3. New multimedia services

3.1 Circuit mode services

In its first version, UMTS offers a basic telephone service over the circuit domain of the core network. To achieve this, the AMR encoder is used to adapt the data rate to radio conditions. When radio conditions are good, it operates at a rate of 12.2 kbit/s, and when they deteriorate, it reduces the rate to 4.75 kbit/s (3GPP TS 26.101 specification).

Release 99 also offers a video-telephony service, completely new compared to GSM. Thanks to this service, the UMTS mobile terminal has immediately established itself as the first telephone for the deaf and mute, who until now had communicated using short messages on their GSM mobile terminals. Of course, the video-telephony service is available to all subscribers. This service uses the...