Call admission control in mobile cellular systems using fuzzy associative memory

Abstract

In a mobile cellular system quality of service to mobile terminals (MTs) is measured by the probability of new call blocking P/sub b/, and the probability of forced termination, P/sub ft/. Since the available bandwidth in a cell is very limited, both P/sub b/ and P/sub ft/ cannot be reduced or avoided simultaneously. Usually keeping the P/sub ft/ below a designated level is accepted as the measure of quality of service. Admission of new calls is controlled to reduce P/sub ft/. However, there are at least three parameters (new call arrival rate, mean duration of calls, and mobility of users) that can and change dynamically. Moreover, these parameters are related with P/sub ft/ via complicated nonlinear equations. Therefore, call admission control (CAC) for maintaining a desired value of P/sub ft/ is a very challenging task. No CAC algorithm has been reported in the past that can function well with dynamic changes to all these three parameters. We proposed an algorithm that addresses this issue. The new algorithm uses a fuzzy controller to adjust the call preblocking load value with the changing traffic parameters. The fuzzy controller makes use of fuzzy associative memory (FAM) to maintain the required QoS. The use of new system in dynamic traffic conditions is illustrated. Providing the required level of QoS, the algorithm also increases the channel utilization. The proposed CAC with FAM is compared and contrasted with previous CACs.