Performance analysis of channel-borrowing handoff scheme based on user mobility in CDMA cellular systems

Code-division multiple-access (CDMA) cellular systems use soft handoff. Although the capacity of CDMA systems is interference-limited in nature, channel shortages may occur because soft handoff uses several channels simultaneously. To cope with this problem, we propose an improved handoff method that borrows channels from stationary calls participating in soft handoff and allocates the borrowed channels to handoff requests by moving calls when a channel shortage occurs. Borrowing from stationary calls is possible because these calls do not undergo fast-fading and do not require receiver diversity. The proposed method is designed to avoid increased interference resulting from channel borrowing. The proposed channel-borrowing handoff scheme is analyzed in a situation involving both moving and stationary calls. A comparison is made between the performances of the typical IS-95-based handoff scheme and the proposed scheme. Numerical results show that the proposed scheme is better than the IS-95 scheme in view of the handoff refused probability, the handoff queuing delay, and total interference.