A QoS-guaranteed fuzzy channel allocation controller for hierarchical cellular systems

This paper proposes a fuzzy channel allocation controller (FCAC) for hierarchical cellular systems. The FCAC mainly contains a fuzzy channel allocation processor (FCAP) which is designed to be in a two-layer architecture that consists of a fuzzy admission threshold estimator in the first layer and a fuzzy channel allocator in the second layer. The FCAP chooses the handoff failure probability, defined as the quality-of-service (QoS) index, and the resource availability as input linguistic variables for the fuzzy admission threshold estimator, where the Sugeno's (1985) position gradient-type reasoning method is applied to adaptively adjust the admission threshold for the fuzzy channel allocator. The FCAP takes the mobility of user, the channel utilization, and the resource availability as input variables for the fuzzy channel allocator so that the channel allocation is finally determined, further based upon the admission threshold. Simulation results show that FCAC can always guarantee the QoS requirement of handoff failure probability for all traffic loads. Also it improves the system utilization by 31.2% while it increases the handoff rate by 12.94 over the overflow channel allocation (OCA) scheme; it enhances the system utilization by 6% and still reduces the handoff rate by 6.746 as compared to the combined channel allocation (CCA) scheme, under a defined QoS constraint.