Channel Estimation with Pilot Reuse in IQ Imbalanced Massive MIMO

In this paper, we investigate channel estimation with pilot reuse for massive MIMO with in-phase and quadrature-phase imbalances (IQI). Firstly, we obtain an augmented real-valued representation for the received signal by processing the real and imaginary parts individually with relative compensation. Then based on the obtained augmented real-valued representation, we perform minimum mean square error (MMSE) estimation for the effective channel which comprises the IQI matrix and wireless channel coefficients. Pilots are reused to reduce the pilot overhead. A lower bound of the effective channel estimation MSE is obtained. Motivated by the optimal conditions under which the lower bound can be achieved, we propose a pilot schedule algorithm. Finally, a least square based method to obtain the relative IQI compensation coefficients is provided. Numerical results verify the performance of the proposed effective channel estimation with pilot reuse.