Conversion from Uplink to Downlink Spatio-Temporal Correlation with Cubic Splines

In FDD systems, uplink spatio-temporal correlation knowledge can be obtained via uplink measurements and time- averaging. Many algorithms however require the knowledge of the downlink correlation, such as transmit beamforming in the case of spatial correlation and user SNR prediction algorithms in the case of temporal correlation. This paper shows a way to convert the uplink spatio-temporal correlation to its downlink counterpart using spline interpolation and two dimensional phase unwrapping techniques. Furthermore, applications are shown which highlight the potential benefit of the proposed algorithm.