Abstract
This paper investigates system performance in the Internet of Things (IoT) with an energy harvesting (EH) unmanned aerial vehicle (UAV)-enabled relay under Nakagami-m fading, where the time switching (TS) and adaptive power splitting (APS) protocols are applied for the UAV. Our proposed system model consists of a base station (BS), two IoT device (ID) clusters (i.e., a far cluster and a near cluster), and a multiantenna UAV-enabled relay (UR). We adopt a UR-aided TS and APS (U-TSAPS) protocol, in which the UR can dynamically optimize the respective power splitting ratio (PSR) according to the channel conditions. To improve the throughput, the nonorthogonal multiple access (NOMA) technique is applied in the transmission of both hops (i.e., from the BS to the UR and from the UR to the ID clusters). The U-TSAPS protocol is divided into two phases. In the first phase, the BS transmits a signal to the UR. The UR then splits the received signal into two streams for information processing and EH using the APS scheme. In the second phase, the selected antenna of the UR forwards the received signal to the best far ID (BFID) in the far cluster and the best near ID (BNID) in the near cluster using the decode-and-forward (DF) or amplify-and-forward (AF) NOMA scheme. We derive closed-form expressions for the outage probabilities (OPs) at the BFID and BNID with the APS ratio under imperfect channel state information (ICSI) to evaluate the system performance. Based on these derivations, the throughputs of the considered system are also evaluated. Moreover, we propose an algorithm for determining the nearly optimal EH time for the system to minimize the OP. In addition, Monte Carlo simulation results are presented to confirm the accuracy of our analysis based on simulations of the system performance under various system parameters, such as the EH time, the height and position of the UR, the number of UR antennas, and the number of IDs in each cluster.
Highlights
In recent years, the Internet of Things (IoT) paradigm has undergone incredible growth and received extensive attention [1,2,3,4,5]
We consider the downlink nonorthogonal multiple access (NOMA) unmanned aerial vehicles (UAVs)-enabled relay (UR) assisted IoT system depicted in Figure 1, where the system model consists of a base station (BS) B, two clusters, and single energy-limited UR U that uses the DF or AF scheme to send the information it collects to the IoT device (ID)
We investigate the impacts of the average transmit signal-to-noise ratio (SNR), the energy harvesting (EH) time, the number of UR antennas and the number of IDs in each cluster on the outage probabilities (OPs) and throughput of the best far ID (BFID) and best near ID (BNID)
Summary
The Internet of Things (IoT) paradigm has undergone incredible growth and received extensive attention [1,2,3,4,5]. Hua et al analyzed an AF UR network in which the UR harvests energy using a power splitting (PS) protocol and derives multiple parameters through joint optimization to maximize the system throughput [17]. In [26], the authors maximized the energy efficiency in a UAV-enabled NOMA downlink network while considering ICSI between the UAV and the IDs. In addition, for an RF EH UR operating based on a PS protocol, the received signal is divided into two parts throughout the whole receiving time. Motivated by the above discussion, we study the performance of a UR IoT communication network using NOMA with ICSI under Nakagami-m fading channels. We investigate a UR-assisted IoT communication network using RF EH and downlink NOMA with ICSI under Nakagami-m fading channels.
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