HAPS Selection for Hybrid RF/FSO Satellite Networks

Abstract

Non-terrestrial networks have been attracting much interest from the industry and academia. Satellites and high altitude platform station (HAPS) systems are expected to be the key enablers of next-generation wireless networks. In this paper, we introduce a novel downlink satellite communication (SatCom) model where free-space optical (FSO) communication is used between a satellite and HAPS node, and a hybrid FSO/radiofrequency (RF) transmission model is used between the HAPS node and ground station (GS). In the first phase of transmission, the satellite selects the HAPS node that provides the highest signal-to-noise ratio (SNR). In the second phase, the selected HAPS decodes and forwards the signal to the GS. To evaluate the performance of the proposed system, outage probability expressions are derived for exponentiated Weibull (EW) and shadowed-Rician fading models while considering the atmospheric turbulence, stratospheric attenuation, and attenuation due to scattering, path loss, and pointing errors. Furthermore, the impact of aperture averaging, temperature, and wind speed are investigated. Finally, we provide some important guidelines that can be helpful for the design of practical HAPS-aided SatCom.

Joint User Association and Beamforming in Integrated Satellite-HAPS-Ground Networks

“…To this end, references [27], [28] focus on the performance analysis of VHetNets and highlight their coverage expansion capabilities. Resource optimization of VHetNets also emerges nowadays as a powerful paradigm for assessing the true benefits of HetNets in solving the digital divide problem, e.g., [29]- [32]. While reference [29] considers the time allocation, power control, and trajectory optimization of UAV-aided space-air-ground networks, reference [30] considers power assignment and transmission protocol in an integrated HAPS-mobile telecommunications (IMT) system.…”

“…While reference [29] considers the time allocation, power control, and trajectory optimization of UAV-aided space-air-ground networks, reference [30] considers power assignment and transmission protocol in an integrated HAPS-mobile telecommunications (IMT) system. References [31], [32] are particularly related to our system model; however, our paper goes beyond both [31], [32] by accounting for the joint user association and beamforming problem in a cross-mode cross-layered interference setup. More specifically, on one hand, [32] studies a hybrid RF/FSO VHetNet consisting of satellites, HAPS, and ground base-stations, and focuses on the systematic performance analysis of the networks.…”

“…References [31], [32] are particularly related to our system model; however, our paper goes beyond both [31], [32] by accounting for the joint user association and beamforming problem in a cross-mode cross-layered interference setup. More specifically, on one hand, [32] studies a hybrid RF/FSO VHetNet consisting of satellites, HAPS, and ground base-stations, and focuses on the systematic performance analysis of the networks.…”

“…On the other hand, [31] proposes an integrated satellite-airborne-ground network and optimizes the user access, power assignment, and HAPSs' location under an orthogonal frequency division multiple access scheme. Differently from both [31] and [32], our paper adopts a multiple-antenna scheme at the HAPS and at the ground base-stations, and optimizes the user association and spatial multiplexing strategies so as to efficiently serve the ground users.…”

HAPS-assisted Hybrid RF-FSO Multicast Communications: Error and Outage Analysis

“…Furthermore, optical beam is limited to masking effects over large distances and the line-of-sight (LOS) connectivity can not be established between the satellites and the multicast users due to shadowing and obstacles. Thus, in satellite communication (SatCom), cooperative relaying in which a HAPS system can be used as an intermediate relay node, can be considered as an effective solution to mitigate the channel impairments [8], [9].…”