Enhancement of Channel Efficiency for CDMA Systems using New Soft Handoff Scheme

Code Division Multiple Access (CDMA) cellular system that provides seamless connectivity is featured by soft handoff, which is accompanied by power control, selection diversity and rake receiver. In IS-95/CDMA-2000 based handoff schemes or systems some handoff calls unnecessarily occupy multiple channels with little contribution to the performance of handoffs. It is noted that new calls are blocked due to the channel resource shortage. In order to efficiently utilize the channel resource those extra channels occupied by handoff calls are grouped into a set called channel convertible set (CCS) by considering the relative mobility of the call. A new scheme called Channel-Conversion with Dynamic Guard channel reservation (CCDG) that reallocates those extra channels in the CCS to new handoff calls when there is no available channel in the system is proposed. According to the variation of the CCS the scheme dynamically adjusts the number of guard channels reserved exclusively for handoff, which still enhances the system performance. It is noted that the proposed scheme can significantly decrease both the number of dropped handoff calls and the number of blocked calls without degrading the quality of communication service.