SWIFT: LARGE: Design and Operating Principles of a Wave-Controlled Holographic MIMO System

大规模多输入多输出（MIMO）网络的容量理论上是无限的，随着天线数量的增加，只要利用传播信道固有的空间相关性。该方案利用这种观察结果，利用新型的“智能反射面”（IRS），可以自适应地修改MIMO信道的空间特性。整个项目的目标是提高频谱效率和共存。为了实现这一目标，该装置采用了一种具有反射特性的超表面，其反射特性可以被编程为接受撞击电磁场并重塑反射场。为了实现共存，撞击IRS的窄束能量可以被重新定向到可能被阻挡传输的接收器上。此外，IRS可以提供非常复杂的反射模式来重新均衡无线信道链路。这个提议的新颖之处在于，相移不是由需要大量庞大的电子连接的单个控制来控制的，而是由发射到反射表面薄波导上的电磁波来控制的。给定这些波导的边界条件，控制波被设计为周期模式的线性叠加，其系数决定相移。该装置的原型将被建立，其控制算法和大规模MIMO网络的控制将被开发。将有四项研究活动。首先，将设计一种具有电磁波控制的新型IRS结构。在第二个活动中，将开发用于IRS单细胞控制的降维算法，以及用于估计信道状态信息的相应方法。第三项活动将侧重于使用机器学习算法，将多个这样的IRS合并到具有许多用户的多单元设置中，以便优化控制相移以及信道状态信息获取和控制功能（如基站切换）所需的大量参数。第四项研究活动将侧重于在点对点MIMO网络中测试我们的新型IRS原型，以证明其通过降维控制变量提高链路性能的能力。所提出的IRS及其控制的发展将实现高频谱效率，同时允许多个不同的同信道网络共存。同时，与基于继电器的替代方案相比，拟议的IRS将具有更低的成本，更高的能源效率和更简单的同步特性。IRS的控制将涉及调度和资源分配的多层方法，以解决多用户干扰和公平性等问题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The capacity of massive multi-input multi-output (MIMO) networks is shown to be theoretically unlimited as the number of antennas grows, provided that the spatial correlation inherent in the propagation channel is exploited. This proposal employs this observation using the assistance of novel “intelligent reflecting surfaces” (IRS) that can adaptively modify the spatial characteristics of the MIMO channel. The overall project goal is to improve spectrum efficiency and co-existence. To achieve this goal, the proposed device employs a metasurface with cells whose reflection properties can be programmed to take an impinging electromagnetic field and reshape the reflected field. For coexistence, a narrow beam of energy impinging on the IRS could be redirected towards a receiver that might otherwise be blocked from the transmission. Furthermore, the IRS can provide very complex reflection patterns to re-equalize the wireless channel links. The novelty of the proposal is the fact that the phase shifts are governed not by individual controls that would require numerous bulky electrical connections, but by electromagnetic waves launched onto thin waveguides on the reflecting surface. Given the boundary conditions of these waveguides, the controlling wave is designed as a linear superposition of periodic modes whose coefficients determine the phase shifts. A prototype of this device will be built and algorithms for its control and the control of the massive MIMO network will be developed.There will be four research activities. In the first, a novel IRS architecture with electromagnetic wave control will be designed. In the second activity, reduced-dimension algorithms for single-cell control of the IRS will be developed, together with corresponding methods for estimating the channel state information. The third activity will focus on the use of machine learning algorithms for incorporating multiple such IRS into a multi-cell setting with many users, in order to optimize the resulting huge number of parameters required for control of the phase shifts as well as channel state information acquisition and control functions such as base station handover. The fourth research activity will focus on testing our novel IRS prototype in a point-to-point MIMO network to demonstrate its ability to improve the link performance by means of the reduced dimension control variables. The development of the proposed IRS and its control will achieve high spectral efficiency while allowing for coexistence of multiple different co-channel networks. At the same time, the proposed IRS will have lower cost, higher energy efficiency, and simpler synchronization properties than alternatives based on relays. Control of the IRS will involve a multi-layer approach for scheduling and resource allocation in order to address issues such as multi-user interference and fairness.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.