Channel state information compression via joint beam/lag selection

Receiving, by a user equipment (UE) in a wireless network from a network node of the wireless network a request for channel state information (CSI) feedback 710 and generating by the UE an array of downlink channel coefficients 720. The UE makes a selection of at least one beam of a plurality of beams and at least one lag from a plurality of lags such that a residual between the array of downlink channel coefficients and a sparse approximation of the array of downlink channel coefficients is less than a threshold. The sparse approximation is based on a sparse representation whose nonzero entries are identified by the at least one beam and the at least one lag, the selection of the at least one beam and the at least one lag being made jointly 730. The UE produces a binary message by encoding at least one identifier of the at least one beam and lag and the sparse representation 740 and sends the binary message to the network node as a response to the request for CSI 750. The corresponding decoding operation by the network node is also defined (see Fig 8).