Capacity analysis of a PMR system with DAB downlink

Several trunked private mobile radio (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. We propose a new asymmetric PMR system comprising a wideband OFDM-based downlink and a narrowband uplink, which not only achieves a better spectral efficiency but also can support high bit rate multimedia applications. The system is shown to have high trunking efficiency since all users are assumed to use the pool of channels available in the wideband downlink. In this paper, we study the performance and capacity of a private mobile radio system using a digital audio broadcasting (DAB) downlink. In particular, we study the efficiency of such a system for voice calls using voice activity detection and statistical multiplexing. Moreover, we show that, the efficiency of the system can significantly increase, if the incoming calls, which can not find an available channel, are allowed to wait a certain amount of time before occupying a channel.