分布式MIMO系统中基于波束成形的能效功率分配技术研究

发布时间：2018-06-06 23:23

本文选题：分布式MIMO系统 + 波束成形　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：随着业务量迅猛增长,无线通信能耗问题日益突出。因此,下一代移动通信系统将致力于追求更高的能量效率(Energy Efficiency,EE),实现绿色通信。分布式多输入多输出(Multiple Input Multiple Output,MIMO)系统能有效降低发送功率,提高覆盖范围。波束成形技术可以定向传输信号,能有效抑制电磁波衰减,提高信号传输距离。为此,本文将结合波束成形技术与MIMO技术研究分布式MIMO系统中能量有效的自适应功率分配方案,以期最大化系统能量效率的同时降低复杂度,为分布式MIMO系统提升能效,实现绿色通信和增强实用性提供理论依据。全文的主要工作如下:1.研究分布式MISO系统中能量有效的功率分配方案。根据能效定义及约束条件,构建系统能效最大化的目标优化函数。基于KKT条件给出最优功率分配解的一般形式,从而将多维求解问题转化成一维求解,并采用朗伯函数和二分法给出最优功率分配解。仿真结果表明,所提算法仅需一次朗伯函数计算或者较少的二分法查找,在获得最优EE性能的同时降低了计算复杂度。2.研究分布式MIMO系统中能量有效的功率分配方案。利用分式规划理论将原目标优化问题转化成标准凸优化形式,并采用卡尔丹公式给出最优功率分配解。考虑到最优方案需要多重迭代,复杂度较高,进而利用系统速率比较紧的下界提出一种次优功率分配方案。仿真结果表明,所提次优方案可获得与最优方案相近的EE性能,同时大幅度降低其计算复杂度,因此取得了性能与复杂度的有效折中。3.研究分布式MIMO系统在发送空间相关信道下能效自适应功率分配,提出了有着最小速率要求的能效功率分配方案,以期满足服务质量要求。给出了最低速率和最大功率约束条件下能效优化问题,该问题为非凸二次约束二次规划(Quadratically Constrained Quadratic Programming,QCQP)问题,很难获得全局最优解。为此,提出了利用系统比较紧的传输速率下界简化优化问题,并由此给出一种低复杂度的次优功率分配方案,在提升EE性能同时实现性能与复杂度的有效折中。
[Abstract]:With the rapid growth of traffic, the problem of wireless communication energy consumption is increasingly prominent. Therefore, the next generation of mobile communication systems will be dedicated to the pursuit of higher energy efficiency and energy efficiency to achieve green communications. Distributed multiple Input Multiple output Mimo system can effectively reduce transmission power and increase coverage. Beamforming technology can transmit signals in a directional way, effectively restrain the attenuation of electromagnetic waves and improve the transmission distance. In order to maximize the energy efficiency and reduce the complexity of the distributed MIMO system, this paper will study the energy efficient adaptive power allocation scheme in distributed MIMO system by combining beamforming technology with MIMO technology, and improve the energy efficiency of the distributed MIMO system. The realization of green communication and the enhancement of practicability provide theoretical basis. The main work of this paper is as follows: 1: 1. The energy efficient power allocation scheme in distributed MISO system is studied. According to the definition and constraints of energy efficiency, the objective optimization function of maximizing system energy efficiency is constructed. Based on the KKT condition, the general form of the optimal power allocation solution is given, and the multidimensional solution is transformed into one dimensional solution, and the optimal power allocation solution is obtained by using the Lambert function and the dichotomy. The simulation results show that the proposed algorithm requires only one Lambert function calculation or less dichotomous lookup, and reduces the computational complexity of the proposed algorithm by obtaining the optimal EE performance at the same time. The energy efficient power allocation scheme in distributed MIMO system is studied. By using fractional programming theory, the original objective optimization problem is transformed into a standard convex optimization form, and the optimal power allocation solution is obtained by using Cardan formula. Considering that the optimal scheme requires multiple iterations and the complexity is high, a sub-optimal power allocation scheme is proposed by using the lower bound of the system with relatively tight system rate. The simulation results show that the proposed sub-optimal scheme can obtain EE performance similar to the optimal scheme, and greatly reduce its computational complexity, thus achieving an effective compromise between performance and complexity. The energy efficiency adaptive power allocation in distributed MIMO systems is studied in the transmission space dependent channel. An energy efficiency power allocation scheme with minimum rate requirement is proposed in order to meet the quality of service (QoS) requirements. In this paper, the energy efficiency optimization problem with minimum rate and maximum power constraints is given. The problem is Quadratically-Quadratically Constrained Quadratic programming QCQP (Quadratically-Quadratic Quadratic Quadratic constrained Quadratic Quadratic programming). It is difficult to obtain a global optimal solution. In this paper, a simplified optimization problem based on the tight lower bound of transmission rate is proposed, and a low-complexity sub-optimal power allocation scheme is proposed to achieve an effective trade-off between performance and complexity while improving EE performance.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN919.3

【参考文献】