On Mutual Information and Capacity in Frequency Selective Wireless Channels

This paper has two major contributions. First, we present measured frequency selective wireless channels and show that there is only a small difference between mutual information and capacity. For single-antenna channels the maximum difference is about 0.15 bit/s/Hz, but typical differences are much smaller. These differences are increased with the number of transmit and receive antennas, achieving a maximum of about 0.4 bit/s/Hz for 2x2 MIMO channels and about 1.8 bit/s/Hz for 4x4 MIMO channels. The second contribution is a simple two-parameter channel model for frequency selective wireless channels, exhibiting the identical behavior in terms of capacity and mutual information than the measured channels. Due to its simplicity, this so-called poor-rich model is especially suitable for fast simulations and for analytical research in the field of information theory.