面向全双工的新型MIMO系统传输优化

Facing with the ever-growing demand for high-rate wireless data services, researchers have recently embarked on introducing full-duplex mechanism into current multiple-input multiple-output (MIMO) systems for higher spectral efficiency. To maximally exploit the merit of full-duplex transmission and the spatial degree of freedom of MIMO channels, one needs to perform elaborate optimization on full-duplex MIMO systems. So far, there have been only a few works relevant to this topic with many theoretical problems remaining unsolved. In this project, by leveraging advanced mathematical optimization theory, we plan to carry out an in-depth study on the transceiver optimization for full-duplex MIMO systems that encompasses practical issues in real applications. Firstly, since it is usually hard to acquire perfect channel state information (CSI), we will investigate robust optimization for full-duplex single-user MIMO systems following the philosophy of statistical and worst-case robustness, respectively. Then, concerning the limitation of sum power constraint under certain circumstances, we will further incorporate generalized power constraints such as per-antenna power constraint into the optimization framework, which characterizes real scenarios more accurately. Finally, we will focus on the extension to full-duplex multi-user MIMO systems. Both transceiver and scheduling algorithms will be carefully designed so as to achieve potential performance gains offered by multi-user transmission.

面对日益增长的高速无线数据业务需求，近年来研究者开始探讨在现有多输入多输出（MIMO）系统中引入全双工机制，以获得更高的频谱效率。为了最大程度地利用全双工传输的优势以及MIMO信道的空间自由度，需要对全双工MIMO系统进行精心的优化设计。目前，关于该方向的研究尚处于起步阶段，仍有诸多理论问题值得探索。本课题将结合工程应用中存在的实际因素，采用先进的数学优化理论，围绕全双工MIMO系统的收发机优化开展深入研究。首先，鉴于精确的信道状态信息（CSI）通常难以获取，分别依据统计鲁棒性和最差情况鲁棒性设计思想，探究全双工单用户MIMO系统的鲁棒传输优化。进而，考虑到总功率约束在某些实际应用中的局限性，在系统优化中进一步融入包括每天线功率约束等在内的广义功率约束，从而更加贴近现实场景。最后，将以上工作推广到全双工多用户MIMO系统中，通过合理优化收发机以及调度算法获得多用户传输提供的潜在性能增益。

本项目充分挖掘全双工通信的内在特性以及多输入多输出（MIMO）信道提供的空间自由度，结合无线通信系统中存在的实际因素，从优化的角度为全双工MIMO系统设计性能优异且利于工程实现的高效信号传输策略。本项目主要围绕全双工中继MIMO系统，研究如下三项研究内容。首先，针对信源和信宿间存在直达链路的场景，研究考虑直达链路的全双工中继MIMO系统传输优化问题，提出具有半闭合形式的最优收发机方案以及具有闭合形式的次优收发机方案，相对于传统全双工和半双工中继传输，所提出的两种方案均能够获得显著的性能增益。之后，考虑由收发机器件非理想特性引起的信号畸变因素，探讨存在信号畸变情况下的全双工中继MIMO收发机优化问题，提出采用块坐标上升（BCA）算法对信源、中继和信宿的波束成形向量进行交替优化，以较低的复杂度提高系统对于信号畸变因素的鲁棒性。最后，针对存在信道状态信息（CSI）误差的全双工中继MIMO系统，研究最小化中断概率的中继波束成形优化问题，提出具有半闭合形式的最优中继波束成形方案，有效改善系统在非理想CSI下的中断概率性能。