Performance evaluation of a soft hand off scheme in CDMA cellular networks

Code division multiple-access (CDMA) schemes are widely used in cellular communications system because they provide high quality, reduced interference and result in high system capacity. In CDMA systems since one carrier frequency is being used, a phenomenon known as soft hand off occurs when a user changes radio resources from one base station to another. In this paper, we propose a soft hand off scheme using a two cell and roaming user probability approach, to properly illustrate the hand off process between the cells of interest. The proposed scheme assumes that calls entering the soft region are immediately assigned two channels. This assumption helps to reduce the blocking probability of new calls in the soft region as opposed to other schemes which do not explicitly cater for such calls. A three dimensional Markov process is created to describe and develop the stochastic behavior of the calls in the system. Performance measures such as new call blocking probability, hand off call blocking probability, channel efficiency, total carried traffic are deduced