The Theory And Anti-Noise Performance Analysis Of PISM-OFDM System

In this article, at first we introduce the basic theory of PISM (Phase Inversion Symmetric Method, PISM), which use the relativity of adjacent channel noise to eliminate noise. Adjacent channel include adjacent frequency band, adjacent time-slot and adjacent airspace. Then we focus on studying the principle of PISM-OFDM system and analyzing its anti-noise performance. Since the spectrum of each sub-carrier is overlap, the noise between adjacent frequency bands exist a strong correlation, which is very suitable for using PISM to improve signal-noise ratio of the system. In this article, some work has been done as follows:1. Testing and analyzing the relativity of adjacent channel noise, the result show that the relativity of the man-made noise is much larger than natural noise. At the same time, we test the relationship between the relativity of noise and the overlap of noise spectrum, demonstrating that when bandwidth is certain, the relativity of noise increase as the overlap increases. When the spectrum has a half overlap, the correlation coefficient is 0.5 approximately. Experimental data will support our study-combining PISM and OFDM technology. 2. Establishing PISM-OFDM system model diagram and using MATLAB software simulation, the simulation results show that under the condition of the same information rate and the same signal-noise ratio, the error rate of the PISM-OFDM is much smaller than OFDM system. When the information rate and the error rate are the same, the signal-noise ratio of the PISM-OFDM is much smaller 3dB than the OFDM system.In addition, we compare the performance of the PISM-OFDM and OFDM systems in theory, finding that theoretical analysis and simulation results are almost the same.3. The PISM-OFDM modulation system is completed based on FPGA chips in Cyclone series, giving the circuit diagram and simulated waveforms of some modules included the string and parallel transformation, constellation mapping, FFT transform. From these waveforms, we can see the output of the each module easily.