The Direct Sequence PHYs: DSSS and HR/DSSS (802.11b)

The Direct Sequence PHYs DSSS and HR DSSS (802 11b)

The intial revision of the 802.11 specification in 1997 had a second physical layer based on direct sequence spread spectrum (DSSS) technology. The DSSS PHY in 802.11 had data rates of 1 Mbps and 2 Mbps. Although it operated at the same speed as the frequency hopping PHY, it quickly became clear that direct sequence technolgies had the potential for higher speeds than frequency hopping technologies. As a result, even though the two had equivalent speeds, direct sequence became the PHY of choice. In 1999, a PHY with data rates of 5.5 Mbps and 11 Mbps was specified in 802.11b. The older 1 and 2 Mbps PHYs and the newer 5.5 and 11 Mbps PHYs are often combined into a single interface, even though they are described by different specifications. (It is usually referred to as "802.11b" support, even though the two lower rates are not part of 802.11b.) This chapter describes the basic concepts and modulation techniques used by the direct sequence physical layers. It also shows how the PLCP prepares frames for transmission on the radio link and touches briefly on a few details of the physical medium itself.

Introduction to Wireless Networking

Overview of 802.11 Networks

11 MAC Fundamentals

11 Framing in Detail

Wired Equivalent Privacy (WEP)

User Authentication with 802.1X

11i: Robust Security Networks, TKIP, and CCMP

Management Operations

Contention-Free Service with the PCF

Physical Layer Overview

The Frequency-Hopping (FH) PHY

The Direct Sequence PHYs: DSSS and HR/DSSS (802.11b)

11a and 802.11j: 5-GHz OFDM PHY

11g: The Extended-Rate PHY (ERP)

A Peek Ahead at 802.11n: MIMO-OFDM

11 Hardware

Using 802.11 on Windows

11 on the Macintosh

Using 802.11 on Linux

Using 802.11 Access Points

Logical Wireless Network Architecture

Security Architecture

Site Planning and Project Management

11 Network Analysis

11 Performance Tuning

Conclusions and Predictions

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802.11 Wireless Networks The Definitive Guide
802.11 Wireless Networks: The Definitive Guide, Second Edition
ISBN: 0596100523
EAN: 2147483647
Year: 2003
Pages: 179
Authors: Matthew Gast
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