A Power Series Approach for Hybrid-Duplex UAV Communication Systems Under Rician Shadowed Fading

Abstract

A hybrid-duplex (HBD) UAV communication system (UCS), i.e., HBD-UCS, to improve spectrum utilization is investigated in this work. By considering the combined effect of fading and shadowing, a comprehensive outage probability analysis of the HBD-UCS under various inter-UAV interference and shadowing scenarios over Rician shadowed fading channels is conducted. It is demonstrated that the ground station (GS) in full-duplex (FD) mode operates at lower outage probability than in half-duplex (HD) mode. Furthermore, the joint detector is shown to achieve lower outage probability than the interference ignorant (II) detector and HD-UCS, even when severe shadowing is encountered. As such, utilizing joint detectors in an HBD-UCS enables multi-UAV networks to achieve high reliability when operating in urban environments. INDEX TERMS Unmanned aerial vehicle, spectrum efficiency, half-duplex, full-duplex, hybrid-duplex, outage probability, rician, shadowing. A. MOTIVATION AND RELATED LITERATURE Although utilitarian, multi-UAV networks are mired with its own set of challenges that must be addressed. Of particular importance is the lack of available spectrum for UAV communications [5], [6]. Despite the allocation of parts of The associate editor coordinating the review of this manuscript and approving it for publication was Jiayi Zhang. the L-band and C-band for UAV control and non-payload communications (CNPC) by the International Telecommunications Union (ITU) [5], spectrum scarcity is still a challenge. In particular, many other existing systems, e.g., aeronautical communication systems, are also operating on both the L-band and C-band [5]-[7]. In this aspect, a hybrid-duplex (HBD) UAV communication system (UCS), i.e., HBD-UCS, can be a direct solution address spectrum scarcity in UAV communications. The HBD paradigm enables UAVs with existing half-duplex (HD) communication systems, i.e., HD-UCS to simultaneously operate on the same spectrum with full-duplex (FD) ground stations (GSs), effectively doubling spectrum efficiency. However, the simultaneous transmission and reception of signals results in self-interference (SI) at the FD-enabled GS, which can be mitigated via passive or active SI mitigation architectures [8], [9]. The former entails introducing path loss and shadowing, e.g., through antenna placements, while the latter involves canceling SI in the analog or digital domain [9]. Even after SI mitigation, residual SI can still remain due to non-ideal FD transceiver impairments, such as carrier phase noise and imperfect

Wireless-Powered Full-Duplex UAV Relay Networks Over FTR Channels

“…In light of this, UAV-assisted wireless networks using SWIPT have received special attention from the scientific community, as the combined use of cooperative communications and SWIPT techniques can simultaneously improve the reliability, spectral efficiency, and energy efficiency of the system (see, for example, [21], [22], [25]).…”

“…As for UAV-assisted wireless networks, in [22], a performance analysis in terms of the outage probability of a HD UAV-assisted cooperative network with a FD ground station was performed for Rician shadowed fading channels. However, in that work, the use of SWIPT techniques was not considered 1 .…”

Addressing spectrum efficiency through hybrid-duplex UAV communications: Challenges and opportunities

“…Separately, other studies, e.g., [14]- [16], [18], [75], [81], have assumed a combination of analog and digital SI cancellation operating in cascade. Specifically, the SI signal undergoes SI mitigation in the analog domain first, before SI cancellation in the digital domain.…”

“…Specifically, the SI signal undergoes SI mitigation in the analog domain first, before SI cancellation in the digital domain. To account for FD transceiver impairments, residual SI is considered in the signal models of [14]- [16], [18], [75], [80], [81]. The strength of the residual SI depends on a variety of factors, including the variance of the phase noise [14]- [16], [18], [75], [80], variance of the SI channel estimation error [14]- [16], [18], [75], [85], quantization noise [75], and transmit power [81].…”

On the ASER Performance of UAV-Based Communication Systems for QAM Schemes

“…A multi-hop UAV based system is analyzed in the presence of both multipath and shadowing effects in [6] in terms of the error rate and the channel capacity performance metrics. Further, outage probability of hybridduplex UAV-assisted communication system is analyzed over Rician-fading scenario in [7] and low-altitude aerial relaying environment in [8]. Outage performance of UAV based communication is analyzed by considering user mobility and fading in [9].…”