Improved LMS predictive link triggering for handover in HAPS communication system

Abstract

In stratosphere, the cell handover performances of high altitude platform station (HAPS) communication system was affected by the quasi-stationary state of platform. The traditional handover algorithms based on the fixed thresholds usually can effectively deal with the handover issue caused by terminals' mobility. However given the platform disturbances, these algorithms show poor handover. At this point, the adaptive handover algorithm was proposed to trigger handover based on signal strength predicted by improved least mean square (LMS). Firstly the power model of quasi-stationary HAPS was established. Secondly the period of handover detection can be set appropriate value according to the speed of user terminals. Then the handover triggering is determined by the relationship between predicted signal strength and confidence level. Simulation results show that compared with traditional fixed thresholds, the proposed algorithm can effectively reduce the number of unnecessary handover, and keeps the ratio of radio link failure less than 1% for different speed terminals.