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This paper proposes a new artificial noise (AN) scheme that combines with the relay selection techniques to improve the physical layer security for a wiretap full-duplex decode-and-forward cooperative network. The communication consists of two phases. In the first phase, the source transmits a message to the selected full-duplex relay, which simultaneously injects AN to mitigate eavesdropping attacks. In the second phase, the selected relay decodes the source message, XORs the source message and AN, and then broadcasts the mixed-signal to the destination. Different form existing schemes, the proposed AN scheme makes the eavesdropper fail in obtaining any information about the source message directly in the second phase. We take into account the correlation of the channel coefficients for the same link during different phases in the performance analysis of AN-aided max-min (MM) and partial (Par) relay selection schemes, and characterize the security-reliability trade-off (SRT) of the proposed schemes by the closed-form expressions of outage probability and intercept probability. Numerical results show that the proposed AN-aided MM/Par relay selection achieves a better SRT performance than the corresponding full-duplex mode assisted AN-aided relay selection scheme in existing literature. Furthermore, the MM scheme outperforms the Par scheme in terms of the SRT, and the SRT of the MM scheme can be substantially improved by increasing the number of relays, while the improvement of the Par scheme is limited. [ABSTRACT FROM AUTHOR]

Relay transmissions play an important role in many types of communication systems. In this paper, we consider packet-level coded transmissions over lossy relay links with the finite-buffer and coding coefficients delivery cost constraints. We propose a low-complexity coding scheme where packets are encoded from sequentially formed random subsets of source packets called batches. The relay recodes only from the buffered packets belonging to the same batch to maintain the code sparsity, lowering the packet header overhead and the decoding complexity compared to the random linear network coding (RLNC). To analyze the performance, we first propose an absorbing Markov chain model to analyze the RLNC transmission over finite-buffer relay links. The finite-length analysis not only provides a lower bound on the completion time using any sparser random codes but also characterizes each individual batch’s transmission of the proposed code. Based on the analysis, another Markov chain is proposed to determine the decoding failure probability and the expected completion time of the batch coding scheme. As shown through analysis and simulations, the proposed scheme achieves higher effective end-to-end rates than RLNC when the coding coefficients delivery cost is considered and is also with much lowered decoding complexity thanks to its sparseness. [ABSTRACT FROM AUTHOR]

This paper addresses the power minimization problem subject to a target quality-of-service (QoS) constraint of two-way relay systems with asymmetric traffic requirements using an amplify-and-forward (AF) relaying mode. By transforming the power minimization problem into a two-stage problem and by using the traffic information together with the short-term channel knowledge, an optimum power control (OPC) technique is first proposed, leading to closed-form solutions for individual transmit power at the relay and the sources. Then, by making use of the available diversity of the multiple-relay channel, the joint design of OPC and relay selection (RS) is investigated, eventually resulting in a joint power control and RS (JPCRS) algorithm with two decentralized RS policies for transmit power minimization. Simulation results are provided to validate the derived expressions and confirm the efficiency of the proposed strategies. It is shown that our proposed strategies can significantly reduce the system transmit power, while ensuring the target QoS of the system, and that the proposed RS algorithm is superior to the conventional max–min and max-sum methods in any traffic and/or channel conditions in terms of energy saving. [ABSTRACT FROM PUBLISHER]

This paper addresses the problem of adaptive power control of a two-way amplify-and-forward (AF) relaying network based on outage probability minimization. Unlike most of the existing works, our network scenario has asymmetric traffic requirements, and each terminal in the network is subject to an individual power constraint in addition to a total power consumption constraint of the network. To fulfill power control, instantaneous or statistical channel state information (CSI) is assumed to be available at the transmitter of each terminal. By dividing the overall power control problem into a few subproblems corresponding to different power constraints, and using the traffic knowledge along with the CSI, two power control strategies, called short- and long-term strategies, are proposed, leading to closed-form solutions for individual transmit powers at the relay and the sources that are adapted to certain traffic requirements and channel conditions. Simulation results are provided to demonstrate the effectiveness of the proposed power control strategies. It is shown that the short-term strategy can achieve a significant performance gain in terms of the outage probability, regardless of symmetric or asymmetric traffics and channels, and meanwhile, the long-term strategy is more appropriate to asymmetric traffic and channel conditions. [ABSTRACT FROM AUTHOR]

This paper studies the information-theoretic metric of outage probability for a half-duplex asymmetric two-way amplify-and-forward (AF) relaying. Unlike current research activities, our main purpose is to examine the impact of traffic asymmetry on system outage probability. First, an exact but two-integral-form outage probability is derived over Rayleigh fading channels. To provide more insight, a closed-form asymptotic outage probability is then obtained. It is shown that the outage probability in the system is determined only by the one-way channel or related to the two-way links, depending on the asymmetric level of the two senders' target rates and the terminals' average transmission powers. Following this analysis, optimum power allocation and opportunistic relay selection are studied to optimize the overall performance of the considered AF scenario. Next, with the aid of traffic knowledge, novel power allocation and relay selection criteria are proposed, followed by an analysis of the outage probability with the relay selection. Simulation experiments are performed to validate the proposed studies in this paper. The results show that the proposed power allocation and relay selection methods can achieve significant performance gains in terms of outage probability, regardless of symmetric or asymmetric traffic and channels. [ABSTRACT FROM PUBLISHER]