基于混合精度DAC的下行去蜂窝大规模MIMO-WPT系统能量效率研究  

Energy Efficiency Research on Cell-Free Massive MIMO-WPT Systems with Mixed-Resolution DACs

作　　者：张尧 赵海涛[2] 夏文超[2] 杨龙祥 朱洪波[2] ZHANG Yao;ZHAO Hai-tao;XIA Wen-chao;YANG Long-xiang;ZHU Hong-bo(Department of Physics and Electronic Information Engineering,Zhejiang Normal University,Jinhua,Zhejiang 321004,China;Department of Communication and Information Engineering,Nanjing University of Posts and Telecommunications,Nanjing,Jiangsu 210003,China)

机构地区：[1]浙江师范大学物理与电子信息工程学院,浙江金华321004 [2]南京邮电大学通信与信息工程学院,江苏南京210003

出　　处：《电子学报》2023年第10期2765-2774,共10页Acta Electronica Sinica

基　　金：国家重点研发计划(No.2020YFB1806608);国家自然科学基金(No.62071246,No.62201285,No.92067201);江苏省自然科学基金-杰出青年基金(No.BK20220054);江苏高等学校自然科学研究(No.21JB510034);国家自然基金委区域创新发展联合基金-重点项目(No.U22A2025)。

摘　　要：本文研究了采用混合精度数模转换器(Digital-to-Analog Converter,DAC)架构的下行去蜂窝大规模多输入多输出无线携能(Multiple-Input Multiple-Output Wireless Power Transfer,MIMO-WPT)系统.该系统中的用户(User Equipment,UE)收集接入点(Access Point,AP)发射的无线射频信号能量,基于加性量化噪声模型对量化后的能量信号建模,并引入混合DAC功耗模型,推导出UE收集到的能量(Harvested Energy,HE)和系统能量效率(Energy Efficiency,EE)闭式表达式.分析关键参数,如DAC精度、高精度DAC占比、AP/UE数目和AP发射功率等对下行WPT性能的影响.设计基于加速投影梯度(Accelerated Projected Gradient,APG)的EE最大化功率控制算法.该算法是一阶优化方法,且能求解出最优功率控制系数的闭式解,因此时间复杂度低,运行耗时短.仿真结果表明,与全低精度DAC结构相比,混合精度DAC结构可以同时改善HE和EE;对于不同高精度DAC占比的混合精度DAC结构,当除高精度DAC外的其余DAC的分辨率设置为5 bit时,在保证实现高HE的同时也可获得最优的EE;在中、低信噪比场景下,可以通过增大AP发射功率来改善系统EE;在UE数目较多的去蜂窝大规模MIMO-WPT系统中,所提的基于APG的功率优化算法不仅使等功率分配方案下的EE提升了约19.5%,而且同基于内点法的功率优化算法相比,运行耗时也大幅降低.A downlink cell-free massive multiple-input multiple-output wireless power transfer(MIMO-WPT)sys⁃tem using the mixed-resolution digital-to-analog converter(DAC)architecture is studied,where the user equipments(UEs)harvest the ratio-frequency energy from downlink signal sent by the access points(APs).Using the additive quantization noise model to construct the energy signal after quantization and introducing a power consumption model to characterize the power consumed by mixed-resolution DACs,closed-form expressions of both harvested energy(HE)and energy effi⁃ciency(EE)are derived.These expressions facilitate analyzing the impacts of key parameters,such as the resolution of DACs,the proportion of high-resolution DACs,the number of APs/UEs,and the transmit power of APs on downlink WPT performance.Aside from this,an EE maximization power control algorithm based on the accelerated projected gradient(APG)technique is proposed.Specifically,the APG-based power control algorithm is a first-order optimization method and can determine the optimal solution in closed form,thus benefiting from low computational complexity and short runtime.Experimental results show that compared with the full low-resolution DAC structure,the mixed-resolution DAC architecture can significantly improve both HE and EE.Besides,for mixed-resolution DAC architectures with different proportions of high-resolution DACs,an optimal EE can be approached along with a better SE when the resolution of DACs(except high-resolution DACs)is set to 5 bits.Moreover,in communication scenarios with medium and low signal-to-noise ratios,it is reasonable to increase the AP transmit power to boost the system EE.At last,in cell-free massive MIMO-WPT sys⁃tems with a large number of UEs,the proposed APG-based power control algorithm not only enhances the EE related to the equal power control scheme by about 19.5%but also significantly reduces the runtime compared to the interior-point-based power control algorithm.

关 键 词：去蜂窝大规模多输入多输出 无线携能 混合精度数模转换器 能量效率 加速投影梯度 

分 类 号：TN915[电子电信—通信与信息系统]