Cooperative HARQ-based Frame Allocation for Optical Satellite/HAP-Assisted Backhaul Networks

The growing interest in free-space optics (FSO)- based, low Earth orbit (LEO) satellite/high-altitude platforms (HAP)-assisted backhaul network has recently attracted research efforts worldwide. This paper addresses the error-control design for reliable vertical backhaul networks supporting multiple ground base stations (BSs). Notably, we propose a design of a cooperative hybrid automatic repeat request (C-HARQ)-based frame allocation mechanism (FAM)/rate adaptation. The design proposal guarantees the latency fairness constraint among multiple ground BSs suffering different turbulence channel conditions. Performance metrics, including system throughput, energy efficiency, and average frame delay, are analytically derived. Selected results confirm the effectiveness of our proposed C-HARQ-based FAM and demonstrate the severe impact of imperfect channel state information (CSI) on our proposed system. Also, the numerical results are verified by Monte-Carlo simulations, along with some in-depth discussions.