Message and State Cooperation in a Relay Channel When the Relay Has Strictly Causal State Information

TL;DR

This paper investigates a relay channel with strictly causal state information at the relay, proposing a cooperative scheme for message and state transmission, deriving capacity bounds, and analyzing a Gaussian case with numerical insights.

Contribution

It introduces a novel cooperative scheme leveraging message and state cooperation in a relay channel with causal state information, and characterizes capacity in special cases.

Findings

Proposed a noisy network coding-inspired scheme for message and state cooperation.

Derived capacity bounds for specific relay channel configurations.

Numerical results demonstrate the benefits of state and message cooperation in Gaussian models.

Abstract

A state-dependent relay channel is studied in which strictly causal channel state information is available at the relay and no state information is available at the source and destination. Source and relay are connected via two unidirectional out-of-band orthogonal links of finite capacity, and a state-dependent memoryless channel connects source and relay, on one side, and the destination, on the other. Via the orthogonal links, the source can convey information about the message to be delivered to the destination to the relay while the relay can forward state information to the source. This exchange enables cooperation between source and relay on both transmission of message and state information to the destination. First, an achievable scheme, inspired by noisy network coding, is proposed that exploits both message and state cooperation. Next, based on the given achievable rate and appropriate upper bounds, capacity results are identified for some special cases. Finally, a Gaussian model is studied, along with corresponding numerical results that illuminate the relative merits of state and message cooperation.