Capacity Bounds for Broadcast Channels with Bidirectional Conferencing Decoders

Abstract

The two-user broadcast channel (BC) with decoders connected by cooperative links of given capacities (known as conferencing decoders) is considered. A novel outer bound on the capacity region is established. This outer bound is derived using multiple applications of the Csiszár-Körner identity. A new achievable rate region for the channel is also presented which is derived by applying Marton’s coding as the transmission scheme, and quantize-bin-and-forward at one receiver and decode-and-forward at the other receiver as cooperative strategy. It is proved that the outer bound coincides with the achievable region for a class of semi-deterministic BCs with degraded message sets. This is the first capacity result for the two-user BC with bidirectional conferencing decoders. This result demonstrates that a one-round cooperation scheme is sufficient to achieve capacity for this class of semi-deterministic BCs with degraded message set. A capacity result is also derived for a new class of more capable semi-deterministic BCs with both common and private messages and one-sided conferencing.