Sub-linear capacity scaling for multi-path channel models

The theoretic capacity of a communication system constituted of several transmitting/receiving elements is determined by the singular values of its transfer matrix. Results based on an independent identically distributed channel model, representing an idealized rich propagation environment, state that the capacity is directly proportional to the number of antennas. Nevertheless there is growing experimental evidence that the capacity gain can be at best scaled at a sub-linear rate with the system size. In this paper, we show under appropriate assumptions on the transfer matrix of the system that the theoretic information-capacity of multi-antenna systems is upper bounded by a sub-linear function of the number of transmitting/receiving links. Copyright (C) 2009 John Wiley & Sons, Ltd.