64 research outputs found
Optimal Precoder Designs for Sum-utility Maximization in SWIPT-enabled Multi-user MIMO Cognitive Radio Networks
In this paper, we propose a generalized framework that combines the cognitive
radio (CR) techniques for spectrum sharing and the simultaneous wireless
information and power transfer (SWIPT) for energy harvesting (EH) in the
conventional multi-user MIMO (MuMIMO) channels, which leads to an
MuMIMO-CR-SWIPT network. In this system, we have one secondary base-station
(S-BS) that supports multiple secondary information decoding (S-ID) and
secondary EH (S-EH) users simultaneously under the condition that interference
power that affects the primary ID (P-ID) receivers should stay below a certain
threshold. The goal of the paper is to develop a generalized precoder design
that maximizes the sum-utility cost function under the transmit power
constraint at the S-BS, and the EH constraint at each S-EH user, and the
interference power constraint at each P-ID user. Therefore, the previous
studies for the CR and SWIPT systems are casted as particular solutions of the
proposed framework. The problem is inherently non-convex and even the weighted
minimum mean squared error (WMMSE) transformation does not resolve the
non-convexity of the original problem. To tackle the problem, we find a
solution from the dual optimization via sub-gradient ellipsoid method based on
the observation that the WMMSE transformation raises zero-duality gap between
the primal and the dual problems. We also propose a simplified algorithm for
the case of a single S-ID user, which is shown to achieve the global optimum.
Finally, we demonstrate the optimality and efficiency of the proposed
algorithms through numerical simulation results.Comment: 12pages, 9 figures, submitted to IEEE Systems Journa
Exploiting constructive interference for simultaneous wireless information and power transfer in multiuser downlink systems
In this paper we propose a power-efficient approach for information and energy transfer in multiple-input single output downlink systems. By means of data-aided precoding, we
exploit the constructive part of interference for both information decoding and wireless power transfer. Rather than suppressing interference as in conventional schemes, we take advantage of constructive interference among users, inherent in the downlink, as a source of both useful information signal energy and electrical
wireless energy. Specifically, we propose a new precoding design that minimizes the transmit power while guaranteeing the quality
of service (QoS) and energy harvesting constraints for generic phase shift keying modulated signals. The QoS constraints are
modified to accommodate constructive interference, based on the constructive regions in the signal constellation.
Although the resulting problem is nonconvex, several methods are developed for its solution. First we derive necessary and
sufficient conditions for the feasibility of the considered problem. Then we propose second-order cone programming and semi definite programming algorithms with polynomial complexity that provide upper and lower bounds to the optimal solution and establish the asymptotic optimality of these algorithms when the modulation order and SINR threshold tend to infinity. A
practical iterative algorithm is also proposed based on successive linear approximation of the non-convex terms yielding excellent results. More complex algorithms are also proposed to provide
tight upper and lower bounds for benchmarking purposes. Simulation results show significant power savings with the proposed data-aided precoding approach compared to the conventional precoding scheme
Simultaneous wireless information and power transfer in modern communication systems
Energy harvesting for wireless communication networks is a new paradigm that allows terminals to recharge their batteries from external energy sources in the surrounding environment. A promising energy harvesting technology is wireless power transfer where terminals harvest energy from electromagnetic radiation. Thereby, the energy may be harvested opportunistically from ambient electromagnetic sources or from sources that intentionally transmit electromagnetic energy for energy harvesting purposes. A particularly interesting and challenging scenario arises when sources perform simultaneous wireless information and power transfer (SWIPT), as strong signals not only increase power transfer but also interference. This article provides an overview of SWIPT systems with a particular focus on the hardware realization of rectenna circuits and practical techniques that achieve SWIPT in the domains of time, power, antennas, and space. The article also discusses the benefits of a potential integration of SWIPT technologies in modern communication networks in the context of resource allocation and cooperative cognitive radio networks
Intelligent Reflecting Surface Aided MIMO Broadcasting for Simultaneous Wireless Information and Power Transfer
An intelligent reflecting surface (IRS) is invoked for enhancing the energy harvesting performance of a simultaneous wireless information and power transfer (SWIPT) aided system. Specifically, an IRS-assisted SWIPT system is considered, where a multi-antenna aided base station (BS) communicates with several multi-antenna assisted information receivers (IRs), while guaranteeing the energy harvesting requirement of the energy receivers (ERs). To maximize the weighted sum rate (WSR) of IRs, the transmit precoding (TPC) matrices of the BS and passive phase shift matrix of the IRS should be jointly optimized. To tackle this challenging optimization problem, we first adopt the classic block coordinate descent (BCD) algorithm for decoupling the original optimization problem into several subproblems and alternatively optimize the TPC matrices and the phase shift matrix. For each subproblem, we provide a low-complexity iterative algorithm, which is guaranteed to converge to the Karush-Kuhn-Tucker (KKT) point of each subproblem. The BCD algorithm is rigorously proved to converge to the KKT point of the original problem. We also conceive a feasibility checking method to study its feasibility. Our extensive simulation results confirm that employing IRSs in SWIPT beneficially enhances the system performance and the proposed BCD algorithm converges rapidly, which is appealing for practical applications
Linear Precoder Design for Simultaneous Information and Energy Transfer over Two-User MIMO Interference Channels
Communication strategies that utilize wireless media for simultaneous information and power transfer offer a promising perspective for efficient usage of energy resources. With this motivation, we focus on the design of optimal linear precoders for interference channels utilizing such strategies. We formulate the problem of minimizing the total minimum mean-square error while keeping the energy harvested at the energy receivers above given levels. Our framework leads to a non-convex problem formulation. For point-to-point multiple-input multiple-output channels, we provide a characterization of the optimal solutions under a constraint on the number of transmit antennas. For the general interference scenario, we propose two numerical approaches, one for the single antenna information receivers case, and the other for the general case. We also investigate a hybrid signalling scheme, where the transmitter sends a superposition of two signals: a deterministic signal optimized for energy transfer and an information carrying signal optimized for information and energy transfer. It is illustrated that if hybrid signalling is not incorporated into the transmission scheme, interference can be detrimental to the system performance when the number of antennas at the receivers is low.}
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