Study On Synchoronization Algorithms And System Design Of CMMB Receiver

Along with the development of communication and information technologies, mobile multimedia broadcasting service is becoming an important application in the broadcasting and television industry. Various mobile multimedia broadcasting standards have been announced, among which China Mobile Multimedia Broadcasting (CMMB) standard is the one worth paying attention to. CMMB uses orthogonal frequency division multiplexing (OFDM) technique and realizes the high speed transmission of audio and video information by making full use of OFDMCharacteristics featured by high spectral efficiency and multipath immunity. However, compared with the single-carrier systems, CMMB system also has some technical barriers, one of which is synchronization. Therefore, this thesis focuses on investigating symbol synchronization, carrier synchronization and clock sample synchronization based on CMMB system.Firstly, this thesis introduces the architecture and key techniques of OFDM-based CMMB system.Then, the broadcasting environment is studied. The complex terrain conditions, which are possibly faced in the terrestrial transmission application of CMMB system. , are studied, too. The symbol synchronization errors, carrier error as well as sampling clock error for the impact of the receiver are analyzed.After that, After the CMMB system applicable to the new synchronization algorithms which are applicable to the CMMB system are selected, namely, Symbol coarse Synchronization and Symbol fine synchronization; carrier integer frequency offset Synchronization, carrier decimal frequency offset Synchronization and carrier decimal tracking; clock sampling synchronization tracking. These algorithms in poor conditions can also obtain good system performance, and estimate exact numerical sync correction values which can meet the requirements of CMMB system.Finally, the CMMB receiver synchronization system is designed to achieve synchronization of the overall program. and the algorithms ,including Symbol coarse Synchronization and Symbol fine synchronization; carrier integer frequency offset Synchronization, carrier decimal frequency offset Synchronization and carrier decimal tracking; clock sampling synchronization tracking, are turned into fixed-points, and are designed into a corresponding hardware implementation structure to adapt to hardware implementation. Also, the compensation structure of the synchronization system is designed to complete the actual algorithm and structure of the compensation part of the system.The program takes full account of the characteristics of the CMMB system, efficiently uses the sync signal which is in front of the OFDM signals as well as the pilots which are mixed in the OFDM signal. The design gives full consideration to the complexity of hardware implementation, and realizes OFDM synchronization under a bad environment, greatly reducing the ICI and ISI.