Cooperative Superposed Transmission in Cellular-Based V2V Systems

Vehicle-to-vehicle (V2V) communication is a critical 5 G scenario demanding stringent safety requirements. As a way of ensuring safe packet exchange between vehicles in a V2V system, we propose a new cooperative transmission scheme employing a signal superposition technique from non-orthogonal multiple access (NOMA), which we call cooperative superposed transmission (CST). In the proposed CST, vehicle user equipments (VUEs) superpose other VUEs' signals that they have received on to their own transmission signals. This allows them to retransmit other users' V2V packets during their packet transmission. The result is high communication reliability because packets can be sent multiple times without intensifying inter-user interference (IUI). We perform a theoretical analysis, then use it to derive a closed-form expression for the link reliability of the proposed CST. Based on this, a new power control and user pairing algorithm is designed to maximize reliability. Simulation results show that the proposed scheme achieves higher reliability and lower latency than the conventional transmission schemes used in cellular-V2V (C-V2V) systems. Moreover, the proposed CST guarantees high reliability in various road environments and system settings.