Collaborative Research: CNS core: Medium: True-Time-Delay based MIMO System and Testbed for Low-Latency Wideband Beam and Interference Management in Millimeter Wave Networks

鉴于6 GHz以下频谱的短缺，毫米波(MmW)频率在新兴的5G网络中发挥了重要作用，这一趋势预计将在下一代继续下去。由于不利的传播条件和高频下的衰减，毫米波网络要求配备大量天线的基站和无线电致密化，以使用窄波束通过定向增益来补偿路径损耗。带有天线阵列的无线电的成本和功耗是一个重大挑战，其体系结构对整个网络堆栈具有根本性的重要性和影响力。随着无线电带宽和天线数量的增加，基于相控阵天线结构的最新方法面临着几个基本问题，包括初始连接和链路管理中令人望而却步的延迟、波束方向的失真、波束形成增益的降低以及在密集部署中抑制干扰的能力。本项目旨在开发和演示一种用于宽带毫米波网络的新型自适应实时延迟(TTD)阵列，以克服相控阵天线的挑战。该方法涉及可调谐射频(RF)电路、天线阵列系统、信号处理和网络协议的共同设计和优化，以实现低延迟接入、宽带波束成形增益和干扰管理。研究工作将进行四项关键工作：推力一号将开发基于TTD阵列的快速波束训练以及针对大调制带宽的毫米波网络的空间干扰检测和估计。其目的是通过信号处理利用TTD阵列中频率相关的天线权重向量来减少波束训练带来的初始接入开销，并开发一种用于密集毫米波网络中同时进行波束训练和干扰估计的低延迟协议设计。推力2号将专注于使用TTD阵列的数据通信设计，以促进多输入多输出(MIMO)多路复用，并抑制来自同频道基站和用户的干扰。主要的挑战是在宽的调制带宽上实现高的波束形成增益，同时有效地消除宽带干扰。推力3号将开发一个试验台，用于评估推力1和2的信号处理算法和协议。它将涉及将广泛可重构的延迟补偿电路和定制的28 GHz毫米波前端集成到一个16元TTD天线阵列中。推力4号将使用推力3中开发的试验台，对基于TTD阵列的波束训练、无斜视宽带波束形成和干扰清零，以及宽带MIMO通信进行实验验证。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。

Given the shortage of spectrum below 6GHz, millimeter wave (mmW) frequencies have played an important role in the emerging 5G networks and this trend is expected to continue in the next generations. Due to unfavorable propagation conditions and attenuation at high frequencies, mmW networks require the densification of base stations and radios equipped with a large number of antennas to compensate path loss via directional gain using narrow beams. The cost and power consumption of radios with antenna arrays present a significant challenge, and their architecture is of fundamental importance and influence on the entire networking stack. State-of-the-art approaches based on phased antenna array architecture are faced with several fundamental problems when radio bandwidth and the number of antennas increases including prohibitive latency in initial connectivity and link management, distortion in the directionality of the beams, reduced beamforming gain, and ability to suppress the interference in dense deployments. This project aims to develop and demonstrate a novel adaptive true-time-delay (TTD) based array for wideband mmW networks and overcome challenges of phased antenna arrays. The approach involves co-design and optimization of tunable radio frequency (RF) circuits, antenna array system, signal processing, and network protocols for low latency access, wideband beamforming gain, and interference management. The research work will pursue four key thrusts: Thrust 1 will develop TTD array-based fast beam training and spatial interference detection and estimation for mmW networks with large modulated bandwidth. The objective is to reduce the overhead in initial access due to beam training by exploiting frequency-dependent antenna weight vectors in TTD arrays through signal processing and develop a low latency protocol design for simultaneous beam training and interference estimation in dense mmW networks. Thrust 2 will focus on the data communication design using TTD arrays to facilitate multiple-input multiple-output (MIMO) multiplexing and suppress interference from co-channel base stations and users. The main challenge is to achieve high beamforming gain over a wide modulated bandwidth together with effective nulling of wideband interferers. Thrust 3 will develop an experimental testbed for the evaluation of signal processing algorithms and protocols from Thrusts 1 and 2. It will involve the integration of widely reconfigurable delay compensating circuits and custom mmW front-end at 28GHz into a 16-element TTD antenna array. Thrust 4 will experimentally validate TTD array-based beam training, squint-free wideband beamforming and interference nulling, and wideband MIMO communications using the testbed developed in Thrust 3.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.