IEEE Std. 802.16 Technique Overview

IEEE Std. 802.16 Technique Overview

nmgmt.cs.nchu.edu.tw

系統暨網路管理實驗室 Systems & Network Management Lab

Reporter：黃文帥2007/09/18

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Contents

What is WiMAX1

Physical Layer2

Frame Structure3


What is WiMAX

Scope: - Specifies the air interface, MAC (Medium Access Control), PHY (Physical Layer).

Purpose: - Enable rapid worldwide deployment of cost-effective broadband wireless access product.

- Facilitate competition in broadband access by providing alternatives to wireless broadband access.

Main advantage: - Fast deployment, dynamic sharing of radio resources and low cost.


What is WiMAX

Deployment


What is WiMAX

Adaptive Modulation Maximize throughput. Minimize average power. Minimize average bit error rate.


What is WiMAX

802.11 is not strictly synchronized.

802.16 is a slotted system and all the transmission must be synchronize.

802.11 uses two-way (Data/ACK) or four-way (RTS/CTS/Data/ACK) handshaking to access channel and transmit data.

802.16 uses a three-way handshaking to set up connection before data transmission (Request/Grant/Transmit).

802.11 does not distinguish control channel and data channel.

In 802.16, the control channel and data channel are separated.

In 802.11, a station must compete for every packet.

In 802.16, a station can reserve multiple slots for the following packets.

802.11 vs 802.16


Physical Layer

Support framing. Support both Time Division Duplex (TDD) and Frequency

Division Duplex (FDD), as well as half-duplex FDD (H-FDD).

Burst transmission format which supports adaptive burst profiling.

- Data allocations within a frame are referred as bursts.

- Transmission parameters, including the modulation and coding schemes (burst

profiles), may be adjusted individually to each SS on a frame-by-frame basis.

- Burst profiles are broadcast via MAC management messages Downlink Channel

Descriptor (DCD) and Uplink Channel Descriptor (UCD) periodically.

- The actual transmission bandwidth is allocated by BS and broadcast in MAC

management messages Downlink MAP (DL-MAP) and Uplink MAP (UP-MAP) in

each frame.

- Adapt to multiple modulation levels ： BPSK, QPSK, QAM-16, QAM-64.

Introduction


Physical Layer

TDD - The UL and DL transmissions occur at different times and usually share

the same frequency. (SS does not receive and transmit data at the same

time)

- A TDD frame has a fixed duration and contains one DL and one UL

subframe, whose durations can vary.

FDD - The UL and DL channels are located on separate frequencies.

- A fixed duration frame is used for both UL and DL transmissions.

- The H-FDD SS does not receive and transmit data at the same time.

PHY Duplexing Option


Physical Layer

TDD Frame Structure

PS (Physical Slot) - A unit of time, depend on the PHY specification, for allocating bandwidth.


Physical Layer

FDD Bandwidth Allocation


Frame Structure

Downlink Subframe

TTG/RTG (Transmit/Receive Transition Gap) - A gap between the downlink burst and the subsequent uplink burst in a time division duplex (TDD) transceiver.


Frame Structure

Uplink Subframe

SSTG (Subscriber Station Transition Gap)


Frame Structure

OFDMA Frame Structure

Documents

IEEE Std. 802.16 Technique Overview