On the simultaneous relay channel with informed receivers

The simultaneous relay channel is investigated where the source is unaware of the channel statistic controlling the communication but knows that this statistic is one of two possible discrete memoryless relay channels. We aim to derive coding schemes capable of transmitting information, regardless of which of these relays is present. First, this problem is recognized as being equivalent to that of sending common and private information to two destinations in presence of two helper relays. In this scenario, each possible relay links becomes a branch of the so-called broadcast relay channel. An inner bound on the capacity region of this channel is derived. Applications of these results arise when the source node is uncertain of the noise levels or the network topology (e.g. due to user mobility the positions of the relay and the destination nodes are unknown). Specific rates are computed for an AWGN relay channel, where the relay node may be absent but the source node is unaware of this.