协作通信中的载波间干扰消除算法研究

发布时间：2018-04-30 02:04

本文选题：协作通信 + 载波间干扰　；参考：《南京大学》2017年硕士论文

【摘要】：高数据速率、高频谱效率、可靠的协作通信技术能显著地增强无线通信系统在吞吐量、覆盖范围、体验质量方面的性能。而协作通信系统中频偏的存在引入了载波间干扰,从而破坏了信宿节点所接收到的信号的编码结构,大大降低了系统的性能。本文致力于消除协作通信系统中的载波间干扰。本文首先研究了同步协作通信的基础技术,包括分布式空时分组码以及它们的译码算法。由此本文总结出并证明了一条定理,即"等价最大似然译码定理"。该定理指出,如果协作通信系统的等效信道矩阵是一个复正交矩阵,那么迫零译码算法等价于最大似然译码算法。"等价最大似然译码定理"的证明过程提出了"简化的迫零译码算法"这一概念。随后本文在"等价最大似然译码定理"的指导下设计出了能完全消除载波间干扰的协作通信方案,适用于任意中继节点数的场景。在这一过程中,本文先学习了两种性能较好的协作通信方案,分别为频域翻转空频码和频率异步分布式Alamouti编码系统。然而这两种方案无法完全消除载波间干扰。因此本文提出并设计了频域翻转的正交空频码,包括二中继的频域翻转Alamouti码以及三中继正交空频码,并给出了任意数量中继节点场景下正交空频码的设计规律。依据"等价最大似然译码定理",本文设计了作用于正交空频码的简化迫零译码算法。正交空频码的翻转操作使得系统的等效信道矩阵复正交化,因此当存在频偏的协作通信系统采用这些正交空频码时,信宿节点仅使用简化迫零译码算法就能获得最大似然译码的效果。理论上的分析指出此传输方案的可靠性与同步协作通信方案的可靠性完全一致。最后本文评估了作用于正交空频码的简化迫零译码算法的性能。性能的评估包括误比特率性能和计算复杂度的评估。评估结果表明,作用于正交空频码的简化迫零译码算法能够完全消除载波间干扰,使系统的可靠性完全不受频偏的影响。即使考虑了协作通信第一阶段的译码错误,这个结论仍然成立。而在计算复杂度的评估上,简化迫零译码算法比现有方法具有更低的复杂度。
[Abstract]:High data rate high spectral efficiency and reliable cooperative communication technology can significantly enhance the performance of wireless communication systems in terms of throughput coverage and experience quality. The existence of intermediate frequency offset in cooperative communication system induces inter-carrier interference which destroys the coding structure of the signals received by the host node and greatly reduces the performance of the system. This paper is devoted to the elimination of inter-carrier interference in cooperative communication systems. This paper first studies the basic technologies of synchronous cooperative communication, including distributed space-time block codes and their decoding algorithms. A theorem called equivalent maximum likelihood Decoding Theorem is concluded and proved in this paper. The theorem points out that if the equivalent channel matrix of cooperative communication system is a complex orthogonal matrix, then the zero-forcing decoding algorithm is equivalent to the maximum likelihood decoding algorithm. " The proof of equivalent maximum likelihood Decoding Theorem puts forward the concept of "simplified Zero-forcing Decoding algorithm". Then under the guidance of the equivalent maximum likelihood Decoding Theorem, a cooperative communication scheme is designed, which can eliminate inter-carrier interference completely and can be applied to the scenario with any number of relay nodes. In this process, we first study two kinds of cooperative communication schemes, which are frequency domain flipped space-frequency code and frequency asynchronous distributed Alamouti coding system. However, these two schemes can not completely eliminate inter-carrier interference. Therefore, the orthogonal space-frequency codes in frequency domain flipping are proposed and designed, including the frequency domain flipping Alamouti codes for two relays and the orthogonal space frequency codes for three relays, and the design rules of orthogonal space frequency codes for any number of relay nodes are given. Based on the equivalent maximum likelihood Decoding Theorem, a simplified zero-forcing decoding algorithm for orthogonal space-frequency codes is designed in this paper. The flipping operation of orthogonal space-frequency codes makes the equivalent channel matrix of the system complex orthogonalization, so when these orthogonal space-frequency codes are used in cooperative communication systems with frequency offset, The maximum likelihood decoding effect can be obtained by using the simplified zero forcing decoding algorithm. The theoretical analysis shows that the reliability of this transmission scheme is consistent with that of synchronous cooperative communication scheme. Finally, the performance of the simplified zero forcing decoding algorithm for orthogonal space-frequency codes is evaluated. Performance evaluation includes BER performance and computational complexity evaluation. The evaluation results show that the simplified zero-forcing decoding algorithm acting on orthogonal space-frequency codes can completely eliminate inter-carrier interference and make the reliability of the system completely independent of frequency offset. This conclusion holds even if the decoding errors in the first phase of cooperative communication are taken into account. In the evaluation of computational complexity, the simplified zero-forcing decoding algorithm has lower complexity than the existing methods.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

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