Relaying for Multiuser Networks in the Absence of Codebook Information

TL;DR

This paper investigates relay-assisted multiuser networks without codebook information, establishing capacity regions for various models using a generalized compress-and-forward strategy and demonstrating its optimality under certain conditions.

Contribution

It introduces new capacity bounds and proves the optimality of the GCF scheme for oblivious relays in multiple network models, extending to M-user and multicast networks.

Findings

Derived new outerbounds for MARC and IFRC with oblivious relays.

Proved the tightness of bounds using GCF scheme.

Extended results to M-user MARC and multicast networks.

Abstract

This work considers relay assisted transmission for multiuser networks when the relay has no access to the codebooks used by the transmitters. The relay is called oblivious for this reason. Of particular interest is the generalized compress-and-forward (GCF) strategy, where the destinations jointly decode the compression indices and the transmitted messages, and their optimality in this setting. The relay-to-destination links are assumed to be out-of-band with finite capacity. Two models are investigated: the multiple access relay channel (MARC) and the interference relay channel (IFRC). For the MARC with an oblivious relay, a new outerbound is derived and it is shown to be tight by means of achievability of the capacity region using GCF scheme. For the IFRC with an oblivious relay, a new strong interference condition is established, under which the capacity region is found by deriving a new outerbound and showing that it is achievable using GCF scheme. The result is further extended to establish the capacity region of M-user MARC with an oblivious relay, and multicast networks containing M sources and K destinations with an oblivious relay.