CIF: Small: Approaching Capacity in High Throughput Communication Systems with Incremental Redundancy

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The growing ability to generate digital information and the hunger to consume that information create a need to communicate information at ever-higher rates. Free-space optical and millimeter wave wireless communication systems strive to achieve rates exceeding 100 Gbps. Optical fiber supports terabit-per-second communications. These systems require high-speed decoding circuits that currently sacrifice performance to meet latency requirements with available computational resources. This research develops new techniques for high-throughput communications with a goal of achieving theoretical performance limits while meeting latency requirements with reasonable complexity. In addition to providing a new path for practical solutions for high-throughput systems, the broader impacts of this research include the training of graduate students to support continued leadership of the United States in communications technology as well as hands-on research experiences for undergraduates to maintain the pipeline that will supply our country?s continuing need for diverse, well-trained, and innovative engineers.This research explores a new paradigm in which many low-complexity decoders work in parallel, decoding variable-length codes with short average block-lengths. Fixed-length codes with short block-lengths cannot approach the Shannon capacity, but variable-length codes with short average block-lengths do approach capacity. Variable-length codes are traditionally implemented with feedback so that incremental redundancy is transmitted only when requested by the receiver. This research transmits incremental redundancy without the use of feedback, utilizing techniques such as network coding and ergodicity to deliver redundancy only to those parallel decoders that need it. The problem of delivering incremental redundancy without feedback is framed as a joint source-channel coding problem with side information at the receiver. The primary goal of this research is to produce low complexity systems that can approach capacity at high throughput.