Coding for Networked Control Systems over Lossy Links

未来十年将见证具有无线通信能力并且能够以自组织和/或集中方式彼此感测、测量、致动、交互和通信的设备的数量的爆炸性增长。这样的设备将出现在汽车、家用电器、可穿戴电子产品、传感器网络、监控系统、各种控制器和许多其他设备中。这些新兴设备的一个通用术语是物联网。如此多的智能设备带来的巨大机遇之一是，它们可以合作、协调、做出联合决策，并通过采取联合行动来影响它们所处的环境。实现这一机会的主要挑战是，这些多个设备或代理必须以分散的方式进行，同时通过不可靠的链路进行通信。虽然通信系统一直不得不处理不可靠的链路，但由于需要交换的控制和感测信号的实时性、动态变化的业务模式以及代理的可能移动性，为通信系统设计的传统方案不再适用。这项建议的目标是促进网络系统的设计和分析，相互作用和沟通，通过嘈杂的通信链路，并建立在调查？构建第一可有效解码的树码的现有工作，该树码可用于在有损擦除链路上可靠地实现任何分布式协议。如何最好地在有损链路的网络上操作分布式异构代理是一个活跃的研究领域。问题包括代理人应该交换什么信息？他们应该如何最好地对测量或控制信号进行编码和编码，以应对网络中的不确定性（延迟或消息丢失）？它们如何促进合作并克服竞争？他们如何以分布式的方式做到这一切？这些非常具有挑战性的问题与传统的通信、网络和控制领域重叠，并以新颖的方式将每个领域的元素联合收割机结合起来。因此，一种能够以整体方式处理这些问题的理论尚未出现。该提案试图通过树码的研究开始这样一个理论，树码是编码中的一种新范式，它允许在有损链路上可靠地实现交互式协议，以及通过因果源编码的研究。树码在近20年前被引入作为信息论和控制之间的桥梁，但由于不存在具有有效解码的显式结构，因此没有获得太多的牵引力。 因果源编码领域甚至更少探索。本论文的主要研究内容包括：（1）设计适用于AWGN和BSC等信道的树型编码;（2）研究控制系统的性能以及信源编码、信道编码和控制器设计之间的相互影响和权衡;特别是因果变换码以及如何在控制设置中优化它们，（4）在擦除链路上实现分布式协议，以及（5）根据控制理论确定度量以指导代码设计。

The coming decade will witness an explosive growth in the number of devices with wireless communication capabilities and that can sense, measure, actuate, interact, and communicate with each other in ad hoc and/or centralized fashions. Such devices will appear in automobiles, household appliances, wearable electronics, sensor networks, surveillance systems, various controllers and many others. A common catch-all phrase for these emerging devices is the Internet-of-Things. One of the great opportunities that such a plethora of intelligent devices presents is that they can cooperate, coordinate, make joint decisions, and influence the environment they are in by taking joint actions. A main challenge in realizing this opportunity is that these multiple devices, or agents, must do so in a decentralized way and while communicating over unreliable links. Although communication systems have always had to deal with unreliable links, because of the real-time nature of the control and sensing signals that need to be exchanged, the dynamically-changing traffic patterns, and the possible mobility of the agents, traditional schemes designed for communication systems are no longer applicable. The goal of this proposal is to facilitate the design and analysis of networked systems that interact and communicate with each other over noisy communication links and builds on the investigators? prior work of constructing the first efficiently decodable tree codes that can be used to reliably implement any distributed protocol over lossy erasure links. How best to operate distributed heterogeneous agents over networks of lossy links is an area of active research. Questions include what information should the agents exchange? How best should they quantize and encode their measurements or control signals to combat the uncertainties (delay or message drops) in the network? How can they facilitate cooperation and overcome the competition? How can they do all this in a distributed fashion? And so on. These very challenging questions overlap with the conventional fields of communications, networking and control and combine elements of each in novel ways. As result, a theory that can deal with them in a holistic manner has yet to emerge. This proposal attempts the beginning of such a theory through the study of tree codes, a new paradigm in coding that allows the reliable implementation of interactive protocols over lossy links, as well as through the study of causal source coding. Tree codes were introduced nearly twenty years ago as a bridge between information theory and control, but did not gain much traction since explicit constructions with efficient decoding did not exist. The area of causal source coding is even less explored. The proposed research has five main thrusts: (1) the design of efficiently encodable and decodable tree codes for other classes of channels, such as AWGN and BSC, (2) the study of the performance of control systems and the interaction and tradeoffs between source coding, channel coding and controller design, (3) the study of causal source coding; in particular, causal transform codes and how they can be optimized in the control setting, (4) implementing distributed protocols over erasure links, and (5) determining metrics from control theory to guide the code design.