Characterization of Soft Handoff in CDMA Systems

Many analytical approaches have been proposed for handoff analysis based on hard handoff in mobile communication systems. In code-division multiple-access (CDMA) systems with soft handoff, mobile stations (MS’s) within a soft-handoff region (SR) use multiple radio channels and receive their signals from multiple base stations (BS’s) simultaneously. Therefore, SR’s should be considered for handoff analysis in CDMA systems. In this paper, an analytical model for soft handoff in CDMA systems is developed by introducing an overlap_region between adjacent cells and the handoff call attempt rate and the channel holding times are derived. Applying these results to a nonprioritized CDMA system, the effects of soft handoff and the mean cell residual time are investigated and compared with hard handoff.