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.