Dual XOR in the Air: A Network Coding Based Retransmission Scheme for Wireless Broadcasting

In this paper, a novel dual XOR hybrid automatic retransmission request scheme XOR²-HARQ is proposed for wireless broadcasting. Distinct from the traditional network coding (NC) based HARQ (NC-HARQ), an additional XOR operation is introduced to dynamically combine lost packets from the individual receiver instead of conducting XOR operation only across lost packets from different receivers. Furthermore, based on the linear block code´s perspective, we optimize the retransmission strategy to yield optimal diversity gain. Analytical results show that conditioned on the same packet error ratio (PER), the retransmission rounds needed for XOR²-HARQ is strictly less than that of NC-HARQ, and the simulation results consolidate our analysis to show a significant reduction of required retransmissions.