Features of FDM
1.The FDM channel carries only one phone circuit at a time.
2.If an FDM channel is not in sue then it is sits idle and cannot be used by other users to increase of share capacity. It is essentially a wasted resources.
3.After the assignment of a frequency channel to user transmission is continuous.
4. The bandwidth of FDM channels are relatively narrow as each channel supports only one circuit per carrier. That is FDM is usually implemented in narrow band systems.
5.The symbol time of a narrow ban signal is larger as compared to the average delay spread. This implies that the amount of inter symbol interference is low and thus little or no equalization is required in FDM narrow band systems.
6.The complexity of FDM systems is lower when compared to TDM system though this is changing as digital signal processing methods improve for TDM.
7.Since FDM is a continuous transmission scheme fewer bits are needed for overhead purpose (such a synchronization and farm in gbits0 as compared to TDM.
8.FDM system have higher systems costs as compared to TDM systems because of single channel per carried designed and the need to use costly band pass filters to eliminate spurious radiation at the base station.
9.FDM requires tight RF flitting to minimize adjacent channel interference.