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Wireless communication - An overview

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wireless overview

  1. 1. Wireless Communication – An overview Aniruddha Chandra ECE Department, NIT Durgapur aniruddha.chandra@ieee.orgECE, NIT Durgapur A. Chandra Wireless - Overview
  2. 2. OutlineWireless Communication – General overviewChallenges in Wireless CommunicationFuture trends and Research areasECE, NIT Durgapur A. Chandra Wireless - Overview
  3. 3. Wireless Communication – General overview Why Wireless? Evolution of Standards Network & Technologies World Statistics India StatisticsChallenges in Wireless CommunicationFuture trends and Research areasECE, NIT Durgapur A. Chandra Wireless - Overview
  4. 4. Why Wireless?•Mobility – Phone for people not for places.•Easy Installation – Rapid deployment,reconfigurable.•Cost Savings – No cable, easy maintenance.•Digital Companion – Voice, message,internet, multimedia. ECE, NIT Durgapur A. Chandra Wireless - Overview
  5. 5. Evolution of Standards• Telegraph 1837 2G 2.5G 3G• Telephone 1876 CDMA 2000 (EV-DV, W-CDMA• Radio Comm 1894 EV-DO) UMTS 2 Mbps 2 Mbps• AM comm radio 1920 CDMA Evolution Path• FM comm radio 1936 EDGE• Mobile Telephone 1940 IS-95B 384 kbps 64 kbps• Cellular mobile 1974 GPRS GSM Evolution• Path Digital Cellular 1991 IS-95A 54 kbps 14.4 kbps• Satellite mobile 1998 GSM, PDC, IS-95 IS-136• 3G cellular 2002 9.6 kbps 9.6 kbps• 4G (expected) 2010 ECE, NIT Durgapur A. Chandra Wireless - Overview
  6. 6. Network & Technologies 2G,2.5G,3GECE, NIT Durgapur A. Chandra Wireless - Overview
  7. 7. World Statistics•20 billion GSMSubscribers•3 billion CDMASubscribers.*March ’06 statistics ( Source www.cdg.org and www.gsmworld.com) ECE, NIT Durgapur A. Chandra Wireless - Overview
  8. 8. India Statistics Company No of % Market Subscribers Share (In million) Bharti 19.57 28.30% BSNL 17.16 24.80% Hutch 15.36 22.20% IDEA 7.37 10.65% Aircel 2.61 3.77% Reliance 1.90 2.75% Spice 1.93 2.79% MTNL 1.94 2.81% BPL 1.34 1.93% Total 69.19 100%GSM subscriber in March’06 (*Source COAI) ECE, NIT Durgapur A. Chandra Wireless - Overview
  9. 9. India Statistics Company No of % Market Subscribers Share (In million) Reliance 15.407 75.72% Tata 23.84% 4.851 HFCL 0.062 0.30% Shyam 0.027 0.13% Total 20.348 100%CDMA subscriber in March’06 (*Source COAI) ECE, NIT Durgapur A. Chandra Wireless - Overview
  10. 10. India Statistics•3.6 million jobs generated directly or indirectly•145billion per annum generated by Mobile industryfor the Govt.•The mobile services industry generates an annualGDP contribution of Rs. 313 billion•1% increase in teledensity →3% increase in rate ofgrowth of GDP ECE, NIT Durgapur A. Chandra Wireless - Overview
  11. 11. India Statistics•Poised to cross 200 millionsubscribers by 2007•Catching up fast with China(282 million – Feb’06) “It is dangerous to put limits on wireless” - Marconi (1932). ECE, NIT Durgapur A. Chandra Wireless - Overview
  12. 12. Wireless Communication – General overviewChallenges in Wireless Communication Wireless Channel Standardization Network Planning Other IssuesFuture trends and Research areasECE, NIT Durgapur A. Chandra Wireless - Overview
  13. 13. Wireless Channel•Limited Power (Size, Weight, Battery Constraints)•Limited BW (Spectrum allocation)•Deep Fading (mainly due to Multipath)•Time Variance of the Channel Multipath•Path Loss (up to 10 dB/km) t0 Time Variance t0+τ1 t0+τ2 ECE, NIT Durgapur A. Chandra Wireless - Overview
  14. 14. Standardization•Backward Compatibility•Interoperability•Integration of Voice & Data Network•Frequency Allocation•Tariff Planning ECE, NIT Durgapur A. Chandra Wireless - Overview
  15. 15. Network Planning•Terrain Survey – Shadow zone, Antenna height & size.•Radio Interference – CCI, ACI, ISI, FDD.•Power Control – Cost, Interference, Security, Safety, BW.•Frequency Reuse•Handoff ECE, NIT Durgapur A. Chandra Wireless - Overview
  16. 16. Other Issues•Network Security•Health Risks Temperature variation inside head due to cell phone use•Social & Economic Issues Change of input characteristics of handset antenna due to hand ECE, NIT Durgapur A. Chandra Wireless - Overview
  17. 17. Wireless Communication – General overviewChallenges in Wireless CommunicationFuture trends and Research areas UWB OFDM MIMO Future???ECE, NIT Durgapur A. Chandra Wireless - Overview
  18. 18. UWB - Introduction•Ultra Wide Band – message sent through narrow pulses that are widely separated in time. Power (Watt/ MHz) 102 101 100 2G•Bandwidth(>1GHz) – bandwidth 10-1 3G, WLAN 10-2 at -10dB points of spectrum exceeds 25% of 10-3 10-4 10-5 UWB center frequency. 10-6 BW 10k 100k 1M 10M 100M 1G 10G (Hz)•Impulse Radio – UWB technology Amp 1 using Gaussian monocycle. t   t  2  v( t ) = A exp− 6π   -1 0 1 t/τ τ   τ  -1 Pulse width(τ) ~ 0.2 to 1.5 nano sec. Gaussian Monocycle ECE, NIT Durgapur A. Chandra Wireless - Overview
  19. 19. UWB - Advantages•Data Transmission – Pulse Reference ‘0’ ‘1’ ‘1’ ‘0’ Position Modulation, 0 ~ pulse transmitted early (-TC). 1 ~ pulse transmitted late (+TC). TP TP -Tc +Tc•Data Rate – from 1Mbps (T =1000 ns) to P40Mbps (TP=25 ns).•Baseband Processing – no up/downconversion, simple design for transmitter andreceiver.•Mitigating Multipath – echocancellation during no transmission period. ECE, NIT Durgapur A. Chandra Wireless - Overview
  20. 20. UWB - ApplicationsUWB is most suitable for•High data rate•Short range low power (Indoor)•High clutter (severe multipath) applications. UWB HDTV and digital media server by Haier Corp. and Freescale Semiconductor ECE, NIT Durgapur A. Chandra Wireless - Overview
  21. 21. OFDM - Introduction•Multi-carrier modulation -Available bandwidth isdivided into several narrow bands and one carrier is used in each W fnarrow band.Serial data stream is divided in N parallel data streams and each 1 2 3 N-1 Nis transmitted on a separate band. W/N f•Orthogonal Carriers - The sub-carrier frequenciesoccupies the zero crossing spectra of other sub-carriers. ECE, NIT Durgapur A. Chandra Wireless - Overview
  22. 22. OFDM - Technology Cyclic Prefix Interleaving Converter Mapping Serial to Coding Parallel D/A converter IFFT LNA/HPA Antenna Convolutional/ BPSK/ QPSK/ 16 Pilot Insertion Reed Solomon QAM/ 64 QAM Zero Padding•Fast serial data stream is transformed into slow parallel data streams - Longer symbol durations.•Symbols are transmitted on different subcarriers – IFFT/FFT pair.•Guard time/ Cyclic Prefix is inserted between consecutive OFDM symbolsECE, NIT Durgapur A. Chandra Wireless - Overview
  23. 23. OFDM - Advantages• Efficient spectrum utilization - Available bandwidth is divided intoseveral narrow bands and the data is transmitted in parallel on these narrow bands.•Combating ISI - Cyclic prefixing CP ISIremoves ISI from previous symbol. CP•Robustness to fading - A frequency selective channel appears as flat inthe narrow bandwidth of sub-carrier.•Right in track - Development in Digital Signal Processing simplifies thegeneration of OFDM signals. ECE, NIT Durgapur A. Chandra Wireless - Overview
  24. 24. OFDM - Challenges•Much more sensitive to synchronization errors thansingle-carrier systems - Synchronization of symbol duration and carrierfrequency is highly essential to maintain orthogonality among the sub-carriers•High peak to average power ratio - OFDM signals have highPeak to Average Power Ratio (PAPR) which leads to Out Of Band (OOB) distortion.Also it requires amplifiers with very high linear characteristics to avoid OOB distortion.•Wastage of bandwidth in cyclic prefix. ECE, NIT Durgapur A. Chandra Wireless - Overview
  25. 25. OFDM - Applications•Used for wideband communication over mobile FM channels.•Asynchronous Digital Subscriber Line (ADSL), High speed DSL, Very high speed DSLuse OFDM for transmission of high rate data.•Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB).•IEEE 802.11a and IEEE 802.11g wireless Local Area Network (WLAN) uses OFDM forsupporting high bit rate.•European Telecommunications Standard Institute’s proposed HIPERLAN2 includesOFDM.•IEEE 802.16 Wireless MAN technology also proposes to use OFDM.•Some authors have also advocated use of OFDM in mobile Ad Hoc networks.ECE, NIT Durgapur A. Chandra Wireless - Overview
  26. 26. MIMOEvolution of Smart Antenna Technologies SISO•Diversity•Beamforming SIMO•Space Division Multiple Access (SDMA)•Multiple Input Multiple Output (MIMO) MISO Transmitter Receiver MIMO ECE, NIT Durgapur A. Chandra Wireless - Overview
  27. 27. MIMO•Why MIMO?  S C = B log 1 +   NTo increase capacity one have to increase signal power exponentially.•With MIMO Capacity increases N fold compared toSISO systems  N t → No. of Transmitters N ≤ min ( N t , N r )   N r → No. of Receivers•MIMO vs. DiversityIn Diversity system same message is sent over multiple channels to improve reliability.In MIMO systems different messages are sent to increase capacity. ECE, NIT Durgapur A. Chandra Wireless - Overview
  28. 28. MIMO - Technology h11 x1h11+x2h12 x1 h12 x1 H-1 h21 x1h21+x2h22 x2 h22 x2 Transmitter Receiver A 2x2 MIMO System •The basic Input-Output Relationship is Y=H.X or,  y1   h 11 h 12   x 1  For 2x2 MIMO system  y  = h  2   21 h 22   x 2    •Receiver has to find X using the relation X=H-1.Y •Considering Noise Y=H.X+N  y1   h 11 h 12   x 1   n 1  For 2x2 MIMO system  y  = h +  2   21 h 22   x 2  n 2     ECE, NIT Durgapur A. Chandra Wireless - Overview
  29. 29. MIMO - Applications•802.11n for WLAN•802.16 for WMAN•802.20 for MBWAMobile Broadband Wireless Access•3G/4G CellularMIMO-HSDPA for 3.5G (10Mbps)•Optical communication (Multi-modeFiber)•High density rewritable optical storage Worlds first laptop with MIMO WLAN technology - Samsung NT-X20 with Airgos True MIMO chip set (802.11a/b/g) ECE, NIT Durgapur A. Chandra Wireless - Overview
  30. 30. Future???•MIMO-OFDM•Turbo Codes•New/ Hybrid Technologies?•Cognitive Radio – Radio with Brain? Cognitive radios will have the ability of devices to determine their location, sense spectrum use by neighboring devices, change frequency, adjust output power, and even alter transmission parameters and characteristics. ECE, NIT Durgapur A. Chandra Wireless - Overview

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