The Impact of Hardware Calibration Errors on the Performance of Massive MIMO Systems

Hardware calibration is a necessary procedure to establish the reciprocity of the uplink (UL) and downlink channels (DL) in a time division duplex (TDD) mode of operation. In practice, any calibration scheme is prone to errors. Such errors result in a residual mismatch between UL and DL channels, which, in turn, can significantly affect the quality of DL transmission. In this paper, we study the effects of the hardware calibration errors on the per-user achievable ergodic rate in the DL of a single cell multi-user massive MIMO system. We consider zero-forcing (ZF) precoding under two different scenarios: first we assume that the UL channel state information (CSI) is known perfectly at the BS; we then consider the case where CSI is acquired with minimum mean squared error (MMSE) estimation. We verify the accuracy of our analytical results through numerical simulations.