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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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