Research And Implementation Of Channel Estimation Technology In Mc-cdma System

Muti-Carrier Code Division Multiple Access (MC-CDMA) technology, which combines OFDM and CDMA, with advantages such as high transmitting speed, strong ability to defend the multi-path effect and high bandwidth efficiency, has been focused on these years and becomes a research hotspot in the communications field. This paper researches on the channel estimation technology in MC-CDMA system.After a brief introduction to the basic principle of MC-CDMA system and the wireless channel model, this paper focuses on the pilot-based channel estimation mainly, which could be divided into channel estimation based on comb-type pilot arrangement and block-type pilot arrangement. Because of the simple structure, LS(Least Square) algorithm has be commonly used in the practical project, but its performance is poor. Kinds of noise reducing algorithms based on the block-type pilot arrangement are mentioned to increase the performance of LS algorithm.The main content of this thesis includes:1. Research on the channel estimation algorithms based on comb-type pilot arrangement. Analyzed the compatible environment of comb-type pilot and the pilot distance selection measure. Ulteriorly, analyzed the effects of the pilot distance to the bit error probability(BER) performance of four algorithms. The results indicate the performance of the algorithms could increase a certain extent, by reducing the pilot distance.2. Research on the channel estimation algorithms based on block-type pilot arrangement. Analyzed the compatible environment of block-type pilot and the pilot distance selection measure. Ulteriorly, analyzed the effects of the Doppler frequency shift to the BER performance of the copy algorithm and the feedback algorithm. The results indicate that the copy algorithm is suitable for the channel of low Doppler shifts and the feedback algorithm is suitable for the channel of high Doppler shifts.3. Research on the average noise reducing algorithm. Analyzed the effect of the number of the pilot symbols continuously inserted to the BER performance of the algorithm. The results indicate that the performance of the algorithm could increase a certain extent, by properly increasing the number of the pilot symbols continuously inserted.4. Research on the time-domain noise reducing algorithms. Analyzed the existent time-domain noise reducing algorithms; Analyzed the effects of pathway-saved number or threshold to the BER performance of the corresponding algorithms;A new time-domain noise reducing algorithm is proposed, which based on the delay informations of the multi-path channel. By using the delay informations of the multi-path channels gotten by the correlation operation and threshold judgement, the new algorithm reduces the noise component of the estimated results of LS algorithm. Analyzed the effect of the threshold adjusting gene to the BER performance; Compared the performance of the time-domain noise reducing algorithms above; The results indicate that the new algorithm is optimal under the low SNR. 5. After the theories researching and simulating above, the paper gives the FPGA implementation scheme of the channel estimation module by VHDL; The scheme is validated by simulation .