Enhancing Spectral Access through Adaptive Terahertz Communication Systems

在过去的几十年里，由于人们创建和共享信息的方式发生了戏剧性的变化，高速无线通信引起了广泛的关注。预计到2020年，满足客户需求的预期数据速率将达到100Gbit/S。然而，目前无线通信系统的速度受到现有发射机和接收机的窄带宽以及对高达60 GHz的电磁频谱的大量使用的限制。这一趋势迫使研究人员将收发信机的载波频率推到更高的频率，以允许在尚未分配给任何特定活动服务的频段上操作。为了增加信道容量，研究人员一直试图在太赫兹频率下工作，该频率覆盖了电磁频谱中0.3-10太赫兹的频率范围。虽然到目前为止还很难开发出具有如此高载波频率的通信系统，但由于最近太赫兹光子学和电子学的进步，人们认为在10-20米距离内以超过100Gbit/S的数据速率运行的数据链路现在是可行的。该项目的研究部分计划开发一种用于室内通信应用的太赫兹载波频率的高数据速率无线通信系统。具有这种能力的系统可以非常适合于下一代室内无线通信系统，如无线局域网和无线个人局域网、Kiosk下载、无线回程、数据中心连接，以及可穿戴设备的实时数据分析。此外，该计划计划通过开发新课程、招募和参与本科生以及组织高中研讨会，将研究与教育和外展活动相结合。在这个项目中，我们设计、制造并实验证明了一个基于自适应二维等离子体光电二极管阵列的定向太赫兹收发系统。这项拟议的工作为利用太赫兹带宽将无线通信数据速率提高到以前无法想象的水平提供了一个全新的视角，因为现有太赫兹发射机的输出功率低且适应性有限。这一限制可以通过使用等离子光混合器阵列来解决，与其他太赫兹发射机相比，等离子光电混合器阵列提供显著更高的太赫兹辐射功率和更高水平的发射机适应性。此外，建议的太赫兹收发系统的自适应特性允许通过波束形成和非视距通信链路补偿意外的对准和阴影效应。虽然理论研究提供了对基于等离子体光混合器阵列和可实现的无线通信数据速率的太赫兹收发系统的基本物理限制的深入理解，但实验工作提供了宝贵的数据来开发在太赫兹频率下的准确信道模型，以便利用适当的通信模式、均衡技术和自适应信号跟踪系统来缓解室内太赫兹通信系统中的信号衰落。

High-speed wireless communication has attracted extensive attention in the past decades because of dramatic changes in the ways people create and share information. The expected data rate to satisfy the needs of the customers is projected to be 100 Gbit/s by 2020. However, the speed of today's wireless communication systems is limited by the narrow bandwidth of existing transmitters and receivers and the heavy use of the electromagnetic spectrum up to 60 GHz. This trend has been forcing researchers to push the carrier frequencies of transceivers to higher frequencies to allow operation at frequency bands which have not been allocated to any specific active service yet. In order to increase the channel capacity, researchers have been trying to operate at terahertz frequencies, which cover the frequency range of 0.3-10 THz in the electromagnetic spectrum. While communication systems with such high carrier frequencies have been hard to develop so far, a data link operating at terahertz frequencies with data rates exceeding 100 Gbit/s over 10-20 meters distance is believed to be viable now thanks to recent advancements in terahertz photonics and electronics. The research component of this program plans to develop such a high data rate wireless communication system at terahertz carrier frequencies for indoor communication applications. A system with this capability can be very suitable for the next generation indoor wireless communication systems such as wireless local area networks and wireless personal area networks, kiosk downloads, wireless backhauling, data center connection, and real-time data analysis for wearable devices. Additionally, this program plans to integrate research with education and outreach activities by developing new courses, recruitment and involvement of undergraduate students, and organizing high-school seminars. During this program a directional terahertz transceiver system based on an adaptive two-dimensional array of plasmonic photomixers operating under novel communication protocols is designed, fabricated, and experimentally demonstrated. The proposed work presents an entirely new perspective on the potential use of terahertz bandwidth for increasing wireless communication data rates to levels that could not be envisioned before due to low output power and limited adaptability of existing terahertz transmitters. This limitation can be tackled through use of plasmonic photomixer arrays that offer significantly higher terahertz radiation powers and higher level of transmitter adaptability compared to other terahertz transmitter candidates. Additionally, the adaptive nature of the proposed terahertz transceiver system allows compensation for accidental misalignments and shadowing effects through beam-forming and non-line-of-sight communication links. While theoretical investigations provide a deep understanding of fundamental physical limitations of terahertz transceiver systems based on plasmonic photomixer arrays and achievable wireless communication data rates, the experimental effort provides valuable data to develop accurate channel models at terahertz frequencies in order to utilize appropriate communication modalities, equalization techniques, and adaptive signal tracking systems to mitigate signal fading in indoor terahertz communication systems.