A Caching Scheme for Session Setup in IMS Network

In IP Multimedia Subsystem (IMS), the session setup delay is a critical value for Quality of Service (QoS). The existing approaches to improve this metric depend on optimization of Session Initiation Protocol (SIP) message transmitting and signaling flows. Unfortunately, some service features are missing considered although they have been used widely in traditional 2G networks. This paper proposes a novel session setup scheme based on caching, upon the investigation of the performance of IMS session establishment. This mechanism involves cache based local routing policy and an adaptive caching algorithm, which can decrease call setup delay effectively as cached information in the terminating Serving-Call Session Control Function (S-CSCF) hit. The analytical model is deduced, as well as the delay and cost ratio functions are presented based on the model. Moreover, the analytical model is validated through the performance simulation in which the performance of the proposed novel method is evaluated against the basic session setup mechanism in terms of cost and delay.