  We introduce Noise Recycling, a method that enhances decoding performance of
channels subject to correlated noise without joint decoding. The method can be
used with any combination of codes, code-rates and decoding techniques. In the
approach, a continuous realization of noise is estimated from a lead channel by
subtracting its decoded output from its received signal. This estimate is then
used to improve the accuracy of decoding of an orthogonal channel that is
experiencing correlated noise. In this design, channels aid each other only
through the provision of noise estimates post-decoding. In a Gauss-Markov model
of correlated noise, we constructive establish that noise recycling employing a
simple successive order enables higher rates than not recycling noise.
Simulations illustrate noise recycling can be employed with any code and
decoder, and that noise recycling shows Block Error Rate (BLER) benefits when
applying the same predetermined order as used to enhance the rate region.
Finally, for short codes we establish that an additional BLER improvement is
possible through noise recycling with racing, where the lead channel is not
pre-determined, but is chosen on the fly based on which decoder completes
first.
