Cooperative Relay Broadcast Channels

TL;DR

This paper investigates the capacity regions of relay broadcast channels with user cooperation, deriving achievable rate regions, outer bounds, and capacity results for both partially and fully cooperative models, demonstrating the benefits of relaying.

Contribution

It introduces new capacity bounds and achievable regions for both partially and fully cooperative relay broadcast channels, including degraded and Gaussian cases, advancing understanding of cooperative communication.

Findings

Achievable rate regions are derived using decode-and-forward schemes.

Outer bounds on capacity are tighter than cut-set bounds.

Fully cooperative channels outperform partially cooperative ones in achievable rates.

Abstract

The capacity regions are investigated for two relay broadcast channels (RBCs), where relay links are incorporated into standard two-user broadcast channels to support user cooperation. In the first channel, the Partially Cooperative Relay Broadcast Channel, only one user in the system can act as a relay and transmit to the other user through a relay link. An achievable rate region is derived based on the relay using the decode-and-forward scheme. An outer bound on the capacity region is derived and is shown to be tighter than the cut-set bound. For the special case where the Partially Cooperative RBC is degraded, the achievable rate region is shown to be tight and provides the capacity region. Gaussian Partially Cooperative RBCs and Partially Cooperative RBCs with feedback are further studied. In the second channel model being studied in the paper, the Fully Cooperative Relay Broadcast Channel, both users can act as relay nodes and transmit to each other through relay links. This is a more general model than the Partially Cooperative RBC. All the results for Partially Cooperative RBCs are correspondingly generalized to the Fully Cooperative RBCs. It is further shown that the AWGN Fully Cooperative RBC has a larger achievable rate region than the AWGN Partially Cooperative RBC. The results illustrate that relaying and user cooperation are powerful techniques in improving the capacity of broadcast channels.