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IEEE Transactions on Communications

Secure Multiuser Communications in Multiple Amplify-and-Forward Relay Networks

Lisheng Fan, Xianfu Lei, Trung Q. Duong, Maged Elkashlan, George K. Karagiannidis

Published Aug 6, 2014• 128 citations
Publisher

Abstract

This paper proposes relay selection to increase the physical layer security in multiuser cooperative relay networks with multiple amplify-and-forward relays, in the presence of multiple eavesdroppers. To strengthen the network security against eavesdropping attack, we present three criteria to select the best relay and user pair. Specifically, criteria I and II study the received signal-to-noise ratio (SNR) at the receivers, and perform the selection by maximizing the SNR ratio of the user to the eavesdroppers. To this end, criterion I relies on both the main and eavesdropper links, while criterion II relies on the main links only. Criterion III is the standard max-min selection criterion, which maximizes the minimum of the dual-hop channel gains of main links. For the three selection criteria, we examine the system secrecy performance by deriving the analytical expressions for the secrecy outage probability. We also derive the asymptotic analysis for the secrecy outage probability with high main-to-eavesdropper ratio. From the asymptotic analysis, an interesting observation is reached: for each criterion, the system diversity order is equivalent to the number of relays regardless of the number of users and eavesdroppers.

DOI
10.1109/tcomm.2014.2345763

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This paper proposes relay selection to increase the physical layer security in multiuser cooperative relay networks with multiple amplify-and-forward relays, in the presence of multiple eavesdroppers. To strengthen the network security against eavesdropping attack, we present three criteria to select the best relay and user pair. Specifically, criteria I and II study the received signal-to-noise ratio (SNR) at the receivers, and perform the selection by maximizing the SNR ratio of the user to the eavesdroppers. To this end, criterion I relies on both the main and eavesdropper links, while criterion II relies on the main links only. Criterion III is the standard max-min selection criterion, which maximizes the minimum of the dual-hop channel gains of main links. For the three selection criteria, we examine the system secrecy performance by deriving the analytical expressions for the secrecy outage probability. We also derive the asymptotic analysis for the secrecy outage probability with high main-to-eavesdropper ratio. From the asymptotic analysis, an interesting observation is reached: for each criterion, the system diversity order is equivalent to the number of relays regardless of the number of users and eavesdroppers.
In this chapter, we will present criteria for user selection and relay selection to enhance the physical layer security in multiuser multi-relay networks. Specifically, for multiuser networks with multiple amplify-and-forward (AF) relays, we present three criteria to select the best relay and user pair. Criteria I and II study the received signal-to-noise ratio (SNR) at the receivers and perform the selection by maximising the SNR ratio ofthe user to the eavesdroppers. To this end, criterion I relies on both the main and eavesdropper links, while criterion II relies on the main links only. Criterion III is the standard max-min selection criterion, which maximises the minimum of the dual-hop channel gains of main links. For the three selection criteria, we examine the system secrecy performance by deriving the analytical expressions for the secrecy outage probability. We also derive the asymptotic analysis for the secrecy outage probability with high main-to-eavesdropper ratio.
In this paper, we study the information-theoretical security of a downlink multiuser cooperative relaying network with multiple intermediate amplify-and-forward (AF) relays, where there exist multiple eavesdroppers which can overhear the message. To prevent the wiretap and strength the network security, we select one best relay and user pair, so that the selected user can receive the message from the base station assisted by the selected relay. The relay and user selection is performed by maximizing the ratio of the received signal-to-noise ratio (SNR) at the user to the eavesdroppers, which is based on both the main and eavesdropper links. For the considered system, we derive the closed-form expression of the secrecy outage probability, and provide the asymptotic expression in high main-to-eavesdropper ratio (MER) region. From the asymptotic analysis, we can find that the system diversity order is equivalent to the number of relays regardless of the number of users and eavesdroppers.
We present two physical layer secure transmission schemes for multiuser multirelay networks, where the communication from M users to the base station is assisted by direct links and by N decode-and-forward relays. In this network, we consider that a passive eavesdropper exists to overhear the transmitted information, which entails exploiting the advantages of both direct and relay links for physical layer security enhancement. To fulfill this requirement, we investigate two criteria for user and relay selection and examine the achievable secrecy performance. Criterion I performs a joint user and relay selection, while Criterion II performs separate user and relay selections, with a lower implementation complexity. We derive a tight lower bound on the secrecy outage probability for Criterion I and an accurate analytical expression for the secrecy outage probability for Criterion II. We further derive the asymptotic secrecy outage probabilities at high transmit signal-to-noise ratios and high main-to-eavesdropper ratios for both criteria. We demonstrate that the secrecy diversity order is min (MN, M + N) for Criterion I, and N for Criterion II. Finally, we present numerical and simulation results to validate the proposed analysis, and show the occurrence condition of the secrecy outage probability floor.
In this paper, we study a downlink multiuser network in which one base station sends its message to one of multiple users, assisted by one of multiple intermediate decode-and-forward (DF) relays. Multiple eavesdroppers exist at the receiver side, and they can overhear the message from the base station, which brings out the issue of information security. We consider moderate shadowing environments so that direct links from the base station to the users and eavesdroppers exist. Maximal ratio combing (MRC) technique is employed at the receivers to combine the signals from the relaying and direct links. We select the best user and relay pair by maximizing the received signal-to-noise ratio (SNR) at the user. We study the effects of the selection on the system secrecy performance by deriving the closed-form expression of secrecy outage probability. We also provide the asymptotic secrecy outage probability with high transmit power and high main-to-eavesdropper ratio (MER). From the asymptotic expression, we can find that the system can achieve the diversity of the total number of users and relays, irrespective of the number of eavesdroppers. Simulation and numerical results are finally demonstrated to verify the proposed studies.
This paper studies the physical-layer security of a task-oriented multiuser amplify-and-forward (AF) relay network, operating in environments with multiple eavesdroppers. In the severe communication scenarios, such as urban areas with heavy shadowing or post-disaster zones, the direct communication paths are unavailable and the secure transmission depends solely on trusted relay nodes. To enhance the system secrecy performance, we introduce a relay–user pairing strategy aimed at minimizing the secrecy outage probability (SOP), taking into account the conditions of both legitimate and intercepting channels. Under Rayleigh fading, we derive closed-form SOP expressions and provide an asymptotic analysis that highlights the system’s diversity gain in the high main-to-eavesdropper ratio (MER) regime. Simulations confirm the validity of our theoretical and asymptotic results. Specifically, the analytical SOP exhibits excellent agreement with simulation ones across a wide MER range, confirming the correctness of the derived expressions. Moreover, the asymptotic expressions closely approximate the simulation results when MER exceeds 15 dB, highlighting their effectiveness for performance evaluation in high MER scenarios. Notably, the proposed relay–user selection strategy achieves a significant reduction in SOP compared to random or fixed pairing methods.
In this paper, we investigate the performance of cooperative amplify-and-forward (AF) multi-relay networks with relay selection strategy over independent and identically distributed (i.i.d.) Nakagami-m fading channels. In this system we study multiuser cooperative relaying to have a secure transmission from source to destination, since transmitted information may be wiretapped by multiple eavesdroppers. The secrecy outage probability is derived in closed-form using signal-to-noise-ratio statistics, while a useful expression is presented for the asymptotically low outage regime. Our results explicitly demonstrate significant improvement of the secrecy outage probability in the multi-relay scenario.