Joint Optimization Of Channel-coding And Modulation For Digital FM Broadcasting

In the informationization process of human society, people's demands for informa-tion diversify are growing rapidly. In the meantime, the electromagnetic condition ofthe wireless channel becomes more complicated and overcrowded. This challenges tra-ditional analog AM and FM radio in its performance and reliability. The existing radiobroadcasting forms nowadays no longer satisfy people's growing demands of spiritualand cultural life. The digitalization of radio broadcasting has become an inevitable trendas the technology develops. Up till now, there still hasn't formed a unified internationalstandard for digital radio in the FM wave band.This thesis focuses on major aspects of FM radio like channel features, systemcomplexity and engineering implementation, then a digital frequency modulation systemcalled DFM is proposed. Channel coding methods and coded-modulation joint optimiza-tion are studied thoroughly to improve the power bandwidth efciency.In the channel coding part a short code-length, irregular, and low density paritycheck (LDPC) coding method is designed which achieves near-Shannon-Limit decodingperformance. A quasi-cycle coding method is further studied to lower the complexityof the receiver. Even if decoding complexity is added into consideration, the decodethreshold of proposed short-code-length, quasi-cycle irregular LDPC coding from theShannon limit is only1dB.In the coded-modulation joint optimization part, a reference design rule for the jointoptimization of coding and modulation is put forward. Applying this design rule on acoded modulation system, we can achieve a better power bandwidth efciency than theexisting multilevel coded modulation and bit-interleave coded modulation while this ruledoes not introduce any iteration between the decoder and the metric unit, thus the powerefciency of the DFM system is significantly improved. This design rule apply well inMIMO systems also without any iteration between the decoder. Compared to the iteratedMIMO, this method reduces the decoding threshold by2.5dB.The DFM broadcasting channel fits a typical flat fading channel. Frequency inter-leaving does not work in this situation and time-interleaving introduces unbearable delayin slow-varying channel. So antenna diversity must be used to solve this flat-fading prob- lem. To simplify the receiver as much as possible, the cyclic delay diversity (CDD)transmitting technology is chosen because of its invisibility to the receiver. This solutiondoes not increase the receiver complexity. A design method is proposed to determine theCCD cyclic delay which achieves a high antenna diversity gain.A prototype system design of DFM has been implemented. The system performancehas been accessed through the simulation.