Outage analysis and finite SNR diversity-multiplexing tradeoff of hybrid-duplex systems for aeronautical communications

In this work, the advantages of joint detection (JD) in a hybrid-duplex unmanned aerial vehicle (UAV) communication system (HBD-UCS) are investigated as a step towards addressing spectrum scarcity in UAV communications. Through extensive outage probability and finite signal-to-noise-ratio (SNR) diversity gain analysis, we showed that the performance of joint detection (JD) is independent of the strength and the data rate of the inter-UAV interference signal. On the contrary, the successive interference cancellation (SIC) detector requires the data rate of the interfering UAV to be less than the ground station before meaningful performance can be seen. At the system level, it is observed that the half-duplex UAV communication system outperforms the HBD-UCS with JD at moderate and high SNR regimes, as the latter is constrained by self-interference at the full-duplex ground station. Lastly, we investigated the multiplexing gain region and showed that the joint detector offers higher diversity gain over a wide range of multiplexing gains over the interference ignorant (II) and the SIC detector.

Novel Air Traffic Management (ATM) strategies are proposed through the Next Generation Air Transportation (NextGen) and Single European Sky for ATM Research (SESAR) projects to improve the capacity of the airspace and to meet the demands of the future air traffic. The implementation of the proposed solutions leads to increasing use of wireless data for aeronautical communications. Another emerging trend is the unmanned aerial vehicles. The unmanned aerial systems (UASs) need reliable wireless data link and dedicated spectrum allocation for its operation. On-board broadband connectivity also needs dedicated spectrum to satisfy the quality of service (QoS) requirements of the users. With the growing demand, the aeronautical spectrum is expected to be congested. However, the studies revealed that the aeronautical spectrum is underutilized due to the static spectrum allocation strategy. The aeronautical communication systems such as air-air and airground communication systems, inflight infotainment systems, wireless avionics intra-communications (WAIC), and UAS can benefit significantly from the introduction of cognitive radio based transmission schemes. This article summarizes the current trends in aeronautical spectrum management followed by the major applications and contributions of cognitive radio in solving the spectrum scarcity crisis in the aeronautical domain. Also, to cope with the evolving technological advancement, researchers have prioritized the issues in the case of cognitive radio that needs to be addressed depending on the domain of operation. The proposed cognitive aeronautical communication systems should also be compliant with the Aeronautical Radio Incorporated (AR-INC) and Aerospace Recommended Practice (ARP) standards. An overview of these standards and the challenges that need immediate attention to make the solution feasible for a largescale operation, along with the future avenues of research is also furnished.

With the growing popularity of unmanned aerial vehicles (UAVs), spectrum management is a pressing issue, particularly for multi-UAV systems. To this end, a hybrid-duplex (HBD) UAV communication system (UCS) consisting of a fullduplex (FD) enabled ground station (GS), and legacy halfduplex (HD) UAVs is proposed in this paper. To model the fading and shadowing environment commonly encountered in UAV communications, a mix of Rician and Rician shadowed fading is assumed. In particular, novel power series approximations of the Rician shadowed fading power probability density function (PDF), and cumulative distribution function (CDF) are presented, along with closed-form outage probability expressions.Performance analysis shows that the proposed HBD-UCS exhibits lower outage probability than the HD-UCS when shadowing is encountered at low signal-to-noise ratios (SNRs). Also, inter-UAV interference has a stronger influence on outage probability decay at low SNR regimes, with lower inter-UAV interference corresponding to a sharper decline in outage probability.

In this work, the outage probability of an unmanned aerial vehicle (UAV) network with hybrid-duplex (HBD) UAV communications is investigated in a stochastic geometry framework. We demonstrate that the HBD UAV communication system (HBD-UCS) can concurrently support more UAVs while achieving higher reliability than the half-duplex (HD) UCS (HD-UCS). Specifically, at low transmit power regimes, it is shown that the HBD-UCS attains lower uplink and downlink outage probability than an HD-UCS, even as the UAV operating altitude is increased.