Optimizing Data Transmission in High Altitude Balloon Networks with Multi-beam Directional Antennas

High altitude balloons (HABs) can be deployed in the stratosphere to provide high capacity connectivity to users in rural and remote areas with their advantages of low cost and easy deployment. In this paper, we propose a software defined HAB-based network (SD-HABN) architecture to efficiently exploit the resource of inter-HAB links. The multi-beam directional antenna equipped on the HAB realizes concurrent transmission. However, this may result in interference because of the over-lapping beams at the receiving side. To mitigate interference and improve network performance, the beam angle adjustment, link scheduling, routing, and data rate controlling are jointly optimized, aiming to maximize the network utility. On account of the coupled relationship between the optimization variables, a novel optimization approach is proposed to solve this problem. The original problem is divided into two problems. The first one is that of optimizing the beam angle adjustment with fixed link scheduling, which is solved by a genetic algorithm. The second one is that of optimizing the routing and data rate controlling with fixed beam angle adjustment, which is solved by generalized bender decomposition. By solving the two problems orderly, the original problem will attain an approximately optimal solution. Simulation results show that the SD-HABN can achieve a high network performance via the joint optimization of beam angle adjustment, link scheduling, routing, and data rate controlling.