Method for handling of unknown LCID values in a multicast channel in a wireless communication system and a device therefor

A method for a User Equipment (UE) operating in a wireless communication system, the method comprising:

• receiving a Medium Access Control (MAC) Control Element (CE) including a first Logical Channel Identifier (LCID) on a Multicast Channel (MCH);
• determining that the first LCID is not one of a plurality of reserved values on the MCH;
• checking whether the UE has joined a Multimedia Broadcast Multicast Service (MBMS) service transmitted on a Multicast Traffic Channel (MTCH) identified by the first LCID;
• discarding at least one field related to the first LCID in the MAC CE, when the first LCID identifies an MTCH, on which an MBMS service that the UE did not join, is transmitted;
• and
• processing remaining parts of the MAC CE, other than the at least one field related to the LCID discarded from the MAC CE.

A User Equipment (UE) operating in a wireless communication system, the UE comprising:

• a receiver and a transmitter;
• and
• a processor, operably coupled to the receiver and the transmitter, wherein the processor is configured to:
• receive a Medium Access Control (MAC) Protocol Data Unit (PDU) including a first Logical Channel Identifier (LCID) and a MAC Service Data Unit (SDU) related to the first LCID on a Multicast Channel (MCH),
• determine that the first LCID is not one of a plurality of reserved values on the MCH,
• check whether the UE has joined a Multimedia Broadcast Multicast Service (MBMS) service transmitted on a Multicast Traffic Channel (MTCH) identified by the first LCID,
• discard a sub-header field including the first LCID and a MAC SDU related to the first LCID in the received MAC PDU, when the first LCID identifies an MTCH, on which an MBMS service that the UE did not join, is transmitted;
• and
• process parts of the MAC PDU, other than the sub-header field and the MAC SDU discarded from the MAC PDU.