多小区网络中的高能效用户接入与传输设计

发布时间：2018-02-20 20:13

本文关键词： 能量效率最差情况鲁棒性信道对角化多小区网络半正定规划异构网络线性规划　出处：《东南大学》2017年硕士论文　论文类型：学位论文

【摘要】：为了降低蜂窝网能耗、提高小区能量效率(EE,Energy Efficiency),绿色网络的概念逐渐引起广泛关注。然而由于能效优化相比于频谱效率(SE,Spectral Efficiency)优化更加复杂,大多场景下很难得到最佳能效传输方案。特别是在实际应用中,信道信息(CSI,Channel State Information)通常在接收端被估计,然后接收端将估计到的信道信息反馈给发送端,该过程中不可避免将产生信息误差及延时。所以通常基站(BS,Base Station)得到的信道信息都存在一定的估计误差,获得准确的信道状态信息非常困难。本文主要针对信道信息误差下的鲁棒性高能效传输设计进行了一系列的研究和优化。首先考虑在发送端信道信息不完全的情况下,论文针对单小区场景的鲁棒性能量效率进行优化。该部分从多输入单输出(MISO,Multiple-Input Single-Output),多输入多输出(MIMO,Multiple-Input Multiple-Output)和中继传输三个场景分别进行分析。针对MISO场景,研究了满足最大化能效的最佳鲁棒性预编码策略,并给出最优预编码的闭式解析解。针对MIMO场景,得到了满足最佳鲁棒性能效的预编码满足信道对角化结构,由此可以将原来复杂的矩阵优化问题等价地转化为简单的标量优化问题,其最佳功率分配满足动态注水形式。针对中继场景,论文将原来复杂的分式中继预编码优化问题转化为一维搜索问题。特别地,在分析几种渐近场景时,论文中给出了简洁的闭式最佳解及其揭示的物理意义。然后论文研究了多小区场景中的鲁棒性高能效传输优化问题。对于多小区场景,鲁棒性波束赋形设计是一个复杂的非凸分式问题,其求解方法无法直接从单小区场景推广获得。为了有效求解该问题,论文通过推导优化其下界,将其转化为半正定规划(SDP,Semidefinite Programming)的迭代优化问题。由于迭代过程可以在多基站之间并行运算,该算法可以实现分布式操作,从而极大地降低计算时延。为了满足用户对于通信网络性能不断增长的要求,由宏基站组成的传统蜂窝网络拓扑也逐渐向在宏基站基础上配备一系列低发射功率节点的网络结构转变,这种不规则的多层网络通常被称为异构网络(HetNets,Heterogeneous Networks)。跟异构网络一样,能量效率也被认为是衡量未来网络性能的一个重要指标。论文最后研究了结合宏基站工作模式选择的高能效小区接入方案。不考虑用户服务质量(QoS,Quality of Service)约束时,论文得到了闭式最佳解。该解为很多系统设计提供了理论指导。进一步考虑用户QoS约束,可以将原来复杂的分式能效优化问题转化为线性规划,从而降低了问题求解的计算复杂度。此外,论文还通过理论推导和数值仿真说明在实际系统中可以通过简单的限制一个用户只被一个基站服务来获得近似最佳的网络能效。
[Abstract]:In order to reduce the energy consumption of cellular network and improve the energy efficiency of the cell, the concept of green network has attracted more and more attention. However, the optimization of energy efficiency is more complex than that of spectrum efficiency. In most scenarios, it is difficult to obtain the best transmission scheme for energy efficiency. Especially in practical applications, the channel information is usually estimated at the receiving end, and then the receiver feedback the estimated channel information to the sender. In this process, information error and delay will inevitably occur. It is very difficult to obtain accurate channel state information. In this paper, a series of research and optimization for robust energy-efficient transmission design with channel information error is carried out. In this paper, the robust energy efficiency of single cell scenario is optimized. In this part, we analyze the multi-input single-output (MISOO), the multiple-input multiple-output (MIMO) and the relay transmission (MISO), respectively. The optimal robust precoding strategy for maximizing energy efficiency is studied, and the closed analytical solution of optimal precoding is given. For MIMO scenarios, a channel diagonalization structure with optimal robust performance is obtained. Thus, the original complex matrix optimization problem can be equivalent to a simple scalar optimization problem, and its optimal power allocation can satisfy the dynamic water injection form. In this paper, the original complex fractional relay precoding optimization problem is transformed into a one-dimensional search problem. In particular, when analyzing several asymptotic scenarios, In this paper, the concise closed-form optimal solution and its physical significance are given. Then, the robust energy-efficient transmission optimization problem in multi-cell scenarios is studied. Robust beamforming design is a complex non-convex fraction problem, whose solution cannot be directly derived from a single cell scene. In order to solve the problem effectively, the lower bound of the problem is optimized by derivation. It can be transformed into an iterative optimization problem of SDP (Semidefinite programming). Since the iterative process can be run in parallel between multiple base stations, the algorithm can implement distributed operations. In order to meet the requirements of the users for the increasing performance of the communication network, The traditional cellular network topology composed of Acer stations is also gradually changing to a network structure with a series of low transmit power nodes on the base of the base station. This irregular multilayer network is often called heterogeneous network. Energy efficiency is also considered to be an important index to measure the performance of future networks. Finally, an energy efficient cell access scheme based on the operation mode of Acer stations is studied. The QoS quality of Service constraints are not considered. In this paper, the closed optimal solution is obtained, which provides theoretical guidance for many system designs. Considering the user QoS constraints, the original complex fractional energy efficiency optimization problem can be transformed into linear programming. In addition, the theoretical derivation and numerical simulation show that in the practical system, the approximate optimal network energy efficiency can be obtained by simply limiting a user to only one base station service.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

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