基于低复杂度分组译码的多用户MIMO系统空时编码技术研究

Space-Time Coding (STC) is one of the promising technologies for multi-user wireless communication systems to transmit data with high-speed and high-quality, and its decoding performance and complexity are the two important factors necessary to be considered before put into practice. Currently, the STCs specially designed for multi-user systems, multi-user layered STC and multi-user jointly designed STC, need high-complexity Maximum Likelihood (ML) decoding to obtain full diversity gain,while using low-complexity decoding means loss of system performance and diversity gain.Just because of this, the project aims to explore the method to improve the performance and design full-diversity STC for multi-user STC coded systems with low-complexity group decoding. First of all, the equivalent channel model and its simplification method are achieved for multi-user layered STC, and a new approach is proposed to analyze the system diversity gain。By changing the traditional grouping schemes of group decoding algorithms, an innovative way to improve the system performance is then proposed and an criterion to choose the optimal grouping scheme which can follow the channel influctuations is studied. At last, based on partial interference cancellation (PIC) group decoding algorithm, full-diversity multi-user STCs together with the design criterion are proposed to further improve the system performance,which can also be extended to general multi-user MIMO systems, such as MIMO interference channel and MIMO X channel.The research in this proposal could provide a low-complexity and easily realized solution for multi-user MIMO system to achieve high-quality transmission.

空时编码技术是多用户无线通信系统实现高速率和高质量传输的关键技术，其译码性能和复杂度是实际应用必须考虑的重要因素。目前针对多用户系统的多用户分层空时码以及多用户联合设计的空时编码均需采用复杂度很高的最大似然译码才能获得全分集，采用低复杂度译码算法则会损失系统性能和分集增益。基于此，本课题旨在探索低复杂度分组译码的多用户空时编码的性能改善方法，主要研究内容包括：获取分组译码的多用户分层空时编码系统等效信道模型及简化方法，提出分析系统分集增益的新途径；创新性地提出通过改变分组译码算法的分组方案来改善系统译码性能，研究随信道状态实时变化的最优分组方案选择准则；结合部分干扰相消分组译码算法，提出全分集多用户空时码和设计准则，并推广到MIMO干扰信道和MIMO X信道等广义多用户系统，进一步改善系统性能。该课题研究可为多用户MIMO系统获取高质量传输提供低复杂度和易于实现的解决方案。

该项目针对多用户MIMO系统中的低复杂度检测和空时编码设计问题进行了研究，并取得了一定成果。空时编码技术是多用户无线通信系统实现高速率和高质量传输的关键技术，其译码性能和复杂度是实际应用必须考虑的重要因素。目前针对多用户系统的多用户分层空时码以及多用户联合设计的空时编码均需采用复杂度很高的最大似然译码才能获得全分集，采用一般的低复杂度译码算法则会损失系统性能和分集增益。通过该项目的实施，利用多用户空时编码矩阵的特点，建立了多用户空时编码系统的通用等效信道模型。基于该信道模型，通过分析分组干扰相消之后经典空时编码系统的等效信道矩阵，研究出干扰相消之后系统模型等价于相关衰落的单用户空时编码系统，结合相关衰落MIMO系统的分析方法，获得了系统的性能和分集增益；分析了迫整干扰相消算法时多用户空时编码系统的系统模型，提出了对应每个用户的空时编码矩阵只要满足非零奇异值属性即可获得全分集增益的多用户空时编码设计准则。该项目研究为低复杂度的多用户空时编码系统检测和空时编码设计提供了性能分析结果和理论支撑，为今后进一步的相关研究工作奠定了基础，低复杂度的优势也为在无线通信系统中的进一步应用展示了良好的前景。