On the high-SNR capacity of noncoherent networks

We obtain the first term in the high signal-to-noise ratio (SNR) asymptotic expansion of the sum-rate capacity of noncoherent fading networks, i.e., networks where the transmitters and receivers-while fully cognizant of the fading law-have no access to the fading realization. This term is an integer multiple of log log SNR with the coefficient having a simple combinatorial characterization. It can be interpreted as the effective number of parallel channels that can be supported by the network, i.e., as the maximal number of point-to-point single-user scalar channels that can be supported by the network in a manner that will allow, with proper power allocation, negligible cross interference. The results hold irrespective of whether the transmitters can cooperate or must operate in an multiple-access regime; irrespective of whether feedback from the receivers to the transmitters is available or not; and irrespective of whether the receivers can cooperate or not.