【作者】 胡紫巍；

【导师】 袁超伟；

【作者基本信息】 北京邮电大学 ， 信号与信息处理， 2013， 博士

【摘要】 随着移动互联网技术和多媒体业务的飞速发展,如何提升无线通信系统的有效性和可靠性是下一代移动通信面临的关键问题。多输入多输出(MIMO)技术可以在不增加带宽和发射功率的情况下成倍地提升系统的频谱效率,成为下一代无线通信中的关键技术。协作中继系统通过节点间共享天线,可以构成一个虚拟MIMO系统,从而实现较高的分集增益和频谱效率。在MIMO和虚拟MIMO系统中采用空时编码技术可以大大提高系统性能,近年来得到了广泛应用。本文对MIMO和协作中继系统中的空时编码技术进行了研究。本论文在国家科技重大专项(2009ZX03002-009-01)和国家自然科学基金(60872149,60672132)的支持下,研究了MIMO和协作中继系统中的空时编码技术。本论文主要工作及创新成果包括：(1)广义平衡空时分组码(EBSTBC)是一种考虑发送端已知信道状态信息的典型空时分组码,该方案编码速率为1,能够实现全分集,并且适用于发送端为任意发射天线数的系统。但是该方案的接收端采用穷举方法计算反馈信息,具有很高的计算复杂度。针对这一问题,本文提出了一种低复杂度的EBSTBC反馈信息计算方法。该方法首先分析了与反馈信息相关的编码增益,并通过两步求最优的的方案确定此次传输的反馈信息。与已有方案相比,所提方案可以在系统可靠性损失很小的情况下,极大地降低接收端计算反馈信息的复杂度。(2)全速率全分集的空时分组码(FRFD-STBC)具有全速率全分集的特性,但是其译码复杂度仍然较高,与调制阶数的平方成正比。为了进一步降低FRFD-STBC的译码复杂度,论文提出了一种基于有限反馈预编码技术的编译码方案。该方案通过设计预编码参数,使得发送信号的实部分量和虚部分量在传输过程中保持正交,因此在接收端可以分别译出信号的实部分量和虚部分量,所提方案译码复杂度与调制阶数呈线性关系,与FRFD-STBC方案相比,所提方案能够以少量的比特反馈为代价,极大地降低了译码复杂度。(3)在多中继节点的协作中继网络中,基于广义ABBA(GABBA)码的分布式空时码能够适用于中继数大于2的场景,且能够保证不牺牲编码速率,但是这种准正交编码方案无法避免传输过程中的干扰,会影响系统的译码性能。为了进一步提升系统的可靠性,本文充分利用接收端信道状态信息,提出了一种基于1比特反馈的改进方案,并将其扩展至反馈信息为相位码本的情形。该方案通过对干扰项的分析,以最大化信号干扰噪声比为目标,设计反馈信息。与已有方案相比,所提方案以1比特的反馈量为代价,显著改善系统的误比特性能。(4)在半双工多中继协作网络中,已有分布式空时码技术只能实现传输效率为1/2,为了提高传输效率,本文提出了一种基于中继选择的连续转发分布式空时码方案。所提方案适用于中继数不少于4的多中继协作场景,在每一时隙依据双中继选择准则选取两个可用中继节点参与下一时隙的协作转发,转发策略采取基于Alamouti分布式空时码的连续放大转发。为了消除连续转发带来的中继间干扰并保证系统的分集增益,本文提出了一种连续干扰消除的方法,并给出了接收端的信号检测算法和三种双中继选择准则。所提方案能够在不损失分集阶数的前提下,使多中继协作系统的传输效率接近1。在相同传输速率下所提方案能够获得比已有分布式空时码更低的误比特率。同时,双中继选择准则的引入还让所提方案对多中继协作系统有更强的灵活性和适用性。更多还原

【Abstract】 With rapid development of Mobile Internet technology and multimedia services, it is an issue problem for next generation wireless communication to increase the effectiveness and reliability of wireless communication system. Multiple-Input Multiple-Output (MIMO) technology is able to extremely upgrade the spectral efficiency, without using more bandwidth or transmit power. And MIMO is recognized as a key technology for next generation wireless communication system. Every node in a Cooperative communication system can share its antenna with others, and a Virtual MIMO system is formed. The system can also achieve good performance in spatial diversity and spectral efficiency. Space-Time Coding technology can bring great performance improvement for MIMO and Virtual MIMO systems, and it has also been widely applied recently. This paper has made a deeply study of Space-Time Coding technology in MIMO and Cooperative communication systems.Under the support of National Significant Science and Technology Special (2009ZX03002-009-01), and The National Natural Science Foundation of China (60872149,60672132), this paper have made a research of Space-Time Coding technology in MIMO and Cooperative communication systems. The main works and innovations can be concluded as follows:(1)Extended Balanced Space-Time Block Coding (EBSTBC) is a special Space-Time Coding scheme considering channel state information available for transmitter. This scheme can guarantee full-diversity while achieving coding rate of1,what’s more, it is also suitable for the base station with any number of transmit antenna. But exhausting search method is applied to calculate the feedback information, which is of great complexity. In order to solve the problem, this paper proposed a low-complexity calculating scheme of feedback information for EBSTBC. First of all, the expression formula correlated to feedback information was investigated and analyzed, and the feedback information for this transmission can be decided due to two-step optimization scheme. Comparing to the former scheme, the proposed scheme can greatly decrease the complexity for calculating feedback information, at the cost of little loss in reliability of the system.(2) Full-Rate Full-Diversity Space-Time Block Coding (FRFD-STBC) has the property of full rate and full diversity, however, its decoding procedure is very complex, and the complexity order is proportional to the square of the modulation order. For the purpose of cutting down the complexity of decoding of FRFD-STBC system, a novel code-and-decode scheme based on limited feedback pre-coding technology is proposed. After carefully design of pre-coding parameter, the real part and the imaginary part of the signal can keep orthogonal during the transmission. And the real part and the imaginary part of the signal can be decoded separately. The complexity order of the proposed scheme is proportional to the linear of the modulation order. Comparing to FRFD-STBC scheme, the proposed scheme can greatly decrease the decoding complexity at the cost of a few bits feedback.(3) In the cooperative networks with several relay nodes, distributed space-time coding based on generalized ABBA (GABBA) codes can be applied to the scenes with more than2relay nodes, and this scheme can also guarantee coding rate. But interference is unavoidable for GABBA codes, and it may affect the system performance. For the purpose of further enhancing the reliability, channel state information is made full use of, an improved scheme with1-bit feedback is proposed, and the feedback information is extended to case of phase codebook. After deeply investigation and analysis of interference term expression, feedback information is design according to maximizing signal to interface plus noise ratio. Compared with the existing scheme, the proposed proposal can achieve a better bit error rate while using one-bit feedback information.(4) Aiming at the problem that only1/2transmit efficiency is achieved for conventional space-time coding in half-duplex multi-relay networks, we proposed an efficient distributed space-time coding scheme based on double-relay selection. Successive relaying mechanism is adopted, and every two available relays are selected to forward signal according to some kind of double-relay selection criterion. The forwarding strategy is amplify-and-forward based on Alamouti distributed space-time coding. To cancel the inter-relay interference brought by successive relaying and insure the reliability, a successive interference cancellation scheme, a signal detection procedure and several double-relay selection schemes are given. The analysis and simulations indicate that the transmit efficiency of the proposed scheme can reach nearly1without any loss in diversity order, and the proposed scheme is able to achieve lower bit-error rate comparing to conventional scheme. Meanwhile, the employ of double-relay selection make the proposed scheme more flexible and applicable for multi-relay networks.更多还原