SPR proxy mechanism for 3GPP Policy and Charging Control System
3GPP has standardized its Policy and Charging Control (PCC) system to provide dynamic policy control combined with real-time charging. The specific guidance on how PCC signaling delay can be reduced in session setup has not been explored in 3GPP standard. To bridge this gap, we propose an SPR proxy mechanism to shorten the PCC record retrieval delay which occurs between two PCC nodes: the Policy and Charging Rule Function (PCRF) and the Subscription Profile Repository (SPR). Our proposed SPR proxy is implemented at the PCRF to store the serving users' PCC records retrieved from the SPR. Once the PCC records are updated by the subscribers, the SPR needs to refresh the SPR proxy in order to retain the record validity. If the PCC record updates in the SPR occur more frequently than the PCC record accesses performed by the PCRF, the SPR will generate many unnecessary refresh operations. The objective of this paper is to propose two delayed refresh schemes to be used alongside the SPR proxy for refresh suppression. Our schemes can dynamically adjust the delayed refresh timer according to the multi-user update rate of PCC records in the SPR. An analytical model and extensive simulation are developed to investigate the SPR proxy performance in terms of the proxy validity and the expected number of refreshes saved. Numerical results show that our SPR proxy mechanism with delayed refresh can significantly shorten the PCC-based session setup delay without significantly diminishing the proxy validity of PCC records.