Capacity bounds for Cooperative diversity

In a cooperative diversity network users cooperate on transmitting each others’ messages; to some extend nodes therefore collectively act as an antenna array. In this paper we derive upper and lower bounds for the information theoretic capacity of 4 node ad-hoc networks with two transmitters and two receivers using cooperative diversity. For comparison, in an N user channel with M antennas at the base station, the high SNR ergodic sum capacity is C ∼ min{N,M} log(SNR)+O(1) in Rayleigh fading. One question considered is if cooperative diversity gives the same kind of multiplicative gain, and the answer is negative at least in the asynchronous case, although if the cooperating nodes are reasonably close together a multiplicative gain is possible up to quite high SNR. Finally, it appears that cooperation among receivers is more efficient and less complex than cooperation among transmitters.