Algorithm Research And Implementation On Multicarrier Synchronization Of CMMB

As a new kind of multimedia, mobile multimedia broadcasting (it can be generally called mobile TV) is drawing more and more people's attention with the rapid development of information technology. The CMMB (China Mobile Multimedia Broadcasting), which adopts Orthogonal Frequency Division Multiplexing (OFDM) technology, is the most advanced in industrialization process and it has a very good development foreground. So, it is very meaningful in reality to research CMMB.The CMMB can resist on frequency-selective fading very effectively, which is produced by multi-path effect, and it has a good performance against multi-path. While the OFDM system is very sensitive to the frequency offset caused by Doppler frequency shift, local crystal oscillator frequency shift and instability. Carrier frequency offset can result inter-carrier interference (ICI),so the CMMB receiver is necessary to synchronize the carrier frequency. In this paper, the algorithm and hardware implementation of multi-carrier synchronization of the CMMB receiver are researched.Multi-carrier synchronization loop of CMMB is comprised of two parts: carrier frequency offset estimation part and carrier frequency correction part. According to different range and stage of frequency offset estimation, the carrier frequency offset estimation part can be divided into three small parts: fractional frequency offset fine estimation in acquisition stage, integer frequency offset coarse estimation and fractional frequency offset fine estimation in tracking stage. The three small parts adopt different algorithm and realization respectively to do frequency offset estimation. The fractional frequency offset fine estimation in acquisition stage adopt two segments of repeating sync sequence and the cyclic prefix (CP) in time domain, while the integer frequency offset coarse estimation uses sync sequence in frequency domain and the fractional frequency offset fine estimation in tracking stage uses pilot in time domain. The carrier frequency correction part employs the correction sequence produced by numerically controlled oscillator (NCO) to correct the carrier frequency.The C model and Verilog HDL register transfer level (RTL) model of this algorithm have finished the simulation and testing. According to the result of simulation and testing, the algorithm of carrier frequency offset estimation and frequency correction can synchronize the carrier very quickly, and it can resist on additive white Gaussian noise (AWGN) and OFDM symbol offset. It can meet the CMMB specification about resisting on frequency offset. The algorithm and realization is relatively simple, and the hardware resource occupied by the carrier synchronization is relatively little. So, it is ready for Application Specified Integrated Circuit (ASIC) tape-out.