Full Duplex-Based Scheduling Protocol for Latency Enhancement in 5G eV2X VANETs

In this paper, we propose a novel scheduling protocol, named full duplex semi-persistent scheduling (FD-SPS) protocol, to support the communications between autonomous vehicles (AVs) in future 5G enhanced vehicle-to-everything (eV2X) ad hoc networks (VANETs). Different from other works, AVs are considered to operate at different autonomous levels. Besides, full duplex (FD) technology is incorporated to provide simultaneous sensing and broadcasting capability, so that AVs can detect signal collisions whilst broadcasting. Furthermore, compared to the standardised cellular V2X (C-V2X) Mode 4 technology, the sensing-based semi-persistent scheduling (SB-SPS) protocol, collision resolution capability is realised. Thus, collided messages can be re-broadcast. A corresponding prioritised re-broadcast mechanism is also proposed. We focus on the latency performance, because the delivery of a message with short delay is of paramount significance in safety-related communications. We evaluate the FD-SPS protocol through both analysis and simulations, and compare it with the benchmark SB-SPS protocol. It is shown that our proposed protocol has enhanced the latency performance, and can be considered to be deployed in future 5G eV2X VANETs. This paper also shows that latency can be enhanced by taken autonomous levels into consideration in future MAC design.