Noisy feedback improves communication reliability

Stark C. Draper, Anant Sahai

Abstract: We show how to exploit a noisy feedback link to implement high-reliability communication. We specify a variable-length coding strategy that achieves the error exponent (in delay) of erasure decoding using any noisy feedback channel which has a positive zero-rate random coding error exponent. Building on this result, we give a second approach that, depending only on the capacity of the feedback link, achieves an error exponent up to half of the Burnashev exponent - the maximum exponent that can be achieved with a noiseless feedback link. The resulting exponent can be far larger than the exponent of erasure decoding, particularly at rates close to capacity