightning rod must be adequately insulated from the mast since in this case the li ghtning rod and the antenna must be separately grounded WLAN Outdoor Guide Release 07 08 39 Appendix 6 1 Antenna gain EIRP and antenna radiation 6 Appendix 6 1 Antenna gain EIRP and antenna radiation characteristics In order to be able to make a statement on the suitability of an antenna for any particular application the technical specifications state data such as an tenna gain radiated power EIRP angle of beam spread and the radiation characteristics of the
16. ccess points in the relevant equipment documentation or in the LCOS re ference manual 3 1 Geometric dimensioning The following basic questions must be answered when designing wireless links What antennas must be used for the desired application How must the antennas be positioned to ensure a problem free connec tion What performance characteristics do the antennas need to ensure suf ficient data throughput within the legal limits Selection of antennas using the BAT Antenna Calculator You can use the BAT Antenna Calculator to calculate the output power of the access points as well as the achievable distances and data rates The pro gram can be downloaded from our website at www hirschmann com After selecting your components access points antennas lightning protec tion and cable the calculator works out the data rates ranges and the an tenna gain settings that have to be entered into the access point Caution Please note that when using 5 GHz antennas additional techno logies such as dynamic frequency selection DFS may be stipulated de pending on the country of use The operator of the wireless LAN system is responsible for ensuring that local regulations are met WLAN Outdoor Guide 16 Release 07 08 Point to point connections 3 1 Geometric dimensioning E resah tme Perschenane WLAN Cast ance Cacudater Oad Taleb Gjates poteen yan Gig fone tee tum teas ed ex Jd TAART 9 0 BAe 1 i wD ve eve Are Prey ee ens
17. central access point or Wireless router is configured as master and the remote WDS stations as slaves 7 EH ACCESS POINT STOCK HEADQUARTER 7 ANTENNA omy IG Ta WLAN Outdoor Guide 1 0 Release 07 08 Introduction 2 2 Components of the wireless LAN system 2 1 6 Wireless links in relay mode In some cases the distance between the access points for connection ex ceeds the range of a single wireless link This may be the case when the di stance between the access points exceeds the radio range or when obstacles exist in the line of site between the two access points In these cases the two end points can be connected by stringing together multiple access points each of which has two WLAN modules Because the intermediate access points often operate solely as relay stations the opera ting mode of these access points is referred to as relay mode P EN AEN Although BAT access points can run several P2P links simultaneously on each wireless module in addition to supporting wireless LAN clients we re commended the use of BAT access points with two wireless modules for per formance reasons 2 2 Components of the wireless LAN system Generally speaking a WLAN system consists of the following components some of which are optional 2 2 1 access points and Wireless router Hirschmann supplies access points and Wireless routers for various applica tions access points are generally used to establish wi
18. cess point is not installed inside the building but outdoors for example directly next to the antenna in order to reduce the length of cable between the antenna and the access point NL f ES lt Safety clearance gt 100 cm dj Potential equali zation line PEL PEL 16mm Cu Age 230V Em nnn SA SL KOEN ACCESS POINT LAN surge ad BAT surge apter arrestor In this case the BAT surge arrestor surge protection adapter is installed di rectly between access point and antenna and grounded for example via the antenna s potential equalization line gt If the access point is installed outside its grounding and that of the BAT surge arrestor are connected with the antenna s conductor for example via the clamps on the antenna s mounting gt The BAT surge arrestor can be fixed directly to the antenna socket de pending on the model of the access point WLAN Outdoor Guide Release 07 08 32 Installation 5 1 Safety advice 5 Installation 5 1 Safety advice Danger Do not mount access points or antennas in weather conditions when lightning may be expected Similarly refrain from connecting or disconnecting cables during weather of this type The components of a wireless LAN can be subject to variations in electri cal charge even in normal weather conditions Please perform all work with the utmost care Note access points antennas and mounting equipment such as masts in tended for out
19. d in the immediate vicinity of the antenna for example on a mast or similar ar rangement WLAN Outdoor Guide Release 07 08 35 Installation 5 3 Mounting antennas 5 3 Mounting antennas The method for mounting the antenna depends on the model s design This section presents the various mounting types as illustrated by examples Please refer to the documentation of the relevant antenna for more precise instructions Caution Please observe the following advice during installation Antennas mounted outside in an exposed location where direct lightning strikes can occur must be protected by a lightning rod installed at a distance of at least 100 cm Antennas mounted outside must be grounded with an adequately dimensioned potential equalization line PEL with a cross section of at least 16 mm Cu The BAT surge arrestor must be used to protect sensitive wireless LAN modules 5 3 1 Selecting where to mount Before mounting any antennas a suitable location should be found that meets the following conditions Mount the antennas in a place offering a good line of sight for transmitting data to mobile wireless LAN clients or remote P2P stations You will find advice on antenna alignment in P2P mode in Chapter Point to point connections P2P mode WLAN Outdoor Guide 36 Release 07 08 Installation 5 3 Mounting antennas Mount antennas as near as possible to the access points The length of the coaxial cable between access
20. de S Safety advice Sector antenna Support T TPC Transmission Power Control U Upper band User group w Wireless router 52 40 49 48 48 11 33 13 43 6 46 47 49 47 49 8 WLAN Outdoor Guide Release 07 08
21. di rections They have very limited vertical spread which determines the an tenna gain Antennas of this type are typically located in the center of open spaces or larger offices to provide even coverage to all clients gt Sector antennas have beams with fairly wide horizontal and vertical an gles for example between 60 and 90 Sector antennas are generally mounted on the wall of a building or in the corner of a room to provide an even coverage often referred to as campus coverage gt Directional antennas have beams with narrow horizontal and vertical an gles for example of 9 Directional antennas are mainly used on rooftops or masts for establishing point to point links that interconnect areas of a network that are separated by a distance gt Polarization diversity antennas antenna diversity WLAN Outdoor Guide Release 07 08 13 Introduction 2 2 Components of the wireless LAN system The transmission of radio signals can suffer from among other things significant signal losses due to reflection and scatter When electroma gnetic waves overlap at the point of reception the strength of the signals may be reduced or completely obliterated interference Transmission quality can be improved with so called diversity methods The polarization diversity method makes use of the electromagnetic polarization of the radio waves The transmitter broadcasts the wireless LAN signals as linearly polarized waves w
22. discharges Any lightning striking this equipment is channeled by a conductor along the shortest path to the groun ding system Intentionally catching the lightning with the arresting equip ment creates a spatial shield where no direct lightning strike is possible The actual design and construction of external lightning protection depends on the prevailing structural circumstances Spatial shield Rd N ra Protective angle 45 Safety clearance gt 100 cm eg lt Lightning rod i lt Conductor Grounding Antenna WLAN Outdoor Guide 24 Release 07 08 Lightning and surge protection 4 3 Internal lightning protection 4 3 Internal lightning protection Internal lightning protection refers to measures which counteract the effects of lightning strikes and surges that may arise despite the external lightning protection These disturbances may for example be triggered when a light ning strike some distance away is subsequently diffused through the power network or by discharges in the atmosphere that are not accompanied by vi sible lightning There are two ways in which these surges can get into a building and then spread Via the connection to the public power supply or via cable entry points for example antennas fixed to the outside of the building The following is a description of how to protect the system form the perspec tive of antennas Protection for equipment connected to the power supply from surges emana
23. ditional radar peaks occur during the COT then a new channel is sel ected automatically WLAN Outdoor Guide 46 Release 07 08 Appendix 6 2 Selecting the frequency band Caution The connection can now be operated for any length of time on the channel selected by the DFS algorithm until either a radar signal is de tected or the radio cell is restarted e g by changing the device configu ration firmware upload or restart DFS is stipulated for the frequency ranges from 5250 5350 MHz and from 5470 5725 MHz It is optional for the frequency range of 5150 5250 MHz Transmission Power Control TPC Dynamic adjustment of the transmission power is intended to reduce radio interference Dynamically adjusting the transmission power makes it easier for the 5250 5350 MHz and 5470 5725 MHz frequency bands to be shared with satellite services TPC is designed to cause an average reduction the transmission power by at least 3 dB compared with the maximum in permitted transmission power TPC determines the minimum transmis sion power necessary to maintain the connection with the partner such as an access point If TPC is not used within these frequency bands then the highest permissible average EIRP and the correspon ding maximum EIRP density are reduced by 3 dB This restriction doe not apply to the frequency range of 5150 5350 MHz Without DFS and TPC a maximum of only 30 mW EIRP is permitted S When DFS and TPC are u
24. door operation must be grounded Never work with access points and antennas if you are not certain of proper ground Please seek advice from a qualified electrician to clarify this issue The installation and mounting of access points and antennas should only be carried out by experienced IT personnel or trained electricians Please obser ve the following notices to avoid accidents Never carry out work of this type alone but with a minimum of two people This ensures that help can be quicker to hand if an accident occurs despi te all safety precautions Only use ladders with the appropriate insulation Do not work in strong winds or rain Wear suitable working clothing such as close fitting clothing and safety shoes with non slip soles If components of the antenna or mountings should be dropped let them fall and do not attempt to catch them Falling antennas masts or cables may come into contact with live contacts and cause electric shock The mounting location should be easily accessible in the interests of fu ture maintenance work or for checking cable connections Before commencing with mounting ensure that you have all the necessa ry tools and accessory parts Similarly ensure that any openings required for the entry of the coaxial or Ethernet cable into the building are already available WLAN Outdoor Guide Release 07 08 33 Installation 5 2 Mounting the access points Danger In the interests of your own safety antennas mast
25. e access points as close as possible to the antennas The length of the coaxial cable between access point and antenna has a considerable influence on the attenuation in the wireless LAN system as a whole thus impacting the available range and data rates for example Maximum separation is also important for an access point and PoE injec tor Some access points have for example an increased power require ment that can only be supplied over a specific length of ethernet cable Detailed advice is available in the documentation for the access point or the PoE injector WLAN Outdoor Guide 34 Release 07 08 Installation 5 2 Mounting the access points Locations where components are mounted outdoors should be as close as possible to the point where the coaxial or Ethernet cables enter the building Excessive stretches of outdoor cabling are exposed to increased danger from the effects of lightning Avoid locations that are very dusty In outdoor areas avoid locations that are close to exposed metallic con ductors such as guttering downpipes etc 5 2 2 Wall mounting Wall mounting is an option for all access points and is a suitable method when the intended antenna location is not too far removed e Sa Pe wih u WY F led Ted En c fi it o nn 5 2 3 Pole mounting If the distance separating the wall mounted access point and the antenna is likely to end up being too large the access point can alternatively be affixe
26. e em al en een H E System inf System nf Note The Point to point entry is only visible in the LANmonitor if the moni tored device has at least one base station defined as a remote station for a P2P connection LANconfig Wireless LAN gt General gt Physical WLAN settings gt Point to Point In the dialog for setting up point to point connections LANmonitor prompts for the information required to establish the P2P connection Is the P2P connection configured at both ends remote base station defi ned with MAC address or station name Is the point to point mode of operation activated Which access point is to be monitored All of the base stations defined as P2P remote stations in the device concerned can be selected here Are both antennas approximately aligned The basic P2P connection has to be working before fine tuning can be performed with the aid of LANmonitor Once signal monitoring has commenced the P2P dialog displays the abso lute values for the current signal strength and the maximum value since star ting the measurement The development of the signal strength over time and the maximum value are displayed in a diagram too WLAN Outdoor Guide 20 Release 07 08 Point to point connections 3 2 Antenna alignment LANCOM 1811 Wireless DSL Adjusting Point to Point WLAN Antennas lof x Check List p Measurement IV Is the P P link configured at both ends Link signal strength Maxim
27. eristics do not indicate absolute transmission po wer or transmission range It merely serves to indicate the percentage of maximum power that is emitted in any given direction Example applications of various wireless LAN antennas Omnidirectional antennas transmit horizontally with equal power in all di rections They have very limited vertical spread which determines the an tenna gain Antennas of this type are typ ically located in the center of larger offices to provide even coverage to all clients However the client adapters should all be at a similar height to receive the best signal from the central antenna 270 Horizontal Vertical Omnidirectional antennas typically have an low antenna gain of 2 to 4 dBi for example Sector antennas have beams with fairly wide horizontal and vertical an gles for example between 60 and 90 Sector antennas are generally mounted on the wall of a building or in the corner of a room to provide an even coverage often referred to as Campus coverage 270 Horizontal Vertical Standard sector antennas have a medium an tenna gain of between 8 and 9 dBi WLAN Outdoor Guide Release 07 08 43 Appendix 6 1 Antenna gain EIRP and antenna radiation Directional antennas have beams with narrow horizontal and vertical an gles for example of 9 Directional antennas are mainly used on rooftops or masts for establishing point to point links that interconnect areas of a n
28. etwork that are separated by a distance 270 270 Horizontal Vertical Directional antennas achieve very high antenna gains sometimes exceeding 20 dBi Most models are suitable for operating either at 5 GHz or 2 4 GHz only Note These examples illustrate the tendency for smaller beam widths to re sult in larger antenna gains Apart from the focusing effect the size of the antenna also contributes to antenna gain Larger antennas ge nera lly re sult in better antenna gain Polarization diversity antennas antenna diversity The transmission of radio signals can suffer from among other things significant signal losses due to reflection and scatter When electroma gnetic waves overlap at the point of reception the strength of the signals may be reduced or completely obliterated interference Transmission quality can be improved with so called diversity methods The polarization diversity method makes use of the electromagnetic polarization of the radio waves The transmitter broadcasts the wireless LAN signals as linearly polarized waves with a fixed direction of polariza tion The polarization may be modified over the radio link by reflection and diffraction so that signals reach the receiver with differing polariza tion Polarization diversity antennas use two signals with a relative pola rization of for example precisely 90 The combination of the two signals results in higher antenna gain Two antennas are connec
29. ightning is cloud earth lightning A so called light ning leader develops from a negatively charged center of a thundercloud This leader descends and when it is between 10 m and a several 100 m from the earth the electrical field strength increases so strongly in exposed places for example at the roof of a house or top of a tree or even the tip of an an tenna that similar and opposite discharges to the lightening leader develop there the so called conductive discharges One of possibly many conductive discharges meets the lightning leader and earths it This determines the point where lightning strikes If an antenna is struck by lightning the instant increase in voltage is conduc ted via the coaxial cable to any connected devices i e the access points in a wireless LAN system and this generally results in their destruction Addi tionally any ungrounded components of a wireless LAN system may be sub ject to sparks or arcing to any earthed metal parts in the vicinity Partial discharges Even if a conductive discharge originates in an antenna it does not necessa rily mean that lightning will strike the antenna In order to feed the conductive discharge in the antenna a momentary electrical impulse flows through the antenna system this is called a partial discharge A partial discharge is the refore a conductive discharge that does not lead to a direct lightning strike These partial discharges can also result in damage to c
30. irschmann Automation and Control GmbH according to the best of our knowledge Hirschmann reserves the right to change the con tents of this manual without prior notice Hirschmann can give no guarantee in respect of the correctness or accuracy of the details in this publication Hirschmann can accept no responsibility for damages resulting from the use of the network components or the associated operating software In addition we refer to the conditions of use specified in the license contract Printed in Germany 30 6 2008 Hirschmann Automation and Control GmbH Stuttgarter Strate 45 51 72654 Neckartenzlingen Tel 49 1805 141538 Content 1 Preface 2 Introduction 2 1 Application scenarios 2 1 1 Campus coverage 2 1 2 Hotspot 2 1 3 Data transfer to mobile objects in industrial environments 2 1 4 Wireless link point to point 2 1 5 Wireless Distribution System point to multipoint 2 1 6 Wireless links in relay mode 2 2 Components of the wireless LAN system 2 2 1 access points and Wireless router 2 2 2 Power supply to the access point 2 2 3 External antennas 2 2 4 Lightning and surge protection equipment 3 Point to point connections 3 1 Geometric dimensioning 3 2 Antenna alignment 4 Lightning and surge protection 4 1 Where do lightning discharges come from 4 2 External lightning protection 4 3 Internal lightning protection 4 3 1 Selecting the lightning and surge protective components 4 3 2 Example applications
31. ith a fixed direction of polariza tion The polarization may be modified over the radio link by reflection and diffraction so that signals reach the receiver with differing polariza tion Polarization diversity antennas use two signals with polarization turned through 90 The two antenna signals result in genuinely impro ved performance with conventional diversity antennas since the stronger of the two signals can be used MIMO technology multiple input multiple output used in wireless LAN standard 802 11n goes a step further These multiple receivers and transmitters can use the horizontally and vertically polarized waves as independent transmission paths and thus transmit double the amount of data on one frequency Two antennas are connected to the access points main and auxiliary ports in order to receive both signals Note For further information on the subject of Polarization diversity anten nas antenna diversity refer to the LCOS reference manual 2 2 4 Lightning and surge protection equipment Besides the central components access point antenna and power supply the most important accessories in a wireless LAN system are those for light ning and power surge protection Lightning and other electrostatic occur rences in the atmosphere can impinge on the wireless LAN system in different ways and cause harm to people machines and equipment The li ghtning and surge protection components guard against the effects of elec
32. ll times WLAN Outdoor Guide 8 Release 07 08 Introduction 2 1 Application scenarios G y a F m ie 2 1 4 Wireless link point to point Whereas the scenarios discussed so far have involved connecting multiple WLAN clients to one access point point to multipoint outdoor wireless LAN systems are particularly advantageous for providing a link between two access points point to point By setting up a wireless link between two access points a distant production building on extensive company premises can be very easily integrated into the company network for example ANTENNA ANTENNA ACCESS POINT A point to point connection can also be used in difficult ter rain such as mountainous areas or islands to provide Internet access in areas where cab ling would be too expensive With a good line of sight between the two access points distances of several kilometers can be bridged by this type of wireless link WLAN Outdoor Guide Release 07 08 9 Introduction 2 1 Application scenarios FR TENG 2 1 5 Wireless Distribution System point to multipoint A special type of wireless link is the connection of several distributed access points to a central point the point to multipoint wireless LAN P2MP is also referred to as a Wireless Distribution System WDS This mode of operation allows for example several buildings on a company s premises to be connec ted to the central administrative building The
33. n direction If this line reaches the outer limit of the ideal radiation sphere then the maxi mum antenna power is radiated in this direction The closer the bold line co mes to the center of the sphere the lower the radiation emitted in that direc tion is These radiation characteristics are generally transferred onto paper for con venience The horizontal radiation characteristics may appear for example as follows We can see that power in the horizontal direction is strongest directly in front of the antenna 0 Within the beam angle shown here power levels are down to just half of the maximum power This angle is delimited by the points where the power line intersects the 3dB line which defines a reduction in po wer by 50 The other lines indicate a drop from maximum power by 6 dB 10 dB and 20 dB The angle between the two directions where power drops to just 50 of the maximum is referred to as the 3dB angle or the half power width WLAN Outdoor Guide 42 Release 07 08 Appendix 6 1 Antenna gain EIRP and antenna radiation For many applications this angle describes the antenna beam width that can be used in practice Because this 3 dB angle can differ greatly between the horizontal and vertical planes these are stated separately in the technical specifications for an antenna If just one angle is stated then generally spea king the angles in the two planes will be the same Note The radiation charact
34. ng of the lightning rod The lightning rod must be able to conduct the complete charge of a lightning strike For this reason it is important to select rods made from highly conduc tive metals for example copper alloys or steel It is important to select rods with a cross section that allows the lightning charge to be conducted without being damaged in general a diameter of between 10 and 16 mm 5 4 2 Distance to the components at risk The height and the safety clearance of the lightning rod to the equipment to be protected e g antenna are used to dimension the lightning rods for a sufficiently large spatial shield Rg Spatial shield eis a Protective angle 45 Antenna ko s m i _ Lightning rod e bad ne lt Conductor Grounding WLAN Outdoor Guide 38 Release 07 08 Installation 5 4 Mounting the lightning rods Distance of the lightning rods from the antenna Positioning the lightning rod a sufficient distance away from the antenna prevents the conducted lightning charge from flashing over to the antenna or other conductive components This distance can be calculated exactly on the basis of se veral factors However in practice a safety clearance of more than 100 cm is generally sufficient Note The distance between lightning rod and antenna has a direct influence on the grounding required by the components Please observe the advice about grounding the lightning rods and grounding the antennas and a
35. ntation with no need for functions such as TPC or DFS gt Widespread wireless LAN client base gt Disadvantages of the 2 4 GHz band Frequency band is also used by Bluetooth microwave ovens etc i e prone to interference gt There are only three non overlapping channels meaning that only three networks can be operated in parallel without interference Advantages of the 5 GHz band The frequency band is not heavily used so that interference from other applications is uncommon 19 non overlapping channels i e several parallel networks can be operated without interference WLAN Outdoor Guide Release 07 08 45 Appendix 6 2 Selecting the frequency band High ranges due to power levels of up to 1000 mW Disadvantages of the 5 GHz band Regulations in Europe demand techniques such as DFS for channel selection and TPC for power control Small wireless LAN client base Note In general we can assume that WLAN systems based on the 2 4 GHz band are best suited to applications where WLAN clients need short range connection to an access point campus coverage hotspots data transfer to mobile objects The advantages of the 5 GHz band lie mainly with point to point systems whereby two access points are connected by a wireless link over longer distances 6 2 2 Special regulations for the 5 GHz band With the 802 11h enhancement of September 2003 the private use of the 5 GHz band was finally possible even outside closed
36. od and antenna or other conductive element of the wireless LAN system is more than 50 cm but less than 100 cm Internal lightning protection Surge protection adapter BAT surge arrestor When Always required Also protects against partial discharges that can damage sensitive wireless LAN modules when there is no direct lightningstrike Where Position as near as possible to antenna connector on the access point Conductor Potential equalization via the building s grounding sy stem using a PE line protective earth 1 5 mm Cu LAN surge adapter When Required to protect LAN cabling and equipment Where As near as possible to the access point s ETH connector Conductor Potential equalization via the building s grounding sy stem using a PE line protective earth 1 5 mm Cu WLAN Outdoor Guide 28 Release 07 08 Lightning and surge protection 4 3 Internal lightning protection 4 3 2 Example applications Depending on where the access points antennas and lightning rods are po sitioned there are numerous combinations of lightning and surge protective equipment The following illustrations show some sample scenarios that are frequently found in practice With this knowledge you will be able to put toge ther the components required for other constellations WLAN Outdoor Guide Release 07 08 29 Lightning and surge protection 4 3 Internal lightning protection E Scenario 1 Antenna in an unexposed place B
37. onnected electronic equipment such as access points unless protective measures are taken Danger Even when there are no visible phenomena such as thunderstorms or a direct lightning strike invisible electrical discharges from the at mosphere can still occur that can lead to sensitive wireless LAN modules or other electronic devices being destroyed or damaged Risks to antennas Antennas for wireless LAN systems are at particular risk from lightning strike as they tend to be mounted in exposed positions and they are designed to be very good electrical conductors The more pointed needle shaped and exposed antennas are the greater the danger posed by a conductive discharge that could result in a direct light ning strike or partial discharge WLAN Outdoor Guide Release 07 08 23 Lightning and surge protection 4 2 External lightning protection Caution Please note that the explanations of lightning protection in this documentation only refer to protection for wireless LAN systems The protection of the buildings themselves and other equipment and asso ciated networks LANs must be installed and planned separately if ne cessary 4 2 External lightning protection External lightning protection includes all measures intended to prevent a di rect lightning strike in the equipment to be protected This includes for example arrester equipment such as lightning rods etc which intentional ly offer an exposed point for electrical
38. outers access points and antennas is available from the corresponding user manual Danger Protecting the components employed from the consequences of lightning strikes and other electrostatic influences is one of the most im portant aspects to be considered when designing and installing wireless LAN systems for outdoor use Please refer to the appropriate notes in Chapter Lightning and surge protection as otherwise Hirschmann cannot provide any guarantee for damage to BAT components The reference manual can be found on the product CD as an Acrobat PDF document It is designed as a supplement to the user manual and goes into detail on topics that apply to a variety of models Danger Safety notices safety notices concerning the mounting and instal lation of wireless LAN system components are to be found at relevant lo cations in the following chapters This documentation was created by several members of our staff from a variety of departments in order to en sure you the best possible support when using your BAT product In case you encounter any errors or just want to issue critics enhancements please do not hesitate to send an email directly to info hirschmann com WLAN Outdoor Guide Release 07 08 5 Preface Note Our online services www hirschmann com are available to you around the clock should you have any queries regarding the topics discussed in this manual or require any further support The
39. reless LAN networks SSIDs or wireless links P2P whereas Wireless routers also provide full router functionality including a WAN interface and further optional functions such as VPN etc Along with classification into access points and Wireless routers the follo wing characteristics are also important when considering the use of wireless LAN devices WLAN Outdoor Guide Release 07 08 11 Introduction 2 2 Components of the wireless LAN system Environmental conditions The various models may be suitable for opera tion in an office environment only or alternatively for tougher conditions such as those found in logistics warehouses A third group has been de signed for operation under extreme weather conditions i e water resi stant and some are for operation in extreme temperatures Standards supported Depending on model type the access points sup port the following standards IEEE 802 11a 5 GHz band IEEE 802 11b or IEEE 802 11g 2 4 GHz band or IEEE 802 11n 2 4 and 5 GHz bands While the 5 GHz band is highly suited to directional radio links due to the higher performance models in the 2 4 GHz band are more sui table for connecting mobile clients Note Please refer to the appendix in this manual for more information on the frequency bands and their permitted use in different countries Number of wireless LAN modules Devices can be fitted with two wireless LAN modules and used as relays for directional radio links over di
40. s E d 0 0147 i e at a distance of 8 km this is almost 1m Example With a distance of 8 km between the antennae the result in the 2 4 GHz band is a mast height above the level of the highest obstruction of approx 13 m in the 5 GHz band 9 m E Antenna power The power of the antennas must be high enough to ensure acceptable data transfer rates On the other hand the country specific legal regulations re garding maximum transmission power should not be exceeded WLAN Outdoor Guide 18 Release 07 08 Point to point connections 3 2 Antenna alignment The calculation of effective power considers everything from the radio modu le in the transmitting access point to the radio module in the receiving access point In between there are attenuating elements such as the cable plug con nections or simply the air transmitting the signals and amplifying elements such as the external antennas Amplification with antenna Free space loss Amplification with antenna Loss through cable Loss through ca plugs and lightning ble plugs and light protection ning protection Output power of the ra Input signal at the ra dio module dio module 3 2 Antenna alignment The precise alignment of the antennas is of considerable importance in esta blishing P2P connections The more central the receiving antenna is located in the ideal line of the transmitting antenna the better are the actual perfor mance and the effective bandwidth
41. s and the groun ding system should only be installed by experienced electricians who are familiar with local conditions and any legal regulations which apply Fur thermore please observe the notices in section Surge and lightning protection and ensure that the grounding system meets requirements 5 2 Mounting the access points The method for mounting the access point depends on the model s design This section presents the various mounting types as illustrated by examples Please refer to the documentation of the relevant access point for more pre cise instructions Caution Please observe the following advice during installation access points installed outside may only be protected from direct lightning strikes with a lightning rod with a safety clearance of more than 100 cm access points installed outside must be grounded with an adequa tely dimensioned potential equalization line PEL with a cross sec tion of at least 16 mm CU The BAT surge arrestor must be used to protect sensitive wireless LAN modules 5 2 1 Selecting where to mount Before mounting any access points a suitable location should be found that meets the following conditions The access points and antennas should not be covered up in order to avo id interference or overheating etc during transmission and reception Choose a location that is as close as possible to the necessary connec tions such as LAN interfaces or power sockets Position th
42. sed a maximum 1000 mW EIRP is permitted as the transmission power compared with 100 mW for 802 11 b g 2 4 GHz DFS and TPC are not possible here The higher maximum trans mission power not only compensates for the higher attenuation of 5 GHz radio waves in air it also makes significantly longer ranges possible than in the 2 4 GHz range Available channels in the 5 GHz band In the available frequency range of 5 13 to 5 805 GHz up to 19 channels are available in Europe divided into frequency ranges for which different condi tions of use may apply 5150 5350 MHz channels 36 40 44 and 48 5250 5350 MHz channels 52 56 60 and 64 5470 5725 MHz channels 100 104 108 112 116 120 124 128 132 136 and 140 Band 3 5725 5875 MHz channels 147 151 155 and 167 WLAN Outdoor Guide Release 07 08 47 Appendix 6 2 Selecting the frequency band The following overview shows which channels may be used in the different regions Note Note Please note that the frequency ranges and radio channels in band 3 are subject to certain restrictions depending on country e g in Germany only permitted for public Broadband Fixed Wireless Access communications providers WLAN Outdoor Guide 4 8 Release 07 08 Appendix 6 2 Selecting the frequency band Frequency ranges for indoor outdoor use in the 5 GHz band The use of the methods described in ETSI 301 893 for reducing mutual inter ference in the 5 GHz band
43. stances that exceed the range of a single P2P connection 2 2 2 Power supply to the access point An alternative to supplying power to an access point via its own internal po wer adapter is to use Power over Ethernet PoE PoE capable network de vices can be neatly provided with power over LAN cabling A power supply for each access point is therefore not necessary significantly reducing the ef fort of installation Power is fed into the LAN at a central location by using a PoE injector a po wer hub or power switch It is important that all eight wires are connected in the LAN cabling Caution PoE injectors available on the market support different stan dards and technical specifications depending on the model Please ensu re that the PoE injector is suitable for the access point being used 2 2 3 External antennas Most BAT access points are supplied with an antenna However for many of the outdoor applications relevant to this documentation additional external antennas are necessary to meet the specialized demands The following sections contain a brief description of the different types of antenna Note Please refer to the appendix in this manual for more information on the typical antenna characteristics of antenna gain EIRP and radiation pat terns WLAN Outdoor Guide 12 Release 07 08 Introduction 2 2 Components of the wireless LAN system gt Omnidirectional antennas transmit horizontally with equal power in all
44. ted to the access point s main and auxiliary ports in order to receive both signals Note Weitere Informationen zum Thema Polarization diversity antennas antenna diversity finden Sie im LCOS Referenzhandbuch Polarization diversity with access points in accordance with IEEE 802 11n access points according to IEEE 802 11n make use of MIMO technology multiple input multiple output to transmit data With this method several antennas are used to transmit and receive data simultaneously WLAN Outdoor Guide 44 Release 07 08 Appendix 6 2 Selecting the frequency band For point to point connections with appropriate access points and anten nas it thus is possible to realize two parallel data connections between transmitter and receiver A dual slant antenna is connected to two antenna sockets on the access point One connection is then transmitted with horizontal polarization while the other is transmitted with vertical polarization Combining the two connections allows significantly higher data transfer rates to be achieved than with previous wireless LAN stan dards H WLAN 802 11n DUAL SLANT DUAL SLANT WLAN 802 11n 6 2 Selecting the frequency band O 6 2 1 2 4 or 5 GHz band One of the first steps in the planning of a wireless LAN system is to determine which frequency band is to be used The following aspects are helpful for de cision making Advantages of the 2 4 GHz band gt Simple technical impleme
45. ting from the public power supply must be planned and implemented by a specialist electrician ACCESS POINT WLAN Outdoor Guide Release 07 08 25 Lightning and surge protection 4 3 Internal lightning protection The central component for internal lightning protection is the BAT surge arrestor surge adapter The employment of the BAT surge arrestor is essen tial under all circumstances despite outer lightning protection measures partial discharges can still give rise to surges that can damage sensitive WLAN modules The BAT surge arrestor is always mounted between the access point and the antenna preferably as near as possible to the antenna If the access point is installed outside its grounding and that of the BAT surge arrestor are con nected with the antenna s conductor for example via the clamps on the an tenna s mounting In addition to this an LAN surge adapter can also be used to reduce possible surges in the ethernet or PoE cable 4 3 1 Selecting the lightning and surge protective components E Classification of surge protective devices So called surge protective devices SPDs are used to protect electrical and electronic devices in buildings These are divided into various categories de pending on the purpose of their application WLAN Outdoor Guide 26 Release 07 08 Lightning and surge protection 4 3 Internal lightning protection Buildings The biggest danger from the effects of lightning strikes lies in
46. ts Caution Please note that in addition to implementing lightning protec tion for wireless LAN systems protection must be separately planned and installed for the building itself and for other equipment The following considerations are intended to assist with planning the com ponents to use External lightning protection Lightning rod When Required if the antenna or any other element of the wireless LAN system is mounted in an exposed position Where At least 50 cm safety clearance to the antenna or other con ductive element of the wireless LAN system and preferably more than 100 cm Conductor Grounding via potential equalization line PEL 16 mm Cu is always required WLAN Outdoor Guide Release 07 08 27 Lightning and surge protection 4 3 Internal lightning protection Danger If the safety clearance is less than 100 cm the grounding of the li ghtning rod must be connected with the grounding of the antenna Antenna potential equalization Separate conductor Via separate potential equalization line PEL 16 mm Cu if there is no lightning rod present antenna not installed in an exposed position Separate conductor Via separate potential equalization cable 16 mm Cu if the safety clearance between the the lightning and the antenna is more than 100 cm Via lightning rod conductor Grounding via the existing potential equalization cable of the lightning rod when the safety clearance bet ween lightning r
47. um I Which access point is to be reached 7 IV Are both antennas approximately aligned me me Initially only one of the two antennas should be adjusted until a maximum va lue is achieved This first antenna is then fixed and the second antenna is then adjusted to attain the best signal quality WLAN Outdoor Guide Release 07 08 21 Lightning and surge protectioh 1 Where do lightning discharges come from 4 Lightning and surge protection 4 1 Where do lightning discharges come from Lightning flashes are electromagnetic discharges that are caused by diffe rences in electric potential Water particles are charged through friction when there is weather movement in the atmosphere The predominantly positively charged particles rise upwards while the negatively charged particles tend to remain at the lower levels This uneven distribution of electrical charge can cause discharges within the clouds that can be observed as cloud to cloud lightning Leader lightning i Lightning discharge Conductive discharge t t 4 4 t t As the earth is predominantly positively charged a difference between the potential of the cloud and the earth arises As soon as this potential diffe rence is large enough leader lightning descends earthwards WLAN Outdoor Guide 22 Release 07 08 Lightning and surge protectiof 1 Where do lightning discharges come from Direct lightning strike The most frequent type of l
48. uni versities to provide students and staff with network access 7 F l WLAN Outdoor Guide Release 07 08 7 Introduction 2 1 Application scenarios 2 1 2 Hotspot A hotspot is a special variant of the campus coverage described above Whe reas campus coverage provides the members of a closed user group with ac cess to a network that includes all the necessary services often at no charge a hotspot provides network access generally restricted to Internet only to wireless LAN clients at a fee In addition to the differences in access point configuration setting up a hotspot requires authentication authorizati on and accounting AAA functions such as those provided by e g Public Spot options Hotspots are generally set up at public locations where people have a short term need to access the Internet such as at airports caf s or hotels l z INTERNET 2 1 3 Data transfer to mobile objects in industrial environments Completely new applications allow wireless LAN systems in industrial envi ronments to transmit data to mobile objects In logistics for example this means that fork lift trucks can stay continuously connected to the company network via the wireless LAN In combination with mobile barcode scanners inventory movements within a warehouse can be monitored in real time and passed on to an ERP system which then provides all employees with up to the minute information on current inventories at a
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