Research On Physical-Layer Schemes For Secure Transmission Based On Spatial Modulation Technology

With the rapid development of mobile communication technology, the security of wireless communication is becoming more and more important. The traditional secure transmission is realized by encryption in the upper layer protocol stack of the system. However, it is faced with a growing threat with the rapid development of computer technology. The physical layer security technology that use the characteristics of wireless transmission channel is another effective method to realize the security of information transmission. Spatial modulation technology has the advantages of high energy efficiency and low detection complexity, so it is expected to be one of the fifth generation mobile communication technology. This thesis studies the application of spatial modulation technology in the multi-antenna system to realize the information security transmission in the physical layer. The main work of this thesis is as follows:1. In the multi-antenna system based on the generalized space shift keying modulation, the scheme of information security transmission realized by the pretreatment of the transmitted signal is researched. The transmitter uses the channel state information feedback by the legitimate user to design reasonable pretreatment weight for preprocessing the transmitted signals. So the signals received by the legitimate user from each transmit antenna have the same phase, which enhance the signals. Futhermore, the transmitter takes a phase rotation to increase the distances among the constellation points, thereby improving the receive performance of the legitimate user and reducing the error rate. However, the phase of each signal received by the eavesdropper is randomly distributed, so the performance of eavesdropper is significantly inferior to the legitimate user. The bit error rate of the legitimate user and the eavesdropper, as well as the secrecy capacity of the system, is analyzed and simulated. The results show that the proposed scheme can significantly reduce the legitimate user's bit error rate, and the secure transmission can be realized even if the channel performance of the legitimate user is worse than that of the eavesdropper.2. The secure transmission scheme using spatial modulation technique and artificial noise is researched. The transmitter utilizes spatial modulation and traditional amplitude-phase modulated signal to transmit information, and the inactive antennas are used to transmit the artificial noise. The artificial noise is designed to locate in the null-space of the legitimate channel, so it has no effect on the information received by the legitimate user, but it suppress the receiving performance of eavesdropper. The expression of the secrecy capacity is given and the power allocation factor of the message signal and the artificial noise is optimized. At the same time, the bit error performance is derived in theory. The simulation results show that the legitimate receiver has better error performance than the eavesdropper, and considerable secrecy capacity is achievable.