tion Buffer/HARQ Reordering Add RLC Header Routing DCCH/DTCH DCCH/DTCH FIGURE 7-24 An illustration of 3GPP LTE AM RLC entity [11] When the transmitting side of an AM RLC entity forms AMD PDUs from RLC SDUs received from an upper layer, or AMD PDU segments from RLC data PDUs to be re-transmitted, it includes relevant RLC headers in the RLC data PDU. The receiving side of an AM RLC entity receives RLC data PDUs, detects duplicate RLC data PDUs, and discards duplicated RLC data PDUs. It reorders the RLC data PDUs, if they are received out of sequence, detects the loss of RLC data PDUs at lower layers, and sends re-transmission requests to its peer AM RLC entity. It further reassembles RLC SDUs from the reordered RLC data PDUs and delivers the RLC SDUs to the upper layer in sequence. At the time of RLC re-establishment, the receiving side of an AM RLC entity reassembles RLC SDUs from the RLC data PDUs that are received out of sequence and delivers them to the upper layer, discarding any remaining RLC data PDUs that could not be reassembled into RLC SDUs, initializing relevant state variables, and stopping relevant timers. The RLC sub-layer provides TM data transfer, UM data transfer, and AM data transfer, including indication of successful delivery of upper layer PDU services to RRC or PDCP. The MAC sub-layer provides data transfer and notification of transmission opportunity (along with the total size of the RLC PDUs) services to the RLC sub-layer. CHAPTER 7 The IEEE 802. 16m MAC CPS (Part II) The RLC sub-layer performs the following functions: Transfer of upper layer PDUs; Error correction through ARQ for AM data transfer; Concatenation, segmentation, and reassembly of RLC SDUs for UM and AM data transfer; Re-segmentation of RLC data PDUs for AM data transfer; Reordering of RLC data PDUs for UM and AM data transfer; Duplicate detection for UM and AM data transfer; RLC SDU discard for UM and AM data transfer; RLC re-establishment; Protocol error detection for AM data transfer. RLC PDUs can be categorized into RLC da