  This paper characterizes the capacity of a class of modulo additive noise
relay channels, in which the relay observes a corrupted version of the noise
and has a separate channel to the destination. The capacity is shown to be
strictly below the cut-set bound in general and achievable using a
quantize-and-forward strategy at the relay. This result confirms a conjecture
by Ahlswede and Han about the capacity of channels with rate limited state
information at the destination for this particular class of channels.
