Length indicator for a protocol data unit in a wireless communications protocol

A data structure for a first layer 2 protocol data unit (PDU) to carry layer 2 service data unit (SDU) data in a wireless communications system, the data structure comprising:

• a sequence number region that holds a sequence number for indicating a sequential ordering of the first PDU in a stream of PDUs;
• a length indicator array after the sequence number region that holds length indicators indicating the ending positions of SDUs carried by the first PDU, the length indicator array having at least a final length indicator, the final length indicator being the last length indicator in the length indicator array and being n bits in length;
• an SDU array having at least a final SDU data block, the final SDU data block being the last segment of the last SDU in the SDU array;
• and
• a padding area of at least 1 bit in length after the final SDU data block that fills the remainder of the first PDU;
• wherein the padding area is less than n bits in length, and no special explicit length indicator is contained in the length indicator array to indicate the presence of the padding area, the length indicator indicating that the ending position of the final SDU data block is the final length indicator in the length indicator array.