Effective SNR Based Handoff Scheme in Heterogeneous Cellular Environments
| The design of handoo 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 tradeoo between expected number of service failures and expected number of handoos, where a service failure is deened 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 handoo algorithm is derived from the optimal solution. Like the standard hysteresis algorithm, the locally optimal algorithm is characterized by a single threshold. A systematic method for the comparison of various handoo algorithms that is akin to the ROC curves of radar detection is presented. Simulation results show that the locally optimal algorithm out-performs the hysteresis algorithm especially in situations where accurate prediction of signal strength is possible. A straightforward technique for adapting the locally optimal algorithm to changing environments is suggested. That natural adaptability is the algorithm's principle advantage over current approaches.