On the impact of soft hand-off in cellular systems

We present a model for soft hand-off in wireless cellular networks. In such networks, due to overlapping cells, hand-offs are not instantaneous and multiple channels may be occupied by a single mobile for a non-zero freeze time period. We provide a mathematical model of wireless cellular networks with soft hand-offs. We examine different performance measures and show that freeze time may have a major impact on the system performance if the mobility rate is not negligible. Both exact and approximate formulations are given. Different fixed-point approximation methods are used to reduce the complexity of the exact solution. Various performance measures such as new and hand-off blocking and probability of a call dropout are carefully examined.