The Research Of TrFO In CDMA2000

In the traditional mobile communication system based on circuit, the network also needs to carry on the speech codec twice, even if the mobile terminal and network all support the same codec method. In this way it not only increases the cost of equipments, but also affect the system performance. Therefore, in order to improve the quality of speech and provide the service of high quality, the 3G system puts forward the technology of TrFO(Transcoder Free Operation). The appearance of TrFO can not only solve the problem of speech, but also save the resource and reduce the network postponement. When the codec method can not be unified, then it puts forward the RTO(Remote Transcoder Operation) technique. The RTO can also save one codec operation.The TrFO that is studied in this article is based on the CDMA2000 core network of IP structure. In the CDMA2000 core network, it improves the network structure by moving the vocoder which was located on the base station controller to the media gateway. The core idea of the TrFO in the article is to avoid the unnecessary codec transform before the establishment of the call, depending on the codec negotiation to unify the whole codec. This article sets the starting line by the codec list supported by the mobile station and MGW, and brings the TrFO basic arithmetic. Besides, combining with the TrFO basic arithmetic, this article designs a few TrFO models in the actual system and verifies the TrFO realization under the different environment. In the meantime, combining the speech test, it reflects the advantage of the TrFO compared with the non-TrFO.The TrFO has important significance to the 3G system. But the TrFO still need a further improvement,for the whole codec can not satisfy the unification and agility in the meantime currently. So how to carry out the unified codec which will be changed agility according to actual situation, will be an issue that needs to be studied continuously from now on.