Inter-High-Altitude-Platform Handoff for Communications Systemswith Directional Antennas

摘要

In this paper, we examine a number of issues relating to the inter-HAP handoff process for broadband communications that operate with fixed or steerable directional antennas, allowing a platform to be replaced either for maintenance or periodic replacement in the case of short-term manned HAPs. Handoff performance was evaluated for both types of antennas based on a number of criteria, such as the antenna's beamwidth, the platforms' height, the position cylinder, and the civil aviation authority (CAA) cylinder. Results showed that for users employing fixed antennas pointing towards the center of the position cylinder, handoff can take place as soon as the new platform enters the cylinder. Users from the center of the service area are required to employ the widest-beamwidth antenna (29°), whereas users at the edge of the service area can employ a narrower beamwidth. Users employing steerable antennas can employ a much narrower beamwidth. However, connections will be dropped for any beamwidth less than 5°, unless users employ two antennas, or the new platform follows a complex flight path, preferably as close as possible (±305 m vertical separation) to the current serving platform.