WiMAX :Taking Wireless To The Max!

1. 8/9/2007 2. Contents <ul><li>Introduction to WiMAX </li></ul><ul><li>Objectives of WiMAX…
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  • 1. 8/9/2007
  • 2. Contents <ul><li>Introduction to WiMAX </li></ul><ul><li>Objectives of WiMAX </li></ul><ul><li>IEEE Wireless Standards </li></ul><ul><li>Features in WiMAX </li></ul><ul><li>Usage Scenario for WiMAX in Public and Private Networks </li></ul><ul><li>WiMAX Protocol Layers </li></ul><ul><li>WiMAX NLOS Coverage & Capacity </li></ul><ul><li>Vendors for WiMAX </li></ul><ul><li>Challenges for WiMAX </li></ul>8/9/2007
  • 3. WhyMAX <ul><li>Ways of connecting to the Internet </li></ul><ul><li>Dial-Up access : through phone line </li></ul><ul><li>Broadband access : through DSL/Cable modem </li></ul><ul><li>Wi-Fi access : through Wi Fi router. </li></ul><ul><li>Limitations </li></ul><ul><li>Dial-Up access : slow speed, phone line is engaged while surfing the net. </li></ul><ul><li>Broadband access : expensive, less coverage </li></ul><ul><li>WiFi access : hot spots are small and sparse coverage. </li></ul><ul><li>Need an Access technology that provides : </li></ul><ul><li>High Speed like Broadband Access </li></ul><ul><li>Wireless and is less expensive than DSL/Cable modem. </li></ul><ul><li>Long Distance Coverage like Cell phone network rather than WiFi. </li></ul><ul><li>The solution is IEEE 802.16 standard : </li></ul><ul><li>WiMAX - Worldwide Interoperability for Microwave access </li></ul>8/9/2007
  • 4. Line-of-Sight (LOS) & Non-LOS type of service. <ul><li>WiMAX system consists of </li></ul><ul><li>Tower station - can provide coverage to a very large area up to 8,000 sqkm. </li></ul><ul><li>- connected to ISP through high bandwidth connectivity (example :T3) </li></ul><ul><li>- can connect to another tower through microwave link (backhaul). </li></ul><ul><li>- allows coverage of the remote areas. </li></ul><ul><li>Receiver station -The receiver and antenna could be in a outdoor unit. </li></ul><ul><li>Type of service : </li></ul><ul><li>LOS :- fixed dish antenna points to WiMAX tower. </li></ul><ul><li> - connection is stronger & stable hence more data throughput. </li></ul><ul><li>- less interference. </li></ul><ul><li>- higher frequency (66GHz) and bandwidth. </li></ul>8/9/2007 NLOS :-Small subscriber antenna connects to tower (WiFi type service) -Lower frequency range of operation (2-11GHz) -lower radio frequency transmission is unaffected by physical obstructions and are able to bend around the obstacles
  • 5. 8/9/2007 PAN LAN MAN WAN IEEE 802.15 Bluetooth ETSI HiperPAN IEEE 802.11 Wireless LAN ETSI HiperLAN IEEE 802.16 Wireless MAN ETSI HiperMAN IEEE 802.16 e IEEE 802.20 (proposed) 3GPP EDGE (GSM) Wireless Technologies – IEEE Standards IEEE 802.21 30 foot radius 300 foot radius 30 mile radius IEEE 802.15.4 ZigBEE
  • 6. 8/9/2007 Objectives of WiMAX Technology
  • 7. 8/9/2007 <ul><li>The most cost-effective solution for carriers to deploy for fixed /Mobile wireless applications </li></ul><ul><li>The WiMAX Forum to certify products for conformance and interoperability based on IEEE 802.16. </li></ul>Interoperability <ul><li>OFDM over single carrier modulation schemes deliver higher data throughput, with more than 1 Mbps downstream and even much higher data rates, even in NLOS. </li></ul><ul><li>Adaptive Modulation increase link reliability and the possibility to keep 64 QAM modulation at wider distance extend full capacity over longer distances . </li></ul>Higher Capacity <ul><li>Techniques for Improving NLOS coverage : a) Diversity (b) Space-Time coding (c )Automatic Retransmission Request (ARQ) </li></ul><ul><li>NLOS advantages are : </li></ul><ul><li>Coverage of wider area, </li></ul><ul><li>Better predictability of coverage </li></ul><ul><li>Lower cost means fewer base stations and backhaul </li></ul><ul><li>Simple RF planning </li></ul><ul><li>Shorter towers and </li></ul><ul><li>Faster CPE install times. </li></ul>Wider Coverage <ul><li>For short distance, CPEs indoor self-installable modems will be similar to cable or DSL and the base stations will be able to use the same chipsets developed for low-cost WiMAX access points. </li></ul><ul><li>Increased volume with higher-level integration of RF chipsets. </li></ul><ul><li>Modem chipsets for Fixed wireless Customer Premise Equipment (CPE) same as that used in PC. </li></ul>Low Cost Objectives of WiMAX…continued
  • 8. Objectives of WiMAX…continued 8/9/2007 <ul><li>Once the Subscriber Station is powered up, It identifies it self by determining the characteristics of the link with respect to the BS. </li></ul>Portability <ul><li>Conforms Multi-Service Level Agreement between Service Provider and End User. </li></ul><ul><li>One Service Provider can offer different SLAs to different subscribers or even to different users on the same Subscriber Station. </li></ul>Service Level Agreement (SLA) <ul><li>The Operator after obtaining the required license for the frequency bands can operate the system in no time. </li></ul>Quick Deployment <ul><li>IEEE 802.16e added key features to support mobility </li></ul><ul><li>Improvements in OFDM & OFDMA physical layers, MIMO and support for idle/sleep mode and hand off will allow full mobility up to 160Km/hr </li></ul>Mobility <ul><li>Supports Dynamic Optimization for the mix of traffic that is being carried. </li></ul><ul><li>Four types of scheduling services available are UGS, rtps,nrtps,BE. </li></ul>Quality of Service (QoS) <ul><li>Supports PTP,PTMP and Ubiquitous coverage </li></ul><ul><li>MAC layer supports PTMP by scheduling a time slot for each Subscriber Station </li></ul><ul><li>A Base Station in a PTP architecture may use narrow beam antenna for long distance coverage </li></ul>Flexible Architecture <ul><li>Supports AES (Advanced Encryption Standard) & 3DES (Triple Data Encryption Standard) </li></ul><ul><li>Provides Operator with strong protection against theft of service </li></ul><ul><li>Built in VLAN support gives protection for data transmitted by different users on the same BS. </li></ul>Higher Security
  • 9. IEEE 802.16 -- Introduction <ul><li>IEEE 802.16 (2001) </li></ul><ul><ul><li>Air Interface for Fixed Broadband Wireless Access System MAC and PHY Specifications for 10 – 66 GHZ (LoS) </li></ul></ul><ul><ul><li>One PHY: Single Carrier </li></ul></ul><ul><ul><li>Connection-oriented, TDM/TDMA MAC, QoS, Privacy </li></ul></ul><ul><li>IEEE 802.16a (January 2003) </li></ul><ul><ul><li>Amendment to 802.16, MAC Modifications and Additional PHY Specifications for 2 – 11 GHz (NLoS) </li></ul></ul><ul><ul><li>Three PHYs: OFDM, OFDMA, Single Carrier </li></ul></ul><ul><ul><li>Additional MAC functions: OFDM and OFDMA PHY support, Mesh topology support, ARQ </li></ul></ul><ul><li>IEEE 802.16d (July 2004) </li></ul><ul><ul><li>Combines both IEEE 802.16 and 802.16a </li></ul></ul><ul><ul><li>Some modifications to the MAC and PHY </li></ul></ul><ul><li>IEEE 802.16e (2005) </li></ul><ul><ul><li>Amendment to 802.16-2004 </li></ul></ul><ul><ul><li>MAC Modifications for limited mobility </li></ul></ul>8/9/2007
  • 10. IEEE 802.16 Introduction 8/9/2007 Different Flavors of WiMAX Source: WiMAX, making ubiquitous high-speed data services a reality, White Paper, Alcatel. 802.16a 802.16 REV d 802.16e Fixed Outdoor <ul><li>Applications </li></ul><ul><li>E1/T1 services for Enterprises </li></ul><ul><li>Backhaul for hotspots </li></ul><ul><li>Limited residential broadband access </li></ul><ul><li>CPE </li></ul><ul><li>External box connected to the PC with outside antenna </li></ul>Fixed Outdoor <ul><li>Applications </li></ul><ul><li>Indoor broadband access for residential users (High Speed Internet & VoIP,…) </li></ul><ul><li>CPE </li></ul><ul><li>External box connected to the PC with built-in antenna </li></ul>Limited Mobility <ul><li>Applications </li></ul><ul><li>Portable broadband access for consumers. </li></ul><ul><li>Always best connected </li></ul><ul><li>CPE </li></ul><ul><li>PC Card </li></ul>
  • 11. 8/9/2007 GSM Speed Mobility WiMAX WLAN UMTS HSDPA Competing Technologies for WiMAX Coverage QoS Mobility Data Rate Price per bit 0 1 0 3 2 4 5 Source: Samsung & Unstrung Insider WiMAX WLAN CELLULAR
  • 12. 8/9/2007 Cellular Network Evolution
  • 13. 8/9/2007 Cellular Network Evolution..Contnd Technology 1G 2G 2.5G 3G 4G Design Began 1970 1980 1985 1990 2000 Implementation 1984 1991 1999 2002 2010 Services Analog voice, synchronous data to 9.6 kbps Digital voice, Short messages Higher capacity, packetized data Higher capacity, Broadband data up to 2Mbps Higher capacity, completely IP oriented, multimedia data Standards AMPS, TACS, NMT, etc. TDMA, CDMA, GSM, PDC GPRS, EDGE, 1xRTT WCDMA, cmda2000 OFDM, UWB Data Bandwidth 1.9 kbps 14.4 kbps 384 kbps 2 Mbps 10 Mbps - 20 Mbps Multiplexing FDMA TDMA, CDMA TDMA, CDMA CDMA FDMA, TDMA, CDMA Core Network PSTN PSTN PSTN, Packet network Packet Network All-IP Networks
  • 14. 8/9/2007 Comparison of Cellular & WiMAX Technologies   Cellular WiMAX Metric EDGE HSDPA 1 X EVDO 802.16-2004 802.16E Technology Family & Modulation TDMA,GMSK & 8-PSK WCDMA(5MHz),QPSK,16QAM CDMA 2K QPSK & 16QAM OFDM/OFDMA QPSK, 16QAM & 64QAM Scalable OFDMA QPSK,16QAM& 64QAM Peak Data Rate 473Kbps 10.8 Mbps 2.4Mbps 75Mbps(20MHz channel); 18Mbps( 5MHz channel) 75Mbps (max) Average user throughput T-Put <130Kbps <750Kbps initially <140Kbps 1-3Mbps 80% performance of fixed usage model Range Outdoor (average cell) 2-10Km 2-10Km 2-10Km 2-10Km 2-7Km Channel BW 200KHz 5MHz 1.25MHz Scalable:1.5-20MHz Scalable:1.5-20MHz
  • 15. 8/9/2007 2-11GHz 10-66GHz 2.4GHz 5.8GHz 2.4GHz 2.46GHz Assigned Spectrum IEEE 802.20 standard: Global Area Network- the final step in area network. This network would have enough bandwidth to offer Internet access comparable to cable modem service, but it would be accessible to mobile, always-connected devices like laptops or next-generation cell phones. upcoming No No No No No Support for full mobility yes Yes No No No No Adaptive Modulation OFDM QAM, PSK OFDM OFDM Frequency hopping, Direct Sequence Frequency hopping, Direct Sequence Modulation system TCP/IP,ATM TCP,ATM Ethernet Ethernet Ethernet Ethernet Transport protocol supported PTMP, PTCM, Mesh PTP,PTCM PTMP PTMP PTMP Point To Multi-Point (PTMP) Network architecture supported Several miles More than a mile 200yards 200yards 200yards 200yards Propagation distance 70Mbps 54Mbps 54Mbps 11Mbps 2Mbps Max throughput 802.16a 802.16 802.11g 802.11a 802.11b 802.11 Feature Wireless Broadband Metrics
  • 16. <ul><li>OFDM/OFDMA Technology. </li></ul><ul><li>Sub channelization. </li></ul><ul><li>Adaptive Modulation. </li></ul><ul><li>Multiple-antenna Technology (MIMO, Beam Forming Technique) </li></ul><ul><li>Transmit & receive diversity (Space-Time Coding at TX, Maximum Ratio Combining at RX) </li></ul><ul><li>Error control techniques (convolution coding, ARQ) </li></ul><ul><li>Power Control Techniques between BS & SS </li></ul>8/9/2007 Features in WiMAX
  • 17. 8/9/2007 OFDM Modulator OFDM De-Modulator Distortion Orthogonal Frequency Division Multiplexing (OFDM) <ul><li>High-speed digital signal is divided into multiple lower speed sub channels that are independent from each other and modulated separately on evenly spaced sub carriers using Fast Fourier Transform (FFT) processors. </li></ul><ul><li>This method reduces effects of Multi-path fading, Delay Spread for lower frequencies. </li></ul><ul><li>Lower transmission power for low-data-rates. </li></ul><ul><li>The missing bits from one channel can be transmitted on other channels and the signal is retrieved. </li></ul><ul><li>OFDM-spread spectrum scheme is used for digital TV and digital audio broadcasting and wireless networking (IEEE 802.11a/g) </li></ul><ul><li>OFDM system must employ TDMA/FDMA technique to accommodate multiple users; OFDM-256 FFT mode is proposed for IEEE 802.16d (WiMAX fixed-service). </li></ul>RF Channel One user Sub carriers Lost bits received from other sub channels
  • 18. 8/9/2007 Serial To Parallel Random Data Generator Modula tion Mapping IFFT Guard Period (Cyclic Prefix) Insertion Parallel To Serial Channel Serial To Parallel Guard Period Removel FFT Demodulation Parallel To Serial OFDM Transceiver Block Schematic
  • 19. 8/9/2007 Insertion of Cyclic Prefix (CP) to mitigate ISI <ul><li>Inter Symbol Interference (ISI) can be eliminated if CP period is greater than channel delay spread. </li></ul><ul><li>CP is a repetition of last samples of data portion of the block that is appended to the data payload. This prevents inter-block interference and less complex equalization at the receiver end. </li></ul><ul><li>But it is an overhead which reduces the bandwidth efficiency. </li></ul>Guard Time
  • 20. 8/9/2007 OFDM Transceiver (Contn..d) OFDM Tx OFDM Rx
  • 21. 8/9/2007 OFDM Technique Transmitted Signal Spectrum Received Signal Spectrum Frequency Single Carrier Mode Level S1 S2 S3 S4 S5 Time Serial Symbol stream used to modulate a single-wide band carrier Symbols have narrow frequency and long symbol time S1 S2 S3 S4 S5 Each of the symbols used to modulate a separate carrier. Orthogonal Frequency Division multiplexing Mode Frequency Frequency Orthogonal Frequency Division multiplexing Mode The light background is transmitted spectrum and the orange portion is received spectrum Frequency Level Single Carrier Mode
  • 22. 8/9/2007 Effect of Sub-channelisation Transmitted DOWN stream of OFDM Spectrum from BS where each slot is a RF carrier Transmitted UP stream of OFDM Spectrum from SS, all the carriers are transmitted but at a ¼ level that transmitted by BS, hence the range is less . Transmitted UP stream of OFDM Spectrum from SS, only ¼ the carriers are transmitted but at same level as transmitted by BS, and hence ¼ the capacity . <ul><li>Sub-channelisation is optional in Upstream in WiMAX. </li></ul><ul><li>Sub –channelisation will enable balanced link budget such that system gain is similar to both uplink & down link. </li></ul>
  • 23. 8/9/2007 Orthogonal Frequency Division Multi-Access (OFDMA) <ul><li>OFDMA is a multi-user OFDM technique. </li></ul><ul><li>WiMAX radio channel is divided into multiple sub carriers and dynamically assigned to multiple users so that sub carrier-group sub channels can be mapped to each user. </li></ul><ul><li>Mitigates problems due to fading and interference based on the location and propagation characteristics of each user. </li></ul><ul><li>Data rates provided to each user can be varied dynamically based on the number of sub carriers assigned to the user using varying size Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) processors. </li></ul><ul><li>OFDMA 128/512/1024/2048 FFT Modes have been proposed for Channel Bandwidths of 1.25/5/10/20MHz respectively in IEEE 802.16e standard (mobile service). </li></ul><ul><li>For example, OFDMA 1024 FFT is used in Korea’s WiBRO. </li></ul>Assign sub carriers as needed OFDMA Modulator OFDM De-Modulator OFDM De-Modulator OFDM De-Modulator Split into sub carriers RF Channel Multi- user Sub carriers
  • 24. 8/9/2007 OFDMA Sub-Carrier Structure & Sub-channelisation <ul><li>OFDMA symbol structure consist of 3 types of sub carriers: </li></ul><ul><li>Data sub-carriers for data transmission. </li></ul><ul><li>Pilot sub-carriers for estimation & synchronization purposes. </li></ul><ul><li>Null sub-carriers for no transmission; used for guard bands & DC carriers. </li></ul>
  • 25. 8/9/2007 OFDMA Symbol structure
  • 26. 8/9/2007 OFDMA Parameters of a typical WiMAX System S.No OFDMA Parameter Value 1 System Channel Bandwidth (in MHz) 10 2 Sampling Frequency (Fp in MHz) 11.2 3 FFT Size (Nfft) 1024 4 Sub-carrier Frequency Spacing (in KHz) 10.94 5 Useful Symbol Time (Tb = 1/f) (in μ sec ) 91.4 6 Guard Time (Tg = Tb/8) (in μ sec ) 11.4 7 OFDMA Symbol Duration (Ts = Tb + Tg) (in μ sec ) 102.9 8 Frame Duration (in milli seconds) 5 9 No of OFDMA symbols 48 10 Down Link PUSC [Null Carriers] 184 Down Link PUSC [Pilot Sub-Carriers] 120 Down Link PUSC [Data Sub- Carriers] 720 Down Link PUSC [Sub -Channels] 30 11 Up Link PUSC [Null Carriers] 184 Up Link PUSC [Pilot Sub-Carriers] 280 Up Link PUSC [Data Sub- Carriers] 560 Up Link PUSC [Sub -Channels] 35
  • 27. 8/9/2007 Up to 17Mbps Up to 33 Mbps Up to 75 Mbps BPSK QPSK BPSK QPSK 16 QAM BPSK QPSK,16 QAM,QAM,64QAM, 256 QAM BPSK QPSK 16 QAM, 64 QAM Max Data Rate Up to 50Km (LoS) Upto 8Km (Near LoS) WiMAX Carrier Serving Area The area of coverage depends on RF Channel Bandwidth of the carrier and the modulation scheme (BPSK,QPSK,16QAM,64QAM) used. (more details in Section: WiMAX NLOS Coverage and Capacity ) For a 20MHz RFcarrier bandwidth and 64QAM modulation scheme and 3Km distance from Base Station, the Data carrying capacity is 75Mbps.
  • 28. WiMAX Multi-Antenna Implementation 8/9/2007 Matrix A Matrix B ( Space-Time Block codin
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