【作者】 李涛护；

【导师】 李建东；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2005， 硕士

【摘要】 深空通信中面临的问题之一就是如何在低信噪比信道环境下可靠地传递信息。为了能在噪声环境中可靠通信，从60年代开始，人们引入了信道编码方式。Turbo码是基于并行级联卷积码结构的纠错码，通过采用长码块结构和多次迭代的译码方法，Turbo码能够达到接近信道容量的极限的译码性能。由于这种优异特性，CCSDS遥测信道编码建议书在保留原编码方案的前提下加入了Turbo码，并维持了与CCSDS封装遥测建议书的兼容性。 根据CCSDS所建议的编码结构，文章给出了通过FPGA技术实现Turbo译码器的一种简洁有效的方法。在实现过程中，本文采用了滑动窗方式译码，并给出了一种完成Log-MAP算法中的max~*函数功能的简单方法。 首先，文章介绍了深空通信的一些背景知识，接着描述了Turbo码的通用编码结构，推导了MAP和Log-MAP两种译码算法的原理。在简要综述了CCSDS标准的编码结构之后，文章分析了影响译码性能的几个因素，然后对硬件实现过程中的相关参数的选取给出了建议。接下来的部分则描述了译码结构和FPGA实现中的相关知识。最后给出了文章设计后的一些心得和结论。更多还原

【Abstract】 In deep space communications,one of the problems is how to transmit message credibly in low signal-to-noise ratio(SNR)channel environment.To achieve reliable communication over a noisy channel,channel coding has been used since 1960s. Turbo codes are error-correcting codes based on parallel concatenation of convolutional codes and can achieve near channel capacity performance with a long block size and many decoding iterations.Due to the near-optimum performance ,Turbo codes have been an add-on option to the CCSDS telemetry channel coding recommendation without modifying the existing coding schemes and retained compatibility with the CCSDS packet telemetry recommendation.Given turbo encoder structure specified by CCSDS, this paper addresses the implementation of a simplified and efficient Turbo decoder in FPGA technology. To implement turbo decoder ,it adopted the sliding window method and devised a way to simplify max* function of Log-MAP algorithm.First,this paper presents some background knowledge of deep space communications.In the next section,it describes Turbo coding/decoding principles and two decoding algorithms:MAP and Log-MAP.After a brief overview of turbo encoder of the CCSDS standard,it analyses those factors that will influence its performance with the experimental results,and introduces how to choose some variables wisely in the implementation of Log-MAP decoder.The dedicated turbo decoder architecture and the FPGA prototype are described in the next section. Finally it gives the overall conclusions of the paper.更多还原