多用户MIMO上下行用户调度与传输技术研究

发布时间：2018-04-04 01:38

本文选题：多用户MIMO　切入点：功率分配　出处：《电子科技大学》2014年硕士论文

【摘要】：随着移动设备逐渐向小巧轻薄的趋势发展,在终端上安装多根天线变得更加困难。为了利用多输入多输出(Multiple Input Multiple Output,MIMO)技术提高小区频谱性能,人们提出了虚拟MIMO(Virtual MIMO)技术。通过将空间上处于不同位置的终端设备联合起来构成一个用户组,从而与基站的多根接收天线之间形成一种特殊的MIMO系统。通过这种方式,大大提高了小区吞吐量和通信质量。Virtual MIMO的核心思想在于设计高效的用户配对算法,即如何选择最佳的用户组合,在减少共信道干扰(Co-channel Interference,CCI)的同时提高系统性能。在终端移动的过程中,信道状态会受快衰落或慢衰落等因素的影响而动态变化,因此需要通过功率控制(Power Control)实时调整基站或者终端的发射功率,保证可靠的通信连接。目前大多数用户调度算法都是基于功率平均分配的前提进行研究,而实际系统中如果用户始终以相同功率通信,则会因为信道的时变特性而导致传输性能恶化。因此,很有必要将用户调度和功率分配进行联合优化设计。波束赋形(Beamforming)技术通过对发射信号和接收信号进行必要的处理,使得终端的信干噪比(Signal-to-interference-plus-noise ratio,SINR)显著增加,以便提升系统容量并抑制干扰。这种技术也可以看做是对发送信号的滤波处理,即一方面通过在发射端设计发射矩阵,使得信号在尽可能对准期望用户的前提下,尽量减少对其它用户的干扰;另一方面通过在接收端设计接收矩阵,使得尽可能的提升期望信号功率,从而抑制干扰信号功率。而用户间的共信道干扰正是用户调度需要解决的关键问题,因此将波束赋形和用户调度联合研究是很有意义的。基于以上的分析,本文将虚拟MIMO用户配对、功率分配以及波束赋形三个方面进行联合设计,主要工作如下:第一章介绍了多用户MIMO用户调度和功率控制的研究现状,并对存在的问题作出了分析。第二章给出了上行虚拟MIMO的信道模型,详细介绍了四种传统的上行配对调度算法的原理及特点并扩展成调度多个用户的情况,最后进行了仿真验证和理论分析。第三章在上行虚拟MIMO的系统模型上,结合基站端的功率控制,提出了一种以最大化和速率为目标的用户配对和功率分配联合算法。通过利用最优化理论中拉格朗日乘子法求出目标函数的最优解。最后针对所提算法与传统的配对算法进行仿真对比,并进行相应的理论分析。第四章在多用户MIMO广播信道传输模型下,在现有算法的基础上对预编码向量的设计做出了优化改进,提出了一种预编码和用户调度的联合算法。最后对所提算法和其他算法进行了性能上的仿真对比,验证了其优越性并作了相应的理论分析。第五章对全文进行了总结,并提出下一步的研究工作。
[Abstract]:With the development of small and thin mobile devices, it becomes more difficult to install multiple antennas on the terminal.In order to improve cell spectrum performance by using multiple Input Multiple output Mimo (MIMO) technology, virtual MIMO(Virtual Mimo (Virtual MIMO(Virtual Mimo) technology is proposed.A special MIMO system is formed by combining the terminal devices in different positions in space to form a group of users to form a special MIMO system with multiple receiving antennas of the base station.In this way, the core idea of greatly improving cell throughput and communication quality. Virtual MIMO is to design an efficient user pairing algorithm, that is, how to select the best user combination, and to improve the system performance while reducing co-channel interference (Co-channel interference).In the process of terminal movement, the channel state will change dynamically due to the influence of fast fading or slow fading, so it is necessary to adjust the transmission power of base station or terminal through power control in real time to ensure reliable communication connection.At present, most of the user scheduling algorithms are based on the premise of power distribution. However, if the users always communicate with the same power, the transmission performance will deteriorate because of the time-varying characteristics of the channel.Therefore, it is necessary to optimize the user scheduling and power allocation.Beamforming technology can increase signal-to-interference noise ratio (Signal-to-interference-plus-noise SINR) significantly by necessary processing of transmitted and received signals in order to increase system capacity and suppress interference.This technique can also be regarded as filtering the transmitted signal. On the one hand, by designing the transmitting matrix at the transmitter, the signal can be targeted at the desired user as much as possible, and the interference to other users will be reduced as much as possible.On the other hand, by designing the receiving matrix at the receiver, the desired signal power can be increased as much as possible to suppress the interference signal power.The co-channel interference between users is the key problem of user scheduling, so it is meaningful to study the joint research of beamforming and user scheduling.Based on the above analysis, the virtual MIMO user pairing, power allocation and beamforming are jointly designed in this paper. The main work is as follows: chapter 1 introduces the research status of multi-user MIMO user scheduling and power control.The existing problems are analyzed.In the second chapter, the channel model of uplink virtual MIMO is given, the principle and characteristics of four traditional uplink pairing scheduling algorithms are introduced in detail, and the scheduling of multiple users is extended. Finally, the simulation and theoretical analysis are carried out.In chapter 3, based on the uplink virtual MIMO system model and the power control of the base station, a joint algorithm of user pairing and power allocation aiming at maximization and rate is proposed.The optimal solution of the objective function is obtained by using the Lagrange multiplier method in the optimization theory.Finally, the proposed algorithm is compared with the traditional pairing algorithm, and the corresponding theoretical analysis is carried out.In chapter 4, under the multi-user MIMO broadcast channel transmission model, the design of precoding vector is optimized and improved on the basis of existing algorithms, and a joint algorithm of precoding and user scheduling is proposed.Finally, the performance of the proposed algorithm is compared with that of other algorithms, and its superiority is verified and the corresponding theoretical analysis is made.The fifth chapter summarizes the full text and puts forward the next research work.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN919.3

【共引文献】