1. A method of a user equipment (UE) in a wireless communication system, the method comprising:in case that a first message to perform a handover from a first base station to a second base station is received, from the first base station, performing a medium
access control (MAC) reset, wherein performing the MAC reset includes stopping a power headroom report (PHR) periodic timer;receiving, from the second base station, first information related to a first uplink resource;
in case that the first uplink resource is first allocated for a new transmission since the MAC reset is performed, starting the stopped PHR periodic timer;
transmitting, to the second base station, a second message to confirm the handover using the first uplink resource;
triggering a PHR, in case that the started PHR periodic timer expires;
receiving, from the second base station, second information related to a second uplink resource; and
transmitting, to the second base station, the triggered PHR using the second uplink resource.