We investigate the secrecy transmission of uplink non-orthogonal multiple access (NOMA) with the aid of energy harvesting (EH) jammers. During each time frame, communication is divided into two phases. At the first phase, the base station (BS) transfers wireless power to EH receivers (EHRs). At the second phase, users perform uplink NOMA transmission to BS, while one of EHRs is selected as a friendly jammer that uses the energy harvested from the previous phase to emit the artificial noise for confusing the eavesdropper. In terms of the requirement of channel state information (CSI), we propose three friendly EH jammer selection schemes, namely random EH jammer selection (REJS) scheme without the requirement of any CSI, maximal EH jammer selection (MEJS) scheme with the CSI between BS and each EHR, and optimal EH jammer selection (OEJS) scheme where both the CSIs from BS to EHRs and from EHRs to the eavesdropper need to be known. Analytical closed-form expressions for the connection outage probability (COP), secrecy outage probability (SOP) and effective secrecy throughput (EST) are derived to evaluate the system performance achieved by the proposed schemes, respectively. Also, the asymptotic analysis is provided to gain further insights. The analytical and numerical results indicate that the proposed schemes can realize better secrecy performance than conventional scheme without an EH jammer. Both the secrecy diversity orders of the REJS and MEJS schemes are one while the OEJS scheme can achieve a full secrecy diversity order. Furthermore, owing to the impact of connection outage, the three schemes converge to the same EST floor with the increase of signal-to-noise ratio (SNR).

Improving Physical Layer Security of Uplink NOMA via Energy Harvesting Jammers

In this paper, we study a multiuser uplink network consisting of one base station (BS), multiple users and one eavesdropper (E), where the users are intended to transmit their confidential messages to BS, while the eavesdropper attempts to tap their transmissions. To improve the transmission secrecy, we propose two friendly jammer selection-aided multiuser scheduling schemes, namely, the random jammer selection-aided multiuser scheduling (RJS-MUS) without knowing the eavesdropper’s channel state information (CSI) and the optimal jammer selection-aided multiuser scheduling (OJS-MUS), where the CSIs of eavesdropper are available. For comparison purposes, the conventional non-jammer selection-aided multiuser scheduling (NJS-MUS) scheme is considered as a benchmark. We derive exact and asymptotic closed-form secrecy outage probability expressions for the conventional NJS-MUS as well as proposed RJS-MUS and OJS-MUS schemes. The numerical results show that the proposed RJS-MUS and OJS-MUS schemes with equal power allocation between the selected friendly jammer and scheduled user perform worse than the conventional NJS-MUS approach in terms of the secrecy outage probability in the low signal-to-noise ratio (SNR) region. As the SNR increases, the secrecy outage performance of RJS-MUS and OJS-MUS schemes substantially improves, which is, in turn, better than that of conventional NJS-MUS approach. Moreover, the secrecy advantage of RJS-MUS and OJS-MUS over NJS-MUS becomes more significant with an increasing SNR. Also, it is shown that for both the RJS-MUS and OJS-MUS schemes, a better secrecy performance can be achieved through an optimal power allocation (OPA) between the scheduled user and friendly jammer. In addition, the proposed RJS-MUS and OJS-MUS schemes with OPA strictly outperform the conventional NJS-MUS approach in terms of the secrecy outage probability.

Secrecy Outage Probability Analysis of Friendly Jammer Selection Aided Multiuser Scheduling for Wireless Networks

This article investigates the physical layer security for a cooperative cognitive radio (CCR) system with energy-harvesting (EH) technique, which consists of a cognitive source (CS), multiple cognitive relays (CRs) and a cognitive destination (CD) as well as multiple eavesdroppers (Es) who are considered to tap the confidential transmission from CS via CRs to CD. Both CS and CRs are equipped with energy-harvesters to harvest energy from the surrounding radio frequency environment. Additionally, in order to guarantee the quality-of-service of primary communications, the transmit powers of CS and CRs are limited by the maximum tolerant power at primary destination. Depending on the availability of channel state information (CSI) of wireless energy links from primary transmitter (PT) to CRs, we respectively propose non-energy aware relay selection (NEARS) and energy aware relay selection (EARS) schemes for protecting the transmission from CS via CRs to CD from leaking to Es. We consider the use of the security-reliability tradeoff (SRT) to measure the performance of NEARS and EARS schemes. For the purpose of comparison, we also carry out the analysis of SRT performance for conventional direct communication (DC). Furthermore, the closed-form expressions of outage probability and intercept probability for NEARS and EARS schemes are derived and numerical results show that the SRT performance of EARS is better than that of DC and NEARS schemes.

Energy-Aware Relay Selection Improves Security-Reliability Tradeoff in Energy Harvesting Cooperative Cognitive Radio Systems

We investigate physical layer security of an uplink NOMA system consisting of one base station, multiple users and one eavesdropper. During each uplink transmission, two users are paired to perform NOMA and another user is opportunistically selected from the remaining idle users to act as a friendly jammer to emit artificial noise for confusing the eavesdropper. To enhance the transmission security for the system, we propose two friendly jammer selection aided uplink NOMA transmission schemes, namely random jammer selection aided uplink NOMA transmission (RJS-UNT) scheme without knowing the eavesdropper’s channel state information (CSI), and optimal jammer selection aided uplink NOMA transmission (OJS-UNT) scheme where the eavesdropper’s CSI is available. For comparison purpose, a non-jammer selection aided uplink NOMA transmission (NJS-UNT) scheme is also considered. Analytical closed-form expressions for the secrecy outage probability (SOP) are derived to evaluate the secrecy performance achieved by the proposed schemes. Also, the asymptotic SOPs are provided to obtain further insights. The analysis and simulation results indicate that the schemes converge to SOP floors with the increasing SNR, while the floors achieved by the RJS-UNT and OJS-UNT schemes are significantly lower than that achieved by the NJS-UNT scheme, showing the security advantage of the proposed schemes.

On the Security Enhancement of Uplink NOMA Systems With Jammer Selection

In this paper, we investigate the performance of secure cellular multiuser two-way amplify-and-forward relay networks, wherein one $N_{a}$ -antenna base station (BS) exchanges information bidirectionally with $K$ single-antenna users (USs) by the assistance of a single-antenna relay node in the presence of a single-antenna passive eavesdropper. We employ user selection coupled with antenna selection (AS) scheme at the BS so as to maximize the end-to-end signal-to-noise ratios. In the considered system, by employing two possible combining techniques at the eavesdropper, viz., maximum ratio combining (MRC) and selection combining (SC), we derive the novel tight closed-form expressions for the secrecy outage probability (SOP) under Rayleigh fading channels. We present an asymptotic secrecy diversity order analysis of the considered system for the large transmit power, and demonstrate that the eavesdropping reduces the secrecy diversity order from $\min (N_{a},K)$ to 1. Further, we present some useful insights into the impact of eavesdropper and number of antennas and users on the SOP performance. It is shown that the eavesdropper has a severe impact on the SOP performance, regardless of number of antennas and users. The numerical and simulation results corroborate our theoretical findings, and demonstrate the influence of eavesdropper and relay positions on the SOP performance. We show that the SOP performance improves significantly when the eavesdropper is far away from the BS and USs. It is also shown that the SOP performance enhances noticeably if the relay location is chosen optimally, for different eavesdropper positions and/or different values of antennas and users. Moreover, our results also reveal that only coding gain rather than diversity gain is achieved by increasing $N_{a}$ and $K$ , because of the dominance of information leakage by the first time phase. Furthermore, results illustrate that the SOP performance under SC technique employed at the eavesdropper outperforms the MRC-based technique for the broad range of transmit power.

Secure Transmission in Cellular Multiuser Two-Way Amplify-and-Forward Relay Networks

This paper analyzes the secrecy outage probability of a cellular downlink system which consists of multiple users, one base station (BS), and one eavesdropper in the presence of co-channel interferers, where the BS transmits its signals to users which are distributed according to a Poisson point process with a fixed density, while the eavesdropper attempts to tap the transmission from the BS to the users. To enhance the transmission security against eavesdropping, we propose two multiuser scheduling schemes, namely, the partial channel state information (CSI) aided user scheduling (PCSI-US) scheme where only the CSIs of users are available without knowing the co-channel interferers’ CSIs and the full CSI aided user scheduling (FCSI-US) scheme which requires the CSIs of both users and interferers. For comparison purposes, the conventional round-robin scheduling scheme is also considered as a baseline. We derive closed-form expressions of the secrecy outage probability for the proposed PCSI-US and FCSI-US as well as conventional round-robin scheduling schemes in co-channel interference (CCI) environments. Numerical results show that the proposed FCSI-US and PCSI-US schemes outperform the conventional round-robin scheduling in terms of their secrecy outage probabilities, where FCSI-US achieves the best secrecy outage performance in CCI environments. It is also demonstrated that increasing the mean number of users has a marginal effect on the secrecy performance of conventional round-robin scheduling, which can significantly decrease the secrecy outage probabilities of PCSI-US and FCSI-US schemes. This further validates the secrecy effectiveness of the proposed user scheduling methods in terms of combating the CCI.

Closed-Form Secrecy Outage Analysis of Cellular Downlink Systems in the Presence of Co-Channel Interference

In this paper, we analyze the secrecy outage probability and computation overhead of a multi-user multi-eavesdropper wireless system which is composed of one cluster head (CH) transmitting to multiple users, while multiple eavesdroppers attempt to tap the transmission from CH to multiple users in the presence of co-channel interference (CCI). To achieve high security and low computation overhead, we present two multi-user scheduling schemes, namely, the switch-and-examine combining with post-selection user scheduling (SECpsUS) scheme and the selection combining-based user scheduling (SCbUS) scheme. For the purpose of comparison, the conventional round-robin scheduling (RRS) is also considered as a benchmark scheme. Furthermore, we derive closed-form secrecy outage probability expressions and analyze computation overheads for the conventional RRS, SCbUS, and SECpsUS schemes. Numerical results and Monte Carlo simulations are provided to verify the correctness of our theoretical secrecy outage analysis and to demonstrate the effect of CCI on the system performance. It is shown that the SECpsUS and SCbUS schemes outperform the conventional RRS scheme in terms of their secrecy outage probabilities, where SCbUS achieves the best secrecy outage performance but at cost of the highest computation overhead, while the conventional RRS scheme has no computation overhead with the worst secrecy performance. Moreover, a flexible tradeoff between the secrecy outage performance and computation overhead can be achieved by the proposed SECpsUS scheme by adjusting a so-called switching threshold. In addition, as the number of users increases, the secrecy outage performance of the SECpsUS and SCbUS is improved significantly, whereas no secrecy benefit is achieved by the conventional RRS scheme.

Secrecy Versus Computation Overhead for Wireless Networks in the Face of Co-Channel Interference

In this study, the authors investigate the security and reliability trade-off (SRT) performance of a multiuser wireless network, where an eavesdropper attempts to overhear the confidential transmissions between a base station and multiple users under the impact of co-channel interference. To enhance the SRT performance of the network, the authors propose two joint user and jammer selection schemes, namely the joint optimal user and random jammer selection (JOU-RJS) scheme and the joint optimal user and optimal jammer selection (JOU-OJS) scheme. For SRT performance comparison purposes, the traditional multiuser scheduling (TMUS) scheme is also considered. The authors derive closed-form outage and intercept probability expressions for the JOU-RJS and JOUOJS schemes. Simulation results show that the SRTs of both JOU-RJS and JOU-OJS schemes are better than that of the TMUS scheme, where JOU-OJS achieves the best SRT performance. Additionally, this study also shows that an expected outage or intercept probability of the TMUS, JOU-RJS, and JOU-OJS schemes can be achieved by giving an appropriate overall rate. Finally, the sum of the outage and intercept probability can be minimised through an optimal power allocation between the selected user and friendly jammer for the proposed JOU-RJS and JOU-OJS.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-com.2019.0438

Fei Wang

Papers

Secrecy Outage Probability Analysis of Friendly Jammer Selection Aided Multiuser Scheduling for Wireless Networks

Closed-Form Secrecy Outage Analysis of Cellular Downlink Systems in the Presence of Co-Channel Interference

Secrecy Versus Computation Overhead for Wireless Networks in the Face of Co-Channel Interference

Security and reliability trade-off analysis of joint user and jammer selection in the face of co-channel interference