This paper considers the security of transmission in buffer-aided decode-and-forward cooperative wireless networks. An eavesdropper which can intercept the data transmission from both the source and relay nodes is considered to threaten the security of transmission. Finite size data buffers are assumed to be available at every relay in order to avoid having to select concurrently the best source-to-relay and relay-to-destination links. A new max-ratio relay selection policy is proposed to optimize the secrecy transmission by considering all the possible source-to-relay and relay-to-destination links and selecting the relay having the link which maximizes the signal to eavesdropper channel gain ratio. Two cases are considered in terms of knowledge of the eavesdropper channel strengths: exact and average gains, respectively. Closed-form expressions for the secrecy outage probability for both cases are obtained, which are verified by simulations. The proposed max-ratio relay selection scheme is shown to outperform one based on a max-min-ratio relay scheme.
This paper considers the security of transmission in buffer-aided decode-and-forward cooperative wireless networks. An eavesdropper which can intercept the data transmission from both the source and relay nodes is considered to threaten the security of transmission. Finite size data buffers are assumed to be available at every relay in order to avoid having to select concurrently the best source-to-relay and relay-to-destination links. A new max-ratio relay selection policy is proposed to optimize the secrecy transmission by considering all the possible source-to-relay and relay-to-destination links and selecting the relay having the link which maximizes the signal to eavesdropper channel gain ratio. Two cases are considered in terms of knowledge of the eavesdropper channel strengths: exact and average gains, respectively. Closed-form expressions for the secrecy outage probability for both cases are obtained, which are verified by simulations. The proposed max-ratio relay selection scheme is shown to outperform one based on a max-min-ratio relay scheme.
This paper investigates the secure communication in a two-hop cooperative wireless network, where a buffer-aided relay is utilized to forward data from the source to destination, and a passive eavesdropper attempts to intercept data transmission from both the source and relay. Depending on the availability of instantaneous channel state information of the source, two cases of transmission mechanisms, i.e., adaptive-rate transmission and fixed-rate transmission are considered. To enhance the security of the system, novel link selection policies are proposed for both cases to select source-to-relay, relay-to-destination, or no link transmission based on the channels qualities. Closed-form expressions are derived for the end-to-end secrecy outage probability (SOP), secrecy outage capacity (SOC), and exact secrecy throughput (EST), respectively. Furthermore, we prove the condition that EST reaches its maximum, and explore how to minimize the SOP and maximize the SOC by optimizing the link selection parameters. Finally, simulations are conducted to demonstrate the validity of our theoretical performance evaluation, and extensive numerical results are provided to illustrate the efficiency of the proposed link selection polices for the secure communication in two-hop cooperative networks.
In this paper, we propose a novel secure buffer-aided decode-and-forward relay selection that amalgamates the benefits of the buffer-state-based relay selection, the max-ratio criterion, the simultaneous activation of multiple source-to-relay links, and the cooperative beamforming in dual-hop networks. More specifically, the proposed scheme is designed for selecting a single or multiple relay nodes for packet reception or transmission based on the buffer states of relay nodes, while avoiding the detrimental effects of both an empty buffer state and a buffer overflow. Analytical bounds on the secrecy outage probability and the average delay are derived for our proposed scheme, based on a Markov chain process, in order to verify the system model of our proposed scheme. Furthermore, we introduce the concept of cooperative jamming into the proposed scheme, in order to interfere with an eavesdropper's reception, while dispensing with the full channel state information associated with an eavesdropper at a central coordinator. Our simulation results demonstrate that the proposed schemes outperform the existing buffer-based secure relay selection schemes, in terms of both the secrecy outage probability and the average delay, as the explicit benefits of our novel introduced concepts.
This article investigates the secure communication in a two-hop cooperative wireless network, where a buffer-aided relay helps forward data from the source to destination, and a passive eavesdropper attempts to intercept data transmission from both the source and relay. To ensure the transmission security and communication quality of service (QoS) of the system, we design novel link selection policies for two cases that the instantaneous channel state information is available or unavailable at the source node. For evaluating the system performance, we then derive the closed-form expressions of end-to-end secrecy outage probability, system throughput and secrecy throughput, respectively. Based on the theoretical performance analysis, we further explore the performance optimization issues, revealing the insightful tradeoffs between the transmission security and QoS. An iterative algorithm is developed to identify the optimal setting of link selection parameters, which is helpful for the practical configuration of link selection policies to satisfy various system performance requirements. Finally, we conduct simulations to validate our theoretical performance analysis, and also provide extensive numerical results to illustrate the efficiency of the proposed link selection policies for ensuring the secure communication in a two-hop cooperative network.
In this paper, we consider a cooperative relay network consisting of a source, a destination, and multiple decode-and-forward (DF) relays in the presence of multiple eavesdroppers, which intend to tap confidential messages transmitted by both the source and the relays. We propose a so-called secrecy maximization oriented relay selection (SMORS) scheme to improve the physical-layer security of wireless communications. In the SMORS scheme, a relay with the maximal secrecy rate is selected among all the DF relays to forward the source signal. We analyze the intercept probability of the proposed SMORS scheme as well as the traditional max-min relay selection scheme. Numerical results show that the proposed SMORS scheme outperforms the conventional max-min relay selection scheme in terms of the intercept probability. Additionally, it is shown that with an increasing number of eavesdroppers, the intercept performance of wireless communications degrades, which can be well addressed using the proposed SMORS scheme through increasing the number of relays. By contrast, increasing the number of relays has little impact on the intercept probability for the conventional max-min relay selection scheme, especially when the number of relays is sufficiently high (e.g., exceeding 20 relays).
Privacy and security have an increasingly important role in wireless networks. A secure communication enables a legitimate destination to successfully retrieve information sent by a source, while it disables the eavesdropper (illegitimate destination) to interpret the intercepted information. Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without encryption. It exploits the physical characteristics of the wireless channel in order to transmit messages securely. They are typically feasible when the source-destination channel is better than the source-eavesdropper channel. Cooperative schemes are a means to improve the performance of secure wireless communications. We propose an improved relay selection scheme, based on source-eavesdropper channel SNR restriction, that will guarantee the best secrecy rate at the destination under QoS condition. Performance has been studied in terms of secrecy rate, outage probability and average error probability. Simulations shows that the proposed scheme outperforms in terms of the secrecy rate at the destination when compared to techniques in the literature.
In this paper, we investigate the secrecy outage performance of decode-and-forward (DF) buffer-aided relaying networks with a multi-antenna destination in the presence of an eavesdropper. In order to take full advantage of the benefits provided by the multiple antennas at the destination and the available relays, we adopt the max-link relay selection scheme and propose a half-duplex and two full-duplex secure transmission schemes for secrecy improvement, i.e., 1) maximal-ratio combining (MRC), 2) maximal-ratio combining/cooperative jamming (MRC/CJ), and 3) zero-forcing beamforming/cooperative jamming (ZFB/CJ). For all proposed schemes, we present exact and asymptotic closed-form expressions of the secrecy outage probability by modeling the dynamic buffer state transitions as a Markov chain. Moreover, simple and informative asymptotic results are provided under both L → ∞ and L → ∞ scenarios (where L denotes the buffer size), from which we can obtain further insights on the secrecy diversity gain and the secrecy coding gain. The highlights of this paper can be summarized as follows: 1) Under L → ∞ scenario, the secrecy diversity gains of all proposed schemes both reach M. When L → ∞, the secrecy diversity gains of MRC, MRC/CJ and ZFB/CJ increase to M (1 + ND), MND and 2M respectively, where M is the number of relays and ND represents the number of antennas at the destination; 2) The secrecy coding gain of the system differs with different schemes, and it improves with the increase of M and ND under both the two scenarios; and 3) Under the scenario L → ∞, ZFB/CJ outperforms MRC and MRC/CJ across the entire signal-to-noise ratio (SNR) range of interest, however, when L→ ∞, ZFB/CJ outperforms MRC/CJ and MRC in the low SNR regime, while the opposite holds in the high SNR regime.