非理想协作下的多小区MIMO协作系统容量分析与优化的研究

The technique of multi-cell MIMO with cell cooperation has been widely recognized as one of the core techniques of future mobile communications. From the perspective of information theory, the study of multi-cell MIMO cooperation systems can help us to understand the characteristics of the considered systems deeply, and then, to provide the guidance for system design and optimization. However, due to the fact that base-stations and mobile terminals are located at different geographic locations, as well as the fact that the information sharing among different base-stations is imperfect, the analysis model of the considered systems is complicated. Hence, the capacity analysis of multi-cell MIMO cooperation systems is still an open problem. In order to study the system capacity and derive the analytic expressions when the cooperation among base-stations is non-ideal, our team will try to introduce the operator-valued free probability theory to solve the above-mentioned problems. Specifically, under the constraint of limited-capacity backhaul link, we first study the system achievable rate when considering the uplink and downlink respectively. In order to make our results more general, different cooperation modes in the considered systems are studied. Furthermore, we consider that there are cooperation clusters in the multi-cell MIMO cooperation systems, and study the capacity of such systems. This is because that, in practical systems, the system ability (such as computing power, backhaul link, etc.) is restricted. Hence, nearby base-stations need to form a cooperation cluster, and then these cooperation clusters constitute the whole system. Finally, based on the derived analytic expressions, we try to find the impact of above-mentioned constraints on the multi-cell MIMO cooperation systems, and propose the optimization criteria.

多小区MIMO协作技术被认为是未来移动通信的关键技术，能有效提高蜂窝系统的频谱利用率和小区边沿用户的服务质量。从信息论角度对其展开研究，有助于深刻理解该系统的特性，为系统的设计与优化提供理论指导。但由于基站和终端的地理分布特性，以及基站间非理想信息交互条件，使得该系统的分析模型复杂，导致对其进行容量分析具有较大的困难，目前仍是学术界积极探讨的热点问题。课题组通过引入算子值自由概率等数学工具，研究系统在非理想协作条件下的可达速率，导出解析表达式。具体而言，将分别从上行和下行两方面研究系统在回馈链路容量受限下的可达速率，为了使结果更具一般性，分析中考虑了系统内的基站具有不同的协作模式。此外，针对实际系统的处理能力限制，基站间协作只能在一定范围内以协作簇的形式进行，将进一步研究引入协作簇后的系统可达速率。将充分挖掘所导出解析表达式的物理意义，探寻各类制约因素对系统性能的影响，提出优化设计准则。