Quality-of-Service differentiation in an integrated services GSM/GPRS network

We develop and analyse a generic model for performance evaluation, parameter optimisation and dimensioning in a \textsc{gsm}/\textsc{gprs} network. The model enables analytical evaluation for a scenario of integrated speech, video and data services, potentially offered in distinct priority classes. While a speech call is assigned a single traffic channel for its entire duration, both video and data calls can handle varying channel assignments. The principal distinction between these elastic call types, is that in case of video calls, a more generous channel assignment implies a better throughput and thus call quality, while for data calls the increased throughput implies a reduced sojourn time. Although a broader variety of models can be designed and analysed within the generic framework, the analytical and numerical results are presented for the \textsc{svd} model integrating speech, video and data calls, and for the \textsc{shl} model, integrating speech and two priority classes of data calls. In both models, an access queue is maintained for data calls which cannot be served immediately upon arrival. Markov chain analysis is applied to derive basic performance measures such as the expected channel utilization, service-specific blocking probabilities (\textsc{gos}), expected video \textsc{qos} (throughput) and expected (priority class-specific) data \textsc{qos} (sojourn times). Furthermore, closed-form expressions are derived for the expected video and data \textsc{qos}, conditional on the call duration or file size, respectively, and on the system state at arrival. As a potential application, these measures can be fed back to the caller as an indication of the expected \textsc{qos}. The included numerical study demonstrates the merit of the presented generic model and performance analysis, and provides \textsc{gsm}/\textsc{gprs} network operators with valuable insight in the \textsc{gos} and \textsc{qos} tradeoffs involved in balancing the various controllable system parameters.