V2X Meets NOMA: Non-Orthogonal Multiple Access for 5G-Enabled Vehicular Networks

Benefiting from widely deployed infrastructure, the LTE network has recently been considered as a promising candidate to support vehicle-to-everything (V2X) services. However, with a massive number of devices accessing the V2X network in the future, the conventional OFDM-based LTE network faces congestion issues due to its low efficiency of orthogonal access, resulting in significant access delay and posing a great challenge especially to safety-critical applications. The non-orthogonal multiple access (NOMA) technique has been well recognized as an effective solution for the future 5G cellular networks to provide broadband communications and massive connectivity. In this article, we investigate the applicability of NOMA in supporting cellular V2X services to achieve low latency and high reliability. Starting with a basic V2X unicast system, a novel NOMAbased scheme is proposed to tackle the technical hurdles in designing high spectrally efficient scheduling and resource allocation schemes in the ultra-dense topology. We then extend it to a more general V2X broadcasting system. Other NOMA-based extended V2X applications and some open issues are also discussed.