TABLE OF CONTENTS The key element in the wireless LAN is the radio interface that is used to transmit the users information over the radio channel. In Chapter 2, we introduced the fundamental issues that govern radio link capacity: bandwidth, received power, and interference. This is where that background will come into play. The purpose is to provide a fuller understanding of the radio technologies being used, and to develop an appreciation of the capabilities and constraints.
In this chapter, we will begin with an overview of the major radio link interfaces defined in the 802.11 specifications. Then we will also take a closer look at the 2.4 GHz ISM and the 5 GHz U-NII unlicensed radio bands and how they are used with 802.11 wireless LANs. We will also review the advantages and disadvantages of moving from 2.4 GHz to 5 GHz. and discuss the tradeoffs involved. We will describe each of the radio link interfaces in detail including the bit rates supported and the modulation techniques employed. Finally, we will look at the impact of pre-standard and nonstandard radio interfaces in enterprise environments.
The IEEE 802.11 standards currently describe three major radio link interfaces with a fourth in development. In reality, each of those radio link interfaces supports a range of bit rates, and each of those fallback rates defines a different transmission system. We will begin with a quick overview of the options in Table 5-1, which was also presented as...
