The Research Of OFDM Modulation And Demodulation Technology Based On Wavelet Transform

In recent years, wireless communication plays a more and more importantrole in people’s life, so people put forward the higher expectation towards thetransmission rate of wireless communication. And because OFDM (orthogonalfrequency division multiplexing) has some advantages like a better anti-fade andanti-inter-symbol interference ability and a higher spectral efficiency, it gets lotsof attention from scholars. However, in practical, the traditional OFDM systemhas some disadvantages. It is easy to bring interference to the system by thefrequency offsets and phase noise in the process of signal transmission and thecomplexity of the system is increased by adaptive modulation technology.Focusing on these disadvantages, this paper proposes the OFDM system based onwavelet theory which not only improves the anti-jamming capability, but alsoreduces the complexity of the system.By the study of wavelet theory, this subject makes a research on waveletfilter bank and two channel filter bank. It is described of the work principle ofthe traditional OFDM system in the paper, then after studying of the advantagesand disadvantages of the system, this paper proposes a new multi-carriermodulation technology which combines the wavelet packet transform with thetraditional OFDM system on the basis of inheriting OFDM advantages that useswavelet transform instead of the Fourier transform of traditional system andplays a role in the modulation and demodulation. And the realizability of thissystem is proved by the discussion. Because different wavelet bases havedifferent characteristics, the paper analyses and compares different wavelet basesby the simulation. And compared with the traditional OFDM systems, the OFDMsystem based on wavelet packet transform has been improved greatly inperformance. On the basis of wavelet packet transform, this paper makes a deep researchon wavelet lifting scheme and proposes an OFDM system based on waveletlifting scheme. This paper focuses on studying the influence of different waveletbases to the OFDM system based on wavelet lifting scheme. By analysis, it canbe concluded that how to choose the best wavelet basis in LWT-OFDM system.Finally it is proved that the bit error rate of this system is better than traditionalsystem by the simulation.