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Conditions for optimality of superposition coding in discrete memoryless broadcast channels
Date Issued
01-02-2019
Author(s)
Abstract
The capacity region of general discrete-memoryless broadcast channels (DMBCs) with two receivers is an open problem of considerable research interest. The optimality of superposition coding in three specific cases of the DMBC is considered. For a DMBC with binary input, symmetric output and output cardinality at most 3, superposition coding is shown to be optimal. For equal-capacity DMBCs with any input cardinality, superposition coding is shown to be suboptimal if each channel has a capacity-achieving input distribution that is not capacity-achieving for the other channel. For an equal-capacity DMBC with binary input, superposition coding is shown to be optimal if and only if the two channels are more-capable comparable even without utput symmetry. These results improve upon the previously known conditions for optimality of superposition coding in DMBCs.