Distributed Transmit Beamforming: Design and Demonstration From the Lab to UAVs
Distributed Transmit Beamforming: Design and Demonstration From the Lab to UAVs
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DOI：
10.1109/twc.2022.3198102
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发表时间：
2021-10
影响因子：
10.4
通讯作者：
Samer S. Hanna;D. Cabric
中科院分区：
文献类型：
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作者：
Samer S. Hanna;D. Cabric
协作无线电可以通过调整它们的信号来扩展它们的通信范围，以确保在目标无线电上进行相干合并。这种技术被称为分布式发射波束形成。波束形成(BF)依赖于BF无线电具有频率同步的载波和为相干合并而调整的相位。通常通过与目的地交换前同步码来满足这两个要求。然而，由于BF旨在增加接收功率，单独发送的前导通常处于低信噪比，并且它们的长度受信道相干时间的限制。这些噪声前导导致频率和相位估计误差，从而导致随机变化的BF增益。为了建立可靠的分布式BF系统，需要在设计中考虑估计误差对BF增益的影响。在这项工作中，假设使用目标引导的BF协议和卡尔曼滤波进行频率跟踪，我们优化了BF无线电的数目和前导长度以获得可靠的BF增益。为此，我们描述了BF增益分布、信道相干时间和设计参数(如信噪比、前导码长度和无线电数目)之间的关系。在实验室和无人机上使用软件定义的无线电通过模拟和实验验证了所提出的关系。
Cooperating radios can extend their communication range by adjusting their signals to ensure coherent combining at a destination radio. This technique is called distributed transmit beamforming. Beamforming (BF) relies on the BF radios having frequency synchronized carriers and phases adjusted for coherent combining. Both requirements are typically met by exchanging preambles with the destination. However, since BF aims to increase the received power, the individually transmitted preambles are typically at low SNR and their lengths are constrained by the channel coherence time. These noisy preambles lead to errors in frequency and phase estimation, which result in randomly changing BF gains. To build reliable distributed BF systems, the impact of estimation errors on the BF gains need to be considered in the design. In this work, assuming a destination-led BF protocol and Kalman filter for frequency tracking, we optimize the number of BF radios and the preamble lengths to achieve reliable BF gain. To do that, we characterize the relations between the BF gains distribution, the channel coherence time, and design parameters like the SNR, preamble lengths, and the number of radios. The proposed relations are verified using simulations and via experiments using software-defined radios in a lab and on UAVs.