Abstract
This paper studies unmanned aerial vehicle (UAV)-aided nonorthogonal multiple access (NOMA)-based mobile-edge computing (MEC) in Internet of Things (IoT) systems in which the uav acts as a relay (UR). Specifically, we consider a scenario with two clusters IoT devices (IDs) (i.e., a high-priority cluster IA and a low-priority cluster IB) with limited resources, so these IDs cannot compute their tasks and must offload them to a base station (BS) through a UR. We propose a protocol named time switching - radio frequency (RF) energy harvesting (EH) UR NOMA (TS-REUN), which is divided into 5 phases. By applying the TS-REUN protocol, the IDs in the two clusters and the UR harvest RF energy from the broadcast signal of the power beacons (PB). Then, the IDs offload their tasks to the MEC server located at the BS. After server processing, the IDs receive the calculation results from the BS via the UR. The effects of both imperfect channel state information (ICSI) and imperfect successive interference cancellation (ISIC) on the REUN-based mec (REUN-MEC) are taken into account. To evaluate the performance of the system, we derive closed-form expressions for the successful computation probability (SCP) and energy consumption probability (ECP) in the Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathfrak {m}$ </tex-math></inline-formula> fading channel. Moreover, we propose an optimization problem formulation that maximizes the SCP by optimizing the position and the height of the UR and the time switching ratio (TSR). The problem was addressed by employing an algorithm based on particle swarm optimization (PSO). In addition, the Monte Carlo simulation results confirmed the accuracy of our analysis based on system performance simulations with various system parameters, such as the number of antennas at the BS, the number of IDs in each cluster, the TSR, and the position and the height of the UR.
Highlights
The Internet of Things (IoT) has been considered an enabling technology for smart homes, smart cities, and space information networks, and it provides abundant device connections and sensors with different applications [1]–[4].As a large number of devices or sensors are connected to the IoT, there is an increasing amount of data and information that needs to be processed and transmitted
We investigate the performance of unmanned aerial vehicles (UAVs) acts as relay (UR) nonorthogonal multiple access (NOMA)-based mobile-edge computing (MEC) systems in practical cases of imperfect channel state information (ICSI) at receiver nodes and imperfect successive interference cancellation (ISIC) [34]
We look at the effects of the average transmit SNR, time switching ratio (TSR), the number of antennas at B, and the number of IoT devices (IDs) in each cluster
Summary
The Internet of Things (IoT) has been considered an enabling technology for smart homes, smart cities, and space information networks, and it provides abundant device connections and sensors with different applications [1]–[4]. The authors of [17] investigated the average ID latency by optimizing UAV positioning, ID association, and time allocation, where the UAV acted as a MEC server as well as a relay Another challenging aspect of deploying the IoT is determining how to provide a sustainable and cost-effective energy supply to large computationally heavy devices. According to the abovementioned issues, there is much work considering UAV-assisted NOMA-based MEC (i.e., a UAV acts as a BS-assisted MEC server; that is, the UAV consumes more energy for computation and flight, so the time for the UAV to communicate information is limited). The problem of EH in the MEC system focuses only on IDs and ignores the problem of EH in UAVs. Motivated by the above issues, the UR- and NOMA-based MEC systems in the IoT are studied in this paper, where UR supports forwarding of tasks from two cluster IDs to a BS.
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