Abstract
This paper considers the distributed beamforming design for a simultaneous wireless information and power transfer (SWIPT) in two-way relay network, which consists of two sources, K relay nodes and one energy harvesting (EH) node. For such a network, assuming perfect channel state information (CSI) is available, and we study two different beamforming design schemes. As the first scheme, we design the beamformer through minimization of the average mean squared error (MSE) subject to the total transmit power constraint at the relays and the energy harvesting constraint at the EH receiver. Due to the intractable expression of the objective function, an upper bound of MSE is derived via the approximation of the signal-to-noise ratio (SNR). Based on the minimization of this upper bound, this problem can be turned into a convex feasibility semidefinite programming (SDP) and, therefore, can be efficiently solved using interior point method. To reduce the computational complexity, a suboptimal beamforming scheme is proposed in the second scheme, for which the optimization problem could be recast to the form of the Rayleigh–Ritz ratio and a closed-form solution is obtained. Numerical results are provided and analyzed to demonstrate the efficiency of our proposed beamforming schemes.
Highlights
Harvesting energy from environment has become a preferred strategy to overcome the key challenge of limited lifetime of devices equipped with battery in wireless networks, e.g., wireless sensor network (WSN) or Bluetooth low-energy mesh (BLE Mesh) network
(3) To avoid the high computational complexity resulting from solving the semidefinite programming (SDP) problem, we find the suboptimal solution by converting the initial problem into the form of the Rayleigh–Ritz quotient, which is of low complexity
Drfre−i,okc(χme/i2v)thehrikeiassnomdurtochdeeencleohddaneansSei gltfoir othmde−i,tkE(hHχteh/2)srgoeiul.aryceisenmocdhoeadnSeinletedol from the kth relay to the energy harvesting (EH) receiver is modeled as g3k d−k,(EχH/2)g3k, where di,k is the distance between Si and the kth relay; di,EH is the distance between Si and the EH receiver; dk,EH receiver; χ is 3 the distance between the kth relay and the is the path loss exponent; and hik, gi, and EH g3k are the independent identically distributed (i.i.d.) Rayleigh fading channels, where i ∈ {1, 2}, k ∈ K
Summary
Harvesting energy from environment has become a preferred strategy to overcome the key challenge of limited lifetime of devices equipped with battery in wireless networks, e.g., wireless sensor network (WSN) or Bluetooth low-energy mesh (BLE Mesh) network. As an e cient energy harvesting technique, simultaneous wireless information and power transfer (SWIPT) has gained considerable research attention in the academic eld [1,2,3,4,5,6]. In [3], considering a multiple-input multiple-output (MIMO) wireless broadcast scenario, where one receiver harvested energy and another receiver decoded information from the signals sent by a transmitter, two practical schemes, namely, time switching (TS) and power splitting (PS), were proposed. Zhao et al [5] considered the security of wireless network for SWIPT, which maximize the achievable secrecy rate subject to sum transmit power constraint at relays and energy harvesting (EH) constraint at the EH receiver. In [6], the MIMO SWIPT system under the condition of imperfect CSI was studied
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