A call control scheme for soft handoff in CDMA cellular systems

Abstract

a new direction-based handoff call control scheme (DBHCCS) for CDMA cellular systems is proposed. In the proposed scheme, a neighbor base station ignores unnecessary soft handoff calls requested by mobile stations which are not actually approaching the neighbor base station, while protecting real soft handoff calls by employing a queue. We proposed a new method of determining the priorities of queued handoff calls. In this method, a mobile station predicts the time when its handoff call is forcedly terminated, by using the changing rate of the received pilot strength from the serving BS and using the current time broadcast by the sync channel of the serving BS as a reference time. The service priority of queued handoff calls is determined based on the predicted forced termination time reported by mobile stations. The performance of the DBHCCS is compared with that of the first-in/first-out (FIFO) scheme and the measurement-based prioritization scheme (MBPS). The simulation results show that the probability of new call blocking for the DBHCCS is lower than that of the FIFO scheme or the MBPS queuing discipline. It is also shown that the probability of forced termination for the DBHCCS is less than or equal to that of the conventional CDMA cellular system with the MBPS queuing discipline.