On the capacity of wireless relaying

We consider wireless relaying: one or more nodes in a wireless (ad-hoc) network assist other nodes in their transmission by partially retransmitting messages. A characteristic of wireless relays - as compared to the work by T.M. Cover and A.A. El Gamal on the relay channel (see IEEE Trans. on Inf. Theory, vol.25, no.5, p.572-84, 1979) - is that they cannot transmit and receive simultaneously at the same frequency. We derive new upper and lower bounds for the capacity of this wireless relay channel. We then apply these result to a 4 terminal network, and show that the gain (considering outage capacity) of using wireless relaying is of the order of 8-9 dB.