MIMO Multidimensional Study On Joint Communication Anti - Jamming Technique

As the development of wireless communication, wireless channels are crowed by many users. Technology of communication jamming becomes more and more advanced due to the signal processing progresses. The jamming technology embodies its progresses not only in higher transmit power, but also in variable and multiple form. Therefor how to solve the problem brought by the progresses of jamming technology has become a important topic for wireless communication. Traditional anti-jamming methods rely on the training code and pilot signals, which means these methods based on reliable synchronization are not available when precise synchronization can not be obtain under strong jamming. As such it is required to design a new muplti-user system adapting to strong jamming environment which is able to block high power interference and isolate multiple users. In addition, the system is required to isolate the multiple users and block the jamming accurately without synchronization under various jamming power. This thesis will focus on the spread spectrum communication systems based on signal processing relying on autocorrelation function. Combining with the properties of jamming existing in spread spectrum communication systems and autocorrelation function of these jamming, schemes of blocking jamming and multiple users isolating are proposed.In chapter two, we introduce the basic principles of signal processing based on autocorrelation function, and wireless communication systems exploring these principles to eliminate jamming. The key technology of this methods is constructing linear independent autocorrelation function vectors to isolate muplti-user signals, and finding the interference-blocking filter in the covariance matrix of received signals. The interference-blocking filter is obtained by covariance matrix decomposition of received signals. It is assumed that the autocorrelation function vectors of users'signal and jamming are linear independent. Although the autocorrelation of jamming is not known by communiction systems, this assumption is reasonable under most circumstance. In chapter three, we study the Direct Sequence Spread Spectrum (DSSS) systems based on autocorrelation domain. We first introduce the principles of DSSS and single-tone jamming. The property of autocorrelation function of DSSS signals is similar with white noise's, whenas it is unrelated with the initial phase of single-tone jamming. We propose schemes which are applicable for blocking single-tone jamming in Gaussian and multi-path channels based on these properties. The simulation results prove that these schemes is effective for blocking interference, and they are insensitive to power of jamming and noise.In chapter four, we study the Frequency Hopping(FH) system based on autocorrelation domain. First of all ,we introduce the FH system and the influence to the FH system brought by multi-tone and follower jamming. The properties of Phase Shift Keying/Frequency Hopping(PSK/FH) signals'autocorrelation function is similar with DSSS signal, and Frequency Shift Keying/Frequency Hopping(FSK/FH) signal is cycle stationary when its hopping frequencies are choosed elaborately. We propose a scheme for PSK/FH to blocking its jamming. And a scheme for FSK/FH to blocking a follower jamming is proposed, which is applicable to white jamming. These schemes are reliable and insensitive to power of jamming and noise, which is proved by the simulation results.Some conclusions are given in the final chapter, and the contributions, disadvantages, and the further research issues of this thesis are pointed out.