Inter-HAP handoff analysis for multi-cell short-endurance HAP communications systems

摘要

In this paper, we investigate an inter-high-altitude platform (HAP) handoff model for multi-cell short-endurance HAP wireless communications systems. Equations are derived to calculate system parameters, such as minimum user beamwidth and handoff opportunity (HO) interval, and system performance, such as handoff success ratio, inter-HAP HO start rate and handoff load, when the current serving platform is replaced either for maintenance or for periodic replacement. Research results show some directions on how to select the trajectory of the platform, user beamwidth and handoff schemes. It is shown that it is better for the replacing platform to fly above and be as close as possible to the current serving platform. A higher altitude adopted by the current serving platform will allow a narrower user beamwidth. Two cellular handoff schemes are presented. It is shown that in the case of users with a wider antenna beamwidth free selection of any handoff destination cell can result in the handoff load being very high. By restricting the handoff destination cell to the cell with the same cell number within the footprints of the two platforms, the handoff traffic can be reduced to a minimum, but the two platforms are required to maintain the same relative cell layout. Copyright © 2010 John Wiley & Sons, Ltd. Received 15 December 2009; Revised 27 September 2010; Accepted 28 September 2010