an scs sends out a trigger message for activating a group of mtc devices through a network . an hss verifies whether or not to transfer the trigger message to the given mtc devices based on subscription information of the group . a group gw broadcasts the trigger message . further , an mme concatenates dl messages addressed to the mtc devices . the group gw distributes , to the mtc devices , the dl messages included in the concatenated message . furthermore , the group gw concatenates ul messages received from the mtc devices . the mme processes the ul messages included in the concatenated message .