The most typical way of allocating a single channel among multiple competing users is Frequency Division Multiplexing (FDM). If the number of users are N, the bandwidth is divided into N equal-sized portions. Each user is assigned one portion. If the number of users are small and constant, FDM is a simple and efficient allocation mechanism.
A telephone trunk can be a simple example of this type. However, when the number of senders is not small and constant or the traffic is heavy, FDM presents some problems. If the spectrum is divided into N regions the number of users currently interested in communicating is less than N, a large piece of valuable spectrum will be wasted.
A telephone trunk can be a simple example of this type. However, when the number of senders is not small and constant or the traffic is heavy, FDM presents some problems. If the spectrum is divided into N regions the number of users currently interested in communicating is less than N, a large piece of valuable spectrum will be wasted.
