A combined channel assignment strategy in a hierarchical cellular systems

This paper proposes a combined channel assignment (CCA) strategy for a hierarchical cellular system. The proposed CCA strategy combines overflow, underflow, and reversible techniques, where new or handoff calls having no available channel to use in the overlaid microcell can overflow to use free channels in the overlaying macrocell, handoff calls from neighboring macrocell can underflow to use the free channel in the microcell, and handoff attempts from overlaying macrocell to overlaid microcell are reversed to use free channels in the microcell if there are idle channels in the microcell. In the simulation, we further compare the CCA strategy with the overflow channel assignment (OCA) scheme and investigate two different hierarchical cellular systems of Strip type and Manhattan type. From simulation results, it is shown that the new-call blocking ratio and forced termination ratio are decreased and the CCA strategy outperforms the OCA scheme.