We investigate the secrecy outage performance for a cooperative unauthenticated relay network where antenna selection is employed at the multi-antenna relay. Both traditional amplify-and-forward (AF) relaying and a cooperative jamming (CJ) protocol are studied. We characterize the exact secrecy outage probability (SOP) for the AF scheme, and analyze the asymptotic behaviour in terms of SOP for the CJ scheme. Although both the unauthenticated relay and the destination perceive diversity gain from antenna selection, we show that as the number of antennas grows, the SOP approaches one for AF, while it approaches zero for CJ. For a fixed number of antennas, we demonstrate that the CJ scheme is better than AF relaying for high SNR, and its SOP approaches zero when the SNR goes to infinity. The theoretical analysis is also validated via several numerical examples.
We investigate the secrecy outage performance for a cooperative unauthenticated relay network where antenna selection is employed at the multi-antenna relay. Both traditional amplify-and-forward (AF) relaying and a cooperative jamming (CJ) protocol are studied. We characterize the exact secrecy outage probability (SOP) for the AF scheme, and analyze the asymptotic behaviour in terms of SOP for the CJ scheme. Although both the unauthenticated relay and the destination perceive diversity gain from antenna selection, we show that as the number of antennas grows, the SOP approaches one for AF, while it approaches zero for CJ. For a fixed number of antennas, we demonstrate that the CJ scheme is better than AF relaying for high SNR, and its SOP approaches zero when the SNR goes to infinity. The theoretical analysis is also validated via several numerical examples.
We investigate a relay network where the source can potentially utilize an unauthenticated amplify-and-forward (AF) relay to augment its direct transmission of a confidential message to the destination. Since the relay is unauthenticated, it is desirable to protect the confidential data from it while simultaneously making use of it to increase the reliability of the transmission. We study the likelihood of achieving simultaneously secure and reliable message transmission via the secrecy outage probability (SOP) of the relay network. We first characterize the SOP for three different schemes: direct transmission, conventional AF relaying, and cooperative jamming. Subsequently, an asymptotic analysis is conducted to determine the optimal policies for different power budgets and channel gains. Numerical results are presented to verify the theoretical predictions of the preferred transmission policies from a secrecy outage perspective.
We investigate the secrecy performance of dual-hop amplify-and-forward multi-antenna relaying systems over Rayleigh fading channels, considering the direct link between the source and the destination. In order to exploit the available direct link and the multiple antennas for secrecy improvement, different linear processing schemes at the relay and different diversity combining techniques at the destination are proposed, namely: 1) zero-forcing/maximal ratio combining (ZF/MRC); 2) ZF/selection combining (ZF/SC); 3) maximal ratio transmission/MRC (MRT/MRC); and 4) MRT/SC. For all these schemes, we present new closed-form approximations for the secrecy outage probability. Moreover, we investigate a benchmark scheme, i.e., cooperative jamming/ZF (CJ/ZF), where the secrecy outage probability is obtained in exact closed-form. In addition, we present asymptotic secrecy outage expressions for all the proposed schemes in the high signal-to-noise ratio (SNR) regime, in order to characterize key design parameters, such as secrecy diversity order and secrecy array gain. The outcomes of this paper can be summarized as follows: 1) MRT/MRC and MRT/SC achieve a full diversity order of M + 1, ZF/MRC and ZF/SC achieve a diversity order of M, while CJ/ZF only achieves unit diversity order, where M is the number of antennas at the relay; 2) ZF/MRC (ZF/SC) outperforms the corresponding MRT/MRC(MRT/SC) in the low SNR regime, while becomes inferior to the corresponding MRT/MRC (MRT/SC) in the high SNR; and 3) all the proposed schemes tend to outperform the CJ/ZF with moderate number of antennas, and linear processing schemes with MRC attain better performance than those with SC.
We investigate a relay network where the source can potentially utilize an untrusted non-regenerative relay to augment its direct transmission of a confidential message to the destination. Since the relay is untrusted, it is desirable to protect the confidential data from it while simultaneously making use of it to increase the reliability of the transmission. We first examine the secrecy outage probability (SOP) of the network assuming a single antenna relay, and calculate the exact SOP for three different schemes: direct transmission without using the relay, conventional non-regenerative relaying, and cooperative jamming by the destination. Subsequently, we conduct an asymptotic analysis of the SOPs to determine the optimal policies in different operating regimes. We then generalize to the multi-antenna relay case and investigate the impact of the number of relay antennas on the secrecy performance. Finally, we study a scenario where the relay has only a single RF chain which necessitates an antenna selection scheme, and we show that unlike the case where all antennas are used, under certain conditions the cooperative jamming scheme with antenna selection provides a diversity advantage for the receiver. Numerical results are presented to verify the theoretical predictions of the preferred transmission policies.
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.
Considering a nonregenerative untrusted relay network, we investigate three different secure transmission strategies, for example, noncooperative strategy, conventional amplify-and-forward (AF) strategy, and cooperative jamming (CJ) strategy. To thoroughly assess the secrecy performance achieved by the three strategies, we derive the closed-form expressions for the connection outage probability and secrecy outage probability regarding each strategy. Based on these expressions, the reliability and security tradeoff (RST) is examined to facilitate the design of the transmitting parameters. We then present the closed-form expression for the effective secrecy throughput (EST) and characterize the overall efficiency of these transmission strategies. Furthermore, we conduct the asymptotic analysis for the secrecy throughput, which enables us to determine the optimal transmission strategy under different scenarios. Our analytical and numerical results demonstrate that compared with the noncooperative and AF strategies, the CJ strategy possesses the best performance in terms of RST. Additionally, we also find that the EST performance of the AF strategy is nearly invariable when the quality of the second hop changes.
In this letter, we offer the secrecy outage probability of the amplify-and-forward (AF) transmission, which consists of one source, one destination, one relay, and one passive eavesdropper. Particularly, we consider that the relay is equipped with multiple antennas while other terminals is utilized with single antenna and apply some diversity techniques (for both the reception and the transmission) in the relay to achieve gains in a secrecy outage performance. Additionally, we analyze the exact secrecy outage probability of the proposed systems in a one-integral form. Finally, some numerical examples are given to verify our provided analytical results for different system conditions.