Abstract This paper proposes combined precoding and artificial noise‐insertion scheme to enhance the secrecy of generalized precoded spatial modulation when the wiretap channel is partially correlated with the legitimate channel. It is shown that randomizing the modulated and spatial symbols prior to artificial noise insertion can significantly enhance secrecy even with a highly correlated eavesdropper channel. The proposed scheme exploits the channel state information (CSI) of the legitimate channel without requiring knowledge of the eavesdropper channel. The security of the proposed system depends on the amount of power allocation and the number of active receive antennas. Simulation results validate the proposed security scheme and show that the hybrid approach proposed outperforms the one that relies on artificial noise transmission.
Abstract This paper proposes combined precoding and artificial noise‐insertion scheme to enhance the secrecy of generalized precoded spatial modulation when the wiretap channel is partially correlated with the legitimate channel. It is shown that randomizing the modulated and spatial symbols prior to artificial noise insertion can significantly enhance secrecy even with a highly correlated eavesdropper channel. The proposed scheme exploits the channel state information (CSI) of the legitimate channel without requiring knowledge of the eavesdropper channel. The security of the proposed system depends on the amount of power allocation and the number of active receive antennas. Simulation results validate the proposed security scheme and show that the hybrid approach proposed outperforms the one that relies on artificial noise transmission.
Abstract In this article, we propose a random quadrature spatial modulation (RQSM) scheme to achieve secure transmission in multiple‐input multiple‐output multiantenna eavesdropper channels. We consider the case in which the eavesdropper has more antennas than that of the legitimate receiver, leading to a strong wiretap channel. In this case, the conventional secure quadrature spatial modulation schemes based on the artificially interfering signals are vulnerable to eavesdropping. On the contrary, the proposed RQSM scheme is able to achieve the physical‐layer security without transmitting artificial noises. Specifically, the bits‐to‐symbol mapping of the proposed RQSM is randomized according to the instantaneous channel state information of the legitimate link. Since in a rich scattering environment, the legitimate and the wiretap channels are generally independent of each other due to the spatial decorrelation property. Thus, the eavesdropper can be considered ignorant of the legitimate channel and cannot decode the confidential messages correctly. We derive the ergodic secrecy rate of the proposed RQSM scheme and show that the secrecy performance does not degrade as the number of antennas at the eavesdropper increases, which also outperforms the conventional jamming strategies. In addition, the bit error rate of the RQSM is also analyzed, which shows that security is achieved without sacrificing the system's reliability. Numerical results validate the theoretical derivations and demonstrate the effectiveness of the proposed RQSM scheme.
In this paper, we present a new secrecy-enhancing scheme for the spatial modulation (SM) system, by considering imperfect channel state information (CSI). In the proposed scheme, two antennas are activated at the same time. One of the activated antennas transmits information symbols along with artificial noise (AN) optimized under the imperfect CSI condition. On the other hand, the other activated antenna transmits another AN sequence. Because the AN are generated by exploiting the imperfect CSI of the legitimate channel, they can only be canceled at the legitimate receiver, while the passive eavesdropper will suffer from interference. We derive the secrecy rate of the proposed scheme in order to estimate the performance. The numerical results demonstrated in this paper verify that the proposed scheme can achieve a better secrecy rate compared to the conventional scheme at the same effective data rate.
Existing secure strategies based on precoding-aided spatial modulation (PSM) ensure the secrecy communication by introducing time-varying interference with extra power towards the eavesdropper, which, however, reduces the energy efficiency. In this paper, we propose two novel schemes to enhance the secrecy performance based on PSM. The first scheme utilizes the random antenna selection (RAS) technique, namely RAS- PSM, to generate zero-forcing (ZF) precoding matrices with randomly activated transmit antennas. It ensures efficient transmission to the legitimate user, while confusing the eavesdropper via the turbulence of RAS without extra power consumption. The second scheme, called hybrid secret PSM (HS-PSM), is an enhanced version of RAS-PSM by introducing the time-varying artificial noise into RAS-PSM. The resulting secrecy rates by the two proposed schemes are theoretically analyzed and evaluated via Monte Carlo simulations as well, whose results demonstrate that RAS-PSM achieves a higher secrecy rate than the existing schemes and HS- PSM is capable of further improving the secrecy performance especially at high signal-to-noise ratio (SNR).
Based on the objective reality of channel estimation error, this paper introduces a novel artificial noise (AN) aided spatial modulation (SM) secrecy-enhancing scheme under imperfect channel state information (CSI). In the proposed scheme, SM is used to activate one antenna from the transmit antennas, and the information symbols will be transmitted with the designed AN at each timeslot. By utilizing the legitimate channel's imperfect CSI, AN is generated across two adjacent timeslots. Because the CSI is known at the legitimate receiver, then it can perfectly cancel the AN. However, the eavesdropper knows nothing of the legitimate channel's CSI, so it can not recover any useful information from the AN. At the receiver, a new detection scheme that detects across two adjacent timeslots is also proposed. With imperfect CSI, the secrecy rate of the proposed scheme is derived over Rayleigh fading channels in order to investigate the performance. Moreover, based on the secrecy performance analysis, the lower bound of the ergodic secrecy rate (ESR), the corresponding closed form of the lower bound, and the approximated expression are also derived. The simulation results verified in this paper prove that the proposed scheme with imperfect CSI can achieve satisfactory performance.
To resist the passive eavesdropping while reserving the same hardware cost and receiver structure of the legitimate receiver, a secure quadrature spatial modulation (QSM) scheme is proposed in this letter. Instead of the information symbol, a mixture of the information symbol and artificial noise is transmitted through the activated transmit antennas. The mixed signals are designed, so that the artificial noise is cancelled at the legitimate receiver but cause random interference to the eavesdropper. The secrecy rate is analyzed and the optimal power allocation between the artificial noise and the information signal is investigated. The influence of the number of the eavesdropper's antennas is discussed. Simulation results show that, for multiple-input-single-output systems, the proposed secure QSM scheme achieves the best secrecy performance among the existing similar schemes by using less radio frequency chains. For multiple-input-multiple-output systems, the secure QSM scheme performs better than the existing secure SM scheme does under the same power constraint and transmission rate.
This paper investigates artificial noise (AN) injection along the temporal and spatial dimensions of a legitimate system to secure its transmissions from potential eavesdropping. In particular, we consider a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system in the presence of a multiple-antenna passive eavesdropper and characterize both the secrecy rate and average secrecy rate of the legitimate system. We assume that the legitimate transmitter knows the full channel state information (CSI) of the links connecting it with its legitimate receiver but does not know the instantaneous CSI of the passive eavesdropper. Closed-form expressions for the secrecy rate and average secrecy rate are derived for the asymptotic case of a large number of transmit antennas. We compare the degrading effects of spatial and temporal AN on the eavesdropper's rate. We also investigate the power allocation between the data and the AN and the power allocation between the spatial and the temporal AN. An upper bound on the secrecy rate loss due to the presence of the eavesdropper is also derived, and computer simulations are carried out to demonstrate the performance of our proposed AN scheme.