Physical Layer Security in MIMO/NOMA in the multiple UEH relaying network with TAS/MRC

In this paper, the physical layer security of multiple-input multiple-output (MIMO) wiretap channels with orthogonal space-time block codes (OSTBCs) and arbitrary antenna correlation is investigated. In our analysis, we consider general correlation matrices with arbitrary eigenvalue distributions. Also, in order to study the impact of the line-of-sight condition on the secrecy performance, the main channel is assumed to undergo Rician fading, while the eavesdropper one experiences Rayleigh fading. An easy-to-evaluate, closed-form expression for the secrecy outage probability is derived, from which an asymptotic analysis is carried out. Representative numerical results are plotted and validated through Monte Carlo simulations. Insightful discussions regarding the impact of the multiple antennas, correlation, and Rician factor on the secrecy outage performance are provided.

In this study, the physical layer (PHY) security performance of orthogonal space‐time block coding (OSTBC) employing a coordinate interleaved orthogonal design (CIOD) is analysed and investigated using two metrics: average secrecy capacity and secrecy outage probability. It is shown that the CIOD system is superior than OSTBC in terms of secrecy outage probability. Closed‐form expressions for PHY security metrics in OSTBC as well as CIOD are presented and compared. Then, an extended model of CIOD with arbitrary number of antennas is considered. Furthermore, the effects of artificial noise and imperfect channel estimation on PHY security of OSTBC and CIOD systems are investigated. The validity of theoretical expressions is verified by simulation, and it is shown that in practical cases the CIOD system has a better secrecy outage performance than that of the OSTBC system.

In this study, the secrecy outage probability (SOP) of a dual-hop energy harvesting (EH) non-orthogonal multiple access (NOMA) system is investigated. In order to improve the signal quality at the transmitter node, the transmitter antenna selection (TAS) method is applied, while the generalized selection combining (GSC) technique is used to increase the reliability at the users and maximum ratio combining (MRC) is utilized at eavesdropper (EVE). In the system, the relay node harvests energy from the signals received from the base station (BS) and transmits messages to the users with the amplify-and-forward (AF) protocol. In the study, the findings for the SOP are presented with Monte Carlo simulations. The study shows that there is a trade-off between harvested energy, data rate and SOP performance, while power allocation factors have an impact on secrecy performance.

Physical layer security in SWIPT-based cooperative vehicular relaying networks

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.

This letter studies physical layer security (PLS) in non-orthogonal multiple access (NOMA) power line communication (PLC) networks. A source node transmits information to two nodes of near and far users with different power allocations. We consider two different cases of eavesdropping: internal and external. The PLC channel and noise are modeled by correlated log-normal fading and Bernoulli-Gaussian random process, respectively. We derive closed-form expressions for the secrecy outage probability (SOP) of both the internal and external cases by applying Gauss-Chebyshev quadrature, which are verified by Monte Carlo simulations. We observe that higher impulsive noise degrades the SOP while higher channel correlation can improve the SOP. In addition, the analytic results reveal the impact of power allocation on the SOP performance.

On the physical layer security of hybrid RF-FSO system in presence of multiple eavesdroppers and receiver diversity

In this paper, we evaluate the secrecy performance of multi-hop cognitive wireless sensor networks (WSNs). In the secondary network, a source transmits its data to a destination via the multi-hop relaying model using the transmit antenna selection (TAS)/selection combining (SC) technique at each hop, in the presence of an eavesdropper who wants to receive the data illegally. The secondary transmitters, including the source and intermediate relays, have to harvest energy from radio-frequency signals of a power beacon for transmitting the source data. Moreover, their transmit power must be adjusted to satisfy the quality of service (QoS) of the primary network. Under the joint impact of hardware imperfection and interference constraint, expressions for the transmit power for the secondary transmitters are derived. We also derive exact and asymptotic expressions of secrecy outage probability (SOP) and probability of non-zero secrecy capacity (PNSC) for the proposed protocol over Rayleigh fading channel. The derivations are then verified by Monte Carlo simulations.

ABSTRACTIn this paper, we consider the physical layer security of a downlink cooperative multiple-input single-output (MISO) non-orthogonal multiple access (NOMA) network over Nakagami-m fading. The network consists of a multi-antenna source, multiple decode-and-forward (DF) relays, and two users with different priority, in the presence of a passive eavesdropper. Specifically, we investigate the secure transmission from the source to the users via the help of the relays, in which the signals of the users might or might not be successfully decoded at the relays. Thus, we aim to design secure communication protocols for the considered system, where transmit antenna selection (TAS), maximal ratio transmission (MRT), and relay selection are employed based on the source-to-relays channel conditions. To characterize the secrecy performance, analytical and asymptotic expressions for the secrecy outage probability (SOP) of the overall system are derived. Our analytical results validated by Monte-Carlo simulations show that the secrecy performance of cooperative NOMA networks can be improved by increasing the number of antennas at the source and the number of relays. Comparing TAS and MRT, we conclude that TAS has lower complexity but can achieve the secrecy performane comparable with MRT. Finally, the results also indicate that our proposed protocol bring more general and practical insights with similar secrecy performance compared with the conventional solution.

Artificial noise (AN) is one of physical layer security techniques, which can realize secure communication. AN is a noise signal which is intentionally transmitted from transmitter along with data signals. Since AN is generated to be canceled out at legitimate receivers, it can prevent eavesdroppers from eavesdropping even if transmitters do not know the existence of eavesdroppers. In spite of its usefulness, most of the AN generation techniques cannot be applied to multiple-input multiple-output (MIMO) systems when the number of antennas at the transmitter is less than that at the legitimate receiver. In this paper, we consider time-domain AN generation techniques for MIMO orthogonal frequency division multiplexing (OFDM) systems. A time-domain AN generation technique is originally proposed for single-input single-output (SISO) OFDM systems. Thus, we first consider to apply the conventional time-domain AN generation technique to MIMO-OFDM systems, and show that this technique requires a large number of antennas at the transmitter and/or a longer cyclic prefix (CP). Next, to solve this problem, we propose another time-domain AN generation technique. Our proposed time-domain AN is generated to be canceled out at the legitimate receiver in the frequency domain, while the conventional time-domain AN is canceled out in the time domain. As a result, the proposed time-domain AN generation technique can be applied to MIMO-OFDM systems, irrespective of the number of antennas and the length of CP. Simulation results can show that the proposed AN achieves the same secrecy rate as the conventional time-domain AN. Moreover, the proposed technique achieves a higher secrecy rate when a MIMO-OFDM system is employed with the antenna configuration to which the conventional time-domain AN generation technique is hard to be applied.

We have considered a dual-hop wireless network consisting of a decode-and-forward (DF) relay in presence of an eavesdropper. Relay can correctly decode and retransmit only if the received signal-to-noise ratio (SNR) meets a particular threshold. The eavesdropper can tap signals both from the relay and the source. The performance of the maximal ratio combining (MRC) and selection combining (SC) diversity at the eavesdropper is investigated. Whether knowledge of channel state information (CSI) at the transmitter is available or not is considered for the performance evaluation in secrecy outage probability and ergodic secrecy rate. Asymptotic analyses of performances are provided. We show that direct link has a significant impact on system secrecy. It is found that secrecy performances are the best if the relay is always able to decode correctly. We also found that knowledge of CSI helps to achieve better secrecy at lower rate. It is observed that unbalance created due to constraint on either of the source-relay link average SNR or relay-destination link average SNR does not yield similar secrecy outage performance but both can limit the secrecy outage performance. On the contrary, it is found that only source-relay link quality can limit the ergodic secrecy rate performance.

The next generation network (5G) promises to offer a wide spectrum of advantages like massive user connections and high mobility. Massive user connection is achieved by incorporating Multiple Input Multiple Output (MIMO). Securing 5G wireless networks is of greater concern because they are developed with the intention of providing exponentially increasing wireless services where a trillion of legitimate users will be involved. Data transmission in 5G networks has been exposed to various security threats such as eavesdropping, jamming, Denial of Service (DoS) attack and Man-In-The-Middle (MITM) attack. The above mentioned threats have the ability of affecting the performance of 5G wireless networks since 5G is a major support system for new use cases. Some of the existing mechanisms employed to deal with the security threats are Physical Layer Security (PLS) and cryptography. PLS is preferred since its primary focus is on physical and Media Access Control (MAC) layer where variations in security between wireless and wired networks occur. The existing PLS approach for security against single cell MIMO eavesdropper is Original Symbol Phase Rotated (OSPR) secure transmission scheme where one base station serves the user terminals in a single cell. Our paper implements OSPR for a multi cell MIMO where multiple base stations serve multiple user terminals located in different cells. This architecture will be referred to as Multi cell MIMO Eavesdropping (MME). The efficiency of multi cell OSPR will be compared with Artificial Noise (AN) generation. The extent to which OSPR gives protection against MIMO eavesdropper is measured in terms of Symbol Error Rate (SER). As SER increases, security of data transmission increases. The efficiency of multi cell OSPR over AN is expected to be 8% and it will be verified in simulation using MATLAB.

In this paper, we present a comprehensive performance analysis of multiple-input multiple-output (MIMO) systems with transmit antenna selection (TAS) and stochastic power allocation (SPA) for the spatially correlated fading channels. Two best transmit antennas that maximize the instantaneous received signal-to-noise (SNR) are selected to transmit the Alamouti scheme and maximal-ratio combining (MRC) is applied at the receiver. With correlation matrices available to the transmitter, SPA is applied on these selected antennas. Two different methods are given to derive the explicit upper bounds on the bit-error rate (BER) performance. Finally we present numerical results to verify our analysis. It is shown that the TAS/SPA scheme can achieve high performance in spatially correlated channels.

In this letter, we introduce the performance of maximal ratio combining (MRC) with weighting errors for physical layer security. We assume both legitimate user and eavesdropper each equipped with multiple antennas employ non ideal MRC. The non ideal MRC is designed in terms of power correlation between the estimated and actual fadings. We derive new closed-form and generalized expressions for connection and secrecy outage probability. Next, we investigate asymptotic behavior of the outage probability for high signal-to-noise ratio in main channel between the legitimate user and the transmitter. The asymptotic analysis provides new insights about actual diversity provided by MRC with weighting errors. We substantiate our claims with the analytic results and numerical evaluations.

This paper analyzes the performance of a hybrid control access scheme for small cells in the context of two-tier cellular networks. The analysis considers MIMO transmit/receive arrays configuration that implements transmit antenna selection (TAS) and maximal ratio combining (MRC) under Rayleigh fading channels when the interfering sources are described using Poisson field processes. The adopted models of aggregate interference at each receive station is modeled as a shot noise that follows a Stable distribution. Furthermore, based on the interference awareness at the receive station, two TAS approaches are considered through the analysis, which are the signal-to-noise (SNR)-based selection and signal-to-interference-plus-noise ratio (SINR)-based selection. In addition, the effect of delayed TAS due to imperfect feedback channel on the performance measures is investigated. New analytical results the hybrid-access scheme's downlink outage probability and error rate are obtained. To gain further insight on the system's behavior at limiting cases, asymptotic results for the outage probability and error rate at high signal-to-noise (SNR) are also obtained, which can be useful to describe diversity orders and coding gains. The derived analytical results are validated via Monte Carlo simulations.