Research On Physical Layer Algorithms In CMMB

Mobile television is one of the modern technological trends expected to rev-olutionize conventional provisioning of broadcast services, and represents an emerging hotbed for multimedia applications because it brings traditional televi-sion services and on-demand audiovisual content to mobile devices. Among var-ious mobile television technologies is China Mobile Multimedia Broadcasting (CMMB), a mature industrial standard developed by the CMMB work group, an organization initiated by China's State Administration of Radio, Film, and Tele-vision. This thesis mainly studies efficient physical layer algorithms for CMMB.The thesis first discusses main modules of CMMB physical layer, analyzes characteristics of wireless mobile radio channels, and exploits the effects that frequency-selective fading or fast fading channels could exert on wireless sig-nals. Also several wireless channel models suitable for the CMMB are summa-rized. The transform process for encoding highly structured LDPC in CMMB based on rapid LU decomposition is derived and the strategy of min-col-prod LU decomposition of sparse matrix is given. Considering the CMMB receiv-ing terminals'constrained capacity of energy and capability to calculate, a low complexity LDPC decoding algorithm is put forward. Frame synchronization and frequency synchronization algorithms taking advantage of the two identi-cal frequency-domain pseudo-random sequences in the frame structure are pro-posed. The algorithms can function reliably under the condition of both low SNR and high frequency offset. Once again, taking into account that the mobile terminal power consumption and computing power is limited, specific channel estimation algorithm is developed. Channel responses at pilot sub-carriers are es-timated through the method of LS and channel responses at the data sub-carriers are obtained through DFT interpolation. The thesis also addresses the uneven distribution of pilot sub-carriers in an OFDM symbol.