协同多点传输中迫零预编码和天线选择技术

MIMO无线传输技术极大地提高了系统的容量，在实际通信系统中，整个网络是一个干扰受限的系统，小区间干扰对MIMO系统传输的影响是显著的，每个相邻小区的基站天线都可以看成一个干扰源．由于基站端数据处理能力的提升和回程容量的增加，多个小区协同多点传输技术引起了人们的广泛关注．目前的大部分工作都是集中于研究系统的容量（吞吐量），而在实际系统中，每个用户的接收等效信噪比（即公平性）对系统的性能如误帧率等有重要的影响．对于每个用户为单天线的情形，研究了总功率受限和每天线功率受限下采用迫零预编码的系统容量和公平性．对两种功率约束条件下的公平性进行了分析，得到了公平性算法的闭式表达式．当每个用户为多天线的情形，为了降低计算的复杂度，引入了信道范数最大的接收天线选择算法，把每个用户为多天线的情形转化成等效的每个用户单天线情形，推导的每用户为单天线的公平性算法仍然适用．仿真结果显示，采用迫零预编码的多小区协作可以使系统性能显著提升．在相同的迫零预编码下，不同的功率分配策略对系统的容量和公平性有显著的影响．和用户为单天线相比，采用天线选择算法可以提升系统的容量和公平性．考虑了用户公平性时的吞吐量和最大系统吞吐量之间的折中关系，并给出了仿真结果．

Zero-forcing precoding and antenna selection research for coordinated multiple point transmission

Communication system capacity is greatly improved by multiple input multiple output （MIMO） wireless transmission technology. In a commercial cellular system, the entire network is essentially an interference- limited system. While the problem of other-cell interference （OCI） is inherent in cellular systems, its affect on MIMO transmission is more significant, because each neighboring base station （BS） antenna element can act as a unique interfering source. Because of the fast improvement in processing capability at BSs and the increase in the backhaul capacity, coordinated multi-cell MIMO communications with cooperative processing among BSs have attracted a significant amount of interest in recent years. Most of the current work is focused on the study of system capacity, but the equivalent SNR of each user （i.e., fairness） has an important influence on system performance, such as the frame error rate. Considering the single antenna configuration for the user, the system capacity and fairness based on a zero-forcing precoding design are studied in the case of the total power and per antenna power constraints. The fairness is analyzed for the two types of power constraints, and a closed solution is given. Considering the multiple antenna configuration for the user, the receive antenna selection algorithm, which maximizes the channel norm, is used to reduce the computational complexity. Thus the case for the user with a multiple antenna configuration is transformed into the case for the user with a single antenna configuration, The fairness algorithm for the user with a single antenna is still applicable. The simulation results show that multi-cell collaboration with zero-forced precoding can significantly improve system performance. In the same zero-forced precoding, different power allocation strategies have a significant affect on system capacity and fairness. Compared with the user with a single antenna, the antenna selection algorithm can enhance system capacity and fairness. The tradeoff between user fairness throughput and maximum system throughput is considered, and simulationresults are also given.