| Since the1980s, The mobile communication system which has experienced1Q2G,3G and the continuing4G has presented a trend of rapid development. There have been emerged Code Division Multiple Access (CDMA), Time Division Multiple Access technology (TDMA) as well as the technology of frequency division multiple access systems (FDMA) and many other advanced technologies. These technologies can provide much more users with the stable transmission service to enjoy the communication at a faster speed. However, due to the continuous increasing in the communication users and the rapid growth of the number of the communication device, Man-made noise has become a problem that we have to face in the wireless communication device. That means the enhancement of the intensity of noise can result in a limited channel which can not match the unlimited communication needs well. The orthogonal frequency division multiplexing (OFDM) is the core of the fourth-generation communications technology, and its main characteristic include making fully use of the bandwidth resources which can easily overlap its sub-carriers. Meanwhile it has many advantages in transmission. For example, It can be effectively overcome the inter-symbol interference through the serial-parallel conversion to the low-speed and the high-speed information flow. Meanwhile each sub-carrier orthogonal can influence each other by Improving channel utilization which has almost doubled and the signal generated by their Fourier transform to assist the use of the integrated chip, and the vertical line can be an effective solution to sparing the space of the band.The inverting symmetrical method is a method of suppressing the interference noise between adjacent channels by using the correlation method, and its main aim is to improve the strength of the signal and to inhibit the noise interference. In this paper, we analysis the noise from the time and frequency aspects. Especially in the time aspect, we tested the natural and artificial noise correlation under the circumstance of delaying the state of the noise. And we analysis the noise by a different center frequency and bandwidth of noise correlation in the correlation of the frequency domain, Meanwhile we analysis the noise with a wide spectrum of different degree of noise correlation to prove that the reverse symmetry method can suppress the noise interference.According to analyzing the OFDM system, this paper identifies the integration method of the inverse symmetry OFDM system. First, we can take the advantage of the inverted symmetry method to improve the relative increase in the duration of each sub-signal coded OFDM system transformation. Second, using the degree of overlapping the sub carriers of the OFDM system, we can improve the transmission system. Therefore, first, we code OFDM based on the band signal which uses the time-domain inversion symmetry method and spreading the idea of8203;8203;spread spectrum. Then through the improving of the frequency domain inversion symmetry method and the original OFDM transmission process, a new PISM-OFDM transmission system is programming. Last we analysis the theory and reach the conclusion, combing with the MATLAB program simulation,... |
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