Algorithm Research Of Timing Synchronization And Frequency Offset Estimation Based On DTMB Standard

The development of digital television represents the degree of a country's level of digital. The conversion of analogue TV to digital TV in China is expected to be completed by 2015. The development of terrestrial digital television is particularly important. Currently, there are three terrestrial digital TV transmission standards in the world. They are the U.S. ATSC, the European DVB-T and the Japan's ISDB. In August 2006, China formulated a standard named as DTMB(Digital TV terrestrial multimedia broadcasting),this brings about a certain challenges to the realization of terrestrial digital television's modulation and de-modulation. The implementation of national standard and the optimization of digital TV receiver performance directly affect the development of digital television, so the algorithm design of Digital TV receiver IP-chip is the key. There are three modules influenced the receiver performance. They are decoding, equalization and synchronization.The main work of this thesis is to study and realize the synchronization of DTMB digital TV receiver. In this thesis, first we introduce and compare those three standards briefly, and we describe the main technology of DTMB system, including constellation mapping, framing structure, TDS-OFDM system and so on. We focus on analyzing the characteristics of the dynamic multipath channel, synchronization error causes and influences, and also sum up the domestic and international existing timing recovery and frequency offset estimation algorithm of digital television terrestrial broadcasting transmission system, discuss the problems in algorithm. We find that the research space in the dynamic multipath channel is huge. And the multi-path processing is also a research challenge.In the thesis, we do some research on a timing recovery algorithm methodology based on PN-sequence frame synchronization, delay-locked Loop and sliding correlation technology. And in order to improve the accuracy of the timing error estimation in the dynamic multi-path channel, we synthesize different echoes correlation results; focus on the research of parasitic peak, pseudo echoes in the envelope and the instability. Computer simulation illustrates timing error can be controlled within the scope of+/-20ppm in the Rayleigh channel with high Doppler frequency.For the low performance of frequency offset estimation module in the dynamic multi-path channel and the difficulty of improving the estimation accuracy and broadening the scope of frequency offset estimation, we proposed an algorithm of frequency offset estimation in DTMB System. The main research work is the discovery of the rules of preliminary phase of frame head in phase shift mode, and utilizing the rules to optimize the fluctuation of frequency offset in dynamic multi-path channel. We changed the delay length and data length in correlation. Computer simulation illustrates the superior performance of the proposed algorithm in the estimation accuracy and the stability of remaining frequency offset. The remaining frequency offset fluctuates within+/-10Hz in high-Doppler multi-path channel, thus improving frequency offset estimation performance in the DTMB system.