The University of British Columbia

A recent study demonstrated that the technique of subpacket retransmission can substantially improve the throughput of an ARQ system. To select the subpackets suitable for retransmission, a cyclic redundancy check (CRC) was employed at the subpacket level. In this paper, we propose a probabilistic subpacket retransmission ARQ (PSR-ARQ) scheme for wireless systems, which does not employ CRC bits at the subpacket level. Rather, we utilize the demodulator's decision statistics to assess the reliability of the decoded subpackets. In the event of an erroneous large packet, the subpacket with the lowest bit-wise posterior probability is retransmitted. Using updated subpacket reliability metrics, individual subpacket retransmissions are continued until the overall CRC of the large packet is verified. By avoiding the use of CRC bits at the subpacket level, our PSR-ARQ scheme exhibits a much lower transmission overhead relative to the benchmark scheme. This translates into a significant improvement in power efficiency (on the order of 6 dB) at a high throughput level.