The Research Of OFDM Technology Based On Phase-inversion Symmetric Method

With the rapid development of wireless network communication and mobile communication, the radio channel resources become more and more tension. It is a problem to be solved in wireless communication that how to further improve the channel utilization and anti-interference ability. Therefore, some researchers have proposed many ways, amony these ways CDMA, OFDM and MIMO multi-antenan are the most impressive technologies. The phase-inversion symmetric method (PISM) our group have been studying in recent years is an effective way to resist strong interference which use the noise correlation. With the help of national fund we have made some significant progress and obtained the Chinese invention patent.This article study a new technology PIS-OFDM which combined PISM and OFDM. The results show that PIS-OFDM is better than OFDM in aspect of anti-noise. After one and a half years, I complete the tasks assigned by my tutor. The main works are as follows.1. The test of noise correlationWe carried out lots of testing about noise correlation in adjacent band and obtained the following results. (1) Man-made noise is the main noise in current wireless channel, and its power is much larger than the natural noise.(2) Adjacent band noise is positive correlate.(3) In the sitution of adjacent band, the smaller the bandwidth, the greater the noise correlation coefficients.(4) In adjacent bands of communication, the man-made noise correlation coefficient is larger than the natural noise correlation coefficient.(5) The overlap of adjacent bands in OFDM communication system is50%, so the noise correlation is very strong.2. Introduce the PISM principle and analyze its anti-noise performance.After analysis, we obtained the SNR gain of PISM is GPISM=2/(1-ρ), Where p is the noise correlationcoefficient. When ρ>0, GPISM>2. Its anti-noise erformance is better than the general diversity technique.3. Combine PISM and OFDM system, this way can improve the anti-interference ability of the OFDM system.Analyze the principle of OFDM technology, Complete basic OFDM system, test its anti-interference ability MATLAB; complete the PIS-OFDM system, test its anti-interference ability by MATLAB,too.The test results show:In the same bandwidth and the same rate, the anti-interference ability of PIS-OFDM system is better than the OFDM system.