Performance of HARQ with Reduced Size Retransmissions Using Network Coding Principles

This paper discusses retransmission approaches to improve the throughput performance of Hybrid-ARQ (HARQ) schemes in a point-to-point single user 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) uplink system. One goal of communication systems is to achieve a reliable transmission with a throughput performance as close as possible to channel capacity. For that, reducing the channel utilization will improve the throughput performance. Instead of sending two retransmission packets for two HARQ processes of one users, a previously published HARQ scheme uses the XOR combining of these packets to get only one retransmission packet with the same size. Similar to this idea, a new varied scheme performs XOR combining of parts of one conventional full retransmission to generate a smaller retransmission packet. Both approaches will reduce the channel utilization. They will be compared with a HARQ system in LTE uplink using a full size retransmission and a half size retransmission. The main focus of this work is the throughput performance evaluation of these schemes in an LTE link-level simulator.