Enhancing the Performance of SIP in UMTS

Session setup time is a critical factor for multimedia applications. Some of the factors that affect the session setup delay are length of SIP messages, bandwidth and packet loss in wireless link This paper aims at reducing the session setup delay in UMTS IP Multimedia Subsystem. We propose compression of SIP header by Text-based Compression using Cache and Blank (TCCB) approach and a caching scheme. In caching scheme, during registration, the address of serving call session control function (S-CSCF) of mobile users are cached at Interrogating-CSCF (I-CSCF). Typically, it takes 300 ms to find the address of called mobile user´s Serving CSCF and it can be minimized using cache. A simulation has been carried out to analyze the effect of SIP header compression and caching scheme. The result shows that for 9.6 Kbps channel, a reduction of 25% is possible and for 19.2 Kbps channel 19% reduction can be achieved.