Abstract
This paper considers the problem of mutual information maximization in a two-hop relay network with simultaneous wireless information and power transfer (SWIPT), where the relay nodes use the power splitting (PS) scheme to harvest the energy for information forwarding. Unlike previous research, this paper focuses on a more practical scenario, where the inputs to the network are assumed to be finite-alphabet signals. Although each node in the network is assumed to have single antenna, we show that the relay network can be regarded as an effective multiple-input multiple-output (MIMO) system. Our goal is to perform the joint optimization on the precoder at source and PS ratio at relays to maximize the mutual information. Although the formulated problem is nondeterministic polynomial-time (NP)-hard, we theoretically analyze the optimal PS ratio; then, by using the structure of optimization problem, a near optimal precoder design based on semidefinite relaxation (SDR) is proposed; further, to reduce the complexity of algorithm, another precoder design based on search technique, which exploiting the structure of precoder, is developed only with a slight performance degradation. Simulation results verify the efficacy of proposed precoder designs.
Highlights
As is well known, relay communication technology, by elaborately designing the network configuration and relaying strategies, can further improve the channel capacity and reduce the energy consumption in wireless networks [1]
The main contributions of this paper are as follows: first, we investigate the problem of maximizing mutual information in a simultaneous wireless information and power transfer (SWIPT)-enabled relay network with finite-alphabet inputs, where the relay nodes have no constant power supply and they need to harvest energy from the radio frequency (RF) signals for information forwarding
For problem (21), we develop two near optimal precoding design methods, which are based on semidefinite relaxation (SDR) and search technique, respectively
Summary
Relay communication technology, by elaborately designing the network configuration and relaying strategies, can further improve the channel capacity and reduce the energy consumption in wireless networks [1]. The goal of precoding is usually to maximize the information rate of the source-destination link. In [2], this goal was achieved by using the source precoder maximizing the signal to noise ratio (SNR) under the constraint of transmit power. For the decode-and-forward (DF) based relay communication networks, [3] proposed a source precoding technique which can balance the direct and relay links and maximize the information rate. For the amplify-and-forward (AF) based networks, [4] developed a relay precoding algorithm, which is designed to maximize the information rate
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