WiMAX Part I PHY Raj Jain Professor of Computer Science and Engineering Washington University in Saint Louis Saint Louis MO 63130 Jain cse wustl edu Audio Video recordings of this lecture are available at http www cse wustl edu jain cse574 10 Washington University in St Louis CSE574s 10 1 2010 Raj Jain Overview What is WiMAX Previous Broadband Wireless Access LMDS MMDS WiMAX PHY Layer Frequency Reuse Subchannelization Frame structure Washington University in St Louis CSE574s 10 2 2010 Raj Jain What is WiMAX Point to Multipoint 50km Point to Point Telco Core Base Stations BSs Uplink UL Downlink DL Rural Areas 120km sec Mobile Users Subscriber Station SSs 70Mbps Congested Areas Washington University in St Louis CSE574s 10 3 2010 Raj Jain Data rate vs Mobility Mobility Vehicular WiMAX Nomadic Cellular WiFi Stationary 0 1 1 10 100 User Link Bit Rate Mbits second Washington University in St Louis CSE574s 10 4 2010 Raj Jain Key Features of WiMAX Works on many bands 2 3 GHz 2 5 GHz 3 5 GHz Scalable Can use any available spectrum width 1 25 MHz to 28 MHz Strong security Open technology like WiFi Reach and mobility like Cellular but much higher data rates High data rate up to 70Mbps Long distance up to 50kms Mobility up to 120 to 150 km hour Data rate vs Distance trade off using adaptive modulation 64QAM to BPSK Offers non line of site NLOS operation Strong QoS Guaranteed services for data voice and video Washington University in St Louis CSE574s 10 5 2010 Raj Jain Prior Attempts LMDS MMDS Local Multipoint Distribution Service 1998 1 3 GHz around 28 GHz band Ka Band 28 GHz Rain effects Multi channel Multipoint Distribution Services 1999 2001 2 1 2 5 2 7 GHz Band Not affected by rain Issues Equipment too expensive Roof top LoS antennas short range LMDS or too small capacity MMDS Modem PoP Washington University in St Louis CSE574s 10 6 2010 Raj Jain WiMAX WiMAX IEEE 802 16 Worldwide Interoperability for Microwave Access 420 members including Semiconductor companies equipment vendors integrators service providers Like Wi Fi Alliance Narrows down the list of options in IEEE 802 16 Plugfests started November 2005 WiMAX forum lists certified base stations and subscriber stations from many vendors http www wimaxforum org Washington University in St Louis CSE574s 10 7 2010 Raj Jain Spectrum Options Washington University in St Louis CSE574s 10 8 2010 Raj Jain Effect of Frequency Higher Frequencies have higher attenuation e g 18 GHz has 20 dB m more than 1 8 GHz Higher frequencies need smaller antenna Antenna Wavelength 2 800 MHz 6 Higher frequencies are affected more by weather Higher than 10 GHz affected by rainfall 60 GHz affected by absorption of oxygen molecules Higher frequencies have more bandwidth and higher data rate Higher frequencies allow more frequency reuse They attenuate close to cell boundaries Low frequencies propagate far Mobility Below 10 GHz Washington University in St Louis CSE574s 10 9 2010 Raj Jain IEEE 802 16 PHYs Function LOS Freq Band Carrier Duplexing WirelessMAN SC Pt to pt LOS 10 66 GHz Single TDD FDD WirelessMAN SCa Pt to pt LOS 2 11 GHz Licensed Single TDD FDD WirelessMAN OFDM 16d Pt to mpt NLOS 2 11 GHz Licensed 256 TDD FDD WirelessMAN OFDMA 16e Pt to mpt NLOS 2 11 GHz Licensed 2048 TDD FDD WirelessHUMAN High speed Unlicensed Pt to mpt NLOS 2 11 GHz License Exempt 1 256 2048 TDD Dynamic Freq Sel Washington University in St Louis CSE574s 10 10 2010 Raj Jain IEEE 802 16 PHY Features Features discussed previously Scalable OFDMA TDD and FDD Adaptive Modulation and Coding Space Time Block Codes STBC Adaptive Antenna System Other Features Subchannelization and permutation Slots tiles and clusters bursts Washington University in St Louis CSE574s 10 11 2010 Raj Jain Frequency Reuse NxSxK frequency reuse pattern N Number of cells per cluster S Number of sectors in a cell K Number of frequency allocations per cell 1X3X3 Washington University in St Louis CSE574s 10 12 2010 Raj Jain Frequency Reuse Cont 1x3x1 1 1x3x3 1 1 1x1x1 2 1 1 1 1 1 1 1 S S 1 1 1 1 1 1 2 1 3 1 3 S S S S 2 1 3 2 1 1 2 1 1 1 1 1 1 1 1 1 3 2 1 3 2 1 1 1 1 1 1 1 1 3 1 3 2 1 2 1 1 1 1 1 3 1 1 3 2 1 1 3 3x1x1 3x3x1 1 1 3 SS 3 3 1 1 3 1 7 3 2 3 2 2 8 4 9 SS 7 3 8 9 5 4 5 2 2 1 1 2 2 SS 3 3 3x3x3 1 2 1 1 2 1 1 6 2 6 2 1 1 3 3 3 1 3 3 3 7 8 7 3 8 3 3 2 2 3 9 4 5 9 2 2 Washington University in St Louis CSE574s 10 13 6 2010 Raj Jain Fractional Frequency Reuse Users close to the BS use all frequency subchannels Users at the cell boundary use only a fraction of available subchannels F1 F1 F2 F3 F3 F2 F1 F2 F3 F1 F2 F3 Washington University in St Louis CSE574s 10 14 2010 Raj Jain OFDM Subcarriers Data subcarriers Pilot Subcarriers Used for channel estimation Guard subcarriers At the edges No power DC subcarrier At the center for frequency band No power Data Pilot Guard Washington University in St Louis DC Guard CSE574s 2010 Raj Jain 10 15 Subchannelization Subchannel Group of subcarriers Each user is given one or more subchannel Subcarriers of a subchannel can be contiguous or distributed Subchannel 1 Contiguous Subchannels allocated based on use s SINR Band AMC Not suitable for mobile applications Washington University in St Louis CSE574s 10 16 2010 Raj Jain Subcarrier Permutations Subcarriers are randomly assigned to a channel and changed every symbol time Frequency hopping All subcarriers are used Full Usage of Subcarriers FUSC Not in WiMAX Forum Profiles Partial Usage of Subcarriers PUSC in WiMAX Forum profiles commonly used Washington University in St Louis CSE574s 10 17 2010 Raj Jain Downlink Partial Usage of Subcarriers Subcarriers are divided in to 6 groups and only some groups may be used in a sector or cell Data and pilots are arranged in clusters of 14 subcarriers over 2 symbols 24 data 4 pilot Clusters are renumbered using a pseudo random numbering scheme The clusters are then divided into 6 groups segments 0 through 5 Subchannel Two clusters from the same group It is possible to allocate some subset of groups to each transmitter in a cell e g 2 groups per sector Washington University in St Louis CSE574s 10 18 2010 Raj Jain Symbols Clusters and Slots PUSC DL 10 MHz 1024 FFT 840 subcarriers 1 DC 183 Guard Total 30 subchannels 30 28 840 subcarriers Subcarriers Cluster 2 symbols 14 subcarriers Frequency Subchannel 28 subcarriers Slot 2 Clusters Pilot Data Symbols Time Washington University in St Louis CSE574s 10 19 2010 Raj Jain Symbols Tiles and Slots PUSC UL …
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