Adaptive handoff algorithms using absolute and relative thresholds for cellular mobile communication systems

In cellular mobile networks, efficient handoff performance entails minimizing unnecessary handoffs without risking desired handoffs which could lead to increased dropped calls. An adaptive relative-threshold (hysteresis) algorithm has been proposed by Senarath and Everitt (see Proc. VTC'93, 1993) to effectively identify and prevent unnecessary handoffs. However, results here show that this adaptive algorithm can cause undesired cell-dragging. We propose an adaptive, absolute-threshold algorithm to be used in combination with the adaptive relative-threshold algorithm to mitigate cell dragging. The performance of the algorithm is investigated for an IS-136 TDMA system using a powerful network level simulator. Results show that, depending on the propagation environment, the proposed algorithm can reduce received signal strength (RSS) based handoff triggers by up to 75% while maintaining a lower call drop-rate and less cell dragging than fixed threshold algorithms.