Cmmb Mobile Digital Tv System, The Carrier Recovery And Clock Synchronization Algorithm

With the rapid development of information technology and telecommunication domain, mobile digital television as an emerging multimedia service has become a popular hotspot. CMMB (China Mobile Multimedia Broadcast) which is issued by China Radio, Film and Television Bureau has adopted STiMi technology as its core transmission technology. STiMi technology is researched and developed independently by Chinese. CMMB system better adapts to the Chinese market and is a very promising mobile digital television system.Synchronization is very important in telecommunication systems, the synchronization error will causes inter-symbol interference (ISI) and inter-carrier interference (ICI), and affects the system performance badly. This thesis deals with the algorithms of carrier frequency recovery and timing synchronization, where timing synchronization includes both symbol timing synchronization and sampling clock synchronization.In the thesis, firstly introduces the mobile digital television standards and the advantages of CMMB system briefly. Secondly based on the OFDM technology, the CMMB mobile digital television system is introduced in detail. Thirdly, after giving a short introduction to the characteristics of wireless channel, the impacts of the synchronization error in CMMB system are analyzed. Based on the CMMB system signal model, symbol timing synchronization error, sampling clock offset error and carrier frequency offset error are analyzed carefully.Clock synchronization includes symbol timing synchronization and sampling clock synchronization. Algorithms of symbol timing synchronization and sampling clock synchronization are proposed in CMMB systems. Symbol timing synchronization includes coarse symbol timing synchronization and fine symbol timing synchronization, and sampling clock synchronization includes coarse sampling clock synchronization and fine sampling clock synchronization. In order to verify the feasibility of clock synchronization algorithms, a series of simulations are performed in Chinese typical channel models, and the simulation results are analyzed finally.Algorithms of carrier frequency synchronization are also proposed in CMMB system. Carrier frequency synchronization includes fraction carrier frequency synchronization and integer carrier frequency synchronization. The fraction carrier frequency synchronization algorithm is based on the two same synchronization signals of the preamble, and the integer carrier frequency synchronization algorithm utilizes the continual pilots of OFDM symbols. In order to verify the feasibility of carrier frequency synchronization algorithms, a series of simulations are performed in Chinese typical channel models, and the simulation results are analyzed finally.