Analysis of the effect of channel sub-rating in unidirectional call overflow scheme for call admission in hierarchical cellular networks

Key goals of call admission control in the next generations of wireless networks are the efficient use of the limited wireless resource and the enhanced quality of service (QoS). Knowing that blocking of handoff calls is less desirable than blocking of new calls and the latter inevitably leads to the reduced resource utilization, we propose in this paper a new call admission control for balancing this tradeoff. It is based on the sub-rating strategy (SRS) implemented in conjunction with unidirectional call overflow in hierarchical cellular networks (HCN). With SRS, an occupied full-rate channel is halved to service a call in progress and a handoff call in parallel. Theoretical models based on 1-D Markov process for a microcell and 2-D Markov chain for macrocell analyses are developed to evaluate the performance of the proposed scheme. We compare the results with that obtained by Shan in [8]. The experimental results certify higher performance in terms of the forced termination probability. Additionally, we evaluate the voice degradation quality due to subrating.