协同无线通信的分布式喷泉编译码技术研究

【作者】 杨玲；

【导师】 文红；

【作者基本信息】 电子科技大学 ， 通信与信息系统（专业学位）， 2012， 硕士

【摘要】 喷泉码是一种新型的删除码,它可以源源不断地产生编码数据包,并灵活地进行码率控制。在实现上,它采用的是一种单向异步传输机制,具有低延迟、高效的特性,对时变信道有很强的适应能力。此外,由于喷泉码的编译码复杂度较低且数据包不要求连续,非常符合深空链路易中断的特点,同时与其它差错控制方式,如混合反馈重传(HARQ)相比,其不需要反馈的特性尤其适合深空通信的需求。但是,喷泉码的性能受码长的影响非常大,所以要想使其具有好的性能就必须用较长的码长。在深空通信中,中继星上飞行器等的承载能力、存储能力等极大受到限制,因此需要设计短帧长好性能的喷泉码,在此基础上,将协同通信的概念扩展到了超远距离的深空信道编码上,因而也就产生了分布式喷泉码。事实证明,分布式编码技术可以有效的提高整个系统的性能。本论文在对短长度喷泉码进行分析的基础上,将分布式编码技术应用于喷泉码中,研究了在多源单中继模型下的分布式喷泉码的性能。在本论文中,我们首先介绍了喷泉码和协同通信的背景知识。对喷泉码中的一类实用码--LT码的编码和译码过程进行了详细的介绍,在此基础上对各种长度的LT码进行了仿真分析,给出不同长度在不同信道删除率下的性能。针对中继传输中LT码的新的应用,我们介绍了分布式喷泉码的基本原理,其中包含了LT码的解卷积过程、源节点的编码规则以及在中继节点处进行的合并规则,具体给出了两信源、单中继模型和四信源、单中继模型的分布式LT码编码方案。并将两种分布式LT码和LT码在删除信道环境下进行了仿真比较,其结果表明：分布式LT码的编码方案可以有效的提高整个系统的性能。最后将HARQ错误控制系统与LT码传输的系统进行了传输效率的比较。更多还原

【Abstract】 Fountain Codes are a new class of erasure codes, which can generate infinite encoded symbols and can control rate flexibly. In implementation, fountain codes adopt a simplex mechanism of asynchronous transfer, which possesses high-efficiency and low-delay, adapts the time-variant of channel easily. In addition, its complexity of encoding and decoding is low and symbol packets do not require to be continuous. Therefore, it is very consistent with characteristics of deep space link easy to break. But performance of fountain codes greatly affected by the code length, the good performance of fountain codes must be used longer code length. In the deep space communications, the device in relays and stars is source energy limited. It is necessary to design short frame length with good performance of fountain codes. Under this basis, we extend cooperative communications concept to long-distance on the deep space channel code, thus arise the concept of distributed fountain codes. It is the fact that system performance can be improved by distributed coding. In order to improve the performance of the cooperative communications system, the distributed LT codes are designed in this paper.In this paper, firstly we introduce fountain codes and cooperative communication background and encoding and decoding process of LT codes that is a kind of good performance fountain code in detail. Extend simulations are given for LT codes with various code lengths under the different delete the probability. For relay transmission LT codes can find the new application. After introducing fundamentals of distributed foundtain codes, including deconvolution of LT codes, the encoding rules at the source and consolidation rules at the relay, the distributed LT codes for the scenarios in which two sources or four sources communicate with a common sink through a relay are described in detail. Analyzing and comparion results of LT code, two-source distributed LT codes and four-source distributed LT codes are provided. The results show that distributed LT codes can offer a significant performance improvement. At last, we compare the transmission efficiency of HARQ error control system with those of system with LT codes.更多还原