Network Configurations for Seamless Support of CDMA Soft Handoffs Between Cell Clusters

Current code division multiple access (CDMA) networks do not support soft handoffs between cell clusters serviced by different mobile switching centers (MSC’s). Three novel network configurations are proposed to overcome this limitation. Configurations I and II employ crosslinks to allow diversity combining of signals. This is accomplished in Configuration III by linking the modified MSC’s serving adjacent cell clusters. In Configuration I, a scheme which reduces the handoff blocking probability by lengthening the handoff transition time is proposed. Configuration II expands overlapping regions of adjacent cell clusters, thus enabling the use of different intercluster handoff regions for different handoff directions to prevent oscillations which may occur in Configuration I, while reducing the necessary number of intercluster handoffs. Configuration III fully shares the trunks to support the highest number of calls among all three configurations. A new mobility model for microcells is developed to enable dimensioning of the trunk groups in each configuration. For Configurations I and II, the optimal partitions of trunk groups into direct and crosslinks are determined by mathematical analyses and computer simulations. For Configuration III, the optimal number of trunks required to interconnect adjacent MSC’s is investigated by computer simulations. The new call and handoff blocking probabilities in all of these configurations are compared.