Impact of phase noise on MIMO channel measurement accuracy

A widespread design for multiple-input multiple-output (MIMO) radio channel measurement devices (sounders) is based on time-division multiplexed switching of a single transmit/receive radio frequency (RF) 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 in the local oscillators. We analyze the impact of phase noise on MIMO channel measurement accuracy and show that it can lead to overestimation of channel capacity of up to 100% in practice. Furthermore, we demonstrate that the impact of phase noise is most pronounced if the physical channel has low rank (typical for line-of-sight or low scattering scenarios). The extreme case of a rank-1 physical channel is analyzed in detail.