EAGER: Terabit DSL

ENGER：在双绞线上以每秒太比特的速度传输数据使用双绞线进行数据传输是亚历山大·格雷厄姆·贝尔于1881年率先提出的。今天，全球安装了超过10亿条这样的双绞线，100多年来，这种基础设施一直是几乎所有电话连接的基础。在20世纪80年代末，数字用户线(DSL)业务被开发出来，其中承载数字数据的RF信号基本上被承载在用于模拟语音信号的相同铜线的顶部。通过数据编码和频率多路复用方面的进步，这些系统现在通常可以以每秒千兆位的速率传输数据。DSL惊人的(且持续的)商业成功在很大程度上源于这样一个事实，即这些服务不需要新的有线或光纤连接(每个客户的安装成本高达数千美元)，而是可以使用现有基础设施向客户提供高比特率。然而，编码和多路复用方面的进步几乎达到了极限，因此进一步提高数据速率的唯一方法是提高RF载波的频率，因为在更高的频率上有更多的可用带宽。拟议的研究将探索使用这些现有的铜双绞线以比以前在DSL系统中采用的频率高得多的频率传输信号。由于这些高频信号在沿着这些不均匀的电缆传播时不可避免地混合在一起，类似的多路复用和编码方案将是必要的。如果这些信号处理方法在高频下仍然有用，并且总的信号损失不是太高，那么这一初步演示将验证以每秒1万亿比特的数据速率操作类似DSL系统的可行性，这远远高于之前所设想的任何速率。这将为固定(而不是无线)数据服务开辟一个全新的领域。这一热切的提议提出了一种全新的方式来思考DSL传输系统。在迄今为止的所有讨论中，使用传输线的语言来描述电磁信号传播的基本物理。传统上，传输线通过在一对电绝缘导体之间传播时变电压来引导电信号。然而，当导波的自由空间波长接近相关维度(例如，两个导体之间的距离)时，使用波导的语言来描述这种传输过程更为合适。受双绞线中电线之间的典型自由空间距离可以达到一毫米量级这一事实的启发，该项目试图研究使用毫米波或太赫兹波作为双绞线电缆上调制数字数据的载波，作为波导。该提案旨在启动布朗大学PI和ASSIA，Inc.工程师之间的研究合作。该公司专门从事软件和信号处理，以实现DSL系统中频谱的有效利用。他们的专业知识，特别是在矢量化(概念上相当于无线系统中的MIMO)领域的专业知识，与PI在毫米波和太赫兹波导方面的专业知识相结合，构成了一个独特的团队，非常适合执行拟议的探索性研究计划。该方法包括对一组模型电缆系统的波导模式(每个可能的输入激励的所有输出模式)的实验表征，从简单的单双绞线到更复杂(和更长)的波导。将研究模式色散、介质损耗和弯曲的影响，结果将被用作ASSIA开发的信道模型的输入，以预测速率和距离性能特性。这项工作代表了对使用毫米波进行远距离导波数据传输这一想法的首次现实探索。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

EAGER: Transmitting data at a terabit per second on twisted copper wiresThe transmission of data using twisted copper-wire pairs was pioneered by Alexander Graham Bell in 1881. Today, there are well over a billion such twisted pairs installed globally, an infrastructure which has been the basis for nearly all telephone connections for over 100 years. In the late 1980s Digital Subscriber Line (DSL) services were developed, in which an RF signal carrying digital data was essentially piggy-backed on top of the same copper wires used for analog voice signals. Through advances in data encoding and frequency multiplexing, these systems can now typically deliver data at gigabit per second rates. The astounding (and ongoing) commercial success of DSL arises largely from the fact that these services do not require new wire or fiber connections (which cost thousands of dollars per customer to install), but instead can deliver high bit rates to customers using the existing infrastructure. However, advances in encoding and multiplexing have nearly reached their limit, so the only way to further increase the data rate is to increase the frequency of the RF carrier wave, since there is more bandwidth available at higher frequencies. The proposed research will explore the use of these existing copper twisted-cables for transmission of signals at much higher frequencies than those that have previously been employed in DSL systems. Similar multiplexing and encoding schemes will be necessary, due to the unavoidable mixing of these high-frequency signals as they propagate along these non-uniform cables. If these signal processing approaches are still useful at high frequencies, and if the overall signal loss is not too high, then this initial demonstration will validate the feasibility of operating a DSL-like system with a data rate of a terabit per second, vastly higher than anything that has been envisioned previously. This would open up an entirely new realm for fixed (not wireless) data services.This EAGER proposal suggests a radically new way to think about DSL transmission systems. In all discussions to date, the fundamental physics of the electromagnetic signal propagation is described using the language of transmission lines. Conventionally, a transmission line guides an electrical signal by propagation of a time-varying voltage between a pair of electrically isolated conductors. However, when the free-space wavelength of the guided wave approaches the relevant dimensions (e.g., the distance between the two conductors), it is more appropriate to describe this transmission process using the language of waveguides. Inspired by the fact that the typical free-space distance between wires in a twisted-wire pair can be on the order of a millimeter, this project seeks to study the use of millimeter waves or terahertz waves as the carriers for modulated digital data on twisted-pair cables, acting as waveguides. This proposal seeks to initiate a research collaboration between the PI at Brown University and engineers at ASSIA, Inc. This company specializes in the software and signal processing that enables efficient use of spectrum in DSL systems. Their expertise, in particular in the area of vectoring (conceptually equivalent to MIMO in wireless systems), combined with the PI's expertise in millimeter-wave and terahertz waveguides, represents a unique team which is ideally positioned to carry out the proposed exploratory research program. The approach involves the experimental characterization of the waveguide modes (all output modes for each possible input excitation) for a set of model cable systems, starting from a simple single-twisted-pair and working up to more complicated (and longer) waveguides. The effects of modal dispersion, dielectric loss, and bends will be studied, and the results will be used as inputs in channel models developed by ASSIA to predict the rate and range performance characteristics. This work represents the first realistic exploration of the idea of using millimeter waves for long-distance guided-wave data transmission.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.