Analyzing and Improving Session Setup Latency of Push-to-Talk over Cellular

Push-to-Talk over Cellular (PoC) system in mobile communication network, such as TD-SCDMA, is considered to have more wide coverage and more flexibility than traditional trunk communication systems. It is ideal for group communication in many cooperative work environments. But the foremost block for wider application of PoC system is the longer session setup latency comparing to other trunk communication systems. This paper analyzes the main cause of the longer call latency and the main research activities about this. A scheme for reducing the session setup latency is provided, which emphasized on the SIP signaling compressed with an improved dictionary-based compression method (IDCM). The prototype of PoC system adopting the scheme is also described and the performance estimation is given. Simulation results show the reduction of session setup latency is achieved.