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Is Non-Unique Decoding Necessary?

In mutiterminal communication systems, signals carrying messages meant for different destinations are often observed together at any given destination receiver. Han and Kobayashi (1981) proposed a receiving strategy which performs a joint decoding of messages of interest along with a subset of messages which are not of interest. It is now well-known that this provides an achievable region which is, in general, larger than if the receiver treats as noise all messages not of interest. Nair and El Gamal (2009) and Chong, Motani, Garg, and El Gamal (2008) independently proposed a generalization called indirect or non-unique decoding where the receiver outputs even if it is unable to disambiguate uniquely some of the messages which are not of interest to it. Non-unique decoding has since been used in various scenarios. In this paper we will try to argue using an operational interpretation why non-unique decoding is superfluous from a rate region point-of-view and can be replaced by an arguably simpler unique joint decoding receiver. We give a line of argument which applies to all instances where non-unique decoding has been employed in the literature.

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