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      • KCI등재

        Outage Analysis and Optimization for Time Switching-based Two-Way Relaying with Energy Harvesting Relay Node

        ( Guanyao Du ),( Ke Xiong ),( Yu Zhang ),( Zhengding Qiu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.2

        Energy harvesting (EH) and network coding (NC) have emerged as two promising technologies for future wireless networks. In this paper, we combine them together in a single system and then present a time switching-based network coding relaying (TSNCR) protocol for the two-way relay system, where an energy constrained relay harvests energy from the transmitted radio frequency (RF) signals from two sources, and then helps the two-way relay information exchange between the two sources with the consumption of the harvested energy. To evaluate the system performance, we derive an explicit expression of the outage probability for the proposed TSNCR protocol. In order to explore the system performance limit, we formulate an optimization problem to minimize the system outage probability. Since the problem is non-convex and cannot be directly solved, we design a genetic algorithm (GA)-based optimization algorithm for it. Numerical results validate our theoretical analysis and show that in such an EH two-way relay system, if NC is applied, the system outage probability can be greatly decreased. Moreover, it is shown that the relay position greatly affects the system performance of TSNCR, where relatively worse outage performance is achieved when the relay is placed in the middle of the two sources. This is the first time to observe such a phenomena in EH two-way relay systems.

      • KCI등재후보

        Transmission Power Minimization with Network Coding for Mobile Terminals in Cellular Relay Networks

        ( Guanyao Du ),( Ke Xiong ),( Dandan Li ),( Zhengding Qiu ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.9

        This paper jointly investigates the bandwidth allocation, transmission strategy and relay positions for two-way transmission aware cellular networks with network coding (NC). Our goal is to minimize the transmission power of mobile terminals (MTs). Consider a cellular system, where multiple MTs exchange information with their common base station, firstly, we propose an efficient bandwidth allocation method and then give a transmission strategy for each MT to determine whether to use relay stations (RSs) for its two-way transmission with the BS or not. To further improve the system performance, the optimal positions of RSs are also jointly discussed. A GA-based algorithm is presented to obtain the optimum positions for RSs. Besides, the impacts of frequency reuse on MT`s transmission power and system spectral efficiency (SE) under different number of relays are also discussed in our work. Numerical results show that the proposed NC aware scheme can extend MTs` battery life at least 6% more than traditional method.

      • KCI등재

        Simultaneous Wireless Information and Power Transfer in Two-hop OFDM Decode-and-Forward Relay Networks

        ( Xiaofei Di ),( Ke Xiong ),( Yu Zhang ),( Zhengding Qiu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.1

        This paper investigates the simultaneous wireless information and power transfer (SWIPT) for two-hop orthogonal frequency division multiplexing (OFDM) decode-and-forward (DF) relay network, where a relay harvests energy from radio frequency signals transmitted by a source and then uses the harvested energy to assist information transmission from the source to its destination. The power splitting receiver is considered at the relay. To explore the performance limit of such a SWIPT-enabled system, a resource allocation (RA) optimization problem is formulated to maximize the achievable information rate of the system, where the power allocation, the subcarrier pairing and the power splitting factor are jointly optimized. As the problem is non-convex and there is no known solution method, we first decompose it into two separate subproblems and then design an efficient RA algorithm. Simulation results demonstrate that our proposed algorithm can achieve the maximum achievable rate of the system and also show that to achieve a better system performance, the relay node should be deployed near the source in the SWIPT-enabled two-hop OFDM DF relay system, which is very different from that in conventional non-SWIPT system where the relay should be deployed at the midpoint of the line between the source and the destination.

      • KCI등재후보

        Secure Beamforming with Artificial Noise for Two-way Relay Networks

        ( Dandan Li ),( Ke Xiong ),( Guanyao Du ),( Zhengding Qiu ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.6

        This paper studies the problem of secure information exchange between two sources via multiple relays in the presence of an eavesdropper. To this end, we propose a relay beamforming scheme, i.e., relay beamforming with artificial noise (RBwA), where the relay beamforming vector and the artificial noise vector are jointly designed to maintain the received signal-to-interference-ratio (SINR) at the two sources over a predefined Quality of Service (QoS) threshold while limiting the received SINR at the eavesdropper under a predefined secure threshold. For comparsion, the relay beamforming without artificial noise (RBoA) is also considered. We formulate two optimization problems for the two schemes, where our goal is to seek the optimal beamforming vector to minimize the total power consumed by relay nodes such that the secrecy of the information exchange between the two sources can be protected. Since both optimization problems are nonconvex, we solve them by semidefinite program (SDP) relaxation theory. Simulation results show that, via beamforming design, physical layer secrecy of two-way relay networks can be greatly improved and our proposed RBwA outperforms the RBoA in terms of both low power consumption and low infeasibility rate.

      • KCI등재

        Outage Analysis and Optimization for Four-Phase Two-Way Transmission with Energy Harvesting Relay

        ( Guanyao Du ),( Ke Xiong ),( Yu Zhang ),( Zhengding Qiu ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.10

        This paper investigates the outage performance and optimization for the four-phase two-way transmission network with an energy harvesting (EH) relay. To enable the simultaneous information processing and energy harvesting at the relay, we firstly propose a power splitting-based two-way relaying protocol (PSTWR). Then, we discuss its outage performance theoretically and derive an explicit expression for the system outage probability. In order to find the optimal system configuration parameters such as the optimal power splitting ratio and the optimal transmit power redistribution factor, we formulate an outage-minimized optimization problem. As the problem is difficult to solve, we design a genetic algorithm (GA) based algorithm for it. Besides, we also investigate the effects of the power splitting ratio, the power redistribution factor at the relay, and the source to relay distance on the system outage performance. Finally, extensive simulation results are provided to demonstrate the accuracy of the analytical results and the effectiveness of the GA-based algorithm. Moreover, it is also shown that, the relay position greatly affects the system performance, where relatively worse outage performance is achieved when the EH relay is placed in the middle of the two sources.

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