在快变无线信道下,接收信号的信噪比呈现大动态变化，给通信系统设计带来挑战。本项目研究快变信道下的自适应编码调制理论与技术：（1）将OFDM快变信道等效为并行的突发与随机差错并存的复合信道，研究适用于快变信道的RS-LDPC级联方法、准循环SC-LDPC码构造与性能分析及低复杂度译码方法，提出新的RS-LDPC级联码结构和可变码率SC-LDPC码；（2）可变权重系数的码率兼容调制（RCM）技术：在不同信噪比区间，使用不同稀疏度和元素大小的映射矩阵，具有速率连续可调、高传输速率和对信噪比估计误差不敏感的优点，提出低复杂度RCM解调方法；（3）利用LDPC编码与RCM调制映射的结构特征，研究LDPC与RCM的联合优化设计方法，提出低复杂度双涡轮解码与解调技术、低差错平台的迭代处理技术；（4）开发系统验证试验平台，将所提技术在实验平台进行验证。本项目研究为改善快变信道下的无线通信性能提供支撑。

In rapidly varying wireless channels，the received signals manifest the feature of rapid variations of signal to noise ratio (SNR) within a wide dynamic range, which brings a challenge to reliable wireless communications. The project will investigate adaptive modulation and coding (AMC) technologies for OFDM systems over time-varying channels, which will help to significantly improve the performance of communication systems. (1) By modeling the rapidly varying channels as a parallel one combined with abrupt and random errors, new methods for RS-LDPC concatenation, construction of SC-LDPC codes, and their performance analysis and low-complexity decoding will be investigated. And new RS-LDPC concatenation structure and rate compatible SC-LDPC codes will be proposed for reliable communications in rapidly varying channels. (2) A new mapping scheme with variable weighting sets for rateless coding modulation (RCM) will be explored by exploiting different mapping matrices under various SNR regimes, making it have the advantages of continuously adjustable and high transmission rate and robustness to SNR estimation errors. And efficient algorithms will be proposed for RCM demodulation to significantly reduce the computational complexity while maintaining the same BER performance. (3) Joint LDPC and RCM optimization will be studied by taking into account the structural features of LDPC coding and RCM mapping matrices, aiming to propose low-complexity turbo techniques for joint LDPC decoding and RCM demodulation, and effective measures to lower the error-floors in the iterative processing. (4) A test platform will be developed for the verification of the proposed schemes. The research of this project will help to enhance the performance of wireless communications over rapidly varying channels.