Radio resource allocation and hybrid multiplexing of voice and data over IP in aGSM/GPRS cellular network

Abstract

Abstract In this study, a first order investigation of the issue of resource allocation between circuit voice, packet data and packet voice was completed. The study was done with reference to the GSM / GPRS air interface. To study the allocation of resources, suitable traffic source models were developed to represent the nature of the traffic offered to the base station subsystem. Circuit voice and packet data were represented using Markovian arrivals and exponentially distributed holding times. Voice over IP was modelled using a two-state Markov modulated Poisson process. The base station subsystem was modelled as a continuous time controller with eight channels (one GSM / GPRS TDMA frame). The radio propagation environment was considered by means of a large-scale propagation model, which would merely alter the load presented to the developed simulator package. From the results of the simulations, it was found that insufficient data resources lead to similar packet delay regardless of the packet size. It was found that if capacity on demand is used, then the data resources could equal the load. In the case of sufficient data channels, with capacity on demand, additional channels have a greater effect on average delay than the probability of it occurring. Prioritisation of VoIP packets did not significantly alter the probability of delay but affected the average packet delay. Packet size had a greater effect on average delay than the probability of delay. In the case of all eight channels being used for VoIP and data, the combined load should not exceed seven erlang, indicating that a higher voice load could be supported with VoIP than with circuit switched voice.