Characterization of the capacity region of two-receiver broadcast channels

Characterize the full capacity region of general two-receiver discrete memoryless broadcast channels, including private and common messages.

Background

The paper considers the capacity problem for the two-receiver memoryless broadcast channel, in which a transmitter sends private messages to each receiver and a common message to both. Although Marton's inner bound is the best-known general achievable region, the paper proves that this one-letter inner bound is strictly sub-optimal for some discrete memoryless broadcast channels. Consequently, the full capacity region remains unresolved even after the paper establishes that Marton's inner bound does not always attain it.

References

This model was originally proposed by Cover (and a detailed definition can be found in Chapters 5, 8), but the full characterization of the capacity region remains one of the most fundamental open problems in information theory for decades.

— Sub-optimality of Marton's Inner Bound for the Two-Receiver Broadcast Channel  (2608.19869 - Huang et al., 20 Aug 2026) in Section 1, Introduction