A locally optimal handoff algorithm

The design of handoff algorithms for cellular communication systems based on mobile signal strength measurements is considered. The design problem is posed as an optimization to obtain the best tradeoff between expected number of service failures and expected number of handoffs, where a service failure is defined to be the event that the signal strength falls below a level required for satisfactory service to the subscriber. Based on dynamic programming arguments, an optimal solution is obtained which, though impractical, can be used as a benchmark in the comparison of suboptimal schemes. A simple, locally optimal handoff algorithm is derived from the optimal solution. Simulation results show that the locally optimal algorithm outperforms the hysteresis algorithm and is competitive with a hysteresis-threshold algorithm proposed by Zhang and Holtzman (see IEEE 44th Veh. Tech. Conf., p.82, 1994). A straightforward technique for adapting the locally optimal algorithm to changing environments is suggested