Legitimate Channel State Information Research Articles

Secrecy Analysis of SSK Modulation: Adaptive Antenna Mapping and Performance Results

In this paper, we investigate the physical layer security based on space shift keying (SSK) in which bit-to-spatial mapping of antenna indices dynamically adapts according to the partial channel state information (CSI) of the legitimate channel at the transmitter (Tx). Further, the Tx also adapts transmit power allocation to each transmit antenna according to partial CSI. Since an eavesdropper (Eve) is not (usually) aware of the legitimate CSI, it cannot successfully decode the antenna index; thus, transmission over the legitimate channel is secured from the wiretapping of Eve. An important virtue of the proposed scheme is that the Tx does not require full CSI of the legitimate and eavesdropper channels to secure the confidential information. The proposed work focuses on the secrecy rate (SR) and bit error rate (BER) of the considered multiple-input single-output system over Rayleigh fading channels. Approximate expressions of Bob's data rate for 2-ary and 4-ary SSK modulations are derived in closed-form. Furthermore, an upper-bound of Bob's data rate for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> -ary SSK modulation is also derived. In order to obtain the secrecy rate for the proposed scheme, we also evaluate Eve's data rate. Analytical results of SR and BER demonstrate the robustness of the proposed scheme. All numerical results are thoroughly verified by using extensive Monte Carlo simulations.

Security-Oriented Trellis Code Design for Spatial Modulation

To achieve physical layer security (PLS) with a flexible implementation, a novel design named security-oriented trellis coded spatial-modulation (SO-TCSM) is proposed in this article, where the transmitter does not know the channel state information (CSI) of wiretapping channels and relies on the legitimate CSI to vary the mapping patterns for the antenna information and the radiated information, aiming at the optimisation of free Euclidean distances between the resultant SO-TCSM symbols. Eavesdroppers cannot decode the confidential information delivered in the legitimate link, as they do not know the legitimate CSI and, hence, have no basis to acquire the transmitter’s mapping pattern of the moment. Moreover, the SO-TCSM symbols are then compensated to maximise their Euclidean distances, which further improves the legitimate receiver’s decoding performance while enhancing the PLS. However, the compensation results in high transmit power when the legitimate channels are in deep fades. To boost the energy efficiency, a constraint is set to limit the transmit power. Under this constraint, the SO-TCSM performance is investigated in terms of bit error rate and transmit power consumption. The outcome of these investigations substantiates that, compared to conventional TCSM designs, our SO-TCSM achieves better performance in the legitimate link with lower decoding complexity.

Secure Single-Input-Multiple-Output Media-Based Modulation

The media-based modulation (MBM) system, which varies its channel state by controlling the on/off status of the radio frequency (RF) mirrors, and embeds additional information bits into the mirror activation pattern, is capable of achieving significant throughput and desirable bit-error-rate (BER) performance. Hence, it has attracted increasing attention from researchers of wireless communication community. In this paper <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> , the information secrecy issue for MBM is investigated, and a secure single-input-multiple-output MBM (SIMO-MBM) system is proposed utilizing physical-layer security techniques. By considering the time-division duplexing (TDD) mode with channel reciprocity property, the legitimate channel state information (CSI) is applied to secure the data transmission of SIMO-MBM. More specifically, on one hand, adaptive phase rotation is imposed on the transmitted signals, where the rotation angle is determined by the phase of legitimate CSI; on the other hand, the mapping rule between the mirror activation pattern and binary bits is changed according to the amplitude of legitimate CSI. The BER performance of the eavesdropper is investigated via theoretical derivations, and the system secrecy mutual information is also derived, based on which the optimal design of the adaptive phase rotation strategy is provided. Theoretical and simulative results demonstrate that the proposed secure SIMO-MBM system is capable of enhancing the data confidentiality whilst keeping reliable data transmission.

Channel-Aware Artificial Intersymbol Interference for Enhancing Physical Layer Security

In this letter, we propose a novel scheme for enhancing the security of the information transfer between resource-limited devices. We select a pulse from a set of $T$ -orthogonal pulses for shaping the data at source ( $S$ ) based on legitimate channel state information (CSI). A destination ( $D$ ) having the CSI, properly samples the output of the matched filter. An eavesdropper ( $E$ ) having no knowledge of the legitimate CSI, may or may not sample correctly, thereby, inducing artificial intersymbol interference (ISI) at the $E$ . We also consider a case where the $S-E$ link is correlated with the $S-D$ link (when $E$ and $D$ are closely located). We derive optimal thresholds at $E$ , $S$ for switching the selection of a pulse in maximizing and minimizing the achievable rate at $E$ , respectively. We derive closed-form expressions for upper bound and lower bound on the secrecy outage probability (SOP) for the independent case. Simulation results show that unlike at $D$ , the symbol error rate (SER) at $E$ saturates at a high SER due to the induced ISI.

An Artificial Noise assisted secrecy-enhancing scheme for Space–Time Shift Keying systems

It is meaningful in practice to explore a secrecy-enhancing Multi-Input-Multi-Output (MIMO) scheme with flexible Radio Frequency (RF) antenna chains as well as low complexity. In this paper, an Artificial Noise (AN) assisted secrecy-enhancing scheme is proposed for the Space–Time Shift Keying (STSK) systems, which has the capability to prevent the passive eavesdropper from eavesdropping the legitimate communication. In the proposed AN-STSK scheme, the transmitter exploits the knowledge of legitimate Channel State Information (CSI) to generate suitable AN with an optimal power fraction in order to introduce interference to the transmit signal. Since the AN resides in the null space of the legitimate channel matrix, the AN can be canceled at the legitimate receiver. First, the secrecy capacity of the proposed AN-STSK scheme has been derived theoretically based on the system model and then resolved by using the Monte Carlo approach. Further, the simulation results of the proposed scheme over the fast fading and block invariant channel have been obtained and studied in detail compared with the traditional AN-Spatial Modulation (SM) scheme. It has been seen that the proposed scheme can improve the secrecy capacity at a cost of a slight increase in Bit Error Rate (BER) through a proper fraction of transmit power allocated to AN. Therefore, the performance trade-offs between the BER and the secrecy capacity can be made in practice. Moreover, it is more effective for the AN-STSK scheme to block the passive eavesdropping when the channel Signal-to-Noise Ratio (SNR) increases since the BER of the legitimate receiver decreases much faster than that of the passive eavesdropper. As a result, the proposed scheme can boost the secrecy capacity at much higher level than the traditional AN-SM scheme in case of the good channel condition.

Secrecy-Enhancing Scheme for Spatial Modulation

In this letter, we propose a new secrecy enhancement scheme for spatial modulation systems by exploiting the knowledge of the legitimate channel state information to rotate the indices of the transmit antennas and the constellation symbols, which are mapped into spatial and constellation bits. A secrecy rate analysis shows that the eavesdropper cannot recover any information carried by spatial and constellation bits. The numerical results on the secrecy rate and the bit error rate verify the effectiveness and robustness of the proposed scheme.

Energy‐efficient optimisation for secrecy wireless information and power transfer in massive MIMO relaying systems

In this study, the problem of energy-efficient power allocation (EEPA) for secrecy wireless information and power transfer in a massive multiple-input multiple-output relay aided secure communication system is well addressed. The relay forwards the signal sent from a source to a legitimate destination with the harvested energy based on a decode-and-forward relaying protocol, while a passive eavesdropper intends to intercept the message. The authors first derive a closed-form expression for the secrecy energy efficiency of the considered system under practical conditions, i.e. no instantaneous eavesdropper channel state information (CSI) and only imperfect legitimate CSI. Then, they propose an EEPA scheme for maximising the secrecy energy efficiency. Finally, simulation results validate the effectiveness of the proposed scheme.

Toward Green and Secure Communications over Massive MIMO Relay Networks: Joint Source and Relay Power Allocation

In this paper, we address the problem of green and secure communications under adverse conditions, i.e., no instantaneous eavesdropper channel state information (CSI) and imperfect instantaneous legitimate CSI. The benefits of a massive multiple-input multiple-output relay are exploited to significantly improve the secrecy energy efficiency (bit per Joule), which is defined as the ratio of secrecy outage capacity and total power consumption. The focus of this paper is on joint power allocation at the source and the relay to maximize the secrecy energy efficiency. Accordingly, two energy-efficient power allocation schemes are proposed under joint and distributed source and relay power constraints. We show that the two schemes asymptotically approach the same saturated energy efficiency. Finally, simulation results validate the advantage of the proposed energy-efficient schemes compared with several baseline schemes.

Artificial Noise Assisted Secure Transmission for Distributed Antenna Systems

This paper studies the artificial noise (AN) assisted secure transmission for a distributed antenna systems (DAS). To avoid a significant overhead caused by full legitimate channel state information (CSI) acquisition, tracking and collection in the central processor, we propose a distributed AN scheme utilizing the large-scale CSI of the legitimate receiver and eavesdropper. Our objective is to maximize the ergodic secrecy rate (ESR) via optimizing the power allocation between the confidential signal and AN for each remote antenna (RA) under the per-antenna power constraint. Specifically, exploiting random matrix theory, we first establish an analytical expression of the achievable ESR, which leads to a non-convex optimization problem with multiple non-convex constraints in the form of high-order fixed-point equations. To handle the intractable constraints, we recast it into a max-min optimization problem, and propose an iterative block coordinate descent (BCD) algorithm to provide a stationary solution. The BCD algorithm is composed of three subproblems, where the first two subproblems are convex with closed-form solutions, and the last one is a convex-concave game whose saddle-point is located by a tailored barrier algorithm. Simulation results validate the effectiveness of the proposed iterative algorithm and show that our scheme not only reduces the system overhead greatly but also maintains a good secrecy performance.

Resource Allocation for a Massive MIMO Relay Aided Secure Communication

In this paper, we address the problem of joint power and time allocation for secure communications in a decode-and-forward massive multiple-input multiple-output (M-MIMO) relaying system in the presence of a passive eavesdropper. We apply the M-MIMO relaying technique to enhance the secrecy performance under very practical and adverse conditions, i.e., no availability of instantaneous eavesdropper channel state information (CSI) and only imperfect instantaneous legitimate CSI. We first provide a performance analysis of secrecy outage capacity, which reveals the minimum required number of relay antennas for achieving a positive secrecy outage capacity. Then, we propose an optimization framework to jointly optimize source transmit power, relay transmit power, and transmission time in each hop, with the goal of maximizing the secrecy outage capacity. Although the secrecy outage capacity is not a concave function with respect to the optimization variables, we show that it can be maximized by first maximizing over some of the variables, and then maximizing over the rest. To this end, we first derive a closed-form solution of optimal relay transmit power, afterward obtain that of optimal source transmit power, and then derive the optimal ratio of the first-hop duration to a complete transmission time. Moreover, several important system design insights are provided through asymptotic performance analysis. Finally, simulation results validate the effectiveness of the proposed joint resource allocation scheme.

Large-Scale MIMO Relaying Techniques for Physical Layer Security: AF or DF?

In this paper, we consider a large scale multiple input multiple output (LS-MIMO) relaying system, where an information source sends the message to its intended destination aided by an LS-MIMO relay, while a passive eavesdropper tries to intercept the information forwarded by the relay. The advantage of a large scale antenna array is exploited to improve spectral efficiency and enhance wireless security. In particular, the challenging issue incurred by short-distance interception is well addressed. Under very practical assumptions, i.e., no eavesdropper channel state information (CSI) and imperfect legitimate CSI at the relay, this paper gives a thorough secrecy performance analysis and comparison of two classic relaying techniques, i.e., amplify-and-forward (AF) and decode-and-forward (DF). Furthermore, asymptotical analysis is carried out to provide clear insights on the secrecy performance for such an LS-MIMO relaying system. We show that under large transmit powers, AF is a better choice than DF from the perspectives of both secrecy performance and implementation complexity, and prove that there exits an optimal transmit power at medium regime that maximizes the secrecy outage capacity.

On Secrecy Rate of the Generalized Artificial-Noise Assisted Secure Beamforming for Wiretap Channels

In this paper we consider the secure transmission with multiple-input, single-output, single-antenna eavesdropper (MISOSE) in fast fading channels where the transmitter knows perfect legitimate channel state information but only the statistics of the eavesdropper's channel. For the MISOSE channels, the artificial noise assisted beamforming proposed by Goel and Negi is a promising technique, where the artificial noise is imposed on the null space of the legitimate channel to disrupt the eavesdropper's reception. Here we propose a generalized artificial noise scheme which allows the injection of the artificial noise to the legitimate channel. Although the generalized artificial noise may cause the leakage of artificial noise at the legitimate receiver, the secrecy rate can still be improved since the covariance matrix of it is more flexible than the heuristic one selected by Goel and Negi. To fully characterize the proposed scheme, we investigate the optimization of its secrecy rate. We first derive the conditions under which the beamformers of the message bearing signal and the generalized artificial noise being the same is optimal. Based on this choice, the complicated secrecy rate optimization problem over the covariance matrices of the message-bearing signal and the generalized artificial noise can be reduced to a much simpler power allocation problem. We also develop an efficient algorithm to solve this non-convex power allocation problem. Numerical results show that our generalized artificial noise scheme outperforms Goel and Negi's heuristic selection, especially in the near eavesdropper settings. In particular, with the aid of the proposed scheme, the regime with non-zero secrecy rate is enlarged, which can significantly improve the connectivity of the network.