The Research On The Technology Of CS Fallback In LTE System

With the rapid development of mobile communication technology, Mobile Broadband had become the main tread of the mobile communication system. The major operators and equipment manufacturers are paying more and more attention to the LTE which had become the main evolution solutions of mobile communication system.In the LTE network construction and the use of LTE access, we cannot receive/transmit the signal of CS. In order to make the terminal in the LTE access to initiate voice service, as well as to receive a voice paging, and to handle the ongoing PS service correctly, we produce the technolog y of CSFB, that is to say, operator has a mature 2G/3G network. In order to protect the CS investment, combined with EPS deployment strategy, we can use original CS domain to provide voice service, and only use the PS domain of LTE network to process data service. Base on this requirement,3GPP proposed the technology of CS Fallback,that is,when the UE in LTE syatem need to handover to the CS to complete the call.It is discussed in this paper focus on TD-LTE system voice fall back pattern, attachments, procedure and called flow.Think about the user sense and the reliability of establish the call and network complexity,then anlysis serval call back method. In CSFB typical issues, such as unopened CSFB features, down to 2G failed, hook doesn’t return such as the 4G, network problems after careful analysis of signaling, and suggesting an optimization solution.Although the CSFB scheme is feasible single standby scheme, it has a lot of problems. It is defined as the international roaming voice scheme by MGMN in the early LTE required system,and also the transitional scheme. This paper is aimed at the problem of CSFB deployment, put forward effective improvement measures. And also has a practical value for improving the pronunciation continuity of LTE system.