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

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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.

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What is WiMAX

Deployment

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What is WiMAX

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

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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

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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

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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

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Physical Layer

TDD Frame Structure

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

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Physical Layer

FDD Bandwidth Allocation

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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.

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Frame Structure

Uplink Subframe

SSTG (Subscriber Station Transition Gap)

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Frame Structure

OFDMA Frame Structure