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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

WiMAX: Broadband Wireless Access

Wireless Networks Spring 2007


802 16 standards development
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


802 16 standards development1
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


Ieee 802 16 protocol architecture
IEEE 802.16 Protocol Architecture

Wireless Networks Spring 2007


Protocol architecture
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


Protocol architecture1
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


Ieee 802 16 services
IEEE 802.16 Services

  • Digital audio/video multicast

  • Digital telephony

  • ATM

  • Internet protocol

  • Bridged LAN

  • Back-haul

  • Frame relay

Wireless Networks Spring 2007


Burst profiles
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


Ieee 802 16 1 frame format
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


Physical layer uplink
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


Physical layer downlink
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


Medium access control mac
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


Radio link control
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


Bandwidth requests grants
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


Requesting bandwidth
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


Mac management messages
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


Mac management messages1
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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