Outage and Rate Evaluation of Drone based Decode and Forward Cooperation for Hybrid Fading Channels

In this paper, we consider a drone as a relay in Cooperative Communication (CC) to improve the network performance in an upcoming wireless network. Drone Assisted CC (DACC) is more useful when the central coordinator (base station) gets disrupted. In such a scenario, the drone works as an aerial relay and provides CC diversity to the end-users. In this article, a Decode-and-Forward (DF) protocol is used as a relaying scheme at the drone, and the Maximal Ratio Combining (MRC) scheme is used at the end-users for combining the direct and relayed signal. Here, we assume Nakagami faded channel among Airto- Ground (A2G) links and Rayleigh faded distribution between Ground-to-Ground (G2G) links. The performance of DA-CC is evaluated in a hybrid channel environment and compared based on drone height, rate, horizontal distance, and transmitted power with the existing Rayleigh and Nakagami faded distributions. The analytical expression of outage probability and the rate have been derived for analysis purposes, and Monte-Carlo simulations are used to verify the analytical results. This work can have security and surveillance applications to improve the network performance in the absence of a central base station

Multiple UAVs as relays : multi-hop single link versus multiple dual-hop links

Unmanned aerial vehicles (UAVs) have found many important applications in communications. They can serve as either aerial base stations or mobile relays to improve the quality of services. In this paper, we study the use of multiple UAVs in relaying. Considering two typical uses of multiple UAVs as relays that form either a single multi-hop link or multiple dual-hop links, we first optimize the placement the UAVs by maximizing the end-to-end signal-to-noise ratio for three useful channel models and two common relaying protocols. Based on the optimum placement, the two relaying setups are then compared in terms of outage and bit error rate. Numerical results show that the dual-hop multi-link option better than the multi-hop single link option when the air-to-ground path loss parameters depend on the UAV positions. Otherwise, the dual-hop option is only better when the source-to-destination distance small. Also, decode-and-forward UAVs provide better performances than amplify-and-forward UAVs. The investigation also reveals the effects of important system parameters on the optimum UAV positions and the relaying performances to provide useful design guidelines

Exploiting UAV as NOMA based relay for coverage extension

Unmanned aerial vehicles (UAVs) aided communication has acquired research interest in many civilian and military applications. The use of UAV as base stations and as aerial relays to improve coverage of existing cellular networks is prevalent in current literature. Along with this, a few studies have proposed the use of non-orthogonal multiple access (NOMA) in UAV communications. In this paper, we propose a network where a ground user and an aerial UAV relay is accessed using NOMA, where the UAV acts as decode-and-forward (DF) relay to extend the coverage of source. The performance of the proposed model is shown by evaluating outage behaviour for different transmit power and fading environments with Monte Carlo simulations. System throughput of proposed network appears to be better than orthogonal multiple access (OMA) based equivalent network. The results show that with an adequate height of the UAV NOMA based relay, quality of service (QoS) of cell edge user is satisfactory

Effective relaying mechanisms in future device to device communication : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, New Zealand

Listed in 2020 Dean's List of Exceptional ThesesFuture wireless networks embrace a large number of assorted network-enabled devices such as mobile phones, sensor nodes, drones, smart gears, etc., with different applications and purpose, but they all share one common characteristic which is the dependence on strong network connectivity. Growing demand of internet-connected devices and data applications is burdensome for the currently deployed cellular wireless networks. For this reason, future networks are likely to embrace cutting-edge technological advancements in network infrastructure such as, small cells, device-to-device communication, non-orthogonal multiple access scheme (NOMA), multiple-input-multiple out, etc., to increase spectral efficiency, improve network coverage, and reduce network latency. Individual devices acquire network connectivity by accessing radio resources in orthogonal manner which limits spectrum utilisation resulting in data congestion and latency in dense cellular networks. NOMA is a prominent scheme in which multiple users are paired together and access radio resources by slicing the power domain. While several research works study power control mechanisms by base station to communicate with NOMA users, it is equally important to maintain distinction between the users in uplink communication. Furthermore, these users in a NOMA pair are able to perform cooperative relaying where one device assists another device in a NOMA pair to increase signal diversity. However, the benefits of using a NOMA pair in improving network coverage is still overlooked. With a varierty of cellular connected devices, use of NOMA is studied on devices with similar channel characteristics and the need of adopting NOMA for aerial devices has not been investigated. Therefore, this research establishes a novel mechanism to offer distinction in uplink communication for NOMA pair, a relaying scheme to extend the coverage of a base station by utilising NOMA pair and a ranking scheme for ground and aerial devices to access radio resources by NOMA

Approaching K-means for multiantenna UAV positioning in combination with a max-SIC-min-rate framework to enable aerial IoT networks

In long-range wireless communication networks, the fading channels described in channel state information are strongly related to distance and the path loss exponent and represent a major challenge in delivering the performance required to support emerging applications. Conveniently, multiple antennas and cooperative relays are efficient solutions that can combat fading channels, thereby improving networking capacity and transmission reliability. This study investigated the use of multi-antenna unmanned aerial vehicle (UAV)s as aerial Internet of Things (IoT) relays and employed their direct line-of-sight benefits to assist IoT wireless networks. To improve the outage probability, system throughput, and energy efficiency (EE), we first considered a combination of transmit antenna selection at the transmitter and the selection combining technique at the receiver to determine the best channel from the pre-coding channel matrix. Using a practical model in a three-dimensional earth environment in combination with the K-means algorithm, we then investigated optimal UAV placement to obtain optimal channel state information for the non-orthogonal multiple access (NOMA) -IoT device cluster globally, thereby ensuring the quality of service for the IoT devices. We introduced a max-successive interference cancellation-min-rate framework for non-ordered NOMA devices, thus deriving theoretical expressions in novel closed forms for two independent scenarios: (i) Rayleigh and (ii) Nakagami- m fading channels. By optimizing the UAV placement, the investigated results applied to the UAV scheme delivered better performance in a NOMA-IoT network than in a terrestrial relay (TR) scheme. Finally, the study examines a variety of models and presents algorithms for Monte Carlo simulations to verify the theoretical results.Web of Science1011517811515