Research Of MIMO Technology Based On Phase-Inversion Symmetric Method

Theoretical study confirmed that, the channel capacity which the MIMO system obtained could approximately grow linearly with the number of the antennas while the number of transceiver antennas was large. However, the actual MIMO system did not always get the theoretical value of the channel capacity, it is because the conclusion above was carried out under the premise of the noise correlation coefficientρ=0 between each channel in the space. In fact, there was a strong correlation between the adjacent channel noise.Combining PISM with MIMO technology could take advantage of the adjacent space noise correlation effectively to improve the SNR of the system output. PISM was first proposed as a communication method by my tutor, and won the 2009 National Natural Science Fund.This paper studied the application of PISM in the airspace, realized the combination of PISM with MIMO technology and solved the problems of the MIMO system in fighting against the noise correlation. Main tasks are as follows:1. Introduced the basic principle of PISM, carried out actual test of the noise correlation coefficient between adjacent channel in the space:Through the anti-noise performance analysis, the conclusion could be got that the system output of PISM could obtain the SNR gain of 2/(1-ρ). Test results confirmed that, while the antenna spacing was less than half the wavelength, the correlation coefficientρcould reach 0.80 or above, then using PISM could make the SNR gain of the system greater than 10, which made it possible for the application of PISM in the space.2. Introduced the basic theory of MIMO technology, proposed a space diversity technology based on PISM——PISM-SD:MIMO system could improve transmission rate by spatial multiplexing technology, or improve performance by spatial diversity technology. The traditional space diversity technology required the antenna spacing large enough to make the noise correlationρ�'0 between each channel, which made the application of diversity technology be limited. PISM-SD system proposed in this paper did not requireρ�'0, the antenna spacing could be very close, so it provided a convenient for the application of this technology in the mobile communication devices. The analysis results showed that, the anti-noise performance of the PISM-SD was better than the diversity techniques with equal gain combining whileρ>1/(1+4/SNR). And the simulation verified the conclusion that PISM-SD was better applied in small SNR environment.3. Introduced the basic theory of layered space-time codes, constructed a kind of BLAST based on PISM——PISM-BLAST: BLAST pursued the maximum rate, had high spectrum efficiency but low performance, so it was always applied in large SNR environment. In view of this situation, the PISM-BLAST proposed in this paper had solved the problem of improving the performance of layered space-time code under the condition of small SNR. Compared variety of decoding methods of layered space-time code with actual examples, gave the coding scheme and decoding algorithm of the PISM-BLAST, and finally verified its anti-noise performance through the MATLAB simulation.