The Anti-Noise Performance Research Of Phase-Inversion Symmetric Method In Time Domain And A Double Input Double Output System

With the change of Communicate environment especially artificial noise which has become the main noise fountain, more attention has been paid on how to use noise correlation to enhance SNR. Eliminating the noise in channel by making use of correlation of band limited noise and the correlation of it's numerical characteristics is the basic theory of Phase-Inversion Symmetric Method, by using this theory, weak signals can be extract from strong noise and the SNR is increased greatly. "Phase-inversion" means that the signal and its reversed signal are sent simultaneously (the inversed signal means that the amplitude is inversed of the signal). "Symmetric" means two signals are disposed in the same way .The interferences also are alike when the two signals are transmitted at the channel. Finally we subtract the inversed signal from the signal in the receive end. If the interferences added into two signals are the same completely, the interferences are eliminated. Generally two interferences may be not homology. But if they are similar, noise also can be partly eliminated by the way of Phase-Inversion Symmetric Method so as to increase the SNR of the system.The available degree and application area is decided by noise correlation coefficientρbetween different noises. The key is how to confirm the size ofρ. Because classical theory assumed that the noise is Adding White Gauss Noise(AWGN), whose noise correlation coefficientρis zero. Because the actual communication system is not unlimited in bandwidth, the noise should be assumed to narrowband Gaussian white noise at lest, in order to be relatively consistent with the actual situation. Therefore, it's necessary to explore the narrow white Gaussian noise relevance in depth.In this paper, the correlation of the narrowband Gaussian white noise in the digital system is analysed in time domain. A new time domain phase-inversion symmetric method is provided, and its anti-noise performance is analysed in theories, the results prove that narrowband Gaussian white noise in the same time slot and adjacent slot has the identified correlation coefficientρ, and the correlation coefficientρonly depends on the character of the filter used. In addition, this paper also presents a Double Input Double Output(DIDO) digital transmission system based on time-domain Phase-Inversion Symmetric Method, it can effectively improve the receiving anti-noise performance. In the same time, its applications have been discussed in this paper.We use professional digital simulation software SYSTEMVIEW to simulate the anti-noise performance of PISM in time domain and DIDO digital communication system. The simulation results show that the narrowband Gaussian noise is relevant between same slot and adjacent slot, and the correlation associated only with the filter characteristics and the length of the integral. The simulation results of DIDO digital communication system show that, in the second output terminal, the first signed power is eliminated by more than 20 dB; but in the first output terminal, the second signal power is also eliminated by more than 20 dB. If carefully debugging, the results will be better. When only PISM signal is transmissed in the channel, with adding Gaussian white noise, the output noise is eliminated by 10 dB.Finally, the summary and the plan are provided in the paper. Improvement of PISM model in time domain and space domain is the emphases in future, and the actual communication system should be researched too.