SWIPT Systems Research Articles

Joint Transceiver Optimization of MIMO SWIPT Systems for Harvested Power Maximization

This letter studies a single-user power splitting-based multiple-input multiple-output system for simultaneous wireless information and power transfer. We aim to maximize the harvested power by joint design of transmit signal covariance matrix and receive power splitting factor under both a system rate constraint and a total power constraint. The harvested power maximization problem is difficult to solve due mainly to the nonconcave objective and the nonlinear coupling of design variables in the constraints. To tackle these challenges, we first derive a good approximation of the problem by ignoring some negligible noise terms and then further simplify it to a more tractable form by well exploiting the problem structure. Based on the Frank–Wolfe algorithm, we propose a simple yet efficient iterative algorithm to address the resulting problem. Numerical results validate the efficiency of the proposed algorithm.

Power Allocation for Secure SWIPT Systems With Wireless-Powered Cooperative Jamming

This letter considers wireless-powered cooperative jamming to secure communication between a transmitter (Tx) and an information receiver, in the presence of an energy receiver (ER), which is termed a potential eavesdropper. The full-duplex jammer harvests energy from the Tx’s information signal and transmits jamming signal at the same time, where the jamming signal not only confounds the ER (potential eavesdropper) but also charges the ER. Our goal is to maximize the secrecy information rate by jointly optimizing the power allocation at the Tx and jammer, while maintaining the harvested energy requirement of the ER. The studied problem is non-convex and we propose the optimal solution based on the Lagrange method. Simulation results show that the proposed scheme significantly outperforms the benchmark schemes.

동시 무선 정보 및 전력 전송을 위한 통합된 수신기 구조 기반의 새로운 검출 기법

본 논문에서는 동시 무선 정보 및 전력 전송 시스템에서 전송률-에너지 영역 관점에서의 근본적인 트레이드오프를 최소화하기 위해 제안되었던 새로운 수신기 구조를 기반으로 복잡도가 낮은 새로운 검출 기법들을 제안한다. 첫 번째로 에너지 하베스팅을 위한 정류된 신호로부터 얻을 수 있는 진폭 정보를 통해 유클리드 거리 기반으로 부호의 진폭을 먼저 검출한 후 기존의 정보 복호화 과정에서 얻을 수 있는 위상 정보를 통해 유클리드 거리를 기반으로 최종 부호를 검출하는 이단 검출 기법을 제안한다. 두 번째로 기존의 정보 복호화 과정을 통해 얻을 수 있는 진폭과 위상 정보를 포함한 유클리드 거리와 에너지 하베스팅을 위한 정류된 신호로부터 얻을 수 있는 진폭정보를 포함한 유클리드 거리를 결합하여 부호를 검출 할 수 있는 유클리드 거리 결합 검출 기법을 제시한다. 모의실험을 통해 부호 에러율과 부호 성공률-에너지 영역, 달성 가능한 전송률-에너지 영역 측면에서 기존의 정보 복호화 기법보다 우수한 성능을 얻음을 확인하였다. In this paper, we propose two novel detection schemes with low-complexity based on the unified receiver architecture which minimizes a fundamental tradeoff at rate-energy region in SWIPT system. The proposed detection schemes are twofold: The two-stage detection scheme and Euclidean distance combination detection scheme. The two-stage detection scheme detects amplitude information of symbols from rectified signals for energy harvesting. In the sequel, it detects symbols based on phase information of baseband signals for information decoding. The Euclidean distance combination detection scheme detects symbols using linear positive-weighted sum of two metrics: Euclidean distance based on baseband signals for information decoding and Euclidean distance based on rectified signals for energy harvesting. For numerical results, we confirm that the proposed detection scheme can achieve better performance than the conventional scheme in terms of symbol error rate, symbol success rate-energy region and achievable rate-energy region.

Maximizing Harvested Energy for Full-Duplex SWIPT System With Power Splitting

In this paper, we consider simultaneous wireless information and power transfer in a full-duplex (FD) communication system consisting of one FD access point A (FD-A) and one FD device B (FD-B), each being equipped with a pair of transmitter-receiver antennas for signal transmission and reception respectively. The power splitting (PS) scheme is adopted at FD-B to receive information and energy concurrently. In order to maximize the energy harvested by FD-B while considering the constraints of signal-to-interference-and-noise ratio (SINR) and maximum transmit power at both nodes, we jointly design the optimal transmit power of FD-A and FD-B, as well as the PS ratio of FD-B. Unfortunately, the primal problem is non-convex and is not always feasible with different parameters. Thus, we first present a set of conditions, under which the feasibility of the primal problem is guaranteed. Then, we derive the closed form of the optimal solution with the aid of analyzing the feasible region of the problem. Furthermore, the influences of the parameters on the maximum harvested energy are theoretically analyzed. Finally, simulation results are provided to verify the optimality of the proposed closed-form solution, to validate the analysis of the impact of parameters on the maximum harvested energy and to show the effectiveness of the proposed design, respectively.

Optimal Design of SWIPT Systems With Multiple Heterogeneous Users Under Non-linear Energy Harvesting Model

This paper investigates the optimal power minimization design of simultaneous wireless information and power transfer systems under non-linear energy harvesting (EH) model, where a multi-antenna hybrid access point (H-AP) simultaneously transmits information and power to multiple heterogeneous users, such as information-energy receivers (IERs), information receivers (IRs), and ERs. Power splitting (PS) receiver architecture is adopted at all IERs. In order to achieve green system design, an optimization problem is formulated to minimize the transmit power of H-AP subject to the required signal-to-interference-plus-noise ratios (SINRs) constraints at IERs and IRs, and the harvested energy constrains at IERs and ERs, by jointly optimizing the beamforming vector at H-AP and the PS ratios at IERs. Since the problem is nonconvex and the employ of the non-linear EH model makes it more difficult to solve, the semidefinite relaxation and variable substitutions are used to handle it. For some cases, we theoretically prove that the globe optimal solution can be guaranteed by using our method, and for rest cases, we discuss its optimality via simulations. Numerical results show that although the traditional linear EH model is feasible for the practical EH circuits in some cases, the corresponding system consumes more transmit power than that under the non-linear model EH. Moreover, the effects of the numbers of users, the required SINRs, and the harvested energy on the system transmit power are also discussed.

Robust Optimization for AN-Aided Transmission and Power Splitting for Secure MISO SWIPT System

This letter investigates a multiple-input single-output secrecy channel, where the legitimate user and the eavesdroppers employ a power splitting scheme for information decoding and energy harvesting (EH), simultaneously. An artificial noise is embedded to the information bearing signal to interfere the eavesdroppers and to harvest power by all receivers (i.e., legitimate user and eavesdroppers). We consider the robust secrecy rate maximization problem subject to the transmit power and the EH constraints by incorporating the norm-bounded channel uncertainty. This robust optimization problem is not convex, and thus, it can be reformulated as a convex one along with matrix transformations and convex conic optimization techniques, which is iteratively solved based on constrained concave-convex procedure-based algorithm. Finally, numerical results are provided to validate our proposed algorithm.

Joint Power Control and Time Switching for SWIPT Systems With Heterogeneous QoS Requirements

The problem of joint power control and time switching is studied for a simultaneous wireless information and power transferring system that supports wireless nodes (WNs) with heterogeneous traffic. Using the stochastic optimization theory, a dynamic algorithm, which can trade average power consumption for WNs’ delay, is proposed to allocate the transmission power and time switching factor jointly. A control parameter is defined in the dynamic algorithm to facilitate the tradeoff.

Joint Optimization of Transmission and Antenna Subarray Formation Receiving for MIMO SWIPT Systems

To reduce hardware complexity of multiple-input multiple-output system with the simultaneous wireless information and power transfer scheme, we propose joint transmission and antenna subarray formation (ASF) receiving optimization scheme which maximizes the achievable rate under the transmit power constraint and the energy harvesting constraint. By relaxing the constraint that ASF matrix should contain limited number of nonzero elements, we employ alternating optimization method to alternatively optimize the transmit covariance matrix and the ASF matrix. We also propose the capacity-loss-based and maximum absolute values algorithms to recover the above constraint on the ASF matrix. It is shown from the simulation results that the proposed schemes outperform the conventional antenna selection scheme.