Patent ID: 8238371

Claim:
A method of processing data units in a mobile communications system, the method comprising: receiving, from an upper entity, a first data unit including a first header and a first payload, and a second data unit including a second header and a second payload; converting a header field of the first header and a header field of the second header into a header field of a third header of a third data unit including the first payload and the second payload; determining a format of the third data unit by an upper entity signaling; and transferring the third data unit to a lower layer, wherein the header field of the first header and the header field of the second header are not fixed in size, wherein the first data unit and the second data unit are Medium Access Control-high speed Service Data Units (MAC-hs SDUs) and the third data unit is a MAC-hs Protocol Data Unit (PDU), wherein the third data unit corresponds to a queue used for a Voice over Internet Protocol (VoIP) service, wherein a Size Index Identifier (SID) field of the third data unit is set to have a length of 4 bits or 5 bits in the queue used for the VoIP service, wherein a queue identifier (queue ID) and a Number (N) field are not included in the third data unit, and wherein a number of bits of a Transmission Sequence Number (TSN) of the third data unit is set to have a length of less than 5 bits.