Support of Scalable Multimedia Services in the Circuit-Switched Domain in GERAN
Original Publication Date: 2005-Jan-25
Included in the Prior Art Database: 2005-Jan-25
Related PeopleOther Related People:
The support of a multimedia service like video telephony or a cellular network like GERAN (GSM EDGE Radio Access Network) usually requires an audio/video codec. This codec produces a data stream which is then transmitted. Due to the combined transport of audio and video data, the service can be either supported (if allowed by radio conditions and/or network resources) or has to be abandoned completely. No graceful degradation, to e.g. an audio-only connection, is available. If the audio and video parts are coded separately, they can be transported via two different and independent channels. In GERAN it would be possible to use DTM (Dual Transfer Mode). This solution, however, has the disadvantage that only a circuit-switched and a packet-switched channel can be combined. While the circuit-switched channel is optimized for the transport of coded voice in the conventional mode (and therefore would be suited well to transport the audio part), the packet-switched channel is not designed to support a conversational service (no guaranteed data rate, long interruptions during cell reselection since no handover is specified). Furthermore, due to different channel coding schemes are available for circuit-switched and packet-switched channels, different delays on these channels will occur which adversely affects synchronization between audio and video.