The Study Of Channel Equalization Based On The QAM Modulation Of OFDM

With the constantly introduction of new communication technologies, the requirements ofcommunication quality and transmission rate are increasingly higher. Orthogonal frequencydivision multiplexing (OFDM) technology is a multi-carrier transmission manner, and it caneffectively improve the bandwidth utilization of communication systems and effectivelycombat the interference caused by the multipath channel. With these advantages, it hasbecome a research focus in recent years.In a wireless communication system, the transmission of data symbols are vulnerable tomultipath effect, Doppler effect and shadow effect. While OFDM is a multi-carriertransmission system, it makes the data symbols in the transmission process producinginter-symbol interference (ISI) and inter-carrier interference (ICI), in order to realize thecompensation of interference signal distortion, channel equalization processing technology isusually used.Firstly, this article gives a brief introduction to the current development of OFDMtechnology and equalization technology, including overview of OFDM systems theory, and itis derived and analyzed for the generation mechanism of inter-symbol interference andinter-carrier interference, then the article describes the QAM modulation and demodulationmechanism in the OFDM system. Subsequently, the article introduces the theory of equalizer,then derives and analyzes several algorithms of channel equalization. And an improvedalgorithm based on modified constant modulus blind equalization algorithm is derived andanalyzed. Finally, it compares the performance in MATLAB simulation among the newproposed algorithm and several traditional algorithms, the simulation results show that thenew algorithm can achieve good tracking for channels with carrier frequency, and eliminateinter-symbol interference. Comparing with constant modulus blind equalization algorithm andmodified constant modulus blind equalization algorithm, the new algorithm has significantlybetter performance in the convergence, equalization effect, robustness and tracking features,meanwhile it is better to adapt equalization processing of wireless channel.