Traffic analysis and modeling in PMR systems

Reliable knowledge of traffic in PMR (Private Mobile Radio) systems is essential for assessing the issues in migration from analog to digital and trunked PMR systems. In this work, we investigated two concepts. First, we modeled the service time distribution of conventional PMR networks by using teletraffic data of a conventional PMR network. It is found that the density of the service time is a shifted exponential which is delayed by 0.7 second. The mean service time is about 2.5 seconds. We showed that voice call arrivals to a transmission trunked PMR network are not Poisson distributed. Analytical and simulation methods based on M/G/C (a C server queue with Poisson input and general service) models may not model the system as well as G/G/C (a C server queue with general input and general service) models. Several trunked PMR systems have been designed over the last decade, most of which have symmetric downlink and uplink channel capacities. These systems may not be spectrally efficient in case of group or broadcast-based voice and data calls, a common feature of PMR systems. Second, we studied a new asymmetric PMR system comprising of a wideband OFDM (Orthogonal Frequency Division Multiplexing)-based downlink, such as Digital Audio Broadcasting (DAB) system. We found that for 2 % GoS and a mean service time of 2.86 second, PMR users that can be supported by the proposed system is 315000.