Algorithm Design On Channel Estimation And Synchronization For CMMB Inner Receiver

China Mobile Multimedia Broadcasting (CMMB) standard is the mobile reception standard of Chinese digital video broadcasting industry. CMMB uses orthogonal frequency division multiplexing (OFDM) techniques as its implementations. OFDM features by high data transmission rate, high reliability and can avoid the effect of intersymbol interference (ISI) effectively. In OFDM inner receiver, the research of channel estimation and synchronization techniques are of paramount importance. Based on the OFDM scheme in CMMB, this thesis focuses on the channel estimation technique, symbol synchronization and carrier synchronization techniques in time domain, exploring the applicable algorithms for CMMB receiver.Firstly, this thesis introduces the major characteristics and physical layer of CMMB standard, and then, the characteristics of wireless channel are briefly depicted, and several channel models are chosen for the simulation platform. The performance of system with nonideal estimated parameters is also analyzed.After that, regarding the issue of CMMB synchronization in time domain, in order to get a quick estimation of initial frequency offset and timing offset, according to features of PN sequences which is band-limited in frequency domain and the explicit study of traditional joint frequency and timing offset estimation algorithm based on maximum correlation (MC) norm, this thesis proposes a weighted MC algorithm to estimate symbol timing offset and carrier frequency offset. Compared with traditional MC algorithm, this algorithm effectively reduces the impact of multi-path in wireless channel to the estimated parameters, achieves a quick initial synchronization, decreases the probability of timing with a positive offset and shortens the range of the estimation offset. At the same time, the error floor of decimal frequency offset estimation with this algorithm can greatly be decreased with high SNR and the precision of estimation is obviously improved.Finally, regarding the issue of channel estimation in CMMB, this thesis studies various techniques related to channel estimation and the mean square error (MSE) reduction algorithm particularly. According to the time slot based frame structure in CMMB, a comprehensive MSE reduction scheme that is applicable in CMMB is proposed based on the traditional DFT filtering technique and the technique of filtering in both time and doppler domain. This comprehensive scheme further depresses the noise taps within maximum delay of wireless channel and improve the decreased performance caused by the compulsory reduction to zero in dopplor domain when using filtering technique in both domains. This scheme is multi-path insensitive and dopplor insensitive, and can improve the performance of system further.