A method for a User Equipment, UE, operating in a wireless communication system, includes triggering power headroom reports (PHRs), in a first Medium Access Control (MAC), entity and a second MAC entity when a first type event occurs in the second MAC entity, wherein the UE is configured with the first MAC entity corresponding to a first base station and the second MAC entity corresponding to a second base station for a radio bearer; triggering a PHR in the second MAC entity only, when a second type event occurs in the second MAC entity, wherein the first type event includes: there are uplink resources allocated for transmission on any cell of the second MAC entity and a required power backoff for the any cell of the second MAC entity has changed more than a threshold, or wherein the first type event includes: there is uplink transmission on any cell of the second MAC entity and a required power backoff for the any cell of the second MAC entity has changed more than a threshold.