Novel Many-to-Many NOMA-Based Communication Protocols for Vehicular Platoons

Future vehicular platoons demand ultra-reliable low-latency communication (URLLC) and high data rates that exceed the capabilities of current vehicular ad hoc network (VANET) standards. To address such demands, we propose novel many-to-many (M2M) non-orthogonal multiple access (NOMA) protocols leveraging millimeter-wave (mmWave) communication to facilitate the exchange of broadcast, multicast, and unicast messages between vehicular platoons. Specifically, we design downlink, uplink, and joint uplink/downlink M2M NOMA schemes that enable full-duplex inter-cluster communication. To enhance performance, we optimize cluster head selection and power allocation jointly, and devise a computationally efficient tailored-greedy algorithm that yields near-optimal performance. Additionally, a super-cluster formation protocol is proposed to further limit the overhead of successive interference cancellation (SIC). Simulation results reveal that in most of the considered scenarios, the joint uplink-donwlink NOMA scheme significantly outperforms orthogonal multiple access (OMA) in sum rate despite imperfect SIC, while reducing latency through simultaneous transmissions. Additionally, each of the proposed NOMA schemes is shown to excel under certain scenarios.