Capacity of Decode-and-forward Cooperative Links with Full Channel State Information

Cooperative diversity is a novel technique to obtain reliable communications, capacity gains and energy savings by mutual relaying among users of wireless networks. This paper proposes a new multiple-input-multiple-output (MIMO) signal model for half-duplex, decode-and-forward cooperative links with multiple relays and derives the instantaneous capacity for coherent relaying when full channel state information is available at source, destination and relay nodes. At the same time, analyzes the optimum relay selection and power allocation for such relaying scheme, showing that capacity achieving strategy does not make use of all potential relays within the networks. Results on this paper suggest logarithmic growth of the capacity with the total number of network users, i.e. potential relays, and better performance for the low SNR regime. Moreover, they show important spectral efficiency gains for small number of co- operating nodes, making relaying diversity practically attractive. Finally, comparison with space-time coded cooperation depicts the influence of channel state information in cooperative links.