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  • 08/28/09 There are basically three different options available today to access the Internet: Broadband access - In your home, you have either a DSL or cable modem. At the office, your company may be using a T1 or a T3 line. WiFi access - In your home, you may have set up a WiFi router that lets you surf the Web while you lounge with your laptop. On the road, you can find WiFi hot spots in restaurants, hotels, coffee shops and libraries. Dial-up access - If you are still using dial-up, chances are that either broadband access is not available, or you think that broadband access is too expensive. The main problems with broadband access are that it is pretty expensive and it doesn't reach all areas. The main problem with WiFi access is that hot spots are very small, so coverage is sparse. What if there were a new technology that solved all of these problems? This new technology would provide: The high speed of broadband service Wireless rather than wired access, so it would be a lot less expensive than cable or DSL and much easier to extend to suburban and rural areas. Broad coverage like the cell phone network instead of small WiFi hotspots This system is actually coming into being right now, and is called WiMAX . WiMAX is short for Worldwide Interoperability for Microwave Access , and it also goes by the IEEE name 802.16 . WiMAX has the potential to do to broadband Internet access what cell phones have done to phone access. In the same way that many people have given up their "land lines" in favor of cell phones, WiMAX could replace cable and DSL services, providing universal Internet access just about anywhere you go. WiMAX will also be as simple as WiFi -- turning your computer on will automatically connect you to the closest available WiMAX antenna. In this Presentation, is on to elucidate how WiMAX works, and what things can be done to make it better and what it could mean for the future of wireless Internet. In practical terms, WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX could potentially erase the suburban and rural blackout areas that currently have no broadband Internet access because phone and cable companies have not yet run the necessary wires to those remote locations.
  • 08/28/09 In practical terms, WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX could potentially erase the suburban and rural blackout areas that currently have no broadband Internet access because phone and cable companies have not yet run the necessary wires to those remote locations. A WiMAX system consists of two parts: A WiMAX tower , similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles (~8,000 square km). A WiMAX receiver - The receiver and antenna could be a small box or PCMCIA card, or they could be built into a laptop the way WiFi access is today. A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection (for example, a T3 line). It can also connect to another WiMAX tower using a line-of-sight, microwave link. This connection to a second tower (often referred to as a backhaul ), along with the ability of a single tower to cover up to 3,000 square miles, is what allows WiMAX to provide coverage to remote rural areas.
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  • 08/28/09 An OFDM carrier signal is the sum of a number of orthogonal sub-carriers, with baseband data on each sub-carrier being independently modulated commonly using some type of quadrature amplitude modulation (QAM) or phase-shift keying (PSK). This composite baseband signal is typically used to modulate a main RF carrier s [ n ] is a serial stream of binary digits. By inverse multiplexing, these are first demultiplexed into N parallel streams, and each one mapped to a (possibly complex) symbol stream using some modulation constellation (QAM, PSK, etc.). Note that the constellations may be different, so some streams may carry a higher bit-rate than others. An inverse FFT is computed on each set of symbols, giving a set of complex time-domain samples. These samples are then quadrature -mixed to passband in the standard way. The real and imaginary components are first converted to the analogue domain using digital-to-analogue converters (DACs); the analogue signals are then used to modulate cosine and sine waves at the carrier frequency, fc , respectively. These signals are then summed to give the transmission signal, s ( t ). The receiver picks up the signal r ( t ), which is then quadrature-mixed down to baseband using cosine and sine waves at the carrier frequency. This also creates signals centered on 2 fc , so low-pass filters are used to reject these. The baseband signals are then sampled and digitised using analogue-to-digital converters (ADCs), and a forward FFT is used to convert back to the frequency domain. This returns N parallel streams, each of which is converted to a binary stream using an appropriate symbol detector . These streams are then re-combined into a serial stream, which is an estimate of the original binary stream at the transmitter.
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Transcript

  • 1. 8/9/2007
  • 2. Contents
    • Introduction to WiMAX
    • Objectives of WiMAX
    • IEEE Wireless Standards
    • Features in WiMAX
    • Usage Scenario for WiMAX in Public and Private Networks
    • WiMAX Protocol Layers
    • WiMAX NLOS Coverage & Capacity
    • Vendors for WiMAX
    • Challenges for WiMAX
    8/9/2007
  • 3. WhyMAX
    • Ways of connecting to the Internet
    • Dial-Up access : through phone line
    • Broadband access : through DSL/Cable modem
    • Wi-Fi access : through Wi Fi router.
    • Limitations
    • Dial-Up access : slow speed, phone line is engaged while surfing the net.
    • Broadband access : expensive, less coverage
    • WiFi access : hot spots are small and sparse coverage.
    • Need an Access technology that provides :
    • High Speed like Broadband Access
    • Wireless and is less expensive than DSL/Cable modem.
    • Long Distance Coverage like Cell phone network rather than WiFi.
    • The solution is IEEE 802.16 standard :
    • WiMAX - Worldwide Interoperability for Microwave access
    8/9/2007
  • 4. Line-of-Sight (LOS) & Non-LOS type of service.
    • WiMAX system consists of
    • Tower station - can provide coverage to a very large area up to 8,000 sqkm.
    • - connected to ISP through high bandwidth connectivity (example :T3)
    • - can connect to another tower through microwave link (backhaul).
    • - allows coverage of the remote areas.
    • Receiver station -The receiver and antenna could be in a outdoor unit.
    • Type of service :
    • LOS :- fixed dish antenna points to WiMAX tower.
    • - connection is stronger & stable hence more data throughput.
    • - less interference.
    • - higher frequency (66GHz) and bandwidth.
    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
    • The most cost-effective solution for carriers to deploy for fixed /Mobile wireless applications
    • The WiMAX Forum to certify products for conformance and interoperability based on IEEE 802.16.
    Interoperability
    • 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.
    • Adaptive Modulation increase link reliability and the possibility to keep 64 QAM modulation at wider distance extend full capacity over longer distances .
    Higher Capacity
    • Techniques for Improving NLOS coverage : a) Diversity (b) Space-Time coding (c )Automatic Retransmission Request (ARQ)
    • NLOS advantages are :
    • Coverage of wider area,
    • Better predictability of coverage
    • Lower cost means fewer base stations and backhaul
    • Simple RF planning
    • Shorter towers and
    • Faster CPE install times.
    Wider Coverage
    • 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.
    • Increased volume with higher-level integration of RF chipsets.
    • Modem chipsets for Fixed wireless Customer Premise Equipment (CPE) same as that used in PC.
    Low Cost Objectives of WiMAX…continued
  • 8. Objectives of WiMAX…continued 8/9/2007
    • Once the Subscriber Station is powered up, It identifies it self by determining the characteristics of the link with respect to the BS.
    Portability
    • Conforms Multi-Service Level Agreement between Service Provider and End User.
    • One Service Provider can offer different SLAs to different subscribers or even to different users on the same Subscriber Station.
    Service Level Agreement (SLA)
    • The Operator after obtaining the required license for the frequency bands can operate the system in no time.
    Quick Deployment
    • IEEE 802.16e added key features to support mobility
    • Improvements in OFDM & OFDMA physical layers, MIMO and support for idle/sleep mode and hand off will allow full mobility up to 160Km/hr
    Mobility
    • Supports Dynamic Optimization for the mix of traffic that is being carried.
    • Four types of scheduling services available are UGS, rtps,nrtps,BE.
    Quality of Service (QoS)
    • Supports PTP,PTMP and Ubiquitous coverage
    • MAC layer supports PTMP by scheduling a time slot for each Subscriber Station
    • A Base Station in a PTP architecture may use narrow beam antenna for long distance coverage
    Flexible Architecture
    • Supports AES (Advanced Encryption Standard) & 3DES (Triple Data Encryption Standard)
    • Provides Operator with strong protection against theft of service
    • Built in VLAN support gives protection for data transmitted by different users on the same BS.
    Higher Security
  • 9. IEEE 802.16 -- Introduction
    • IEEE 802.16 (2001)
      • Air Interface for Fixed Broadband Wireless Access System MAC and PHY Specifications for 10 – 66 GHZ (LoS)
      • One PHY: Single Carrier
      • Connection-oriented, TDM/TDMA MAC, QoS, Privacy
    • IEEE 802.16a (January 2003)
      • Amendment to 802.16, MAC Modifications and Additional PHY Specifications for 2 – 11 GHz (NLoS)
      • Three PHYs: OFDM, OFDMA, Single Carrier
      • Additional MAC functions: OFDM and OFDMA PHY support, Mesh topology support, ARQ
    • IEEE 802.16d (July 2004)
      • Combines both IEEE 802.16 and 802.16a
      • Some modifications to the MAC and PHY
    • IEEE 802.16e (2005)
      • Amendment to 802.16-2004
      • MAC Modifications for limited mobility
    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
    • Applications
    • E1/T1 services for Enterprises
    • Backhaul for hotspots
    • Limited residential broadband access
    • CPE
    • External box connected to the PC with outside antenna
    Fixed Outdoor
    • Applications
    • Indoor broadband access for residential users (High Speed Internet & VoIP,…)
    • CPE
    • External box connected to the PC with built-in antenna
    Limited Mobility
    • Applications
    • Portable broadband access for consumers.
    • Always best connected
    • CPE
    • PC Card
  • 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.
    • OFDM/OFDMA Technology.
    • Sub channelization.
    • Adaptive Modulation.
    • Multiple-antenna Technology (MIMO, Beam Forming Technique)
    • Transmit & receive diversity (Space-Time Coding at TX, Maximum Ratio Combining at RX)
    • Error control techniques (convolution coding, ARQ)
    • Power Control Techniques between BS & SS
    8/9/2007 Features in WiMAX
  • 17. 8/9/2007 OFDM Modulator OFDM De-Modulator Distortion Orthogonal Frequency Division Multiplexing (OFDM)
    • 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.
    • This method reduces effects of Multi-path fading, Delay Spread for lower frequencies.
    • Lower transmission power for low-data-rates.
    • The missing bits from one channel can be transmitted on other channels and the signal is retrieved.
    • OFDM-spread spectrum scheme is used for digital TV and digital audio broadcasting and wireless networking (IEEE 802.11a/g)
    • OFDM system must employ TDMA/FDMA technique to accommodate multiple users; OFDM-256 FFT mode is proposed for IEEE 802.16d (WiMAX fixed-service).
    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
    • Inter Symbol Interference (ISI) can be eliminated if CP period is greater than channel delay spread.
    • 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.
    • But it is an overhead which reduces the bandwidth efficiency.
    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 .
    • Sub-channelisation is optional in Upstream in WiMAX.
    • Sub –channelisation will enable balanced link budget such that system gain is similar to both uplink & down link.
  • 23. 8/9/2007 Orthogonal Frequency Division Multi-Access (OFDMA)
    • OFDMA is a multi-user OFDM technique.
    • 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.
    • Mitigates problems due to fading and interference based on the location and propagation characteristics of each user.
    • 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.
    • 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).
    • For example, OFDMA 1024 FFT is used in Korea’s WiBRO.
    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
    • OFDMA symbol structure consist of 3 types of sub carriers:
    • Data sub-carriers for data transmission.
    • Pilot sub-carriers for estimation & synchronization purposes.
    • Null sub-carriers for no transmission; used for guard bands & DC carriers.
  • 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 coding) ( Spatial Multiplexing) MIMO (Multiple Input-Multiple Output) Open Loop MIMO Closed Loop MIMO Beam forming (Transmitter Adaptive Antenna)
  • 29. 8/9/2007
    • Open loop MIMO : The Communication channel does not utilize the information of propagation channel.
    • MATRIX A MIMO : A single data stream is replicated and transmitted over multiple antennas.
    • The redundant data streams are each encoded using mathematical algorithms known as Space-Time Block codes so that the transmitted signal is orthogonal to the rest reducing self-interference and increases receiver’s capability in distinguishing the signals and extends coverage .
    • MATRIX B MIMO : The signal to be transmitted is split into multiple data streams and is transmitted from a different BS transmit antenna operating in the same time –frequency resource allocated for the receiver. The receiver distinguishes the actual and multipath signal by employing diversity techniques.
    • MATRIX B MIMO technique increases channel capacity.
    WiMAX Multi-antenna implementation …. Contnd
  • 30. 8/9/2007 Serial to Parallel Converter TX Diversity Coding [S0, -S1*] [S1, -S0*] (Alamouti Coding) IFFT IFFT DAC/ RF DAC/ RF Diversity Techniques at TX & RX in WiMAX Rx Tx1 Tx2
    • X is the output of the encoder and S0,S1 are input symbols into the encoder. * is complex conjugate of the symbol.
    • The rows of the matrix represent Tx antennas and columns the time. Each element of the matrix indicates which symbol is to be transmitted from which antenna and when.
    • Maximum Ratio Combining : Combines the outputs of all the antennas to maximize the received signal energy to noise ratio.
    RF/ ADC FFT Diversity Combining S0 -S1* S1 -S0* Time Tx Antennas X =
  • 31. 8/9/2007 MIMO Matrix A & B operation The receive signals can be expressed as : RX1(f)= (H1,1(f) x TX1)+ (H2,1(f) x TX2) RX2(f) =(H2,2(f) x TX2) + (H2,1(f)x TX1) MIMO Matrix A
    • The Code works with a pair of symbols such that they are transmitted in two time slots from two antennas.
    • The Data rate is same as that enters the encoder.
    • MIMO Matrix A techniques improve the coverage area.
    MIMO Matrix B S0 S1
    • The Code works with a pair of symbols such that they are transmitted in one time slot from two antennas.
    • The Data rate is DOUBLE as that enters the encoder.
    • MIMO Matrix B techniques improve the capacity of the system.
    TX1 TX2 RX1 RX2 H1,1 (f) H2,1 (f) H2,2 (f) H1,2 (f) S0 -S1* S1 -S0* Time Tx Antennas X = TX1 TX2 RX1 RX2 H1,1 (f) H2,1 (f) H2,2 (f) H1,2 (f) Tx Antennas Time X =
  • 32. 8/9/2007 AirSpan’s 16e USB mobile device AirSpan’s EasyST 4 X 90 ○ antennas built into the vertical cone Source: AirSpan Wimax Product Datasheet
  • 33. 8/9/2007 BS Beam Forming Technique (Adaptive Antenna System) SS SS F1 F1 F1 Beam forming (AAS): Channel information is conveyed from WiMAX CPE to the WiMAX BS. Based on the info, the BS utilizes signal processing techniques to calculate weights to be assigned to the transmitter controlling the phase and amplitude of the signal. Then the optimal radiation pattern is steered into the direction for communication SS
  • 34. 8/9/2007 Adaptive Antenna System(AAS) -Contnd
    • AAS combines antenna arrays with sophisticated signal processing to enhance SNR for higher throughput by reducing interference.
    • When receiving a signal beam forming can increase the gain in the direction of wanted signals & decrease the gain in the direction of interference & noise.
    • When transmitting a signal, beam forming can increase the gain in the direction of signal and null others who interfere with the transmitting signal
    • AAS can deliver 10-15 dB of improvement in link budget relative to single antenna systems. In mobile WiMAX application, the active interference management assures a spectral efficiency of 3bps/Hz
  • 35. 8/9/2007 RF Power Control Techniques SS HIGH LOW Transmitter RF Power Level Receive Level LOW HIGH Increase Power Control Message BS
    • RF signal power level output of a SS is first determined by the received signal power level and is adjusted by commands from the BS
    • Reduces interference to nearby cell sites.
  • 36.
    • In Private Networks
    • Used by single organization, institution or business to offer secure, reliable voice ,data & Video.
    • Quick and easy deployment is high priority.
    • Configuration is Point-to-Point & Point-to-Multipoint.
    • Typical private networks suitable for WiMAX application :
    • (1) Cellular Back haul
    • (2) Wireless Service Provider Backhaul
    • (3) Banking Networks
    • (4) Education Networks
    • (5) Public Safety
    • (6) Off-Shore Communications
    • In Public Networks
    • Resources are shared by private individuals or businesses
    • Requires a cost-effective means of providing ubiquitous coverage for all users.
    • Offers voice, data and video communications.
    • Security is of critical importance in the network and require built-in VLAN support and data encryption method.
    • Typical public networks suitable for WiMAX application:
    • (1) Wireless Service Provider (WSP) access network.
    • (2) Rural Connectivity
    8/9/2007 Usage Scenario for WiMAX :
  • 37.
    • Advantage of WiMAX for Cellular Operators
    • Leasing backhaul facilities from Carrier Telecom Companies is cost prohibitive.
    • WiMAX provides Point-to-Point links up to 30miles (50Km) ,with data rates capable of supporting multiple E1/T1s.
    • Cellular Operators can use WiMAX equipment to backhaul Base Station traffic to their Network Operating and Switching Centers.
    • Based on the availability of spectrum for WiMAX in different countries, cellular backhaul application may or may not cover nation wide coverage.
    • Wired solutions to provide backhaul in rural and sub-urban areas is not cost effective.
    • DSL or other cable technologies cannot give sufficient bandwidth for cellular backhaul, particularly for upcoming 3G networks.
    • WiMAX is the obviously advantageous .
    8/9/2007 WiMAX in Private Networks (1) For Cellular Back haul Subscriber Station Subscriber Station NOC & Switching center Cell Site Cell Site Base Station WiMAX network Internet PSTN
  • 38. 8/9/2007 WiMAX in Private Networks (2) For Wireless Service Provider (WSP) Backhaul.
    • Advantage of WiMAX for Wireless Service Provider (WSP)
    • If the access network uses Wi fi equipment , the overall WSP network is referred to as Hot Zone.
    • As WSPs typically offer voice,data and video, the built in feature of WiMAX will help prioritize and optimize the backhaul traffic.
    • WiMAX equipment can be deployed quickly, facilitating a rapid rollout of the WSP Network.
    • WiMAX is the obviously advantageous to WSPs
    Base Station Subscriber Station Wi Fi Hotspot WiMAX Access Network Internet PSTN WiMAX backhaul Subscriber Station Video
  • 39. 8/9/2007 WiMAX in Private Networks (3) For Banking Network.
    • Advantage of WiMAX for Banking Networks
    • WiMAX data encryption offers excellent link security.
    • Broad coverage and high capacity allows Banks regional office to be connected to Branch office and ATMs
    • WiMAX offers high degree of scalability of traffic.
    • WiMAX QoS is used to prioritize voice (telephony among branches), data (financial transactions,email,internet & intranet) and video (Surveillance,CCTV) traffic.
    • WiMAX is obviously advantageous to banking networks
    Regional office BS ATM surveillance VoIP phones SS WiMAX network Branch office SS surveillance Internet PSTN
  • 40. 8/9/2007 School Board office BS SS Distance education WiMAX network VoIP phones LAN Distance education Instructor School A School B WiMAX in Private Networks (4) For Education Network.
    • Advantage of WiMAX for Education Networks
    • School boards use WiMAX networks to connect school & board offices with in a district.
    • Key requirements for a school system are NLOS, high bandwidth (>15Mbps),PTP & PTMP capability and large coverage footprint.
    • WiMAX QoS can deliver full range of communication requirements, including telephony voice, Internet & intranet access data) and distance education video) between school board office & all schools in the district.
    • WiMAX is obviously advantageous to Education networks
    VoIP phones SS LAN students Internet PSTN students
  • 41. 8/9/2007 WiMAX in Private Networks (5) For Public Safety Network. Dispatch LAN Server Ambulance Police Disaster recovery Fire Services Control Center/ Head Office Admin Terminals
    • Advantage of WiMAX for Public Safety Network
    • Public safety agencies like Fire,Police,Search & Rescue can benefit from WiMAX networks.
    • In addition to two-way radio between dispatch and on-site emergency response team, the WiMAX network can relay video images and data.
    • This data can be relayed to the expert teams of medical or emergency staff, who can analyze the situation in real-time.
    • WiMAX takes over the advantage over wireline networks in emergency situation, which require access to information while on the move.
    • WiMAX is obviously advantageous to Public Safety Networks
    Internet PSTN
  • 42. 8/9/2007 WiMAX in Private Networks (6) For Off-shore Communication
    • Advantage of WiMAX for Off-Shore Communication
    • Oil & Gas producers can benefit from WiMAX with communication links between land-based facilities to Oil rigs and platforms.
    • Remote operations include remote trouble shooting of complex equipment problems, site monitoring and data base access.
    • Basic communication includes voice telephony, email, internet access and video conferencing.
    • As facilities are in the off-shore and oil rigs are temporarily located and moved with in the oil or gas field, WiMAX is better solution than over wired solutions.
    • WiMAX is obviously advantageous to Off-Shore Communication
    Internet PSTN Service Boats Operator Laptop Surveillance Camera Drilling Platform Surveillance Camera Drilling Operators Drilling Platform Off-Shore On- Shore SS SS BS
  • 43. WiMAX in Public Networks (1) In Wireless Service Provider (WSP) Access Network.
    • Advantage of WiMAX for WSP Access Network
    • Wireless Service Providers use WiMAX network to provide connectivity to both residential (voice, data & video) and business (voice & internet) customers
    • WiMAX built-in QoS mechanism is highly suited for mix of traffic carried by WSP.
    • WiMAX QoS MAC supports multi-level services rendering a common network platform, offering voice, data& video to end customer.
    • Cellular Operators who have customer base can expand their market presence with WiMAX deployment.
    • WiMAX is obviously advantageous in WSP access network.
    • WiMAX implemented by Unwired in Australia with 200 BS in 1200Sq Km with 25000 subscriber base.
    8/9/2007 Internet PSTN BS VoIP phones SS LAN students SS surveillance Residential Business/Manufacturer/SOHO/ School/University Internet Cafe VoIP phone Video Services Video Services
  • 44. 8/9/2007 WiMAX in Public Networks (2) For Rural Connectivity.
    • Advantage of WiMAX in Rural Connectivity
    • Service Providers can deploy WiMAX to deliver services to under-served markets in rural and sub-urban areas where there is little or no infrastructure is available.
    • Since WiMAX provides an extended coverage, it is a cost –effective solution than a wireline solution, in delivering services in sparsely populated areas and also helps to improve their local economies.
    • WiMAX is obviously advantageous in Rural Connectivity.
    Internet PSTN BS SS SS VoIP Phone surveillance Business Institute SS LAN Rural Community
  • 45. 8/9/2007 SNMP Management VLAN APPLICATIONS IN WiMAX Office Building Subscriber 2 WiMAX BS VLAN 230 VLAN 231 VLAN 230 VLAN 231 MDU VLAN 10 VLAN 11 VLAN12 Subscriber 1 Subscriber n WiMAX FWA Sector WiMAX FWA Sector WiMAX SS WiMAX SS VLAN Switch (Port based switching on subscriber) VLAN 230 Private Network VoIP Service Provider Core Network Element Manager VLAN 10 VLAN 10 & 11 802.1Q VLAN Aware L2 Switch VLAN 45 VLAN 21 VLAN 230 VLAN 45 VLAN 11 VLAN 21
  • 46. BASE STATION 8/9/2007 ABS4000 symmetryOne airlink™ Base station of SR Telecom PHY Layer Characteristics
    • symmetry Base Station
    • Supports both 1MHz & WiMAX sectors
    • Consists of (1) RF subsystem (on the tower). (2) Digital subsystem.
    • Digital subsystem consists of circuit packs meant for dedicated interface to backhaul network, air link processing, voice & data processing and NMS.
    • RF subsystem consists of circuit packs and antenna components for analog signal processing.
    • Communication between RF subsystem & digital subsystem is through a digital base band signal carried over optical fiber interface.
    Air Interface 802.16-2004 (s/w upgradeable to 802.16e) Frequency Range 1.5GHz FDD(1427-1517MHz);2.3GHz FDD(2300-2500MHz) 2.5GHz TDD(2500-2690MHz);2.5GHz FDD(2500-2690MHz) 3.5GHz TDD(3300-3800MHz);3.5GHz FDD(3300-3800MHz) 10.5GHz FDD (10.15-10.65GHz) Channel BW & Peak Sector Capacity (at 64 QAM ¾ coding) (For TDD,capacity =UL + DL traffic). 1.5 FDD : 1.75(6.5Mbps),3.5(13.1Mbps) 2.3 FDD : 1.75(6.5),3(11.2),3.5(13.1),5(18.8),5.5(20.6),6(22.4),7(26.0) 2.5 TDD: 1.25(4.7),2.5(9.4),4.375(16.3),5(18.8),8.75(32.6),10(3.75) 3.5 TDD: 1.75(6.5),3(11.2),5(18.8),7(26.0) 10.5 FDD:3(11.2),5(18.8),7(26.0Mbps) Duplexing FDD (With Half-FDD SS support) TDD RF Access scheme OFDM 256 FFT (Software upgradeable to SOFDMA) Adaptive Modulation 64QAM,16QAM,QPSK,BPSK Max RF Transmit Power 31dBm Antenna Antenna Gain Omni, Sectoral or Panel. Polarization: Vertical or dual slant +/- 45 0 17.5dB (typical) Receiver Sensitivity -101dBm (BPSK ½),-84dBm(1.75MHz channel) (64QAM ¾) Diversity Two-branch TX/RX Polarization diversity & Maximum Ratio Combining (MRC) Space Time Coding Alamouti Coding Forward Error Correction Reed Solomon & Convolution coding (FEC ) rates ½, 2/3 & ¾. Sub-channeling 2,4,8 and 16 channels Sectors Up to 6 Services: Physical port:RJ45 100Base-T per WiMAX sector Network Interface for voice : VoIP over 100Base-T Network Segmentation : VLAN:IEEE802.1Q/802.1D(802.1p) Convergence Sub layer : Ethernet 802.3 & IP over Ethernet service Packet Switching :Layer-2 switching enables easy internetworking with routers,gateways,firewall,IP phones & PBX,media gateways,Wi-fi base stations,IPDSLAM.
  • 47. 8/9/2007 Circuit Pack of symmetry™ Base Station
    • BS Circuit pack summary
    • WSBC: Implements IEEE 802.16 MAC & OFDM PHY layer
    • WBRU: Provides WiMAX air interface radio for one sector. Each sector has two radios providing diversity
    • TIF: Provides interface between WBRUs for a sector and digital equipment shelf through fiber optic interface.
    • SMP: Supports configuration, fault detection and equipment redundancy switching for BS circuit packs.
    • BCP: Provides synchronization & timing signals to BS Modules generates the network, airlink, system timing for the BS.
    • ESI: Supplies Interface of the BS circuit pack to External Synchronization Sources such as E1/T1 or GPS.
  • 48. Customer Premise Equipment (Subscriber Station)
    • Customer Premise Equipment is a WiMAX Equipment interfaced with customer device to transact the data.
    • Placement of CPE depends upon Transmitted power, Antenna gain and Environmental condition etc.
    • CPE needs external power source to operate and is provided by the indoor connector adapter through Ethernet cable (PoE IEEE 802.3af).
    • CPE consists of integrated radio and digital card that supplies 10/100Base –T Ethernet LAN subscriber data interface and links CPE with BS via the air interface.
    8/9/2007 symmetryOne™ SSUCPS5000 CPE of SR Telecom PHY Layer Characteristics Air Interface 802.16-2004 (s/w upgradeable to 802.16e) Frequency Range 1.5GHz FDD(1427-1517MHz);2.3GHz FDD(2300-2500MHz) 2.5GHz TDD(2500-2690MHz);2.5GHz FDD(2500-2690MHz) 3.5GHz TDD(3300-3800MHz);3.5GHz FDD(3300-3800MHz) 10.5GHz FDD (10.15-10.65GHz) Channel BW & Peak Sector Capacity (at 64 QAM ¾ coding) (For TDD,capacity =UL + DL traffic). 1.5 FDD : 1.75(6.5Mbps),3.5(13.1Mbps) 2.3 FDD : 1.75(6.5),3(11.2),3.5(13.1),5(18.8),5.5(20.6),6(22.4),7(26.0) 2.5 TDD: 1.25(4.7),2.5(9.4),4.375(16.3),5(18.8),8.75(32.6),10(3.75) 3.5 TDD: 1.75(6.5),3(11.2),5(18.8),7(26.0) 10.5 FDD:3(11.2),5(18.8),7(26.0Mbps) Duplexing H-FDD,TDD,TC-HFDD RF Access scheme OFDM 256 FFT (Software upgradeable to SOFDMA) Adaptive Modulation 64QAM,16QAM,QPSK,BPSK Max RF Transmit Power 22dBm Antenna Integrated Panel Receiver Sensitivity For 1.75MHz cahnnel: -100dBm (BPSK ½) ,-83dBm (64QAM ¾) Diversity Two-branch TX/RX Polarization diversity & Maximum Ratio Combining (MRC) Space Time Coding Alamouti Coding Forward Error Correction Reed Solomon & Convolution coding (FEC ) rates ½, 2/3 & ¾. Sub-channeling 2,4,8 and 16 channels Services: Physical port: RJ45 10/100Base-T Voice Services Interface : VoIP over 100Base-T Network Segmentation : VLAN:IEEE802.1Q/802.1D(802.1p) Convergence Sub layer : Ethernet 802.3 & IP over Ethernet service Packet Switching :Layer-2 switching enables easy internetworking with routers,gateways,firewall,IP phones & PBX,media gateways,Wi-fi base stations,IPDSLAM.
  • 49. IEEE 802.16 Protocol Reference Model 8/9/2007
  • 50. 8/9/2007 ATM Ethernet IP ATM Ethernet IP MAC Convergence Layer (service specific) MAC CPS (Common part sub layer ) Physical Layer Physical Layer Authenticate Encrypt Data Transfer Session Setup (Parameter Negotiation) Polling Access Requests Physical WiMAX Protocol Layers RF power Secret Key Secret Key MAC CPS (Common part sub layer) MAC Convergence Layer (service specific) MAC Privacy Layer MAC Privacy Layer RADIO RADIO
  • 51. 8/9/2007 Primary Management (2nd setup) Secondary Management (optional) -DHCP-TFTP-SNMP Transport -User Data WiMAX Connection Types Basic Connection (1 ST setup) -Power Control-Timing BS
  • 52. IEEE 802.16 MAC -- Highlights
    • WirelessMAN: Point-to-Multipoint and optional mesh topology
    • Connection-oriented
    • Multiple Access: DL TDM & TDMA, UL TDMA;UL OFDMA & TDMA, DL OFDMA & TDMA (Optional)
    • PHY considerations that affect the MAC
      • Duplex: TDD, FDD, FDX FDD BS and SS, HDX FDD SS
      • Adaptive burst profiles (Modulation and FEC) on both DL and UL
    • Protocol-independent core (ATM, IP, Ethernet)
    • Flexible QoS offering
      • Constant Bit Rate Service (e.g. T1/E1 or VoIP),
      • real time-Variable Bit Rate Service (e.g. MPEG Video),
      • non real time-Variable Bit Rate Service (e.g. FTP) ,
      • Best Effort Service (e.g. internet browsing at home)
    • Strong security support
    8/9/2007
  • 53. Duplex Scheme Support
    • The duplex scheme is Usually specified by regulatory bodies, e.g., FCC
    • Time-Division Duplex (TDD)
      • Downlink & Uplink time share the same RF channel
      • Dynamic asymmetry
      • does not transmit & receive simultaneously (low cost)
    • Frequency-Division Duplex (FDD)
      • Downlink & Uplink on separate RF channels
      • Full Duplexing (FDX): can Tx and Rx simultaneously;
      • Half-duplexing (HDX) SSs supported (low cost)
    8/9/2007
  • 54. 8/9/2007 WiMAX Duplex Transmission BS TRANSMIT RECEIVE A) Frequency Division Duplex f1 f2 TRANSMIT RECEIVE B) Time Division Duplex f1 TRANSMIT RECEIVE C) Half -Frequecny Division Duplex(H-FDD) f1 f2
  • 55. 8/9/2007 Implementing Scalable OFDMA in WiMAX PHY Layer Starting with 802.16-2004, there have been extensions to support from 128 up to 2048 FFT points inside an RF channel (called scalable –OFDMA ) to improve efficiency for lower bandwidth channels and improve performance for higher bandwidth channels while keeping sub-carrier spacing to be constant.
  • 56. IEEE 802.16 MAC – OFDM PHY TDD Frame Structure 8/9/2007 DL Sub frame Frame n-1 pre. Time Adaptive Frame n Frame n+1 UL sub frame FCH DL burst 1 DL burst n UL MAP Broadcast Control msgs ... UL burst 1 UL burst m DL MAP DCD opt. UCD opt. ... DL burst 2 UL TDMA DL TDM pre. pre.
  • 57. IEEE 802.16 MAC – OFDM PHY FDD Frame Structure 8/9/2007
  • 58. IEEE 802.16 MAC addressing and Identifiers
    • SS has 48-bit IEEE MAC address
    • BS has 48-bit base station ID
      • Not a MAC address
      • 24-bit operator indicator
    • 16-bit connection ID (CID)
    • 32-bit service flow ID (SFID)
    • 16-bit security association ID (SAID)
    8/9/2007
  • 59. IEEE 802.16 MAC – Convergence Sub-Layer (CS)
    • ATM Convergence Sub-Layer:
      • Support for VP/VC switched connections
      • Support for end-to-end signaling of dynamically created connections
      • ATM header suppression
      • Full QoS support
    • Packet Convergence Sub-Layer:
      • Initial support for Ethernet, VLAN, IPv4, and IPv6
      • Payload header suppression
      • Full QoS support
    8/9/2007
  • 60. IEEE 802.16 MAC -- CS – Packet Convergence Sub-Layer
    • Functions:
      • Classification: mapping the higher layer PDUs (Protocol Data Units) into appropriate MAC connections
      • Payload header suppression (optional)
      • MAC SDU (Service Data Unit), i.e, CS PDU, formatting
    8/9/2007 Packet PDU (e.g., IP packet, Ethernet Packet) PHSI MAC SDU = CS PDU Payload Header Suppression Index Optional, Depending on upper layer protocol
  • 61. IEEE 802.16 MAC – Common Part Sub layer – MAC PDU Format 8/9/2007 CRC (optional) MAC PDU payload (optional) Generic MAC Header (6 bytes) LEN msb (3) H T CID msb (8) LEN lsb (8) Generic MAC Header Format (Header Type (HT) = 0) BW Req. Header Format (Header Type (HT) =1) msb lsb E C Type (6 bits) RS v C I EKS (2) RS v HCS (8) CID lsb (8) BW Req. msb (8) H T CID msb (8) BWS Req. lsb (8) E C Type (6 bits) HCS (8) CID lsb (8) HT: Header Type CI: CRC indicator HCS: Header Check Sequence EC: Encryption Control EKS: Encryption Key Sequence Type: Payload type LEN: Length of Packet RSV: reserved. CID :Connection Identifier
  • 62. IEEE 802.16 MAC -- CPS -- Three Types of MAC PDUs
    • Data MAC PDUs
      • HT = 0
      • Payloads are MAC SDUs/segments, i.e., data from upper layer (CS PDUs)
      • Transmitted on data connections
    • Management MAC PDUs
      • HT =0
      • Payloads are MAC management messages or IP packets encapsulated in MAC CS PDUs
      • Transmitted on management connections
    • BW Req. MAC PDUs
      • HT =1; and no payload, i.e., just a Header
    8/9/2007
  • 63. IEEE 802.16 MAC -- CPS – Data Packet Encapsulations 8/9/2007
  • 64. IEEE 802.16 MAC – CPS – Uplink Service Classes
    • UGS: Unsolicited Grant Services
    • rtPS: Real-time Polling Services
    • nrtPS: Non-real-time Polling Services
    • BE: Best Effort
    8/9/2007
  • 65. IEEE 802.16 MAC – CPS – Uplink Services: UGS
    • UGS: Unsolicited Grant Services
      • For CBR or CBR-like services, e.g., T1/E1.
      • The BS scheduler offers fixed size UL BW grants on a real-time periodic basis.
      • The SS does not need to send any explicit UL BW req.
    8/9/2007
  • 66. IEEE 802.16 MAC – CPS – Uplink Services: rtPS
    • rtPS: Real-time Polling Services
      • For rt-VBR-like services, e.g., MPEG video.
      • The BS scheduler offers real-time, periodic, UL BW request opportunities.
      • The SS uses the offered UL BW req. opportunity to specify the desired UL BW grant.
      • The SS cannot use contention-based BW req.
    8/9/2007
  • 67. IEEE 802.16 MAC – CPS – Uplink Services: nrtPS
    • nrtPS: non-real-time polling services
      • For nrt-VBR-like services, such as, bandwidth-intensive file transfer.
      • The BS scheduler shall provide timely (on a order of a second or less) UL BW request opportunities.
      • The SS can use contention-based BW req. opportunities to send BW req.
    8/9/2007
  • 68. IEEE 802.16 MAC – CPS – Uplink Services: BE
    • BE: Best Effort
      • For best-effort traffic, e.g., HTTP, SMTP.
      • The SS uses the contention-based BW request opportunities.
    8/9/2007
  • 69. WiMAX QoS profiles 8/9/2007 Source: symmetry™ WiMAX Product Summary of S.R.Telecom, Canada. Application rtCBR rtVBR nrtVBR BE Band Width (Kbps) Latency (ms) Jitter (ms) VoIP √ √ 6-87 <150 <10 Video Conference √ √ 128-1500 <150 <10 Interactive Gaming √ √ √ <85 <80 - Streaming Media, VoD √ √ <2000 <250 - Internet Applications √ √ >512 <250 - File and Rich Media Download √ √ >512 <250 - Wi Fi Hot Spot & Internet Café Backhaul √ >1000 <250 - Remote Office/ VPN √ √ >1000 <250 - 1. Latency limit is not enforced by the system for nrtVBR,BE services. Jitter limit is not enforced by the system for nrtVBR, rtVBR, BE services
  • 70. IEEE 802.16 MAC – CPS – Bandwidth Grant 8/9/2007
    • BW grants are per Subscriber Station:
      • Allows real-time reaction to QoS need, i.e., SS may re-distribute bandwidth among its connections, maintaining QoS and service-level agreements
      • Lower overhead, i.e., less UL-MAP entries compare to grant per connection
      • Off- loading base station’s work
      • Requires intelligent subscriber station to redistribute the allocated BW among connections
  • 71. IEEE 802.16 MAC – CPS – BW Request/Grant Mechanisms
    • Implicit requests (UGS): No actual requests
    • BW request messages, i.e., BW req. header
      • Sends in either a contention-based BW req. slot or a regular UL allocation for the SS; he special B
      • Requests up to 32 KB with a single message Request
      • Incremental or aggregate, as indicated by MAC header –
    • Piggybacked request (for non-UGS services only)
      • Presented in Grant Management (GM) sub-header in a data MAC PDU of the same UL connection
      • is always incremental
      • Up to 32 KB per request for the CID
    • Poll-Me bit
      • Presented in the GM sub-header on a UGS connection
      • request a bandwidth req. opportunity for non-UGS services
    8/9/2007
  • 72. IEEE 802.16 MAC – CPS -- Contention UL Access 8/9/2007
    • Two types of Contention based UL slots
      • Initial Ranging
        • Used for new SS to join the system
        • Requires a long preamble
      • BW Request
        • Used for sending BW req
        • Short preamble
    • Collision Detection and Resolution
      • Detection: SS does not get the expected response in a given time
      • Resolution: a truncated binary exponential backoff window
  • 73. IEEE 802.16 MAC – CPS – Automatic Repeat reQuest (ARQ)
    • A Layer-2 sliding-window based flow control mechanism.
    • Per connection basis.
    • Only effective to non-real-time applications.
    • Uses a 11-bit sequence number field.
    • Uses CRC-32 checksum of MAC PDU to check data errors.
    • Maintain the same fragmentation structure for Retransmission.
    • Optional.
    8/9/2007
  • 74. IEEE 802.16 MAC addressing and Identifiers
    • SS has 48-bit IEEE MAC address
    • BS has 48-bit base station ID
      • Not a MAC address
      • 24-bit operator indicator
    • 16-bit connection ID (CID)
    • 32-bit service flow ID (SFID)
    • 16-bit security association ID (SAID)
    8/9/2007
  • 75. IEEE 802.16 MAC – CPS – Automatic Repeat reQuest (ARQ)
    • A Layer-2 sliding-window based flow control mechanism.
    • Per connection basis.
    • Only effective to non-real-time applications.
    • Uses a 11-bit sequence number field.
    • Uses CRC-32 checksum of MAC PDU to check data errors.
    • Maintain the same fragmentation structure for Retransmission.
    • Optional.
    8/9/2007
  • 76. IEEE 802.16 MAC – Privacy Sub-layer (PS)
    • Two Major Functions:
      • Secures over-the-air transmissions
      • Protects from theft of service
    • Two component protocols:
      • Data encryption protocol
      • A client/server model based Key management protocol (Privacy Key Management, or PKM)
    8/9/2007
  • 77. IEEE 802.16 MAC – PS -- Security Associations
    • A set of privacy information, e.g., encryption keys, used encryption algorithm
    • Three types of Security Associations (SAs)
      • Primary SA: established during initial registration
      • Static SA: provisioned within the BS
      • Dynamic SA: dynamically created on the fly
    • Identified by a 16-bit SAID
    • Connections are mapped to SAs
    8/9/2007
  • 78. IEEE 802.16 MAC – PS -- Multi-level Keys and Their Usage
    • Public Key
      • Contained in X.509 digital certificate
      • Issued by SS manufacturers
      • Used to encrypt AK
    • Authorization Key (AK)
      • Provided by BS to SS at authorization
      • Used to derive KEK
    • Key Encryption Key (KEK)
      • Derived from AK
      • Used to encrypt TEK
    • Traffic Encryption Key (TEK)
      • Provided by BS to SS at key exchange
      • Used to encrypt traffic data payload
    8/9/2007
  • 79. IEEE 802.16 MAC – PS -- Data Encryption
    • Use DES (Data Encryption Standard) in CBC (Cipher Block Chaining) mode with IV (Initialization Vector).
    • CBC IV is calculated from
      • IV parameter in TEK keying info; and
      • PHY synchronization field in DL-MAP.
    • Only MAC PDU payload (including sub-headers) is encrypted.
    • MAC PDU headers are unencrypted.
    • Management messages are unencrypted.
    8/9/2007
  • 80. WiMAX Throughput Calculation
    • The net usable throughput of WiMAX system will depend on
    • 1. Coverage Calculations :
    • a) On the choice of OFDM parameters
    • Channel Spacing (dependent on spectrum profile).
    • Number of FFT points or sub-carriers inside a channel.
    • Sub-carriers used as pilot channels.
    • Sub-carriers used as guard channels.
    • Symbol duration (including guard period)
    • Modulation & FEC coding rates.
    • b) On Path Propagation Loss Model used
    • Erceg Model for Fixed WiMAX, COST231 for Mobile WiMAX
    • c) Characteristics of the WiMAX System.
    • System Gain Parameters of Tx,Rx, heights of Antennas as TX, Rx, Receiver Sensitivity of the System
    • d) Sectorization & Frequency Re-use
    • No of Sectors in a Cell Site,
    • No of frequencies that can be used in a cell.
    • e) Geographic Area to be Covered
    • 2. Capacity Calculations
    • No of CPEs used
    • Over Booking Factor
    • Average Traffic Demand
    8/9/2007
  • 81. Fixed -WiMAX Network Design Flow Sequence 8/9/2007 Frequency Band Path loss Model System Gain Link Budget Calculations Modulation/Coding Type Channel Bandwidth Overbooking Factor Average Traffic Demand Cell/Sector range Cell/Sector Capacity Geographic Area Size Network Eqpt Demand Eqpt Prices OPEX CAPEX Economic Results No of CPEs Capacity Demand
  • 82. 8/9/2007 OFDM Parameters Sno OFDM Parameters Value Choice BW=3.5MHz units Choice BW=1.75MHz units 1 Sampling Frequency (Fs) 7/6 (undersampling) or 8/7 (over sampling) x BW 4 MHz 2 MHz 2 Carriers N FFT 256 256   256   3 Data Carriers (Nused) 192 192   192   4 Useful Time (Tb) NFFT /Fs 64 μsec 128 μsec 5 Subcarrier Spacing (Δs) Fs/NFFT 15.625 KHz 7.8125 KHz 6 Guard time/ Useful Symbol time ratio (Tg/Tb) 1/32,1/16,1/8,1/4 1/32   1/32   7 Cyclic Prefix Time (Tg) Tb/32 2 μsec 4 μsec 8 Symbol Time (Ts) Tb+ Tg 66 μsec 132 μsec 9 Bandwidth Efficiency [(Fs/BW)x(Nused+1)/(NFFT)] 86 % 86 % 10 Total Data channel baud rate (for Nused=192 data carriers)in Kbps (192x (1/Ts) 2909.0909 Kbps 1454.5454 Kbps
  • 83.
    • Single sub-carrier baud rate = 1/(66 μ sec) = 15.152 KBaud .
    • Total Data Channel baud rate = 192 * 15.151KBaud = 2.909MBaud
    • As a large portion of PDU (Physical Data Unit) is allocated for Cyclic Redundancy Check (CRC), Forward Error Correction (FEC), and /or Convolution Coding.
    • There are two convolution rates per modulation rate yielding 8 different modulation levels as follows:
    • (1) BPSK ½ (2) BPSK ¾ (3) QPSK ½ (4) QPSK ¾ (5) 16QAM ½ (6) 16QAM ¾
    • (7) 64QAM 2/3 (8) 64QAM ¾
    • ½, 2/3 and ¾ refer to the fraction of the PDUs allocated for actual user data; the rest is management, CRC bits
    • Net usable throughput for 3.5MHz RF channel for various modulation scheme is as follows:
      • For BPSK ½ : 2.909 Mbps x ½ = 1.45 Mbps For 16QAM ½ : 11.636 X ½ = 5.82 Mbps
      • For QPSK ½ : 5.818 Mbps x ½ = 2.909 Mbps For 16QAM ¾ : 11.636 X ¾ = 8.73 Mbps
    • In practice, bandwidth tends to be lower by 5% to 7% for a general point-to-point link.
    WiMAX Throughput Calculation for RF Channels Table :Throughput and Modulation Modulation Type Used Bits /Baud Throughput (Mbps) BPSK 1 2.909 QPSK 2 5.818 16QAM 4 11.636 64QAM 6 17.454
  • 84. 8/9/2007 WiMAX System Link Budget   S. no   Parameter Units   Downlink (Value) Uplink (Value) Remarks 1 Carrier Frequency MHz 2500   2 Duplexing   TDD   3 Multiple Access   TDMA   4 Modulation   adaptive BPSK,QPSK,QPSK,16-QAM,64-QAM   5 Channel Bandwidth (BW) MHz 3.5 3.5   6 Sampling Frequency (8/7 x BW) MHz 4 4   7 Number of Sub channels used EA 0 16     Transmitter   Base Station (BS) Subscriber Station (SS)   8 Input power (Pi) dBm 32 23   9 Height of Tx antenna (Htx) meters 30 6   10 Height of Rx antenna (Hrx) meters 6 30   11 Tx antenna gain Gi dBi 17 15   12 Tx feeder loss dB 0 0 Optical fiber medium to connect IDU & ODU  at BS 13 Other connector losses dB 4 0   14 EIRP =Tx power +GTx-miscellaneous losses at TX dBm 45 38     Receiver   Subscriber Station Base Station   15 Sub channelization Gain (optional in UL) dB 0 12.04 subchannelisation gain = 10xlog(no of sub channels) 16 RX sensitivity (typical for 3.5MHz & BPSK)** dBm -102.59 -114.63 With Subchannelisation gain in Uplink 17 Receiver antenna gain( Gr) dBi 15 17   18 Receiver feeder loss dB 0 4   19 Total System Gain: EIRP+GRx-Rxfeeder loss(-Rx Sensitivity) dB 162.59 165.63     Margins         20 Fade Margin for 99.995% reliability (as per ITU-R P.530 Recommendation) dB 10 10   21 Maximum allowable path loss dB 152.59 155.63   Receiver Sensitivity= -102+SNR(Rx)+10.log(Fs.(Nused/Nfft).(Nsubchannels/16)) ; Nused : 200; Nfft= 256; Nsubchannels:16 by default if no sub channels are used.
  • 85. A= 20log(4Πd0/λ) where d0 = 100mtrs ξ= (a-b*(Hbs)+ c/(Hbs)) ξ is path-loss exponent Type C terrain is considered for Path Loss Model as example… 8/9/2007 Erceg Path Loss Model ( recommended model by IEEE 802.16 BWA Team) Path Loss (PL)= A + 10ξlog(d/d0)+ΔLf+ΔLh+S for d>d0 (d0 =100mtr)   Terrain A [Hilly areas with moderate -to-Heavy tree density] Terrain B [Intermediate Terrain with moderate tree density] Terrain C [Flat terrain with light tree density] a 4.6 4 3.6 b 0.0075 0.0065 0.005 c 12.6 17.1 20 a,b,c are constants representing certain terrain type. d is the distance between Base Station (BS) and Receive antenna (Rx) in meters. Δ Lf = frequency correction term : = 6*log(f/2000); f is frequency in MHz Δ Lh= receive antenna height correction term: = -10.8log(Hss/2) for Terrain A,B; -20log(Hss/2) for Terrain C. S is shadow fading component. (8.2-10.6dB depending on the terrain and tree density type). 8.2 dB for Terrain C
  • 86. 8/9/2007 Calculation of coverage radius using Erceg Model
    • A = 20log(4Πd0/λ) where d0 = 100mtrs
    • = 20*LOG(((4*22/7*100)/(300/2500)),10) ; Where λ (meter) = 300/Freq in MHz ; Freq =2500 MHz
    • = 80.40406772
    • ξ ( Path-loss Component) = (a-b*Hbs+ c/Hbs);
    • = 3.6-(0.005*30)+(20/30) a = 3.6; b= 0.005 ;c = 20 ( for Type ‘C’ terrain )
    • = 4.116666667
    • 10ξ Log(d/d0); where d is the Max Radial Distance to be calculated ; d0 =100mtrs
    • = 10 * 4.1167 *LOG((7.2*1000/100),10) ; for d = 7.2 Km
    • = 76.46019
    • ΔLf = 6*log(f/2000); f is frequency in MHz
    • = 6*LOG((2500/2000),10)
    • = 0.5814601
    • ΔLh = -20log(Hss/2) for Terrain C.
    • = -20*LOG(6/2,10) = -9.542425094
    • S (shadowing Component) = 8.2 dB for Terrain C
    • Total Path loss (in dB) = A + 10ξlog(d/d0)+ΔLf+ΔLh+S = 156.039 (Max allowable path loss from Link Budget calculation)
    • P rx= Ptx +Gtx +Grx-connector loss-Total Path loss +Receiver Sensitivity- Fade Margin
    • = -92.603 dBm [ Receiver Sensitivity for BPSK (-102.692dBm); Fade Margin of 10dB as per ITU-R P.530 ]
    For BPSK -1/2 , Maximum Coverage Radius for above set of parameters is 7.2Km
  • 87. 8/9/2007 * Guard Period is taken as 1/32 of Symbol Time for 3.5 MHz RF Channel OFDM-256 in the above calculation NLOS Coverage and Capacity (range limited) at 2.5 GHz Using Erceg Path Loss Model Modulation Coding Rx Sensitivity (for RF Channel 3.5MHz) Max Bit rate (Mbps) * Max radial distance of coverage (in Km) Adaptive Modulation Coverage area in a hexagonal cell of radius 7.2Km Coverage % % Capacity in a Sector(in Mbps) BPSK -1/2 1/2 -102.692 1.454 7.20 38.04 28.22 0.410 QPSK-1/2 1/2 -99.693 2.909 6.10 18.10 13.43 0.391 QPSK-3/4 3/4 -97.892 4.363 5.50 34.94 25.93 1.131 16-QAM-1/2 1/2 -92.692 5.818 4.10 8.11 6.02 0.350 16-QAM-3/4 3/4 -90.892 8.727 3.70 13.73 10.19 0.889 64-QAM-2/3 2/3 -86.392 11.636 2.90 4.29 3.18 0.370 64-QAM-3/4 3/4 -84.692 13.09 2.60 17.58 13.04 1.707 Total Coverage Area (in sq km) 134.78 100.00 5.248 Data Throughput in a Sector (Mbps) Base Station Capacity with 3 Sectors (in Mbps) 15.745
  • 88. 8/9/2007 Adaptive Modulation Distribution Distance (Km) 7.2 2.6 2.9 3.7 4.1 5.5 6.1 25.93% 13.43% 28.22% 6.02% 10.19% 3.18 % 13.04% QPSK 1/2 BPSK 1/2 QPSK 3/4 16QAM-1/2 16QAM-3/4 64QAM-2/3 64QAM-3/4 1.45Mbps 2.90 Mbps 4.36 Mbps 5.81 Mbps 8.72 Mbps 11.63 Mbps 13.09 Mbps
  • 89. Markets for WiMAX 8/9/2007
  • 90. Vendors active in WiMAX space 8/9/2007 Source: ‘ The Business of WiMAX : Deepak Preekh-pg271-John Wiley & Sons Publications 2006 RF Chip Vendors Service Providers Eqpt Vendors & OEMs Atheros AT&T Alcatel RF Magic BT Alvarion RF Integration China Motion Airspan Sierra Monolithics Covad Aperto Skyworks FT Motorola Baseband Vendors Reliance Navini Beecem PCCW NextNet Sequans Quest Proxim Intel (e.g. Intel 5110 (Rosedale) Telenor Redline Fujitsu SR Telecom
  • 91. 8/9/2007 Challenges for WiMAX Source: ‘ The Business of WiMAX : Deepak Pareekh-pg95-100-John Wiley & Sons Ltd- 2006 Area of concern Issue Solution at Present RF Interference
    • Overlapping Interference from an adjacent BS can generate random noise.
    • Un Licensed solutions have to contend with more interference than licensed solutions
    Can be addressed by sub-channelisation, adaptive modulation, proper network design, filtering & antenna technology Infrastructure Placement
    • The physical structure that supports the BS must be RF friendly.
    NLOS performance is improved in 802.16-2004 due to improved resistance to multi-path interference. Deployment costs
    • Increased number of cell sites, due to using higher frequency bands will incur higher acquisition/leasing & construction costs.
    • The cost & time involved in obtaining building permits are barriers for a non-incumbent service provider.
    WiMAX uses all IP-core, which supports scalable user traffic for a given amount of network resources which means lower cost .
  • 92. Challenges for WiMAX … contnd 8/9/2007 Source: ‘ The Business of WiMAX : Deepak Pareekh-pg95-100-John Wiley & Sons Ltd- 2006 Area of concern Issue Solution at Present Unfinished Business
    • 802.16 addresses MAC & PHY layers. Issues such as call control, session management, security, roaming are still not addressed.
    • WiMAX BS is unaware of adjacent BS as a result seamless mobility is not addressed.
    • Power management issues will reduce the performance in handling traffic from users at the edge of the cell, where inter cell interference is high.
    Portable broadband connection can be adequate enough in addressing the needs of high bandwidth data users. Uncertain Economics
    • Deploying mobile network is a costly proposition for another green field mobile operator.
    IEEE 802.16e (Mobile WiMAX) network supports features like High speed data rate, high-speed vehicular support (120Km/hr), seamless handoff which can differentiate from other mobile services.
  • 93. References
    • IEEE802.16-2004
    • Alcatel White Paper: WiMAX, making ubiquitous high-speed data services a reality
    • Intel White Paper: Understanding WiMAX and 3G for Portable/Mobile Broadband Wireless
    • WiMAX Forum: www.wimaxforum.org
    • Lawrence Harte: Introduction to 802.16 WiMAX – Althos Publishing house 2006
    • http://en.wikipedia.org/wiki/WiMax
    • Motorola White Paper: A practical guide to WiMAX antennas: Beam forming.
    • WiMAX Forum White Paper: Can WiMAX Address Your Applications ? By Westech Communications OCT 2005
    • SR Telecom - symmetry™ Product Data Sheets.
    • Deepak Pareek – ’The Business of WiMAX ’-John Wiley & Sons Ltd- 2006
    8/9/2007
  • 94. Thank You for Your Attention Prepared By K. R A G H U N A T H 8/9/2007