WiMAX for Broadband Wireless Access full report

[seminar class]

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WiMAX: Broadband Wireless Access
 802.16 Standards Development
 Use wireless links with microwave or millimeter wave radios
o 10-66 GHz
o 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
 802.16 Standards Development
 Provide efficient transport of heterogeneous traffic supporting QoS
 Capable of broadband transmissions (2-75 Mbps)
o Accommodate both continuous and bursty traffic
Mobile extensions: 802.16e
 IEEE 802.16 Protocol Architecture
 Protocol Architecture
 Physical layer functions:
o Encoding/decoding of signals
o Preamble generation/removal
o Bit transmission/reception
 Medium access control layer functions:
o On transmission, assemble data into a frame with address and error detection fields
o On reception, disassemble frame, and perform address recognition and error detection
o Govern access to the wireless transmission medium
Protocol Architecture
 Convergence layer functions:
o Encapsulate PDU framing of upper layers into native 802.16 MAC/PHY frames
o Map upper layer’s addresses into 802.16 addresses
o Translate upper layer QoS parameters into native 802.16 MAC format
o Adapt time dependencies of upper layer traffic into equivalent MAC service
 IEEE 802.16 Services
Digital audio/video multicast
 Digital telephony
 ATM
 Internet protocol
 Bridged LAN
 Back-haul
 Frame relay
 Burst Profiles
 Each subscriber station negotiates a burst profile with the base station
 Burst profiles decided based on QoS needs and channel conditions
o Harsher environment demands more robust profiles
o Favorable environment allows efficient profiles
 IEEE 802.16.1 Frame Format
Header - protocol control information
o Downlink header – used by the base station
o Uplink header – used by the subscriber to convey bandwidth management needs to base station
o Bandwidth request header – used by subscriber to request additional bandwidth
 Payload – either higher-level data or a MAC control message
 CRC – error-detecting code
 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
 Physical Layer: Downlink
 Continuous downstream mode
o For continuous transmission (audio/video)
o Simple TDM scheme is used for channel access
o Frequency division duplex (FDD)
 Burst downstream mode
o For bursty transmission (IP-based traffic)
o DAMA-TDMA scheme for channel access
o FDD with adaptive modulation, frequency shift division duplexing (FSDD), time division duplexing (TDD)
Medium Access Control (MAC)
 Connection-oriented
o 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
 Radio Link Control
 Power control and paging
Transition among burst profiles
 Downlink burst profile change
o Subscriber station monitors downlink quality
o Requests a new profile
o Granted if base station judges possible
 Uplink profile change
o Base station monitors the uplink signal quality
o Specifies the new profile’s usage code when granting subscriber bandwidth in a frame
Bandwidth Requests & Grants
 Two kinds of subscribers
o Grant per connection (GPC)
o 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
Requesting Bandwidth
 Unsolicited grants
o No need to request bandwidth for services that generate fixed units of data periodically
o Negotiated at connection setup time
 Send a bandwidth request MAC packet
 Piggyback request within MAC data packet
 Polling by base station
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
 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