Advantages of FDMA

Traditionally FDMA has been favoured for use in radio systems, where the path delays introduced by multipath propagation give rise to intersymbol interference effects which become significant when the differential path delay becomes a significant part of the symbol period. By keeping the symbol duration high, which implies M-ary signalling over narrow frequency slots, the delay problem can often be ignored. (With modern signal processing, the implementation of channel equalization techniques has meant that this delay spread problem need no longer constrain the symbol rate used, allowing much faster data rates over air and hence opening up the possibility of TDMA solutions as an alternative to FDMA.)
Another advantage of FDMA is that the bandwidth of the TX and RX circuitry is kept to a minimum (particularly the bandwidth over which power amplifiers are to be made linear), and the signal processing task for data generation and detection is kept as simple as possible.

Examples of FDMA use include the first-generation cellular telephones and the majority of two-way radio systems in use by taxi companies, trucking fleets, emergency services and so on.