Information-Theoretic Analysis of MIMO Channel Sounding
The large majority of commercially available Multiple-Input Multiple-Output (MIMO) radio channel measurement devices (sounders) is based on Time-Division Multiplexed Switching (TDMS) of a single transmit/receive radio frequency chain into the elements of a transmit/receive antenna array. While being cost-effective, such a solution can cause significant measurement errors due to phase noise and frequency offset in the local oscillators. In this paper, the authors systematically analyze the resulting errors and show that, in practice, overestimation of channel capacity by several hundred percent can occur. Overestimation is caused by phase noise (and to a lesser extent by frequency offset) leading to an increase of the MIMO channel rank.