On VoIP session setup delay using SIP over correlated fading channels

In this paper, the session setup delay of the session initiation protocol (SIP) is studied. The session setup delay is a relevant metric for evaluating real-time services signaling: it has a direct impact on the user satisfaction as the user expects to wait the same time as in GSM or PSTN. The transmissions on both forward and reverse channel are assumed to experience Markovian errors. The session setup delay is evaluated for different transport protocols and with the use of the radio link protocol (RLP). An adaptive retransmission timer is proposed to optimize SIP performances. Using numerical results, we find that SIP over UDP instead of TCP can make the session setup up to 30% shorter. Also RLP reduces drastically the session setup delay down to 8s even in environment with high frame error rate (10%) and significant correlation in the fading process (f_DT=0.02)