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.
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.
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.
The security of information over wireless channels has always been an important aspect of wireless communication research. In this paper, the secrecy performance of a spatial modulated system with an artificial noise is investigated over the Rayleigh channel, and the corresponding secrecy rate is analyzed in the presence of imperfect channel state information (CSI). Based on the secrecy performance analysis, the ergodic rates and the corresponding lower bounds of the legitimate receiver and eavesdropper are, respectively, derived. As a result, the closed-form lower bound of ergodic rate of the legitimate receiver is obtained, and the lower bound of ergodic rate of the eavesdropper and the corresponding ergodic secrecy rate (ESR) can be achieved by calculating the mean values. To avoid the mean operation and reduce the complexity, the closed-form approximated expression of ESR is also derived. This theoretical ESR can include the one under perfect CSI as a special case and has the value close to the corresponding simulation. Thus, it can provide good performance evaluation for the artificial-noise-aided spatial modulation system with imperfect CSI. Simulation results verify the effectiveness of the theoretical analysis. The system with imperfect CSI is found to have low ESR as compared to the one with perfect CSI due to the estimation error. Moreover, initially, the ESR increases with increasing power of artificial noise, but then, due to the total power constraint, it starts decreasing.
Secrecy transmission is investigated for a cooperative jamming scheme, where a multi-antenna jammer generates artificial noise (AN) to confuse eavesdroppers. Two kinds of eavesdroppers are considered: passive eavesdroppers who only overhear the legitimate information, and active eavesdroppers who not only overhear the legitimate information but also jam the legitimate signal. Existing works only treat the passive and active eavesdroppers separately. Different from the existing works, we investigate the achievable secrecy rate in presence of both active and passive eavesdroppers. For the considered system model, we assume that the instantaneous channel state information (CSI) of the active eavesdroppers is available at the jammer, while only partial CSI of the passive eavesdroppers is available at the jammer. A new zero-forcing beamforming scheme is proposed in the presence of both active and passive eavesdroppers. For both the perfect and imperfect CSI cases, the total transmission power allocation between the information and AN signals is optimized to maximize the achievable secrecy rate. Numerical results show that imperfect CSI between the jammer and the legitimate receiver will do more harm to the achievable secrecy rate than imperfect CSI between the jammer and the active eavesdropper.
Secrecy transmission is investigated for a cooperative jamming scheme, where a multi-antenna jam-mer generates artificial noise (AN) to confuse eavesdroppers. Two kinds of eavesdroppers are considered: passive eavesdroppers who only overhear the legitimate information, and active eavesdroppers who not only overhear the legitimate information but also jam the legitimate signal. Existing works only treat the passive and active eavesdroppers separately. Different from the existing works, we investigate the achievable secrecy rate in presence of both active and passive eavesdroppers. For the considered system model, we assume that the instantaneous channel state information (CSI) of the active eavesdroppers is available at the jammer, while only partial CSI of the passive eavesdroppers is available at the jammer. A new zero-forcing beamforming scheme is proposed in the presence of both active and passive eavesdroppers. For both the perfect and imperfect CSI cases, the total transmission power allocation between the information and AN signals is optimized to maximize the achievable secrecy rate. Numerical results show that imperfect CSI between the jammer and the legitimate receiver will do more harm to the achievable secrecy rate than imperfect CSI between the jammer and the active eavesdropper.