Phone Number Translation Delay in PCS Systems with ATM Backbones

Abstract

Future wired networks with an ATM backbone will need to support PCS and wireless subscriber services. One of the key functions required to support PCS and wireless subscribers with non-geographic phone numbers (NGPN) will be the ability to efficiently identify which Home Location Register (HLR) database serves the subscriber. (Note that the same functionality is also needed to serve subscribers with portable phone numbers.) In a previous paper we have presented a scheme for NGPN translation based upon distributed, dynamic hashing. The scheme uses a hash function in the Visitor Location Registers (VLR)and a set of distributed Translation Servers (TS) which store the NGPN-to-HLR mapping.In this paper we present a preliminary investigation of the additional call setup delay introduced by the NGPN translation scheme we have proposed. We develop a queuing network model for both the one-stage and two-stage versions of our NGPN translation scheme, and we investigate the impact of two key aspects of our scheme, namely the use of hashing and of caching. A poor choice of hash function can lead to imbalanced loading at the TS. We quantify the impact of this imbalance for an example scenario. We also show that caching at the VLR can substantially reduce the mean translation delay. Finally we consider the use of the two-stage scheme and a second-level cache when the translation load increases.KeywordsHash FunctionTranslation ServerLoad ImbalanceVisitor Location RegisterHome Location RegisterThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.