Performance Modelling of GSM GPRS mobile system with MOSEL

Recently all major mobile network providers have introduced the General Packet Radio Service GPRS onto their GSM networks However the performance of these system is still under eval uation This paper presents a modelling frame work of GSM GPRS system with di erent parti tioning strategies using the Modelling Speci cation and Evaluation Language and package MOSEL The investigated scenarios comprise a wireless GSM GPRS cell supporting voice calls and data packets under complete partitioning CPS and par tial sharing PSS cell capacity handling schemes The two schemes are modelled using some queueing network models described by MOSEL and solved numerically The data tra c is modelled using the Generalised Exponential distribution to capture some variability The numerical results are vali dated using simulation Key word Wireless GSM GPRS cell Par tial Sharing Sheme PSS Queueing Network Model QNM Generalized Exponential GE dis tribution MOSEL Introduction Queueing models as a powerful tool are widely used in both computer and telecommunication net works Most evaluation and performance measures are based on the simulation method and numerical solution of Markov models The Modelling Speci cation and Evaluation Language MOSEL provides a high level easy approach towards modelling systems based on QNMs It has additionally a set of compilers that allow the study of the modell using di erent perfor mance evaluation packages mostly based on Markov approach This fact has restricted the range of distributions to exponential The aim of this pa per is extend the capability of MOSEL to capture distribution with higher variability by approximat ing them with the Generalised Exponential GE distribution which is basically a exponential batch process with geometrically distributed batach sizes GE wuill be explored later in this paper Capacity of the Global System for Mobile Telecommunications GSM of radio interference in the wireless cell is divided into discrete channels and operates incircuit switched mode Extension of these models have been made to capture the packet switched behaviour introduced by the Gen eral Packet Radio Service GPRS which has been added to GSM to allow data packet communication with higher rates than those provided by a single GSM channel The GSM GPRS architecture will be shown in Figure The user terminal will cangenerate nor mal voice call and data packets Voice calls are served by the GSM system and the data packet will be through the GPRS system The GSM voice call will use normal air interfaces and go through the Base Station Controller BSC and the Mobile Sta tion Controller MSC and nally to the xed Pub lic Land Mobile Network PLMN On the other hand GPRS data packets will use the added Serv ing GPRS Support Node SGSN which in turn will transfer the data through the Gateway GPRS Sup port Node GGSN to Public Data network PDN The architecture of the models can be modelled by suitable queueing network models QNMs us ing MOSEL Resources for GPRS tra c can be re served statically or dynamically whereas a combi nation of both is possible Di erent cell capacity partitioning schemes for handling the transmission ISBN: 1-9025-6009-4 © 2003 PGNet