| Orthogonal frequency division multiplexing is a key technology in the modern communication system of multi-carrier modulation.The advantages of combating frequency-selective random fading and achieving high bandwidth efficiency rate makes it becomes one of the candidates in the development of future communication.Channel estimation in OFDM system is important in signal processing,and the accuracy of the estimation will directly affect the quality of the whole communication system.In the first,this paper focus on analysing the propagation characteristics and the fading characteristics of wireless channel.According to the multipath fading,the paper has done in-depth research in channel estimation and equalization,putting forward appropriate improvement in traditional estimation algorithm and traditional equalization algorithm.Traditional LMMSE estimation algorithm channel estimation should be deal with complex matrix,and the algorithm needs to predict the priori knowledge of the channel,but it is difficult apply to the time-varying wireless channel.According to the defect of the traditional LMMSE estimation algorithm,the paper puts forward an improved LMMSE channel estimation algorithm.The improved algorithm mainly use weighted average method to estimate subcarrier channel frequency response.The experimental results show that the performance of the proved algorithm is better than LS algorithm and the singular value decomposition LMMSE estimation algorithm,and the bit error rate is close to traditional LMMSE algorithm.In the modern communication system,as the number of multipath time delay and the subcarrier increasing,the system will be more and more complex in processing signal.After the channel estimation,the channel equalization technology can help the deep-fading signal to make some necessary "compensation".Traditional channel equalization would increase the complexity of the receiver equipment and the user’s inconvenience.But the pre-equalization can solve this problem.Introducing the limited precoding technique in the pre-equalization,added an appropriate scheme between the sender and the receiver equipment before the channel equalization.this methods can not only reduce the complexity of the system,also effectively improve the performance of channel estimation.The simulation experiment indicates that the improved equalization algorithm perform better than the traditional equalization algorithm and linear equalization algorithm. |
