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WiMAX: Broadband Wireless Access

WiMAX: Broadband Wireless Access. 802.16 Standards Development. Use wireless links with microwave or millimeter wave radios 10-66 GHz 802.16a extension to 2-11 GHz Use licensed spectrum (unlicensed too in 802.16a) Metropolitan in scale Provide public network service to fee-paying customers

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WiMAX: Broadband Wireless Access

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  1. WiMAX: Broadband Wireless Access Wireless Networks Spring 2007

  2. 802.16 Standards Development • Use wireless links with microwave or millimeter wave radios • 10-66 GHz • 802.16a extension to 2-11 GHz • Use licensed spectrum (unlicensed too in 802.16a) • Metropolitan in scale • Provide public network service to fee-paying customers • Point-to-multipoint architecture with rooftop or tower-mounted antennas Wireless Networks Spring 2007

  3. 802.16 Standards Development • Provide efficient transport of heterogeneous traffic supporting QoS • Capable of broadband transmissions (2-75 Mbps) • Accommodate both continuous and bursty traffic • Mobile extensions: 802.16e Wireless Networks Spring 2007

  4. IEEE 802.16 Protocol Architecture Wireless Networks Spring 2007

  5. Protocol Architecture • Physical layer functions: • Encoding/decoding of signals • Preamble generation/removal • Bit transmission/reception • Medium access control layer functions: • On transmission, assemble data into a frame with address and error detection fields • On reception, disassemble frame, and perform address recognition and error detection • Govern access to the wireless transmission medium Wireless Networks Spring 2007

  6. Protocol Architecture • Convergence layer functions: • Encapsulate PDU framing of upper layers into native 802.16 MAC/PHY frames • Map upper layer’s addresses into 802.16 addresses • Translate upper layer QoS parameters into native 802.16 MAC format • Adapt time dependencies of upper layer traffic into equivalent MAC service Wireless Networks Spring 2007

  7. IEEE 802.16 Services • Digital audio/video multicast • Digital telephony • ATM • Internet protocol • Bridged LAN • Back-haul • Frame relay Wireless Networks Spring 2007

  8. Burst Profiles • Each subscriber station negotiates a burst profile with the base station • Burst profiles decided based on QoS needs and channel conditions • Harsher environment demands more robust profiles • Favorable environment allows efficient profiles Wireless Networks Spring 2007

  9. IEEE 802.16.1 Frame Format • Header - protocol control information • Downlink header – used by the base station • Uplink header – used by the subscriber to convey bandwidth management needs to base station • Bandwidth request header – used by subscriber to request additional bandwidth • Payload – either higher-level data or a MAC control message • CRC – error-detecting code Wireless Networks Spring 2007

  10. Physical Layer: Uplink • Stations transmit in in their assigned allocation specified in an initial map • Uplink sub-frame may also contain contention-based allocations for initial system access • Uses a DAMA-TDMA technique • Error correction uses Reed-Solomon codes • Modulation scheme based on QPSK, 16-QAM or 64-QAM Wireless Networks Spring 2007

  11. Physical Layer: Downlink • Continuous downstream mode • For continuous transmission (audio/video) • Simple TDM scheme is used for channel access • Frequency division duplex (FDD) • Burst downstream mode • For bursty transmission (IP-based traffic) • DAMA-TDMA scheme for channel access • FDD with adaptive modulation, frequency shift division duplexing (FSDD), time division duplexing (TDD) Wireless Networks Spring 2007

  12. Medium Access Control (MAC) • Connection-oriented • All services inherently connectionless mapped to a connection • Connections referenced using a 16-bit connection identifier (CID) • Management channels and transport channels for contracted services Wireless Networks Spring 2007

  13. Radio Link Control • Power control and paging • Transition among burst profiles • Downlink burst profile change • Subscriber station monitors downlink quality • Requests a new profile • Granted if base station judges possible • Uplink profile change • Base station monitors the uplink signal quality • Specifies the new profile’s usage code when granting subscriber bandwidth in a frame Wireless Networks Spring 2007

  14. Bandwidth Requests & Grants • Two kinds of subscribers • Grant per connection (GPC) • Grant per subscriber (GPSS) • Both classes request bandwidth per connection for QoS guarantees • For GPC, bandwidth explicitly guaranteed to connection • For GPSS, bandwidth aggregated into a single grant for SS Wireless Networks Spring 2007

  15. Requesting Bandwidth • Unsolicited grants • No need to request bandwidth for services that generate fixed units of data periodically • Negotiated at connection setup time • Send a bandwidth request MAC packet • Piggyback request within MAC data packet • Polling by base station Wireless Networks Spring 2007

  16. MAC Management Messages • Uplink and downlink channel descriptor • Uplink and downlink access definition • Ranging request and response • Registration request, response and acknowledge • Privacy key management request and response • Dynamic service addition request, response and acknowledge Wireless Networks Spring 2007

  17. MAC Management Messages • Dynamic service change request, response, and acknowledge • Dynamic service deletion request and response • Multicast polling assignment request and response • Downlink data grant type request • ARQ acknowledgment Wireless Networks Spring 2007

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