Optimal deployment strategy of airships for near-space communication system using multiobjective advanced evolutionary algorithm

This paper presents a near-space communication system (NSCS) using advanced deployment strategies to gain high throughput. The airships are deployed according to the user's location, assuming robust backbone network characteristics such as signal path loss, fading factor, routing efficiency, and safety issues among bi-connected airships. Due to the independent flying nature of airships, it is very attractive to deploy them as aerial base stations and construct airborne networks to provide service for on-ground users. However, it is quite challenging to optimally deploy multiple airships for on-demand coverage while maintaining the connectivity among airships. A balance between the network parameters, i.e., capacity and coverage area, should be maintained for optimal deployment of the airships. We have derived the maximum throughput of NSCS, including system parameters, as a multiobjective optimization problem subjected to efficient routing protocol and safety constraints. A decomposition-based advanced multiobjective evolutionary algorithm (AMOEA/D) is adopted to solve the deployment optimization problem. The proposed algorithm is motivated by the non-dominated solutions that maintain population diversity over the variable space. Two designed test problems, that is, the L-shaped hotspot problem and nine hotspot problems, are also investigated. Numerical results show that the proposed method improves the system performance compared with benchmark external archive-guided MOEA/D (EGA-MOEA/D) and non-dominated sorted genetic algorithms (NSGA-II) by 10.46% and 3.84%, respectively. This figure illustrates the system model of the near-space communication system. It consists of multiple airships with the same characteristics following identical communication protocols. All airships hover at the same altitude and serve as aerial base stations at any particular instant. The coverage area of each airship depends on its altitude and communication range. These airships can serve all the users within the coverage area.image