【作者】 李辉；

【导师】 邹卫霞；

【作者基本信息】 北京邮电大学 ， 信息与通信工程， 2017， 硕士

【摘要】 随着互联网时代的蓬勃发展,人们对无线通信的传输速率和传输带宽提出了更高的要求,因此易于集成大规模天线、具有大量频谱资源的毫米波通信受到了广泛关注。然而毫米波频段信号的高路径损耗特性决定了其必须采用波束赋形技术来增加链路预算,因此本论文主要针对毫米波模拟波束赋形技术展开了以下研究。1)毫米波模拟波束赋形技术本质上其实就是波束搜索,其也可被称为基于波束切换的波束赋形技术。本文首先从波束搜索复杂度的角度总结了现有关于毫米波模拟波束赋形的研究成果:主要包括了IEEE 802.1 1ad两阶段搜索方案、基于梯度上升的搜索算法和二分搜索算法。然后在多径信道条件下,分析了上述三类算法无法适用于多径环境的缺陷,针对该缺陷,设计了基于二分分级搜索策略的多径环境下波束搜索方案。该方案在每一级搜索过程中,选取的波束数目均大于等于多径数,即增加了获得多个局部最优通信波束的概率,并在最细波束搜索阶段,对之前通过多级搜索获得的多对局部最优波束进行选择性地删除,最后在多个局部最优波束及其相邻波束中确定出可用备选通信波束,对于发射端来说,在这多个备选波束中也包含了全局最优通信波束。仿真表明,在多径环境下,本文所提方案能够以非常高的成功率找到多个备选通信波束,且复杂度远低于穷举搜索法;较二分搜索法,本方案获得全局最优通信波束的成功率远大于上述三类分级搜索算法。2)对于移动目标的跟踪问题,数字波束跟踪技术已经非常成熟,但是该技术并不适用于单链路的模拟波束赋形天线结构。IEEE 802.11ad标准中规定波束跟踪策略为:采用切换探测与原通信波束相邻波束的方式来实时跟踪用户,该方案的缺陷主要是可跟踪范围非常小。因此,在视距通信(Line of Sight, LOS)条件下,本文设计了一个基于分级搜索策略的快速波束跟踪方案,该方案采取回跳至某一级搜索进程并从这一级开始继续往下进行波束搜索的方式扩大了波束跟踪的范围。仿真表明,本方案较IEEE 802.11ad标准,扩大了波束跟踪范围,在大规模天线阵列下,其复杂度性能更优。更多还原

【Abstract】 With the prosperity of the Internet, larger wireless transmission rate and bandwidth is needed. Because of its ease of integration of large-scale antennas and rich frequency resources, the millimeter-wave communication has been widely concerned. To compensate the large path loss characteristic of the millimeter-wave signal, the beamforming technique is used to increase the link budget. Therefore, the thesis mainly researches the millimeter-wave analog beamforming technology.1) The essence of millimeter-wave analog beamforming technology is beam search, which may also be referred to as switched-beam-based beamforming technology. In this thesis, we first summarize the existing research on millimeter-wave analog beamforming from the perspective of beam search complexity: including two-stage search scheme in IEEE 802.11 ad, gradient-ascent-based search algorithm and binary search algorithm. And then, by analyzing the above three types of algorithms’defects in multipath channel, a multi-path beam search scheme based on binary search algorithm is proposed. In this scheme, the number of selected beams in each level is greater than or equal to the number of paths, so it can increase the chance of finding several local optimal beams.And in the stage of finest beam search, we selectively delete beams, then we can obtain the available communication beams among a plurality of local optimal beams and their adjacent beams. Furthermore, for the transmitter we can also get the global optimal beam from these local optimal beams. The simulation results show that, comparing with exhaustive search algorithm, it has almost the same success rate and lower search complexity to get a number of alternative beams.Comparing with binary search algorithm, the proposed algorithm has higher success rate to find the global optimal communication beam in multipath environment.2) For keeping track of moving objects, the digital beam-tracking technology is mature. But this technology can’t be applied to single-link analog beamforming antenna structure. IEEE 802.11 ad standard specifies beam tracking strategy as detection of the original communication beam’s adjacent beams, but its tracking range is very small. Therefore, a fast beam-tracking scheme based on hierarchical search strategy is designed for LOS scenarios in the thesis. This scheme expands the tracking range by stepping back to a certain search level and then continuing the binary search process. Simulation results show that the proposed scheme has better performance than IEEE 802.11ad especially on large-scale antenna array.更多还原