On the Capacity of the Relay Channel with Known State at the Source

We investigate the general relay channel with state that is noncausally known at the source. We first present a multiletter characterization of the capacity using the Gelfand-Pinsker encoding scheme. We then tailor the result to the general Gaussian relay channel with additive interference noncausally known at the source and compute a closed-form lower bound to the capacity using the joint dirty paper coding (DPC) and multidimensional linear relaying. We finally demonstrate that a potentially suboptimal evaluation of the proposed lower bound can simultaneously outperform known state-of-art coding strategies including DPC with signal description or state description along with compress-and-forward, noisy network coding and decode-and-forward.