A method for operating an access node, the method comprising: sending , by the access node to a user equipment, UE, a frequency domain density reduction rate indicator and a frequency shift index indicator for one or more channel state indicator reference signal, CSI-RS, resources, wherein the frequency domain density reduction rate indicator indicates a number of physical resource blocks, PRBs, skipped between successive CSI-RS transmissions and the frequency shift index indicator indicates a shift of a CSI-RS starting PRB; wherein the frequency domain density reduction rate indicator and/or the frequency shift index indicator corresponding to each CSI-RS resource in an active set of K CSI-RS resources are sent during a radio resource control, RRC, configuration stage of a CSI-RS resource configuration process; wherein at least one frequency domain density reduction rate indicator and/ or at least one frequency shift index indicator configured during the RRC configuration stage is reconfigured for at least one CSI-RS resource in an activated set of N CSI-RS resources during an activation/release stage of the CSI-RS resource configuration process by sending, to the UE, uplink grants and/or medium access control, MAC, control elements, CE; and wherein at least one frequency domain density reduction rate indicator and/or at least one frequency shift index indicator configured during the RRC configuration stage and/ or at least one CSI-RS resource in the activated set of N CSI-RS resources configured during the activation/ release stage of the CSI-RS resource configuration process is reconfigured by sending, to the UE, downlink control information, DCI. sending , by the access node to a user equipment, UE, a frequency domain density reduction rate indicator and a frequency shift index indicator for one or more channel state indicator reference signal, CSI-RS, resources, wherein the frequency domain density reduction rate indicator indicates a number of physical resource blocks, PRBs, skipped between successive CSI-RS transmissions and the frequency shift index indicator indicates a shift of a CSI-RS starting PRB; wherein the frequency domain density reduction rate indicator and/or the frequency shift index indicator corresponding to each CSI-RS resource in an active set of K CSI-RS resources are sent during a radio resource control, RRC, configuration stage of a CSI-RS resource configuration process; wherein at least one frequency domain density reduction rate indicator and/ or at least one frequency shift index indicator configured during the RRC configuration stage is reconfigured for at least one CSI-RS resource in an activated set of N CSI-RS resources during an activation/release stage of the CSI-RS resource configuration process by sending, to the UE, uplink grants and/or medium access control, MAC, control elements, CE; and wherein at least one frequency domain density reduction rate indicator and/or at least one frequency shift index indicator configured during the RRC configuration stage and/ or at least one CSI-RS resource in the activated set of N CSI-RS resources configured during the activation/ release stage of the CSI-RS resource configuration process is reconfigured by sending, to the UE, downlink control information, DCI. <EOS>