Method and apparatus for efficient channel state information dissemination for mu-mimo transmission schemes based on outdated channel state information

Abstract

A method and apparatus is disclosed herein for channel state information dissemination for multi-user (MU) multiple-input multiple-output (MIMO) (MU-MIMO) transmission schemes based on outdated channel state information. In one embodiment, a method for disseminating channel state information (CSI) coefficients from a first user terminal, where each CSI coefficient corresponds to the CSI previously observed by the first user terminal during transmission resource blocks used by a base station to communicate information to a second set comprising at least one user terminal and not including the first user terminal, comprises: broadcasting by the base station the channel state information (CSI) of each user terminal in the second set of user terminals, on the subset of transmission resources used by the base station to communicate information to each user terminal in the second set; receiving observations of these transmissions by the first user terminal; performing, at first user terminal, eavesdropper channel selection of a subset of CSI coefficients between the base station and the eavesdropping first-user terminal for uplink CSI feedback, the subset chosen out of the set of CSI coefficients between base station and the first user-terminal on the transmission resources used by the base station to communicate information to each user terminal in the second set; scheduling the subset of the selected CSI coefficients for uplink transmission; and transmitting the subset of the selected CSI coefficients via the uplink transmission.