Covariance Based Linear Precoding for Full Rank Channels

We make two contributions to the field of FDD transmit processing for multi-user MISO systems: first the concept of covariance based linear precoding is extended to spatio-temporal channels with full rank covariance matrices. Within, the variance true approximation of all signal components allows the formulation of the receive signal exclusively basing upon covariance knowledge and thus the derivation of optimal linear precoding solutions. Second, the derived chip level signal model demonstrates, that the spatial transmit processing on the pilot channel has pivotal influence on the performance of precoding approaches for data channels in general. Through the consideration of the receive filter in the mobile devices, the effects of transmitter side processing on pilot channels can be included into the optimization of precoders for data channels yielding drastic performance enhancements with respect to state of the art techniques.