9
Multiple Access Methods
In practice, it is not enough that a single high data rate stream can be transmitted through the air from the transmitter to the receiver. Rather, wireless communication systems must be able to serve tens or even hundreds of users simultaneously with multimedia applications requiring very high data rates. The method allowing several users to communicate simultaneously is called multiple access (MA). In this chapter different strategies to implement multiple access are presented.
In a cellular system, the coverage area is divided into parts called cells. Each cell has a base station, which is connected with all user terminals inside the cell. In cellular telecommunication systems, the transmission from the base station to a user terminal (downlink, forward link) and the transmission from a terminal to the base station (uplink, reverse link) must be separated. Traditionally downlink and uplink transmissions use different frequencies or they occur consecutively. These two options are referred to as frequency division duplexing (FDD) and time division duplexing (TDD) [8]. The method allowing several users to communicate simultaneously inside a cell is called a multiple access technique. The capacity of multiple access techniques refers to the maximum number ...
