Models for pre-emption of packet data by voice in slotted cellular radio networks

Cellular radio networks supporting both circuit switched voice and packet switched data services aim to maximise the resource utilisation through efficient sharing of the resource. These sharing algorithms can use pre-emption to give voice service priority over data, thus preserving the grade of service for voice at the expense of delaying data calls. This paper develops models for a pre-emptive voice and data system, with a particular focus on GPRS. The model is based on an assumption of independence between the voice and data traffic. These models allow estimates of (i) the probability that a voice call causes pre-emption of a data call, as well as (ii) the probability that a data call will be delayed due to either being pre-empted by a voice call while in progress or due to not finding free resources at its initial attempt. The results show that a Poisson model for data traffic gives the best results for pre-emption probability when compared with measurements taken from a GSM/GPRS network.