Channel Encoding Study And Its Application And Implementation In TD-SCDMA

This thesis introduces three major technique standards in the third generation mobile communications system: CDMA2000, WCDMA and TD-SCDMA. A comparison among these three standards and their interface prameters in air are provided. It also briefly covers the importance of TD-SCDMA in the developing 3G communications network of China.In the digital communications system, channel encoding is a coding to decrease the bit error ratio(BER) and to improve the reliability. Channel coding acts as the key role to improve communication quality. To increase the reliability of radio channel, TD-SCDMA system mainly adopts three coding schemes: no coding, convolutional coding and Turbo coding.After a brief description of Sub-Grouping code, the codec theory and circuit implementation of convolutional code are described in detail. The Turbo coding and MAP decoding algorithm are analyzed in detail. To decrease the complexity of MAP algorithm, two modified algorithms, Log-MAP and Max-Log-MAP, are proposed with certain sacrifice of BER. Those key parameters which determine the performance of Turbo code are emulated using Log-MAP algorithm in Gaussing White Noise channel. The emulation performance curve and summary are also provided.After introducing the basic concepts and structure of channel coding in TD-SCDMA, each individual module in channel coding is described in detail. With the thorough study of those modules, emulation and implemented with C program and Matlab, some valuable conclusions are drawn.