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Institution of Engineering and Technology eBooks

Physical layer security for multiuser relay networks

Lisheng Fan, Trung Q. Duong

Published Oct 15, 2017• 0 citations
Publisher

Abstract

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.

DOI
10.1049/pbte076e_ch7

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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.
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.
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 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.
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.
This paper investigates the effect of untrusted relay on the secrecy outage probability of amplify- and-forward relay networks with the help of direct links and multiple users. We consider three selection criteria which are based on the direct and relaying link. The impacts of both the direct and relaying links on SOP performance is studied by deriving the closed-form analytical SOP as well as the asymptotic expressions. Simulation results are provided to confirm the theoretical analysis. It can be found that the diversity order of optimal selection criterion is equal to the number of users, while the diversity order of the sub-optimal criterion based on relaying links is equal to one.
This paper investigates the physical-layer security of the modify-and-forward (MF) protocol in multi-relay and multieavesdropper networks. Three relay selection critera are developed according to the channel state information (CSI) acquisition. CriterionI requires the CSI of all main channels for relay selection. Criteria II and III rely only on the CSI of the source-relay and relay-destination channels, respectively. We derive the exact secrecy outage probability (SOP), probability of nonzero secrecy capacity, and the ergodic secrecy rate in the closed forms. The €-outage secrecy capacity is also evaluated. Asymptotic analysis of the SOP explicitly reveals that the secrecy diversity order of criterionI depends on the total number of relays, whereas those of criteriaII and III are 2 and 1, respectively. The probability of nonzero secrecy capacity asymptotically decreases with the SNR of the wiretap channel as the eavesdropper is close to the source and relays. CriterionI is always superior to criteriaII and III in terms of the ergodic secrecy rate and €-outage secrecy capacity. Simulations results also demonstrated that the €-outage secrecy capacity deteriorates as the SNR of the eavesdropper's channel increases.