Variable-rate for the basic speech service in UMTS

A variable-rate approach for the user channel in a code division multiple access (CDMA)-based mobile system is proposed. The statistics of the different kinds of information to be transmitted, in the case of voice services, are discussed, together with the management of the variable-rate resulting channel. Possible alternatives are indicated, presenting the functions allocated to a variable-rate control unit. Some indications are given about contention problems, caused by simultaneous requests of high bit rates by both speech and signalling processes, thus exceeding the physical channel capacity.