Analyzing Packet Delay Across A GSM/GPRS Network

In this paper we study two major sources of packets delay in the GSM/GPRS wireless network, at Base Station and at GGSN node. Fisrt, for the former one, we present an analytical model to study the performance of channel sharing schemes to support both circuit switched voice and packet data services in a GSM/GPRS network. We study three channel sharing schemes: 1) fixed sharing in which cell channels are statically partitioned into two sets one for voice calls and the other for data traffic; 2) partial sharing in which ndatachannels are reserved for data while the remaining N − ndatachannels are shared by voice and data with preemptive priority for voice calls; and 3) complete sharing in which all the channels shared by voice and data with preemptive priority to voice calls. We investigate several key issues such as call blocking rate and mean packet delay for different cell loads with the data source modeled by a Markov Modulated Poisson Process (MMPP). We validate the mathematical model through simulations and quantify the impact of the data source model and the voice call load on the mean packet delay for different channel sharing schemes. Secondly, for another souce causing delay, we present the analytical model to quantify the benefit of replicated GGSN with load balancing architecture.Our results show that replicated GGSN architecture with load balancing policy can significantly reduce the packet delay even when the total GGSN capacity remains constant.