Sum-Rate Analysis for High Altitude Platform (HAP) Drones with Tethered Balloon Relay

TL;DR

This paper introduces a novel interference alignment method for high altitude platform drones using a tethered balloon relay, enabling maximum sum-rate communication without channel state information, and identifies an optimal balloon altitude for best performance.

Contribution

It proposes a new interference alignment technique utilizing a tethered balloon relay to maximize sum-rate in HAP drone communications without CSI.

Findings

Theoretical derivation of capacity for the M×N X network with tethered balloon relay.

Simulation results confirm the maximum sum-rate achievable without CSI.

Existence of an optimal balloon altitude for maximizing sum-rate.

Abstract

High altitude platform (HAP) drones can provide broadband wireless connectivity to ground users in rural areas by establishing line-of-sight (LoS) links and exploiting effective beamforming techniques. However, at high altitudes, acquiring the channel state information (CSI) for HAPs, which is a key component to perform beamforming, is challenging. In this paper, by exploiting an interference alignment (IA) technique, a novel method for achieving the maximum sum-rate in HAP-based communications without CSI is proposed. In particular, to realize IA, a multiple-antenna tethered balloon is used as a relay between multiple HAP drones and ground stations (GSs). Here, a multiple-input multiple-output X network system is considered. The capacity of the considered M*N X network with a tethered balloon relay is derived in closed-form. Simulation results corroborate the theoretical findings and show that the proposed approach yields the maximum sum-rate in multiple HAPs-GSs communications in absence of CSI. The results also show the existence of an optimal balloon's altitude for which the sum-rate is maximized.