Interference Rejection Techniques In Digital TV Terrestrial Broadcasting System

Compared with the other two kinds of digital TV broadcasting modes (satellite and cable), digital TV terrestrial broadcasting faces a much more complicated channel, many kinds of interferences exist. Due to the buildings, transportation, trees, etc., transmitted signal arrives at the receiver through many paths, different path have different attenuation and delay, which is called multi-path interference; what's more, in each path the signal phase arrive at the receiver is different, causing a phenomenon called fading; the additive white Gaussian noise interference always exists; co-channel interference is caused when analog TV and digital TV broadcast at the same channel (simulcast); when the receiver is in the mobile reception mode there is a additional doppler frequency shift.The thesis concentrates on receiver techniques of single carrier mode of Chinese Digital TV Terrestrial Broadcasting (DTTB) standard. Main interferences and interference rejection techniques are analyzed and researched. The current interference rejection techniques are studied and some improvements are presented:A new method combining FFT to remove co-channel interference is proposed. Hardware implementation result shows its feasibility.Accounting on 4QAM-NR mode in Chinese DTTB standard, a new NR code decoding method is proposed. Since NR code is concatenated with Low Density Parity Code (LDPC), the new method actually is a method to extracting Log-Likely Ratio (LLR) from received symbols. Simulation shows that the new method is 0.2-0.6dB (in different LDPC code rates) better than current method.Decision Feedback Equalizer (DFE) is used to remove Inter-Symbol Interference (ISI) caused by multi-path interference. But DFE faces a problem of Error Propagation in severe interference channel, which means that when the decision is not reliable and the incorrect decisions will propagate through the feedback filter in DFE, this propagation will in turn cause even more incorrect decisions. In Chinese DTTB standard NR code is presented to combine DFE with NR code to reduce the phenomenon of error propagation. The principle is analyzed and the performance enhancement is obvious through simulation results.