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

In this paper, we propose a fuzzy channel allocation controller (FCAC) for hierarchical cellular systems. FCAC is designed to contain base-station interface module, resource estimator, performance evaluator, and fuzzy channel allocation processor (FCAP). FCAP is a two-layer fuzzy logic controller that consists of a fuzzy admission threshold estimator in the first layer and a fuzzy channel allocator in the second layer. In the fuzzy admission threshold estimator, it chooses the handoff failure probability and the resource availability as input linguistic variables, and applies the Sugeno position-gradient type reasoning method to adaptively adjust threshold values for the fuzzy channel allocator. In the fuzzy channel allocator, it takes the mobility of users, the channel utilization, and the resource availability as input variables, and it intends to enhance the channel utilization by balancing utilization between macrocell and microcells.