Research On Smart Jamming For MIMO System

In recent years, with the continuous development of the military thoughts and communication systems, the role of jamming is becoming increasingly important. Multiple input multiple output(MIMO) system has been widely used in military and civilian fields due to its high frequency spectrum utilization and large capacity. However, when faced with MIMO system, the application of traditional jamming methods are greatly limited because of high jamming power, easy exposure and lack of persistence. Furthermore, it has brought a great challenge to the jamming strategies with the development of anti-jamming technology in recent years. Aiming at the weak points of a certain communication system, smart jamming tries to disrupt certain parts of the digital signal with low jamming power for the purpose of hiding itself. Therefore, the smart jamming for MIMO system has great application prospect. This thesis mainly conducts a series of exploratory studies on the smart jamming for MIMO system.Firstly, the characteristics of MIMO and OFDM systems are analyzed, and the common synchronization and channel estimation algorithms are introduced, which lay a foundation for the following analysis of the influence of smart jamming on synchronization and channel estimation.Then, the jamming strategies based on the pilot nulling and the training sequence nulling are analyzed. In order to reduce the prior information of the target signal, such as the channel state information, an improved channel estimation jamming strategy is proposed. In this jamming strategy, the reconstructed pilot from the eavesdropper is transmitted to cause pilot pollution and channel estimation error. In order to overcome the influence of the relative time delay between the jamming signal and the target signal, the synchronization cheating strategy is proposed. False correlation peak will be generated in the receiver's process of synchronization. The proposed jamming strategies are proved to be reasonable and efficient through some simulations.Finally, an improved estimation algorithm for antenna number based on Gerschgorin disks estimation is proposed to ensure the satisfactory estimation performance under low SNR condition. So, the reference is provided for the jammer's selection of antenna number.Furthermore, the construction strategy of jamming signal based on the second-order statistics is proposed to reduce the prior information of the frame parameters. Then, the jamming signal can be constructed from the second-order statistics to achieve effective jamming performance under low jamming power. Simulation results show that the strategy can obtain satisfactory jamming performance on the basis of further reducing the prior information of the target signal.