Abstract
This paper investigates the system achievable rate for the multiple-input multiple-output orthogonal frequency division multiplexing (MIMO–OFDM) system with an energy harvesting (EH) relay. Firstly we propose two protocols, time switching-based decode-and-forward relaying (TSDFR) and a flexible power splitting-based DF relaying (PSDFR) protocol by considering two practical receiver architectures, to enable the simultaneous information processing and energy harvesting at the relay. In PSDFR protocol, we introduce a temporal parameter to describe the time division pattern between the two phases which makes the protocol more flexible and general. In order to explore the system performance limit, we discuss the system achievable rate theoretically and formulate two optimization problems for the proposed protocols to maximize the system achievable rate. Since the problems are non-convex and difficult to solve, we first analyze them theoretically and get some explicit results, then design an augmented Lagrangian penalty function (ALPF) based algorithm for them. Numerical results are provided to validate the accuracy of our analytical results and the effectiveness of the proposed ALPF algorithm. It is shown that, PSDFR outperforms TSDFR to achieve higher achievable rate in such a MIMO–OFDM relaying system. Besides, we also investigate the impacts of the relay location, the number of antennas and the number of subcarriers on the system performance. Specifically, it is shown that, the relay position greatly affects the system performance of both protocols, and relatively worse achievable rate is achieved when the relay is placed in the middle of the source and the destination. This is different from the MIMO–OFDM DF relaying system without EH. Moreover, the optimal factor which indicates the time division pattern between the two phases in the PSDFR protocol is always above 0.8, which means that, the common division of the total transmission time into two equal phases in previous work applying PS-based receiver is not optimal.
Highlights
The orthogonal frequency division multiplexing (OFDM) is a key transmission technology to provide higher spectral efficiency, which has been adopted in various standards, Du and Yu SpringerPlus (2016)5:654 e.g., IEEE 802.11n and 3GPP-Long Term Evolution (LTE)
Contributions In this paper, we focus on the Simultaneous wireless information and power transfer (SWIPT) for a two-hop multiple-input multiple-output (MIMO)–OFDM DF relaying system, where a source transmits its information to the destination with the help of an energyconstrained relay
It is shown that the relay position greatly affects the system performance of both protocols, and relatively worse achievable rates are achieved when the relay is placed in the middle of the source and the destination
Summary
Introduction The orthogonal frequency division multiplexing (OFDM) is a key transmission technology to provide higher spectral efficiency, which has been adopted in various standards, Du and Yu SpringerPlus (2016)5:654 e.g., IEEE 802.11n and 3GPP-Long Term Evolution (LTE). The combination of MIMO and OFDM technologies is believed to be further able to improve the system performance. Efforts have been made to apply MIMO and OFDM technologies together to the next-generation wireless communication systems in order to support high data rates and provide high spectral efficiency (Loa et al 2010; Guvensen and Yilmaz 2013). The next-generation wireless communication systems are expected to support multiple users and to guarantee the quality of service (QoS). In wireless sensor networks (WSN) or wireless body area networks (WBAN), the nodes are usually powered by batteries which have limited lifetime. Once the power is exhausted, the batteries need to be replaced or recharged (Abreu et al 2014)
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