NOMA-dependent Low-Powered Retransmission in Sensing-based SPS for Cellular-V2X Mode 4

This paper proposes a retransmission strategy using the non-orthogonal multiple access (NOMA) in the PC5-based cellular-V2X mode 4 (called mode 4) to mitigate the channel congestion. The proposed strategy has two key ideas. The first idea is to allow each node (e.g., a car or a pedestrian) to retransmit its packet at lower transmission power than its original packet in the first transmission. The second idea is that each node aims to synchronize its low-powered retransmission with the first transmission of its neighbor node. The two key ideas boost the PRR through diversity effects by mitigating interference and providing power differences with widely deployed receivers. Our simulations highlighted that the proposed strategy outperformed the existing NOMA with retransmissions in mode 4 by 29%.