A method of providing a fronthaul interface in a cloud radio access network, CRAN, having a baseband unit, BBU, and at least one radio unit, RU, remote from the BBU, the method comprising: providing radio frequency interface, RF, functionality in the RU; providing physical layer, PHY, functionality split between the BBU and the RU, wherein downlink, DL, precoding is implemented in the RU; and providing transmission of reference signals from the BBU to the RU separately from transmission of data from the BBU to the RU, including: - adding a flag to a control-plane, C-plane, message to indicate that associated U-plane data in the reference signals transmission from the BBU to the RU contains reference signals and is to be stored locally at the RU based on at least one of subframe, symbol, xRAN resource block, XRB, and resource element, RE; - locally storing, by the RU, the transmitted reference signals based on at least one of subframe, symbol, XRB and RE associated with the reference signal; - indicating a location of the reference signals by using a resource element mask, reMask; - automatically inserting, in RU transmissions, the locally stored reference signals with the data based on at least one of subframe, symbol, XRB and/or RE; - enabling said flag with new contents and new reMask to update the reference signals; - invalidating previous storage for the corresponding XRB; - sending update to reference signals as stand-alone packets using a C-plane section type for precoding at RU, avoiding to combine said update with said data. providing radio frequency interface, RF, functionality in the RU; providing physical layer, PHY, functionality split between the BBU and the RU, wherein downlink, DL, precoding is implemented in the RU; and providing transmission of reference signals from the BBU to the RU separately from transmission of data from the BBU to the RU, including: - adding a flag to a control-plane, C-plane, message to indicate that associated U-plane data in the reference signals transmission from the BBU to the RU contains reference signals and is to be stored locally at the RU based on at least one of subframe, symbol, xRAN resource block, XRB, and resource element, RE; - locally storing, by the RU, the transmitted reference signals based on at least one of subframe, symbol, XRB and RE associated with the reference signal; - indicating a location of the reference signals by using a resource element mask, reMask; - automatically inserting, in RU transmissions, the locally stored reference signals with the data based on at least one of subframe, symbol, XRB and/or RE; - enabling said flag with new contents and new reMask to update the reference signals; - invalidating previous storage for the corresponding XRB; - sending update to reference signals as stand-alone packets using a C-plane section type for precoding at RU, avoiding to combine said update with said data. - adding a flag to a control-plane, C-plane, message to indicate that associated U-plane data in the reference signals transmission from the BBU to the RU contains reference signals and is to be stored locally at the RU based on at least one of subframe, symbol, xRAN resource block, XRB, and resource element, RE; - locally storing, by the RU, the transmitted reference signals based on at least one of subframe, symbol, XRB and RE associated with the reference signal; - indicating a location of the reference signals by using a resource element mask, reMask; - automatically inserting, in RU transmissions, the locally stored reference signals with the data based on at least one of subframe, symbol, XRB and/or RE; - enabling said flag with new contents and new reMask to update the reference signals; - invalidating previous storage for the corresponding XRB; - sending update to reference signals as stand-alone packets using a C-plane section type for precoding at RU, avoiding to combine said update with said data.