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The conventional reconfigurable intelligent surface (RIS) is limited to reflecting incident signals, thereby imposing constraints on the placement of the transmitter and receiver, which hinders achieving comprehensive signal coverage across an entire area. This paper investigates a simultaneously transmitting and reflecting (STAR)-RIS-aided simultaneous wireless information and power transfer (SWIPT) system with a nonlinear energy harvesting model under three different RIS transmission protocols: energy splitting (ES), time switching (TS), and mode switching (MS). The objective of this paper is to maximize the weighted sum power (WSP) of all energy harvesting receivers (EHRs) while ensuring fairness in the collected power among them. This is achieved by jointly optimizing the transmit beamforming at the base station (BS) and the transmission and reflection coefficients at the STAR-RIS, subject to rate constraints for information decoding receivers (IDRs), transmit power constraint at the BS, and coefficient constraints of each element at the STAR-RIS corresponding to the three protocols. Solving this optimization problem poses challenges because of the complicated objective function and numerous coupled optimization variables of the ES STAR-RIS. To address this complexity, an efficient alternating optimization (AO) approach is proposed as an iterative solution method that achieves suboptimal results. The AO algorithm is then extended to MS STAR-RIS and TS STAR-RIS. Specifically, for MS STRA-RIS, binary constraints in the STAR-RIS coefficient optimization subproblem are handled using the first-order approximation technique along with the penalty function method. For TS STAR-RIS, apart from optimizing BS transmit beamforming and STAR-RIS coefficients subproblems, the transmission and reflection time allocation of STAR-RIS also needs optimization. Numerical findings demonstrate that compared to conventional RIS-aided systems, utilizing three different protocols in a STAR-RIS-aided system can enhance power collection at EHRs while expanding the receiver placement range. Furthermore, TS STAR-RIS performs best when the IDRs do not require high achieved rates. Otherwise, ES is the best choice. [ABSTRACT FROM AUTHOR]

Recently, with the development of nanotechnology and the emergence of new materials, Wireless Nanosensor Networks (WNSNs) have been presented. To address the problems of link instability in WNSNs and poor adaptability of the EBCNF framework to network topology changes, a reliable multi-path routing based on link stability called RMRLS is proposed. Based on the EBCNF framework, this protocol introduces a path similarity judgment model to judge the similarity between paths. In the route establishment process, the link stability evaluation model is used to measure the stability of each path and as a criterion for path selection. Then alternative route is selected through the routing similarity judgment model. Optimal path and backup path are two routing paths to cope with changes in the network topology. The simulation results show that the RMRLS protocol has advantages in energy efficiency, data packet transmission success rate and average throughput, which are 28.84% lower, 53.8% higher, and more than double compared to EBCNF at a distance of 10 mm, respectively. These findings proved the RMRLS protocol's capacity to significantly boost the stability and reliability of the network. [ABSTRACT FROM AUTHOR]

One of the most well-known uses of smart cities has been massive multimedia offerings. But the enormous demand for device-to-access point (D2A) communication has significantly increased the energy consumed and the greenhouse impact. As a result, energy-harvesting-based two-way access points (AP) and space shift keying (SSK) modulation are used to analyse the error performance of smart users in the smart city. Communication between smart users and a centralised AP is crucial in a smart metropolis. In this instance, energy harvesting at the two-way AP over the Saleh–Valenzuela channel has been taken into consideration using the simultaneous wireless information and power transmission (SWIPT) system. For smart users, SWIPT can remove the need for battery replacement or meet energy needs. In contrast, SSK modulation is a less complex method that does not need as many radio-frequency chains, inter-antenna synchronisation, or inter-channel interference for multiple-input-multiple-output transmission. Applying multi-user selection combining, smart sensors' average bit error probability efficiency is derived in closed form. The numerical and simulation assessment results demonstrate how energy harvesting affects the system's effectiveness. [ABSTRACT FROM AUTHOR]

Neighbourhood area network (NAN) performance is analyzed with space shift keying (SSK) modulation and energy harvesting-based cooperative amplify-and-forward (AF) relaying. Wifi-enabled home appliances (HAs) can transfer the information to the utility control centre through the smart meter (SM) in the NAN. The HAs in NAN work on a power-saving mechanism, and they drastically increase the spectral efficiency. The Markov chain dynamically models the number of active HAs in the smart grid (SG) network. Moreover, simultaneous wireless information and power transfer combined with AF relaying-based SM helps overcome the rising demands of SG communication by providing an enhanced data rate, low latency, shorter coverage, widespread connectivity of the massive number of devices along with energy-efficiency. Mathematical expressions for average bit error probability are derived for NAN over mixed Saleh–Valenzuela and Rician fading channel based on the multi-user selection combination. The Monte Carlo simulation verifies the numerical results. The result illustrates that the SG NAN performance can be improved by combining SSK modulation with energy harvesting schemes. [ABSTRACT FROM AUTHOR]

This work aims at achieving the secrecy rate (SR) enhancement in amplify-and-forward (AF) relay-aided simultaneous wireless information and power transfer (SWIPT)-NOMA network via control-jamming (CJ) whilst satisfying the constraints on total transmit power budget. Here, in order to coordinate the information processing and energy-harvesting (EH), power-splitting (PS) protocol is deployed at the relay. For comparison purposes, in addition to CJ, the SR of with-jamming (J) and without-jamming (WJ) conditions are also highlighted in the existence of an eavesdropper (Eve). Moreover, the analytical expression for Ergodic SR is evaluated at the NOMA users under the CJ scenario. Next, to maximize the SR of the users further, an optimal power allocation (OPA) scheme has been adopted, which involves both particle swarm optimization (PSO) and Lagrangian multiplier (LM)-based approaches to acquire the optimized power factors of various nodes of the network. In addition, we analyzed the affect of major parameters such as: J → E v e distance, transmit signal-to-noise ratio (SNR), and R → E v e distance on the SR by exploiting distinct jamming scenarios. Finally, a significant secrecy performance gain in terms of SR is verified with proposed CJ over other jamming conditions and OPA over the fixed power allocation (FPA) and it is confirmed through Monte-Carlo based simulations. [ABSTRACT FROM AUTHOR]

To further address the energy constraint problem and improve the secrecy performance of unmanned aerial vehicle (UAV) systems in the fifth generation (5G)-enabled Internet of Things, we consider a secure UAV system with simultaneous wireless information and power transfer in the presence of a full-duplex active eavesdropper, which eavesdrops on confidential information and transmits malicious jamming signals simultaneously. In particular, the UAV is powered by a constrained onboard battery that can harvest energy from the ambient radio frequency signals. The trajectory of the UAV, power splitting ratio, and transmitting power are jointly optimized to maximize the secrecy rate of the system. Owing to the non-convexity of the problem, we propose an alternative optimization algorithm by applying successive convex approximation and block coordinate descent methods. The simulation results show the proposed joint optimization algorithm can promote the average secrecy rate of the system as compared with other benchmark schemes. [ABSTRACT FROM AUTHOR]

We study a downlink cooperative non-orthogonal multiple access (NOMA) system in which a base station (BS) serves two paired users on the same frequency band simultaneously, and the near user acts as an energy-constrained relay for the far user since there is no direct link between the BS and the far user due to physical obstacles or heavy shadowing. To replenish energy of the near user for relaying, we enable the near user to harvest energy from BS signals by adopting the simultaneous wireless information and power transfer (SWIPT) technique. Different from the linear energy harvesting (EH) model used in most of the existing literature, we adopt a non-linear model for EH. By considering the non-linear features of the practical circuits, we aim to minimize the BS energy consumption while ensuring the minimum required transmission rate of both users. Since the formulated problem contains coupled power and time resource variables, it is challenging to solve it directly. Thus, we propose an optimal power-time resource allocation algorithm by decoupling the variables properly. Simulation results verify the theoretical analysis and show the performance of the considered system. [ABSTRACT FROM AUTHOR]

This paper considers an unmanned aerial vehicle (UAV)-assisted communication system with simultaneous wireless information and power transfer (SWIPT). In modeling the composite channel, the probability of line-of-sight (LoS)/non-LoS is taken into account, along with log-normal shadowing. Moreover, for small-scale fading, Nakagami-m and Rayleigh distributions are considered for the LoS and non-LoS (NLoS) conditions, respectively. For enabling radio-frequency (RF) energy harvesting, a hybrid power-splitting (PS) and time switching (TS) based architecture is considered at the UAV. In order to provide relay cooperation to the remote mobile user, the UAV performs decode-and-forward (DF) operation. To examine the system performance, we first derive the outage probability (OP) expression utilizing the Gauss–Hermite quadrature for different shadowing and fading channel combinations. In addition, the system throughput and energy efficiency expressions are obtained for both shadowed and un-shadowed channels and verified through Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

In cooperative communication, relay reduces the stored energy for its own transmission due to the energy consumption for forwarding the information from source node. In this paper, simultaneous wireless information and power transfer (SWIPT) for OFDM-based cooperative communication is proposed to save the relay's energy by harvesting the radio frequency (RF) energy from source node. Subcarrier allocation based SWIPT (SA-SWIPT) is designed to use different subcarrier sets for information decoding and energy harvesting. In the first phase, the relay uses the SA-SWIPT to receive information and energy from source node. And in the second phase, the relay forwards the information both from source node and itself to the destinations using the energy collected from source node. The transmission rates of the relay in DF and AF modes are maximized by jointly optimizing subcarrier allocations and subcarrier powers, respectively, while ensuring the required transmission rate of source node and the energy supply of relay. An efficient iterative optimization algorithm is proposed to solve the proposed optimization problem through Lagrangian dual decomposition. Simulation results show the convergence of the optimization algorithm after very few iterations and explains the potential benefits for using SA-SWIPT in the OFDM-based cooperative communication. [ABSTRACT FROM AUTHOR]

In view of the existing computation offloading research on fog computing network scenarios, most scenarios focus on reducing energy consumption and delay and lack the joint consideration of smart device rechargeability. This paper proposes a deep deterministic policy gradient-based intelligent rechargeable fog computation offloading mechanism that is combined with simultaneous wireless information and power transfer technology. Specifically, an optimization problem that minimizes the total energy consumption for completing all tasks in a multiuser scenario is formulated, and the joint optimization of the task offloading ratio, uplink channel bandwidth, power split ratio and computing resource allocation is fully considered. Based on the above nonconvex optimization problem with a continuous action space, a communication, computation and energy harvesting co-aware intelligent computation offloading algorithm is developed. It can achieve the optimal energy consumption and delay, and similar to a double deep Q-network, an inverting gradient updating-based dual actor-critic neural network design can improve the convergence and stability of the training process. Finally, the simulation results validate that the proposed mechanism can converge quickly and can effectively reduce the energy consumption with the lowest task delay. [ABSTRACT FROM AUTHOR]

Energy harvesting technology can solve the problem of users' energy consumption in disaster areas. When disasters occur, some users are trapped and unable to recharge and need to collect power from neighboring users to transmit information. To solve the battery charging and information transmission problems of trapped user in disaster scenario, this paper proposes a relay-based on simultaneous wireless information and power transfer (SWIPT) energy harvesting and information transmission time allocation optimization algorithm. In this relay system, trapped user serves as the source node, the neighboring user terminals charge it in SWIPT mode and serve as relays to forward the information of trapped user to the base station. Under the constraint of collecting energy, the optimization problem of maximum system transmission rate is established. By studying the dual correlation of two-hop transmission and using Lambert' W function, the optimal ratio of energy harvesting time of trapped user to total time and the optimal ratio of the information transmission time of the trapped user to total information transmission time of relay system are obtained. Simulation results show that the proposed algorithm can provide energy for trapped user and improve data transmission rate. [ABSTRACT FROM AUTHOR]

In this paper, in order to improve the performance of wireless fifth generation (5G) communication system and save power consumption, the research objectives of optimal power allocation and maximizing the total user rate in a multi-user cluster in the downlink of non-orthogonal multiple access (NOMA) access system are realized based on the simultaneous wireless information and power transfer (SWIPT). A SWIPT-NOMA system assisted by dynamic unmanned aerial vehicle (UAV) relay is constructed. The UAV relay dynamic programming under two-hop communication was firstly studied, and the global optimal power allocation strategy for downlink users of SWIPT-NOMA system is found. Finally, the optimal relay selection algorithm was used to maximize the total user rate, which was verified by Monto Carlo simulation. Simulation results show that compared with the traditional FDMA system scheme, the performance of the proposed system model in terms of outage probability, energy consumption and total user rate of multi-user cluster deployed in dynamic UAV relay system under different distribution scenarios is better than that of the benchmark scheme. [ABSTRACT FROM AUTHOR]

Simultaneous wireless information and power transfer (SWIPT) has recently attracted researchers and may help to satisfy future technology demands. SWIPT allows wireless power transfer (WPT) and wireless information transfer (WIT) to coexist based on shared resources. Recent studies have shown that, due to the nonlinearity of the rectifiers, high-PAPR (peak to average power ratio) waveforms provide better performance in terms of energy harvesting, making the design of power signals essential. In addition, these power signals should consume the smallest amount of resources for the WIT. In this paper, a new waveform design is proposed where the information and power signals are superposed using the same frequency and time resources. The power signal is composed of a high peak modulated rectangular wave sent during the cyclic prefix of the orthogonal frequency-division multiplexing (CP-OFDM) system, which is discarded at the information receiver, such that it does not interfere with the OFDM data symbol. Although the pulse is restricted to be within the cyclic prefix, there might be a small amount of interference caused by channel dispersion. Simulations and measurements show that a good choice of signal parameters can minimize interference on the information symbols and simultaneously provide good performance in terms of energy harvesting. [ABSTRACT FROM AUTHOR]

This paper presents two protocols in non-orthogonal multiple access (NOMA) network, namely base station (BS), based power splitting protocol (PSR) and BS based time switching protocol (TSR), for simultaneously wireless information and power transmission (SWIPT) based unmanned aerial vehicles (UAVs) which are employed in power domain NOMA based UAV communication network. The system model with k types of the UAV, one BS, and two users' devices is investigated in our work. Besides, a strategy of UAV selection is also studied. Closed-form expressions of outage probability and throughput for UAVs and both users' devices are derived. In particular, the outage probability is determined for both perfect and imperfect SIC. The numerical results show that the performance for BS-based PSR outperforms that for BS-based TSR. The analytical results match Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Aiming at high energy consumption and information security problem in the simultaneous wireless information and power transfer (SWIPT) multi-user wiretap network, we propose a user-aided cooperative non-orthogonal multiple access (NOMA) physical layer security transmission scheme to minimize base station (BS) transmitted power in this paper. In this scheme, the user near from BS is adopted as a friendly relay to improve performance of user far from BS. An energy harvesting (EH) technology-based SWIPT is employed at the near user to collect energy which can be used at cooperative stage. Since eavesdropper in the downlink of NOMA system may use successive interference cancellation (SIC) technology to obtain the secrecy information of receiver, to tackle this problem, artificial noise (AN) is used at the BS to enhance security performance of secrecy information. Moreover, semidefinite relaxation (SDR) method and successive convex approximation (SCA) technique are combined to solve the above non-convex problem. Simulation results show that in comparison with other methods, our method can effectively reduce the transmitted power of the BS on the constraints of a certain level of the secrecy rates of two users. [ABSTRACT FROM AUTHOR]

In this work, a novel resource allocation scheme is proposed to find the optimal time-switching and power-splitting factors in a SWIPT assisted non-orthogonal multiple access (NOMA) relay network with combined time switching and power splitting protocol. The system model consists of a source node broadcasting a multiplexed NOMA signal to the far and near user via an amplify-and-forward energy harvesting relay node in a Rayleigh-flat-fading channel environment. Here, effective SNR maximization at both the near and far users is formulated as an optimization problem under total transmit power constraint and to deal with this both the Lagrangian multiplier approach and differential-evolution algorithm have been exploited. Furthermore, performance study is presented about the comparison of proposed scheme with the fixed allocation scheme in terms of outage probability under the impact of distinct target rates, relay locations, and channel conditions. Finally, the simulation results signify the performance improvement in the system with the optimal values obtained from the proposed scheme over the fixed time and power splitting factors. [ABSTRACT FROM AUTHOR]

As one of the basic supporting technologies of 5G system, wireless sensor networks technology is facing a new challenge to improve its transmission energy efficiency. This paper considers combining simultaneous wireless information and power transfer (SWIPT) technique and routing technique, and applying them to multi-hop clustered wireless sensor networks (MCWSN), where each node can decode information and harvest energy from a received radio-frequency signal. And the relay nodes in MCWSN can utilize the harvest energy to forward data to their next hop nodes according to the routing scheme. First, we formulate an energy-efficient routing problem of MCWSN with SWIPT. Then, a heuristic energy efficient cooperative SWIPT routing algorithm (EECSR) is presented to find a transmission path with the maximum energy efficiency. Specifically, in EECSR, the resource allocation problem in each hop of the path is transformed to some equivalent convex optimization problems, which are resolved via dual decomposition. Moreover, a distributed routing protocol based on EECSR is proposed. As far as we know, this is the first solution that considers energy efficiency optimization based on routing and SWIPT in MCWSN. Simulation results show that our EECSR algorithm has high energy efficiency and good robustness. And our distributed routing protocol has better real-time performance than traditional protocols. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the resource allocation scheme for an unmanned-aerial-vehicle-enable (UAV-enabled) two-way relaying system with simultaneous wireless information and power transfer (SWIPT), where two user equipment exchange information with the help of UAV relay and harvest energy through power splitting (PS) scheme. Under the transmission power constraints at UEs and UAV relay, a non-convex intractable optimization problem is formulated which maximizes the sum retained energy of two UEs while satisfying the minimum signal-to-noise ratio requirement. We decouple the complicated beamforming and PS factor optimization problem into three solvable subproblems and propose an efficient alternating optimization scheme. Subsequently, in order to reduce the complexity, a robust scheme based on generalized singular value decomposition (GSVD) is designed. Finally, numerical results verify the robustness and effectiveness of the two proposed schemes. [ABSTRACT FROM AUTHOR]

It is expected that many small battery-operated devices will connect to next generation of cellular networks. In this work, a two-way wireless link is considered, where due to slow variations of the channel, forward link (FL) and reverse link channels are reciprocal, and the remote device's battery is charged via wireless energy harvesting. We analyze the performance of a two-way link setup, with very low complexity signal processing at the node that relies on battery, and consists of antenna selection and maximum ratio combining-based multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) techniques, wherein FL simultaneous wireless information and power transmission is assumed to be utilized. By mathematical tractability, a closed-form analytical expression for probability of outage, ergodic capacity and bit error rate are derived and compared with simulation results. It is shown that the assumed low complexity setup achieves full diversity in both cases of MISO and MIMO. [ABSTRACT FROM AUTHOR]

Device to device (D2D) communication that provides high data rate proximity based direct communication between users, along with simultaneous wireless information and power transfer (SWIPT) that extracts energy from the received RF power, can achieve high energy and spectral efficiencies together with low latency communication. Heterogeneous networks, that employ efficient frequency reuse, provide high gains in the coverage and capacity of the cellular networks. SWIPT helps in converting the harmful interference, incurred by the frequency reuse of D2D tier underlaying the Hetnet, into energy that can be stored for the future. This work presents a resource allocation and power control scheme for SWIPT enabled underlay D2D networks, designed to improve the energy efficiency and the amount of energy harvested while ensuring the minimum required data rates for the users. Resource allocation is performed using a stable many-to-one matching game model inspired from Gale-Shapley algorithm. Two techniques of SWIPT, namely power splitting SWIPT and time splitting SWIPT, are considered and the resource allocation schemes are designed for both. Simulation results demonstrate the superior performance of the proposed algorithm compared to an existing work in single tier network with power splitting SWIPT. The work is extended to a typical 5G HetNet scenario, and extensive simulations are done to compare the performance of the two SWIPT architectures in the HetNet scenario. [ABSTRACT FROM AUTHOR]

The traditional simultaneous wireless information and power transfer (SWIPT) system uses a part of signals to decode information, and the other part is used for harvesting energy, so that the device can be charged while working. However, the problems, such as the independent antenna and the feeble signal power and energy, greatly restrict the area of rate-energy region, thus leading to a big deviation between the theoretical value and the actual value. To solve these problems, a transmission scheme of SWIPT based on time reversal (TR) is proposed. Considering the general multi-input and single-output wireless communication system, on the one hand, the temporal and spatial focus of TR is used to increase the signal strength at the receiving end, on the other hand, the Kronecker model is used to theoretically build the transmission process on the condition of relevant antennas. After that the closed expression of the rate-energy region will be derived. The correctness of the formulary in different conditions is verified through the results of Monte Carlo simulation. The area of the rate-energy region is increased remarkably by comparing with the performance of SWIPT-MISO. [ABSTRACT FROM AUTHOR]

Simultaneous wireless information and power transfer (SWIPT) has been widely used in multi-input single-output (MISO) systems to transmit information and energy simultaneously from the base station (BS) towards the users. The traditional approach used in the literature is based on space-division multiple access (SDMA) method by using the multi-user linear precoding technique, where the information decoding is done by considering the multi-user interference as noise. Recently, the novel rate-splitting multiple access (RSMA) method, based on partially decode the multi-user interference and partially treat that interference as noise, has been shown to outperform the SDMA method in multi-user MISO systems. Motivated by the superior performance of RSMA, we consider a multi-user MISO SWIPT system applying the RSMA method, where multiple energy-constrained users are equipped with a power-splitting structure to harvest energy and decode information simultaneously. In particular, we investigate the optimal precoders and power-splitting ratios design to minimize the total transmit power at the BS, subject to constraints of the minimum data rate for users, minimum energy harvesting by users, and maximum power at the BS. The proposed solution for the formulated non-convex problem is based on two phases. First, we convert the non-convex problem into bilevel programming where the upper optimization problem is solved by using particle swarm optimization. Second, we propose two algorithms to solve the inner optimization problem based on a semidefinite relaxation method or a successive interference cancellation method. Numerical results show that RSMA achieves significant improvement over SDMA in reducing the total transmit power. [ABSTRACT FROM AUTHOR]

To achieve a high reliable and energy-saving green communication, we investigate a multisource simultaneous wireless information and power transfer (SWIPT)-based coded cooperation where the relay can realize information decoding and energy harvesting. Firstly, a class of naturally rate compatible low-density parity-check (LDPC) codes–quasi-cyclic repeat-accumulate (QC-RA) codes is introduced, and the joint parity-check matrix corresponding to the QC-RA codes employed by the multiple sources and relay is deduced. Based on the joint parity-check matrix, we jointly design the QC-RA codes to cancel all the short girth cycles. Then, by exploiting the rate compatible characteristic of QC-RA codes, we propose a new SWIPT protocol—codeword splitting protocol for the proposed system, which has the characteristics of lower complexity, higher efficiency, no strictly bit synchronization limitation, and less hardware requirement. The results show that the bit error rate (BER) performance of the proposed system employing jointly designed QC-RA codes clearly outperforms that of general RA codes. Theoretical analysis and numerical simulations also demonstrate the superiority of the proposed codeword splitting protocol. [ABSTRACT FROM AUTHOR]

In this paper, we study the unmanned aerial vehicles (UAV) assisted relaying communication system, where a UAV acts the mobile relay and provides the information transfer from the source to the destination. The simultaneous wireless information and power transfer techniques are considered at the UAV relays, where the UAV harvests energy from the source node, and exclusively uses the harvested energy for the data relaying. To maximize the system throughput, we jointly consider the UAV trajectory optimization and resource allocation problem, where the UAV trajectory is optimized the UAV positions to harvest the benefits of the line-of-sight links, and resource allocation, including power allocation and the subcarrier allocation, is used to achieve optimal network performance with the power constraints. An alternating maximization algorithm is proposed to solve the optimization problem, in which the UAV trajectory optimization and resource allocation are solved iteratively to maximize the total throughput. Compared with other benchmarks, the proposed algorithm can achieve higher throughput by the benefits from UAV trajectory optimization and resource allocation. [ABSTRACT FROM AUTHOR]

Wireless energy harvesting and information transfer (WEHIT) is a new paradigm in cooperative communication networks. WEHIT enables energy constrained cooperative communication nodes to harvest the energy needed for information transmission from electromagnetic radiation sources. Energy harvesting via radio frequency (RF) signals reduces the reliance on the supply of power grid, which makes it suitable for deployment in cooperative networks given that RF signals can concurrently carry wireless energy and information. This paper presents a review on RF energy harvesting in cooperative communication networks and the various techniques to simultaneously achieve wireless information and power transfer (SWIPT). Moreover, application advantages and disadvantages are specified. The major challenges of the SWIPT approach are enumerated. Solutions to these challenges are highlighted for future research. [ABSTRACT FROM AUTHOR]

In simultaneous wireless information and power transfer system (SWIPT), additional resource allocation for power transfer degrades system performance. Therefore, how to allocate power and time to data transmission and energy transfer is very important for the performance of time switching-based SWTPT system. In this paper, we propose a time switching-based full-duplex SWIPT system combined with self-energy recycling since self-interference harvesting is more efficient than simultaneous data transmission if the magnitude of self-interference is sufficiently large. Proposed system has additional self-energy recycling phases compared to the conventional time switching-based full-duplex SWIPT system. Considering the limitation of maximum transmission power, proposed system is optimized transmission time as well as power. For the validity of the proposed system, we show the bi-convexity of proposed system and propose an iterative algorithm for optimization of proposed system. In simulations, we compare proposed system with the half-duplex system without simultaneous data transmission phase and the full-duplex system without self-energy recycling phase. Simulation results show proposed system consume less energy than the conventional systems. [ABSTRACT FROM AUTHOR]

In multi-antenna simultaneous wireless information and power transfer (SWIPT) system, beamforming strategy has been widely analyzed due to the increasing signal strength. It can not only increase the signal strength in the direction of the antenna array but also reduce the interference strength, which is a good option for SWIPT system to achieve directional transmission of information and energy. However, the traditional beamforming strategy only uses single beamforming vector, and it does not consider the differences between information and energy in SWIPT system. Actually, interference can also be collected as energy. Based on the traditional beamforming strategy, the resources in SWIPT system are not properly utilized. Therefore, this paper proposes a joint beamforming strategy in multi-input and single-output (MISO) SWIPT system. We extend the traditional single beamforming vector into two beamforming vectors to realize independent control of information and energy based on time switching (TS) receiving mode. In information receiving phase, information beamforming vector is used to carry specific user’s information for information alignment. Since there is an orthogonal relationship between information beamforming vector and channel gain vector, we can achieve to eliminate interference and realize error-free information transmission. In energy receiving phase, energy beamforming vector is used to carry user’s energy. Energy beamforming vector and channel gain vector do not require the orthogonality so that the interference can also be collected as energy. In this paper, we model it as a transmission power optimization (TPO) problem, which is a complex non-convex problem. We firstly transform it into a convex problem, and then, it can be solved using CVX toolbox. Simulation results show that the proposed strategy could increase the energy collection at the same transmission power and also decrease the transmission power at the same energy collection. [ABSTRACT FROM AUTHOR]

This paper investigates the multi-cell coordinated beamforming (MCBF) design for secure simultaneous wireless information and power transfer (SWIPT) in both centralized and distributed manners. In each cell, one transmitter serves multiple information receivers (IRs) and energy receivers (ERs) with the non-linear energy harvesting (EH) model. Meanwhile, several eavesdroppers (Eves) intend to intercept the confidential information transmitted for IRs. To achieve a secure transmission, the artificial noise (AN) is embedded in the transmit signals of each transmitter. The proposed design is formulated into a power-minimization problem to guarantee the IRs’ information and ERs’ energy requirements while avoiding the information being intercepted by Eves. Since the problem is non-convex and not easy to solve, a solution method based on semi-definition relaxation (SDR) is proposed and the global optimum is proved to be guaranteed with full channel state information (CSI). We further present a distributed AN-aided MCBF for the system by using alternating direction method of multipliers (ADMM), with which each transmitter is able to calculate its own beamforming vectors and AN covariance matrix based on its local CSI. Simulation results show that our proposed distributed design converges to the global optimum obtained by the centralized one. It is also shown that by employing AN, the total required power of the system is reduced and the effect of AN on the system performance decreases with increment of transmit antennas. Compared with traditional linear EH model, optimizing the system under the non-linear EH one avoids false output power at the ERs and saves power at the transmitter. [ABSTRACT FROM AUTHOR]