Reliable Communication with Feedback: Coding Schemes and Fundamental Limits

双向通信系统的两端各有一个发送器/接收器，双向信息流使得使用某种反馈来帮助对抗信道噪声和不确定性成为可能。长期以来，人们已经认识到，当信道有记忆时，反馈不仅可以帮助增加容量，而且为了满足性能目标，它实际上可能导致复杂性和时延的降低。然而，在利用反馈能力方面，实践与理论之间的差距仍然很大。这是一项关于反馈通信系统的理论驱动设计和实践驱动理论的研究项目。设计和分析方法紧密结合香农理论和现代编码理论，通过稀疏图码的反馈和信任传播译码的协同结合，研究可靠传输和联合信源-信道编码的实现方案，以利用即使是少量反馈的力量来改善延迟率折衷。为了帮助弥合理论和实践之间的差距，该项目的一个主要重点是分析与传统模型不同的技术独立的基本限制，以及性能指标，如以很小一部分容量传输时的指数错误率下降。

Two-way communication systems, with a transmitter/receiver at each end, are ubiquitous.The bi-directional information flow gives rise to the possibility of using some kind of feedback in order to help combating channel noise and uncertainty.It has long been recognized that feedback not only can help increase capacity when the channel has memory, but it may actually lead to decreased complexity and delay in order to meet performance targets. However, the gulf between practice and theory remains wide as far as taking advantage of the capabilities of feedback.This is a research project on both theory-driven design and practice-driven theory of feedback communication systems. Methods of design and analysis are tightly coupled and guided by the teachings of both Shannon theory and modern coding theory.Through the synergistic combination of feedback and belief propagation decoding of sparse-graph codes, the projects studies implementable schemes for both reliable transmission and joint source-channel coding that can harness the power of even a modicum of feedback in order to improve delay-rate tradeoffs. To help bridge the gap between theory and practice, a major thrust of the project is on the analysis of technology-independent fundamental limits departing from conventional models and performance measures such as the exponential error rate decrease when transmitting at a fraction of capacity.