On the Interaction Between SIP and RLC Error Recovery in Session Establishment over Satellite-UMTS

Abstract

The transport of SIP signaling for session establishment over the satellite radio interface is not efficient due to the inherent characteristics of SIP coupled with the unreliable wireless links and the larger satellite propagation delay. One way to improve the session set-up performance is to conceal the link-related losses from the upper layers by utilizing link layer retransmission based on the UMTS Radio Link Control acknowledged mode (RLC-AM) mechanisms. Nevertheless, due to link layer protocols operating independently from higher layer protocol, the interaction between the link-layer transmission and end-to-end transmission can become complicated and this may lead to poor system performance and resource utilization if the setting of timers at the two layers is incompatible. In this paper, we investigate the problem of the possible competing error recovery between the end-to-end retransmissions implemented at the higher layers with the local retransmissions at the lower layers. More specifically, we look into the interaction between the session layer (SIP) own reliability mechanisms with the link layer (RLC) retransmission scheme, and study different schemes to minimize the undesirable effect of both layers responding to the same loss events. This is made possible by making SIP and RLC to be ‘more co-operative’ through different degree of awareness between these two error recovery schemes.