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Simultaneous wireless information and power transfer (SWIPT) is a method through which users can simultaneously obtain energy and receive data from the base station (BS). This allows them to charge their batteries, which have limited power capacity, and enhance the quality of service (QoS). Nevertheless, this technology encounters the double near-far issue, where users located at the edges of the cell experience insufficient energy due to energy path loss, resulting in a decrease in system performance. In this investigation, we integrate the self-energy recycling technology with a D2D communication system that enables full-duplex operation. By employing this technology, the D2D cell edge user (DCEU) can harvest energy from self-interference and utilize it to transmit data to the nearest D2D cell center user (DCCU). The DCCU combines its data with the DCEU and sends it to the BS using uplink non-orthogonal multiple access (NOMA). Both the DCCU and DCEU use a significant amount of energy when transmitting data, which negatively affects the quality of service (QoS). The goal of this research is to decrease the overall energy consumption of the DCEU and DCCU while maintaining their QoS. The defined problem is complex due to time and power limitations, as well as the presence of self and NOMA interference. To address this issue, we utilize a technique that combines time and power allocation. The numerical results demonstrated that the proposed scheme consumes 28.12% and 40.67% lesser amount of energy as compared to the baseline schemes. [ABSTRACT FROM AUTHOR]

The concept of integrating cooperative communication in non-orthogonal multiple access (NOMA) based networks (also known as cooperative NOMA) is inspired by the need to enhance network scalability with guaranteed fair resource allocation. However, sustaining the cooperative NOMA (C-NOMA) network lifetime becomes a challenging problem due to the energy bottleneck of the devices acting as relays for weak users. To alleviate this problem, the integration of radio frequency-based energy harvesting technique known as simultaneous wireless information and power transfer (SWIPT) in C-NOMA networks has been proposed. In this article, we present an extensive review of various contributions to the performance analysis of SWIPT-aided C-NOMA networks. To begin with, we identify critical guidelines needed for efficient network design. Moreover, we present an illustration of the system model in order to understand the fundamental relationship among different network components from a technical perspective. Further to this, we categorize and present an in-depth review of notable studies based on the type of relay employed, the number of relays deployed and the type of communication protocol adopted. Finally, we identify open areas worth exploring for future research works. [ABSTRACT FROM AUTHOR]

In next-generation heterogeneous networks, device-to-device communications are a key enabler to support a wider and diverse range of applications. They play an important role to guarantee the performance and quality of service requirements for the future ultra-dense networks. D2D-enabled cellular networks allow user equipment to communicate directly without any or with a partial association with macro base stations or with small base stations. In this paper, we propose a distance-based dynamic approach to minimize the interference and to guarantee QoS for diverse types of users equipment, such as macro user, small user and D2D user. The mode selection is used for minimize the interference and to guarantee QoS for both cellular and D2D communication links. Moreover, we investigated hybrid simultaneous wireless information and power transfer to achieve the higher data rates while guaranteeing the minimum harvested energy. Additionally, our scheme employs a transmit antenna selection criterion to exploit the spatial diversity gain of a multiple antennas for small base station. Results obtained show that coverage probability is improved in macro and small base stations links, when compared with traditional neighbor-based methods, we validate the theoretical findings and demonstrate that significant performance gain over orthogonal multiple access scheme in terms of spectral efficiency can be achieved by the proposed algorithms in a SWIPT-enabled NOMA system where we show the energy efficiency. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel energy-efficient resource optimization scheme in non-orthogonal multiple access (NOMA) networks with simultaneous wireless information and power transfer (SWIPT). In this system, we consider practical imperfect channel information that accounts for random channel delays and channel estimation errors. Additionally, the small cell users (SCUs) in a heterogeneous network (HetNet) can harvest energy from the small base station (SBS) signal by energy harvesting. Based on the non-linear energy harvesting (NEH) model, the problem of maximizing energy efficiency with imperfect channel state information (CSI) is formulated. Since the formulated problem is a probabilistic mixed non-convex optimization problem, a two-stage algorithm is developed to jointly optimize sub-channel matching and power allocation. In particular, the problem is first transformed into a non-probabilistic problem through the relaxation method. For the sub-channels matching problem, a low-complexity many-to-many matching algorithm is designed to achieve dynamic matching based on the preference lists. For the power allocation problem, the closed-form transmission power of SCUs can be derived by the Dinkelbach method and Lagrangian dual approach. Simulation results show that the proposed scheme can achieve higher energy efficiency than existing linear energy harvesting (LEH)-NOMA and NEH-OFDMA schemes, with improvements of 37.99 % and 84.69 % , respectively. [ABSTRACT FROM AUTHOR]

In this paper, we evaluate the secrecy performance in terms of secrecy outage probability (SOP) for Internet of things (IoT) enabled multi-relaying non-orthogonal multiple access (NOMA) networks with energy harvesting over Nakagami- m fading channels. Specifically, we consider the scenario that a power-constrained source and N (N ⩾ 1) IoT relays first harvest energy from a dedicated power beacon under a time switching mode, and then the source sends a confidential information to a legitimate user via a selected IoT relay, which forwards the decoded signal together with its own information data under a NOMA protocol to two legitimate users in the presence of an eavesdropper. Moreover, a two-stage relay selection criterion is also adopted to enhance the system's secrecy performance. As a benchmark, we also adopt a random relay selection scheme to analyze the secrecy performance. To clearly reveal the benefits of our proposed schemes, the analytical expressions for SOP under those two schemes have been obtained and validated through Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

This paper investigates a cooperative non-orthogonal multiple access (NOMA) system designed for multiple users. It integrates simultaneous wireless information and power transfer (SWIPT) while accounting for the imperfections in successive interference cancellation (SIC). In this scenario, a nearby user functions as a relay for a more distant user. Through the utilization of a power splitting (PS) protocol, the nearby user adeptly manages both energy harvesting and decoding signals from users. A user pairing strategy is employed, aiming to guarantee a significant contrast in channel gains between users within each pair. Subsequently, the power allocation coefficients and PS factor for each cluster are derived to optimize the performance of nearby users and amplify the overall system throughput. This optimization takes into account the individual target rates of each user while accommodating the presence of imperfect SIC. Numerical results affirm the enhanced performance of the nearby user, showcasing greater system throughput and minimal outage probability compared to existing schemes, even in the presence of imperfect SIC. [ABSTRACT FROM AUTHOR]

The development of nanotechnology and the emergence of new materials such as graphene make wireless nanosensor networks (WNSN) based on electromagnetic communication possible. Due to the energy, computing power and transmission distance carried by nano-nodes are extremely limited, nanonetworks are usually ultra-dense, so nanonetworks are usually cluster-managed. Aiming at the problem of data transmission failure caused by poor link quality or insufficient energy in inter-cluster transmission, a relay node selection algorithm (RNS-AHP) based on simultaneous wireless information and power transfer (SWIPT) and analytics hierarchy process (AHP) is proposed. The algorithm is based on the SWIPT cooperative communication model, and uses the AHP to calculate the weights of four factors: the distance of the relay node, the channel capacity, the remaining energy of the relay node and the signal-to-noise ratio of the relay node receiver in the process of relay node selection. According to the weight, the weight of the candidate relay node is obtained as the selection criterion of the relay node. The simulation results show that the RNS-AHP algorithm can improve the average throughput, the success rate of data packet transmission and the energy efficiency. [ABSTRACT FROM AUTHOR]

In this study, we examine the performance of simultaneous wireless information and power transfer (SWIPT)-enabled two-way amplify-and-forward relay networks operating over κ − μ distributed channels. We adopt a three-node wireless communication system in which two source nodes communicate with one another in half-duplex mode through a battery-enabled relay node. In order to facilitate simultaneous energy harvesting through the radio-frequency signals and information transmission activities at the relay node, we use a time switching (TS) technique. At the destination nodes, the selection-combining technique is applied to utilize the two intended signals received through both direct and relay links. We obtain analytical expressions for the cumulative distribution function (CDF) and moment-generating function (MGF) in the system under study. We derive expressions for the outage probability (OP) and average symbol error rate (ASER) for a general-order coherent rectangular quadrature amplitude modulation scheme using the derived CDF expression. Additionally, we investigate the ASER for non-coherent modulation schemes using the derived MGF expression. The system's diversity order is examined by employing the asymptotic OP. We also emphasize the impact of the TS factor, energy conversion efficiency, and fading characteristics on the investigated network. To validate the analytical expressions, we perform Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

In scenarios where traditional ground base stations (BS) are unavailable, Unmanned Aerial Vehicles (UAVs) serve as aerial BS for enabling Internet of Things (IoT) communications. This paper introduces a UAV-based downlink communication model, specifically designed to address the challenge of UAVs' limited energy resources. Our approach innovatively employs simultaneous wireless information and power transfer (SWIPT) technology, enabling the UAV to concurrently transmit information and energy to IoT devices, a crucial capability in remote or emergency areas. The core of our contribution lies in the meticulous optimization of the UAV trajectory, power splitting (PS) ratio, and communication scheduling. These optimizations are vital for maximizing energy efficiency (EE), thereby reducing the energy consumption of the UAV while ensuring high-quality communication services. The dual objectives of amplifying EE and curtailing flight time are integrated into our model, conventional solution methods fall short in addressing this non-convex optimization problem, compounded by the complexities of UAV trajectory, PS ratio, and scheduling constraints. To overcome these challenges, we reformulate the problem as a Markov Decision Process (MDP). We then leverage the powerful reward maximization capabilities of deep reinforcement learning (DRL) to enable the UAV to take optimal, energy-efficient actions in each time slot. Our simulation results are promising, indicating that the DRL algorithm effectively optimizes the UAV trajectory and significantly enhances EE. The outcomes of our research reveal a marked improvement in UAV EE along the optimized trajectory, outperforming several alternative trajectories. Furthermore, we demonstrate that a dynamic PS ratio is more effective than a fixed ratio, highlighting the superiority of our approach. This synergy of trajectory optimization and adaptive PS ratio adjustment represents a significant advancement in efficient, sustainable UAV-enabled IoT communication, particularly under challenging conditions where conventional communication infrastructures are lacking. [ABSTRACT FROM AUTHOR]

In this paper, we study the joint impact of residual hardware impairments (RHIs) and imperfect channel state information (ICSI) on cooperative non-orthogonal multiple access (NOMA) multi-relay networks. The communication between source and destinations is achieved with the aid of multiple relays with limited energy which can harvest energy from a nearby power beacon (PB). Two representative scenarios are considered: (i) The communication between the base station (BS) and the far users are realized only by the relays while the near users can receive information from both the BS and relays; (ii) The direct links between the BS and the far users exist. To evaluate the performance of the considered network, the exact analytical expressions of the outage probability for the far users and the near users are derived in closed-form. To gain deeper insights, we carry out the asymptotic outage analysis in the high signal-to-noise ratio (SNR) regime and the diversity orders for the two cases are discussed. Based on the derived results, we investigate the throughput by quantifying the impact of RHIs and ICSI on the network performance. Numerous results are presented to verify the theoretical analyses and show: (1) There exist error floors of the outage probability caused by RHIs and ICSI; (2) The direct links can improve the system performance of the two scenarios; (3) There exists an optimal power allocation factor to maximize the outage performance, especially for the far users. [ABSTRACT FROM AUTHOR]

This study investigates the performance of user equipments (UEs) and IoT devices in a multi-user (MU) multiple-input single-output (MISO) configuration based non-orthogonal multiple-access (NOMA) system. The proposed model includes a base station surrounded by many users and a number of dispersed IoT devices. In the considered MU IoT network scenario, power allocation coefficients are set to ensure that both the relaying UE and the targeted IoT device experience increased performance. To assist the intended IoT device with weak channel conditions, an optimal user selection method is developed that picks a UE with comparatively better reception, and thereby the selected UE acts as relay forward node utilizing the simultaneous wireless information and power transfer protocol. The characterization of a key performance metric, i.e., the outage probability is derived by adopting a two-step procedure. First, quadratic forms of signal to interference plus noise ratio (SINR) at the relaying UE and the signal-to-noise ratio (SNR) and SINR at the intended IoT device are constructed. Then, using the indefinite quadratic form approach, we arrive at closed-form expressions for the outage probability (OP) of intended IoT device under linearly dependent beamformers. To validate the analytical expressions provided in this study, simulations are performed. We demonstrate that by utilizing the proposed user selection technique in MU-MISO-NOMA system decreases the OP of the intended IoT device by 40% on average. Furthermore, utilizing multiple transmit antenna elements decreases the OP of the intended IoT device by approximately 10%. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we derive and analyze the average Energy Harvested and average achievable downlink rate expressions for the formulated SWIPT enabled system. Rician channel modeling is used for simulation because the distance between Base Station and Users are assumed to be close and thus Line of Sight component is included. After initializing appropriate parameters, definite and accurate expressions and approximate expressions are derived. Results are simulated and analyzed to validate the theory and the derived expressions, by varying efficiency, Rician factor and Path loss exponent. [ABSTRACT FROM AUTHOR]

Vehicle to everything (V2X) is emerging as a promising application scenario of next generation mobile communications. In V2X systems, a series of applications (information transmission, in-car entertainment, etc.) rely on the limited vehicle battery. However, most prior work limits to the automatic piloting, channel measurement/estimation and high speed transmissions, seldom study has been done on the battery-limited for V2X. In light of this, here we investigate the problem of the downlink beamforming design for signal-to-interference ratio balancing in a V2X-SWIPT environment with imperfectly estimated channels at the base station, where a practical non-linear energy harvesting model is considered. The problem is further transformed into a two-layer optimization problem, where we solve the inner-level problem by exploiting S-Procedure, and the outer-level problem through bisection approach. Finally, simulation results are carried out to confirm that the proposed robust beamforming design obtains a favorable result in applications of practical interest. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the secrecy energy efficiency (SEE) optimization of the multiple-input single-output (MISO) system. First, transmission beamforming vector is designed to achieve the SEE maximization subject to the constraints of transmission power, minimum secrecy rate threshold and harvested energy threshold. The optimization problem belongs to the category of fractional optimization, which is non-convex and is very difficult to tackle. In order to solve the optimization problem, we propose an algorithm that can obtain a near-optimal solution, which consists of outer-tier and inner-tier iterations. For the outer-tier iteration, we first employ the Dinkelbach method to convert the fractional objective function into a polynomial form, and then transform the optimization problem into a difference of concave (DC) programming. For the inner-tier iteration, we employ the first-order Taylor expansion and successive convex approximation (SCA) method to solve the DC optimization problem. Then, we analyze the computational complexity of the proposed algorithm. In addition,we prove that the rank relaxation is tight. The simulation results show that the SEE performance of our proposed algorithm is obviously superior to that of secrecy rate maximization scheme and zero-forcing scheme. [ABSTRACT FROM AUTHOR]

A nanonetwork is comprised of nanoscale sensors and communicating devices facilitating communication at the nanoscale, which is a promising technology for application in health applications such as intra-body health monitoring and drug delivery. However, the communication performance within a nanonetwork is substantially limited by the energy loss as the Electromagnetic (EM) wave propagates along the channel. Energy harvesting for nanosensor networks can provide a way to overcome the energy bottleneck without considering the lifetime of batteries. Moreover, relaying protocols for nanoscale communications have been proposed to improve the communication performance and extend the transmission distances among nanosensors within nanonetworks. The combination of energy harvesting and a relaying protocol provides an emerging solution not only to overcome the aforementioned energy issues but also enhance the system performance. Therefore, in this paper, simultaneous wireless information and power transfer nanonetworks in the Terahertz (THz) Band (0.1-10 THz) is proposed. An amplify and forward (AF) relaying nanonetwork in this band is investigated, where the relay harvests energy from the received THz signal which is then consumed to forward the information to the destination. Performance based on both time-switching and power-splitting protocols is analyzed. The numerical results show the optimal power-splitting ratio and time switching ratio that achieves the maximum throughput at the destination as well as the impact of transmission distance on system performance. It is seen that the power-splitting protocol gives greater throughput than that of the time-switching protocol. [ABSTRACT FROM AUTHOR]

Wireless NanoSensor Network (WNSN) is a brand-new type of sensor network with broad application prospects. In view of the limited energy of nano-nodes and unstable links in WNSNs, we propose an energy balance cluster network framework (EBCNF) based on Simultaneous Wireless Information and Power Transfer (SWIPT). The EBCNF framework extends the network lifetime of nano-nodes and uses a clustering algorithm called EBACC (an energy balance algorithm for intra-cluster and inter-cluster nodes) to make the energy consumption of nodes more uniform. Simulation shows that the EBCNF framework can make the network energy consumption more uniform, reduce the error rate of data transmission and the average network throughput, and can be used as an effective routing framework for WNSNs. [ABSTRACT FROM AUTHOR]

Providing a stable and perpetual source of energy to charge battery-powered wireless communication devices is viewed as a major challenge in wireless communication systems. This challenge leads to the trending research area where radio frequency signals are being exploited for energy harvesting purposes. The technique for achieving this is known as simultaneous wireless information and power transfer (SWIPT). In recent studies on SWIPT, the massive Multiple-Input-Multiple-Output (MIMO) aided energy harvesting has attracted considerable attention from the research community. This can be attributed to the high energy delivery rate of massive MIMO antenna systems due to their capacity to focus transmitted signals in the direction of the intended receivers. However, SWIPT in massive MIMO networks requires an optimal design to achieve a proper balance between different conflicting network objectives. In this article, we aim to discuss various contributions to SWIPT in massive MIMO networks in order to address critical design issues. In particular, we focus on the widely adopted approach to resolving SWIPT-related issues in massive MIMO networks, that is, the resource allocation design. We also extend our discussion to studies dedicated to solving critical design challenges. In this regard, we take into consideration the energy efficiency and security aspect of the system design. Finally, we identify potential areas that can be explored for future research work. [ABSTRACT FROM AUTHOR]

This paper investigates the secure transmission for simultaneous wireless information and power transfer (SWIPT) in the cell-free massive multiple-input multiple-output (MIMO) system. To develop green communication, legitimate users harvest energy by the hybrid time switching (TS) and power splitting (PS) strategy in the downlink phase, and the harvested energy can provide power to send uplink pilot sequences for the next time slot. By in-built batteries, the active eavesdropper can send the same pilots with the wiretapped user, which results in undesirable correlations between the channel estimates. Under these scenarios, we derive the closed-form expressions of average harvested energy and achievable rates, and propose an iterative power control (PC) scheme based on max–min fairness algorithm with energy and secrecy constraints (MMF-ESC). This scheme can ensure the uniform good services for all users preserving the distributed architecture advantage of cell-free networks, while meeting the requirements of energy harvested by legitimate users and network security against active eavesdroppers. Besides, continuous approximation, bisection and path tracking are jointly applied to cope with the high-complexity and non-convex optimization. Numerical results demonstrate that MMF-ESC PC scheme can effectively increase the achievable rate and the average harvested energy of each user, and decrease the eavesdropping rate below the threshold. Moreover, the results also reveal that PS strategy is superior in harvesting energy in terms of more stringent network requirements for average achievable rates or security. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the energy efficiency (EE) performance of non-orthogonal multiple access (NOMA) enabled full-duplex (FD) coordinated direct and relay transmission (CDRT) system (i.e., NOMA-FD-CDRT system). Firstly, we consider a two-user scenario, where the base station (BS) can directly communicate with the near user, while it requires the help of a dedicated FD relay node to communicate with the far user. In the second part, we consider that there are two near users and two far users in the system. To improve the EE, we consider integrating the simultaneous wireless information and power transfer (SWIPT) technique at the FD relay. We formulate an analytical expression for the overall EE of the SWIPT-assisted NOMA-FD-CDRT system. We determine optimal power allocation (OPA) for the downlink users at the BS that maximizes the EE. An iterative algorithm based on Dinkelbach method is proposed to determine the OPA vector. With the help of detailed numerical and simulation investigations, it is demonstrated that the proposed OPA can provide significant enhancement of EE of the considered SWIPT-assisted NOMA-FD-CDRT system. [ABSTRACT FROM AUTHOR]

High performance UAV-assisted communications system using simultaneous wireless information and power transmission (SWIPT) in mm-wave band is presented. UAV is a moving relay powered from a ground source through a power-splitting mechanism. In mm-wave band we utilize antenna array to increase the antenna gain while keeping array size small and practical. The radiation pattern of the UAV antenna is continuously adjusted to peak towards the source and destination. Two array geometries, a line and a cross, are designed for UAV antenna. We achieve near optimal pattern, utilizing innovative low power switches instead of phase shifters which are high power consuming components and using them here defies the purpose. We maximize the end-to-end cooperative throughput by optimizing the UAV power profile, power-splitting ratio profile, antenna weights (0, 1), and UAV trajectory for amplify-and-forward (AF) protocol. We consider two cases. Case1: UAV transmits and receives data simultaneously along two predefined trajectories. The antenna weights for line and cross arrays are optimized utilizing genetic algorithm. The power profile and, power-splitting ratio profile are also optimized using the penalty method. Case2: UAV accumulates the data and power along an optimal trajectory until it reaches the vicinity of target, when it transmits data at high bit rate. Here we define the optimization of parameters mentioned in Case1, while at an optimal point along the trajectory, as sub-problem1, and finding the next optimal point as sub-problem2. Sub-problem1 is solved using the genetic algorithm and dual decomposition method. Sub-problem2 is then solved using successive concave optimization. The overall problem, i.e. cooperative throughput, is solved by reciprocal iteration over the two sub problems. The simulation results show the proposed mm-wave band cross array antenna and switches can overcome the high frequency propagation losses, hence, achieving higher power harvest and data rates. The achieved higher data throughput outperforms the conventional single antenna low frequency systems. [ABSTRACT FROM AUTHOR]

In this paper, a radio-frequency (RF) energy harvesting enabled cognitive radio network (CRN) is considered in the presence of transceiver hardware impairments (HIs). Herein, one of the secondary nodes (SNs) exploits simultaneous wireless information and power transfer (SWIPT) technology to harvest energy from the primary signal and provides relay assistance for the primary transmission. We consider multiple antennas at the primary nodes (PNs) to ensure better link reliability and spectrum sharing to mitigate the spectrum scarcity. In the first phase, relaying SN uses non-linear energy harvester circuit to harvest energy from the RF signals received from PN using the power splitting approach. In the second phase, the same SN adds its own signal intended for the other SN along with the primary signal and broadcasts the combined signal. Assuming the network to operate in a Nakagami- m fading environment, the performance of the considered CRN is evaluated in terms of outage probability and system throughput. Also, we formulate two optimization problems to minimize the OP and maximize the system throughput. The Karush–Kuhn–Tucker conditions are used to obtain the closed-form solution of the constrained convex optimization. Numerical results are provided to examine the performance impact concerning different system and channel parameters. [ABSTRACT FROM AUTHOR]

In this paper, we consider a cooperative relaying system (CRS) empowered by simultaneous wireless information power transfer (SWIPT) and non-orthogonal multiple access (NOMA) where SWIPT and NOMA are implemented for their energy and spectral efficiencies, respectively. We analyze error performance of the considered CRS-SWIPT-NOMA and derive exact closed-form average bit error probability (ABEP) over Nakagami- m fading channels which is perfectly-matched with computer simulations. The considered CRS-SWIPT-NOMA outperforms the benchmark (no energy harvesting) significantly which is very promising for green communications. Then, we discuss diversity order of the CRS-SWIPT-NOMA and, with extensive simulations, we revealed that it is equal to minimum shape parameter (i.e., m) between nodes. Lastly, we investigate the effects of SWIPT and NOMA parameters on the error performance and discuss the optimum parameters in terms of minimum ABEP. We also discuss the relay position to improve the performance of the CRS-SWIPT-NOMA. [ABSTRACT FROM AUTHOR]

Space shift keying (SSK) modulation performance is analyzed with simultaneous wireless information and power transfer (SWIPT) based cooperative amplify-and-forward (AF) relaying system over the Nakagami- m fading channel. SWIPT technique can remove the need for power supply at the relays in cooperative communication. In contrast, SSK is a low complex index modulation technique that eliminates inter antenna synchronization, inter-channel interference and reduces the number of radiofrequency chains. Closed-form expression for average bit error probability (ABEP) is derived using a single AF relay with selection combining (SC) at the receiver, and an Upper bound ABEP expression is derived for multiple AF relays with the direct link (DL) from source to destination. The partial relay selection (PRS) technique has been proposed with energy harvesting (EH) to reduce the hardware complexity compared to the multiple relays. Numerical and computer simulation results are presented with the discussion. The result demonstrates that EH with SSK modulation can improve the system performance. [ABSTRACT FROM AUTHOR]

In this paper, maximum achievable throughput of downlink decode-and-forward (DF) multiple input multiple output (MIMO) simultaneous wireless information and power transfer (SWIPT) relaying system is investigated. In the considered network, a/two MIMO relay(s) can harvest power and transfer information simultaneously. In this paper, three possible scenarios are taken into account. In the first scenario, there is no direct link between the base station (BS) and the users; indeed, the information transfer is done between the BS and the users via a relay. In the second one, some users get service directly via the BS and other part of them receive the BS's transmitted information via the relay. In the third scenario, there are two relays alongside the direct link. In the all scenarios, the allocated powers to the spatial sub-channels of the BS-relay, the relay-users links and the BS-users links as well as power splitting ratio (PSR) at the relay(s) are optimized. Based on the complicated form of optimality conditions in the all scenarios, two novel power allocation algorithms proposed which can find the optimal solution with a low convergence time. Indeed, the throughput maximization problem is separated into two sub-problem. A novel algorithm couples this sub-problems based on the optimal conditions, which are obtained through convex optimization framework. It should be noted that PSR optimization is carried out based on the sub-gradient method. Moreover, the power allocation and PSR optimization are successively done. Simulation results validate the efficiency of the proposed methods in terms of optimality and convergence time. [Display omitted] • In the first scenario, optimum power allocations and beamforming are proposed in a MIMO DF SWIPT relaying systems with no direct link between users and BS. • In the second scenario, some direct users are added to the first scenario. Another algorithm is provided to maximize the achievable rate by applying the first algorithm. • To generalize the second proposed algorithm, we consider the third scenario in which there are 2 relays. • Two schemes of the PSR optimization are taken into account in all scenarios. The PSRs and assigned powers are optimized in successive manner. • Numerical results reveal the efficiency of the proposed algorithms in terms of throughput and convergence time in comparison with the benchmarks. [ABSTRACT FROM AUTHOR]

In this study, we examine an emerging Multiple-Input-Multiple-Output (MIMO) Non-Orthogonal Multiple Access (NOMA) network which combines Transmit Antenna Selection (TAS) and Simultaneous Wireless Information and Power Transfer (SWIPT) protocols. A pre-coding channels matrix was designed to aid the TAS protocol. We deployed a strong user as a relay to assist a weak user. Three cooperative MIMO-NOMA network scenarios were investigated. In the first scenario, we assumed the relay was deployed with (i) Decode-and-Forward (DF), (ii) Amplify-and-Forward (AF) with Fixed Gain (FG) and (iii) AF with a Variable Gain (VG) protocols to improve system performance over the first scenario. In scenario (iii), we investigated an amplify coefficient based on the maximum of instantaneous CSI and obtained the Outage Probability (OP) in novel closed form. The analytical results showed that although the Base Station (BS) sent information and energy at the same instant, the OP performance at the relay was sufficient due to assistance from multi-antennas and the TAS protocol. However, the OP performance at the user under cooperation with a relay using the AF-VG protocol achieved better system performance than the DF and AF-FG protocols. We proved and verified the analytical results with Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) and full duplex (FD) relaying are two promising techniques to enhance the spectral efficiency of the fifth generation (5G) wireless networks. Simultaneous wireless information and power transfer (SWIPT) technique has recently emerged as an effective solution to improve the energy efficiency of wireless networks. This paper investigates outage and throughput performance of SWIPT enabled FD cooperative NOMA network under power splitting relaying (PSR) protocol, i.e., SWIPT enabled FD-PSR-NOMA network. We assume a single cell network consisting of a base station (BS) and two pre-paired users, i.e., a near user and a far user, where the near user acts as FD relay to assist the BS for information delivery to the far user, and power splitting (PS) technique is used at the relay for energy harvesting (EH). We derive analytical expressions for the outage probabilities experienced by the downlink users, system outage probability and delay limited system throughput under imperfect successive interference cancellation (i-SIC). We also derive analytical expressions for outage probabilities and throughput of SWIPT enabled half duplex (HD) cooperative NOMA network under PSR, i.e., SWIPT enabled HD-PSR-NOMA network. The optimal power allocation (OPA) factor at the BS and optimal power splitting (OPS) factor at the relay that independently minimizes the asymptotic system outage probabilities of SWIPT enabled FD/HD-PSR-NOMA networks are determined. Further, we explore the jointly optimal power allocation and power splitting factor that minimize the system outage probability. Furthermore, we derive analytical expression for the OPS factor that maximizes the asymptotic system throughput. We provide extensive numerical and simulation results to establish that system outage and throughput improve significantly under the proposed schemes. [ABSTRACT FROM AUTHOR]

Ultra-high reliability communications are greatly vital for massive user connections and network sensors such as Internet of Things (IoT) devices in the beyond 5th generation (B5G) communication networks. Simultaneous Wireless Information and Power Transfer (SWIPT) has evolved as an efficient strategy through prolonging the battery life by harvesting energy from radio-frequency (RF) signals. Moreover, cooperative relay sensors in IoT network can enhance the network coverage. In this paper, we investigate the multiple-input multiple-output (MIMO) SWIPT relaying systems with direct link, where the relay node splits the received RF signals into two power streams, one for information decoding (ID) and the other for energy harvesting (EH). Under per-antenna power constraints, the relay node forwards the ID signal to the destination. We propose a channel diagonalization scheme based on singular value decomposition (SVD) and eigenvalue decomposition (EVD) to design the precoding matrix of source and the amplifying matrix of relay respectively. Moreover, the closed-form expression of the optimal power splitting (PS) factor diagonal matrix is obtained to maximize the sum-rate of MIMO SWIPT relaying system. Finally, the efficiency of proposed precoding and PS factor design is verified by the presenting numerical results. • We propose a MIMO SWIPT relaying system with direct link. The system distinguishes from the existing TS scheme SWIPT relaying system, since the relay applies the PS scheme and the PS factors of diverse relay antennas are disparate. • The precoding structures of transceivers under the power constraint are provided and the achievable sum-rate of MIMO SWIPT relaying system is derived. • The optimal relay PS factor matrix is obtained to maximize the achievable sum-rate of the relaying system. • Numerical results are conducted to verify the effectiveness of the proposed precoding and PS factor design. [ABSTRACT FROM AUTHOR]

Unpredictable nature of fading channels and difficulty in tracking channel state information pose major challenge in wireless energy harvesting communication system design. In this work, we address relay selection problem for wireless powered communication networks, where the relays harvest energy from the source radio frequency signals. A single source–destination pair is considered without a direct link. The connecting relay nodes are equipped with storage batteries of infinite size. We assume that the channel state information (CSI) on the source–relay link is available at the relay nodes. Depending on the availability of the CSI on the relay–destination link at the relay node, we propose two relay selection schemes and evaluate their outage probability. Availability of the CSI at the relay node on the relay–destination link considerably improves the performance due to additional flexibility in the relay selection mechanism. Due to absence of CSI throughout the network at the time of transmission path selection, the analysis of the problem is not tractable. Therefore, we relax our assumptions on availability of CSI and closed-form expressions of the outage probability as a function of the amount of the available harvested energy are derived for both CSI availability cases. Finally, we numerically quantify the performance for the proposed schemes and compare the outage probability for fixed and equal number of wireless powered forwarding relays. [ABSTRACT FROM AUTHOR]

• OFDM-NOMA. • CR. • SWIPT. In order to enhance the capacity and extend the lifetime of nodes for green Internet of Things (IoT), the non-orthogonal multiple access (NOMA) is applied to cognitive orthogonal frequency-division multiplexing (OFDM) systems, along with simultaneous wireless information and power transfer (SWIPT). Firstly, an uplink SWIPT-based cognitive OFDM-NOMA system model is proposed where the power splitting (PS) mode is applied to harvest energy from radio frequency signals. Then, we investigate the problem of maximizing the sum data rate of uplink transmission by jointly optimizing sensing duration, user matching, and power allocation constrained by the transmit power and harvested energy. In order to decouple the strong relations among variables, the proposed optimization problem is decomposed into three sub-problems, i.e., the optimization of sensing duration, the optimization of user matching based on the matching theory, and the optimization of power allocation. We propose an alternate iteration algorithm to jointly solve the three sub-problems. Furthermore, two cognitive modes are employed in this paper: overlay mode and underlay mode. The performance of sum rate as well as harvested energy is evaluated, while simulation results are shown to verify the convergence of the proposed algorithm. It is shown that the proposed algorithm can not only perform the subcarrier allocation efficiently, but also behave well in terms of sum data rate subject to the required energy. [ABSTRACT FROM AUTHOR]

Due to the advantages of high mobility, flexible maneuverability and fast deployment, Unmanned Aerial Vehicle (UAV), which can be usually served as aerial communication platform, not only supports information transmission in the Internet of things (IoT), but also provides reliable power supplement for low-power wireless devices. Considering an UAV-enabled Orthogonal Frequency Division Multiplexing (OFDM) network where subcarriers are divided into two groups for information transmission and energy harvesting, respectively, a joint UAV trajectory optimization and communication design scheme is proposed based on Simultaneous Wireless Information and Power Transfer (SWIPT) technology. Under the given average harvested energy for users, the objective of the scheme is to maximize the average achievable rate for all users by jointly optimizing UAV trajectory, user scheduling, subcarrier and power allocation. To solve the formulated optimization problem, it is transformed into two subproblems to optimize resource allocation and UAV trajectory, respectively. The former is a mixed integer non-convex optimization problem. To solve it, a three-variable alternative iteration algorithm is proposed to obtain the optimal user scheduling, subcarrier and power allocation. Since the latter is non-convex, it can be transformed into convex optimization problem by relaxing objective function and constraint to obtain the optimal trajectory. Simulation results demonstrate that the proposed algorithm has good convergence and the proposed UAV-enabled OFDM network has better performance. [ABSTRACT FROM AUTHOR]

In relay-based cooperative communications (RBCC) system, the energy problem of relays is a significant issue needs to be addressed. In the last few years, the simultaneous wireless information and power transfer (SWIPT) technique has been introduced to solve that matter. SWIPT technique aims to carry data and power over the wireless signals from the source node to the destination for the relays system. The SWIPT technique can be implemented utilizing two protocols. The first one has been introduced as time switch relay (TSR) protocol, which is time division between energy harvesting and data transmission. The second one has been introduced as power switch relay (PSR) protocol based on power division between two mentioned processes. The time or power fraction directly affects the quality of service (QoS) parameters in SWIPT-based cooperative communication systems. This paper aims to maximize effective capacity by implementing an optimization to find the optimum time or power fraction of energy harvesting in relays system utilizing TSR or PSR protocols. The optimization is applied using Lagrange multipliers while simulation results are used to verify the theoretical results obtained from the optimization process. In addition, outage probability of the source-relay-destination link is analyzed in both TSR and PSR protocols. [ABSTRACT FROM AUTHOR]