Investigation of front-end requirements for MIMO-systems using downlink pre-distortion

In this paper the influence of front-end imperfections on the reciprocity of the entire up- and downlink system frequency responses is studied for systems with single- or multi-antenna transmitters and receivers. Based on a scattering matrix approach, front-end influences such as unequal transceiver gains and antenna mismatching are integrated into the base band system frequency responses which are used for examination of hardware requirements and calibration procedures. Additionally, some link-level simulations are performed for a joint pre-distortion system with single-antenna users and a multi-antenna base station.