entation and packing information which was used in the initial transmission. In the case of ARQ block re-trans- mission with rearrangement, a single ARQ block may be fragmented into a sequence of multiple ARQ sub-blocks. A MAC PDU payload is constructed from one or more ARQ sub-blocks. The ARQ sub- blocks are sequentially numbered using ARQ block SUB_SN (SSN). The size of an ARQ sub-block is defined by ARQ_SUB_BLOCK_SIZE, which is fixed. The ARQ sub-block is maintained during re- transmission. Figure 7-3 illustrates ARQ block initial transmission and re-transmissions. Two options for re-transmission are shown, i.e., with and without rearrangements of the failed ARQ blocks. The ARQ feedback Information Element (IE) is defined for the receiver to indicate the reception status of an ARQ block (initial transmission) and an ARQ sub-block. The ARQ feedback IE is transported either as part of an extended header (piggybacked) within a MAC PDU or a standalone MAC control message. The ARQ feedback IE supports cumulative and selective ACK. In cumulative ACK, ARQ SN or ARQ SUB_SN are reported to indicate successful reception. In selective ACK, each bit of the ACK MAP indicates the error or success of ARQ blocks. The transmitter can request ARQ feedback poll to update the reception status of the transmitted ARQ blocks. In the downlink, an ABS may assign unsolicited bandwidth for the MS to send ARQ feedback information. The receiver sends ARQ feedback IE when these three conditions are met: (1) ARQ feedback polling request is received from the transmitter; (2) an ARQ block has been missing for a predetermined period; and (3) an ARQ discard message is received from the transmitter. The following parameters characterize an ARQ operation [2]: ARQ_SN_MODULUS: the number of unique ARQ sequence values equal to 1024; ARQ_WINDOW_SIZE: the maximum number of ARQ blocks with consecutive Block Sequence Number (BSN) in the sliding window of ARQ blocks that is managed by the receiver and the transmitter; ARQ_BLOCK_LIFETIME: the maximum time