Research On Channel Coding And Modulation In Digital Amplitude Modulation Broadcasting System

With the quick development of digital technology, computer hardware and wireless communication, analog radio broadcasting meets more challenge. With the grow up of mobile communication and internet, many competitors against wireless terrestrial radio appear, such as mobile digital video broadcasting etc. Additionally, with the mass of electronic radio, the environment for broadcasting becomes worse and worse. The quality of traditional analog radio can not satisfy the requirement of the listeners. And analog radio broadcasting has many disadvantages: awesome listening effect, unique service and easy to be distorted. In a word, it's a trend to use digital radio broadcasting to replace analog radio broadcasting.Focus on mid- and short-wave channels below 30MHz, the dissertation considers some key technologies in digital amplitude radio, including channel coding and modulation. Research shows that low-density parity-check codes (LDPC) has perfect performance close to Shannon limit and low decoding complexity, LDPC-based coding modulation scheme will be studied. According to the state of the art on digital radio broadcasting and trends on it, orthogonal frequency division modulation (OFDM) is selected as in digital radio broadcasting system.Because there are many channels which are memorable, decoding on channel with memory for LDPC is studied. Focus on finite-state Markov channel, an improved decoding algorithm for LDPC based on noise soft-decision is presented and the corresponding factor graph representation is given. The algorithm consists of two parts: standard sum-product algorithm (SPA) for LDPC and forward-backward (FB) algorithm for Markov channel. The performance is improved by passing soft-decision for noise between the two parts. Considering more cycles in the factor graph with the introduction of Markov channel node, we use the probabilistic scheme to update the message during the iterations for decoding.In communication system, it's necessary to adapt channel code rate to different channel state. One of strategies is using different code with different code rate, but it is difficult to implement. Other strategy is using rate-compatible punctured code, in which some parity bits are punctured systematically in the transmitter. The thesis discusses punctured low-density parity-check code, analyzes sum-product decoding algorithm for punctured LDPC using Gaussian Approximation (GA) over Additive...