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Wireless Communication- Multiple access Techniques

Many mobile users to share simultaneously a finite amount of radio spectrum to achieve high capacity by simultaneously allocating the available bandwidth to multiple users. In telephone systems, it is possible to talk and listen simultaneously and this effect, called duplexing. Frequency division duplexing (FDD): provides two distinct bands of frequencies for every user. The forward band provides traffic from the base station to the mobile, and the reverse band provides traffic from the mobile to the base. The frequency split between the forward and reverse channel is constant throughout the system. Time division duplexing (TDD): uses time instead of frequency to provide both a forward and reverse link. TDD allows communication on a single channel (as opposed to requiring two simplex or dedicated channels) and simplifies the subscriber equipment since a duplexer is not required.