Communication schemes for platooning in V2X networks

Abstract

In this dissertation, vehicle-to-everything (V2X) communications for vehicle platooning is addressed. Vehicle platooning is maily classified into three main operational types, which are a network control-based method through vehicle-to-network (V2N) communications, a method controlled via vehicle-to-vehicle (V2V) communications within a platoon, and a method through simultaneous support of V2N and V2V communications. In this dissertation, to support vehicle platooning with V2X communications, two detailed research topics are investigated. In the first study, we proposed efficient V2V groupcast schemes for vehicle platooning in a V2V network. In V2V groupcast for vehicle platooning, the leading vehicle serving as the platoon head delivers packets to the other vehicles within the platoon, and retransmission of groupcast, in general, is implemented in two ways. The first traditional retransmission scheme is to repeatedly conduct retransmission for a predetermined number of times without receiving acknowledgment signals from receiving vehicles, and in the second scheme, initiation of retransmission is determined according to the acknowledgment signal. Although the former scheme is very easy to implement, it may lead to inefficient resource utilization due to excessive retransmissions. For the latter, the same problem arises when link quality between source vehicle user equipment (S-VE) and destination VE (D-VE) is constantly poor. Therefore, in the first study, we propose a groupcast scheme that improves the groupcast success rate (GSR) and minimizes total time consumption (TTC) by formulating a Markov decision process (MDP). Simulation results show that the GSR and resource utilization efficiency of the proposed scheme are significantly improved as compared with the traditional schemes. In the second study, platoon head selection-based vehicle platooning handover (VPH) schemes and vehicle platooning communication (VPC) schemes are investigated in a V2X network, where both V2I/N and V2V communications are involved. We consider two types of platoon heads, communication platoon head (C-PH) and handover platoon head (H-PH), which are responsible for VPH and VPC, respectively. The purposes of this study are to analyze the influence of platoon head selection on handover probability and link outage performance, to present three VPC schemes based on C-PH selection, and to derive the closed-form analytical expressions for overall link outage probability of the proposed VPC schemes with consideration of H-PH selection. In simulation, it is confirmed that by properly selecting an H-PH that performs group handover, the probability of VPH can be reduced and the overall link outage probability can be also reduced. In addition, we validate the analytical expressions for the derived link outage probability of the three proposed VPC schemes by simulation and show that the VPC scheme 3, which exploits instantaneous channel information for selecting C-PH, yields far superior performance over the other two VPC schemes in terms of lin outage.