热点论文与带您领略5G/6G基础研究的最新进展——图书馆前沿文献专题推荐服务（36）

2021-03-30

 

        在上一期前沿文献中推荐中，介绍了5 G/6G热点技术的最新进展，选取的文献包括：高移动性5G-HetNet上下行资源动态分配的深度强化学习、通过基站充电实现无人机无线电能传输以及无人机能量消耗、毫米波系统中用于低延迟小区发现的灵活束宽波束扫描，以及毫米波OFDM分布式天线系统的混合波束赋形设计。
        在本期的文献推荐中，继续介绍5G/6G基础研究方面的最新进展，包括：一种基于数字超表面空分及频分复用的无线通信方案、用于动态可调谐毫米波超材料移相器的空气桥肖特基二极管、通往6G之路-通信工程师面临的十大物理层挑战、以及网络模拟器在机器学习辅助5G/6G网络中的应用，供相关领域的科研人员参考。
 
领域一 一种基于数字超表面空分及频分复用的无线通信方案
A wireless communication scheme based on space- and frequency-division multiplexing using digital metasurfaces
Lei Zhang, etc.
Nature Electronics, 2021, 4: 218–227
Digitally programmable metasurfaces are of potential use in wireless multiplexing techniques because they can encode and transmit information without using traditional radio-frequency components such as antennas or mixers. Space–time-coding digital metasurfaces can, in particular, manipulate the propagation direction and harmonic power distribution of electromagnetic waves, making them suitable for space- and frequency-division multiplexing. However, while digital metasurfaces have been used for wireless communication, these systems could implement signal modulation only in the time domain. Here, we report a wireless communication scheme that uses space–time-coding digital metasurfaces to implement both space- and frequency-division multiplexing. By encoding space–time-coding matrices through multiple channels, digital messages can be directly transmitted to different users at different locations simultaneously, without the need for digital-to-analogue conversion and mixing processes. To illustrate this approach, we have built a dual-channel wireless communication system based on a two-bit space–time-coding digital metasurface and use it to transmit two different pictures to two users simultaneously in real time.
 
领域二 用于动态可调谐毫米波超材料移相器的空气桥肖特基二极管
Air-bridged Schottky diodes for dynamically tunable millimeter-wave metamaterial phase shifters
Evangelos Vassos, etc.
Scientific Reports, 2021
A low loss metamaterial unit cell is presented with an integrated GaAs air-bridged Schottky diode to produce a dynamically tunable reflective phase shifter that is capable of up to 250° phase shift with an experimentally measured average loss of 6.2 dB at V-band. The air-bridged Schottky diode provides a tuneable capacitance in the range between 30 and 50 fF under an applied reverse voltage bias. This can be used to alter the resonant frequency and phase response of a split patch unit cell of a periodic metasurface. The air-bridged diode die, which is flip-chip soldered to the patch, has ultra-low parasitic capacitance and resistance. Simulated and measured results are presented which verify the potential for the attainment of diode switching speeds with acceptable losses at mmWave frequencies. Furthermore the study shows that this diode-based unit cell can be integrated into metamaterial components, which have potential applications in future mmWave antenna beam-steering, intelligent reflecting surfaces for 6G communications, reflect-arrays, transmit-arrays or holographic antennas.
 
领域三 通往6G之路：通信工程师面临的十大物理层挑战
The Road to 6G: Ten Physical Layer Challenges for Communications Engineers
Michail Matthaiou, etc
IEEE Communications Magazine, 2021, 59(1): 64-69
While the deployment of 5G cellular systems will continue well into the next decade, much interest is already being generated toward technologies that will underlie its successor, 6G. Undeniably, 5G will have a transformative impact on the way we live and communicate, but it is still far away from supporting the Internet of Everything, where upward of 1 million devices/km 3 (both terrestrial and aerial) will require ubiquitous, reliable, low-latency connectivity. This article looks at some of the fundamental problems that pertain to key physical layer enablers for 6G. This includes highlighting challenges related to intelligent reflecting surfaces, cell-free massive MIMO, and THz communications. Our analysis covers theoretical modeling challenges, hardware implementation issues, and scalability, among others. The article concludes by delineating the critical role of signal processing in the new era of wireless communications.
 
领域四 网络模拟器在机器学习辅助5G/6G网络中的应用
Usage of Network Simulators in Machine-Learning-Assisted 5G/6G Networks
Francesc Wilhelmi, etc.
IEEE Wireless Communications, 2020, 28(1): 160-166
Without any doubt, Machine Learning (ML) will be an important driver of future communications due to its foreseen performance when applied to complex problems. However, the application of ML to networking systems raises concerns among network operators and other stakeholders, especially regarding trustworthiness and reliability. In this article, we devise the role of network simulators for bridging the gap between ML and communications systems. In particular, we present an architectural integration of simulators in ML-aware networks for training, testing, and validating ML models before being applied to the operative network. Moreover, we provide insights into the main challenges resulting from this integration, and then give hints discussing how they can be overcome. Finally, we illustrate the integration of network simulators into ML-assisted communications through a proof-of-concept testbed implementation of a residential WiFi network.

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