Impact of the number of ISM-band ad hoc relay channels on the performance of iCAR systems

One of the common problems faced by the wireless service providers worldwide is coping with congestion or hot spots. To handle this hot spot problem, methods that combine the existing cellular networks with ad hoc networks have been proposed. Integrated Cellular and Ad Hoc Relay (iCAR) system employs ad hoc relay stations (ARS's) within the cellular network to balance traffic loads efficiently and to share channels between cells via primary and secondary relaying. The Ars's operate in the ISM band, and therefore, do not cause interference to the cellular band. When analyzing the performance of iCAR systems, there are several factors that should be taken into account. These factors include the coverage area of the ARS's, the number of ARS channels, the placement of ARS's, etc. In this paper, the impact of the number of ARS channels on the performance of iCAR system is studied. To this end, a multi-dimensional Markov-chain analysis is performed for a simplified two-cell system model. Results show that, with a proper amount of ARS coverage within each cell the call blocking probabilities can be decreased significantly with a small number of channels. Results also suggest that by increasing the number of ARS channels perfect load balancing can be achieved.