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Wireless Local Loop (WLL) By: Panos Tzanos Vladimeros Vladimerou Derek Starr.

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Presentation on theme: "Wireless Local Loop (WLL) By: Panos Tzanos Vladimeros Vladimerou Derek Starr."— Presentation transcript:

1 Wireless Local Loop (WLL) By: Panos Tzanos Vladimeros Vladimerou Derek Starr

2 Presentation Outline What is WLL? What is WLL? Differences with mobile cellular systems Differences with mobile cellular systems –Why WLL? System Analysis System Analysis –examples The future of WLL The future of WLL

3 Definition What is WLL? What is WLL? - WLL is a system that connects subscribers to the local telephone station wirelessly. Systems WLL is based on: Systems WLL is based on: –Cellular –Satellite (specific and adjunct) –Microcellular Other names Other names –Radio In The Loop (RITL) –Fixed-Radio Access (FRA).

4 A general WLL setup

5 WLL services Desirable: Desirable: –Wireless feature should be transparent –Wireline Custom features Other: Other: –Business related »Hunt groups, »Call transfers »Conference calling –Calling cards, coin phones –V.29 (9600bps) –ISDN (64kbps)

6 WLL should provide… Toll-quality service Toll-quality service Expand from a central office to about 5 miles Expand from a central office to about 5 miles Low license cost Low license cost Subscriber costs equivalent or better than copper Subscriber costs equivalent or better than copper

7 Ideas for U.S. market Supplement Copper Lines Supplement Copper Lines –Easier third telephone line –Data service Fixed Mobile Users Fixed Mobile Users –Take phone wherever you want / charged on 2 levels –“home” could mean neighborhood –Charged regular mobile rate if you’re on the road

8 Cost Considerations Wireless cost is constant over distance for WLL Wireline depends on distance AND terrain

9 Situations “made” for WLL Environments where 3 rd line is degraded might be cheaper to go wireless Environments where 3 rd line is degraded might be cheaper to go wireless Where it’s impossible to lay copper (3 rd world, small islands) Where it’s impossible to lay copper (3 rd world, small islands) Business parks, industrial areas Business parks, industrial areas Speedy deployment, stop gap application till wireline is in Speedy deployment, stop gap application till wireline is in – days for activation

10 Developed vs. Developing Developed: Wireline service Developed: Wireline service –Firmly established, cellular penetration is relatively high –Incumbent operator would use it to install 2 nd, 3 rd lines, coverage to rural areas –2 nd or 3 rd competitive operator deploy it for fast & cost effective deployment –Quick way to establish market presence –cellular complement to their offerings

11 Developed vs. Developing Developing Developing –Quick & easy to deploy in countries with little copper line service, so as to accommodate people on enormous waiting lists for basic service –Low maintenance costs –Allows more competition in provider market

12 Examples UK UK –150 PTOs have licenses for wireless –Focus on regional networks –WLL Commercial services »Ionica, Atlantic Telecom, Scottish Telecom Poland Poland –Most exciting market in eastern Europe –Local loop is the bottleneck –150,000 WLL lines since 1996 (15% of new) –Ericsson, Motorola contracts

13 Connection Setup PSTN Switch function WLL Controller AM HLR Transceiver WASU Trunk Air Interface U WLL T WLL Wireless Access Network Unit(WANU) –Interface between underlying telephone network and wireless link –consists of Base Station Transceivers (BTS) Radio Controller(RPCU) Access Manager(AM) Home Location Register(HLR) WANU Wireless Access Subscriber Unit(WASU) Wireless Access Subscriber Unit(WASU) –located at the subscriber –translates wireless link into a traditional telephone connection

14 Important Results of Fixed to Fixed Propagation in WLLs Signal channel is not a Rayleigh fading channel: Signal channel is not a Rayleigh fading channel: –Power control algorithms are simpler and can be utilized more effectively Channel Randomness is lost: Channel Randomness is lost: –Makes analysis difficult Pathloss exponent is considerably smaller (Why?): Pathloss exponent is considerably smaller (Why?): –20dB/dec compared to 40dB/dec –Decreases cell capacity –Allows for larger coverage area

15 Fixed to Fixed Propagation(cont’d) No handoffs necessary: No handoffs necessary: –Decreases hardware costs and system complexity –Increases quality of service through accurate traffic predictions Allows usage of directional antennas: Allows usage of directional antennas: –Can greatly reduce interference and increase cell capacity -30dB 30dB 0o0o 60 o -40dB 10dB 0o0o 120 o 180 o BS antennaSubscriber antenna

16 In-Cell Interference (CDMA) I = (N h – 1)  S  N h  S I = (N h – 1)  S  N h  S  voice activity factor  h = total # of houses S = power received at cell site from every house

17 Out-of-Cell Interference Pathloss: 20dB/dec as opposed to 40dB/dec Pathloss: 20dB/dec as opposed to 40dB/dec  need to take in account more tiers Only from houses whose antennas are directed at the center cell base station Only from houses whose antennas are directed at the center cell base station

18 Interference from Another Cell Blue area is region of interferers for C Blue area is region of interferers for C It is Not a perfect pie shape It is Not a perfect pie shape If w = (1/2)*(antenna width) If w = (1/2)*(antenna width) (in radians) (in radians) W = w+2sin -1 ((R/D)sin(w/2)) W = w+2sin -1 ((R/D)sin(w/2)) If w<<1 and R<

19 Per-Tier Interference Integration over W and all the cells at tier n yields: Integration over W and all the cells at tier n yields: I n = [  N h Sw/(3sqrt(3))][1/n] for n>4 Interference is proportional to antenna width w and inversely proportional to the tier number. Interference is proportional to antenna width w and inversely proportional to the tier number. Decreasing the antenna width can greatly reduce interference. Decreasing the antenna width can greatly reduce interference. As the number of tiers approaches infinity, so does the total interference. Therefore, system capacity is a function of the total number of tiers in the system. As the number of tiers approaches infinity, so does the total interference. Therefore, system capacity is a function of the total number of tiers in the system.

20 Capacity comparison for 5 MHz spectrum allocation Detail IS-95 CDMA IS-136 TDMA ETSI (GSM) MobileWLLMobileWLLMobileWLL Chan. BW (kHz) # channels E b /N 0 7 dB 6dB18dB14dB12dB12dB Freq. Reuse Effective Chan. Per sect Erlangs per cell Per MHz

21 Comparison WLL Mobile Wireless Wireline Good LOS component Mainly diffuse components No diffuse components Rician fading Rayleigh fading No fading Narrowbeam directed antennas Omnidirectional antennas Expensive wires High Channel reuse Less Channel reuse Reuse Limited by wiring Simple design, constant channel Expensive DSPs, power control Expensive to build and maintain Low in-premises mobility only, easy access High mobility allowed, easy access Low in-premises mobility, wiring of distant areas cumbersome Weather conditions effects Not very reliable Very reliable

22 Examples of services provided Marconi WipLL (wireless IP local loop) Marconi WipLL (wireless IP local loop) –Based on Frequency hopping CDMA –Internet Protocol 64kbps to 2.4Mbps rates Committed Information Rate or best effort service Lucent WSS (wireless subscriber system) Lucent WSS (wireless subscriber system) –800 to 5000 subscribers per switch –Uses FDMA/FDD 12 Km to 40Km coverage GoodWin WLL GoodWin WLL –DECT standards –9.6 kbps rate –Specified conditions -5°С...+55°С, % humidity

23 Future of WLL / Overview Depends on Depends on –economic development –existing infrastructure of a region Offers Offers –market competition –quick deployment –relatively reliable service at low costs

24 Forecasts 800M projected new lines by M in developing countries

25 Questions ? Basie station

26 References

27 References (DECT standard)

28 References Wideband CDMA personal communications system featuring IDSN compatibility Reed Fisher, Henri Suyderhoud, Toshiro Kato, Atushi Fukasawa and Takuro Sato ©1997 IEEE Performance Analysis of WCDMA WLL Protocol Seong Won Shum, Sang Hwan Lee, Minsoo Suk, Hang Gu Bahk Hyundai Electronics ICCT’98 Beijing, China Capacity of a Wireless Local Loop Network based on GSM Thomas Klingenbrunn, Preben Mogensen Center for Person Kommukation, Aalborg University © 1998 IEEE Network Management Applications for wireless local loop Jelena Vucetic Paul Kline Dynamic Telecomminications, Inc. 1998

29 Implementation of code acquisition and code tracking loop for CDMA wireless local loop system Jae-Wook Chung, Jin-Su Kim, Young-Gyun Jeong, Jeong-Suk Ha Electronics and Telecommincations Research Institute, Yusong, Taejon, Korea ©1998 IEEE Implementation of Base Station Receiver for CDMA Wireless Local Loop System Jae W. Chung, Jin S. Kim, Y. G. Jeong, J. S. Ha Electronics and Telecommincations Research Institute, Yusong, Taejon, Korea ©1997 IEEE Wireless Local Loop – Propagation Environment Measurements and analysis Levin M., Katz E., Gil A., Freedman A., Matityahu I., Dilmon D. Wireless Systems Tadiran Telecommunications, Israel 1996 IEEE Issues and challenges of implementing a wireless local loop based telephone access network T.Minero, T. Babji NEC cororation, JAPAN © 1997 IEEE References

30 Wireless local loop: why the slow take up? Andrian May, Electronics Communication Engineering Journal 1998 A Wideband CDMA based Wireless Local Loop Protocol Mehmet Ulema and Young Ki Yoon Daewoo Telecom R&D Center © 1999 IEEE An Implementation of Wireless Local Loop fixed Station Sang Sik Lim, Mobile Telecommunication Division Electronics and Telecommunications Research Institute, Taejon, Korea © 1998 IEEE A comparison of wireless local loop with competing access technologies W. Webb, Electronics & Communication Engineering Journal 1998 Estimate of Uplink in Overlaid Macrocell/Multi-Microcell CDMA WLL Systems J. S. Roh, S. Y. Kim, S. J. Cho, S. C. Son, S. E. Cho H. J. Kang References

31 References Wireless Local Loop Made For the USA? David Kopf, Peter Meade, America’s Network November 1996 The Performance of DS-CDMA For Wireless Local Loop Q. Bi, D.R. Pulley 1996 IEEE Wireless Local Loop: Architecture, Technologies and Services Anthony R. Noeprel, Hughes Network Systems, Yi-Bing Lin CSIE/NCTU 1998 IEEE


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