I. Introduction
According to relevant research, it is anticipated that by 2023, the number of intelligent Internet of Things (iIoT) devices worldwide will achieve 21.5 billion [1], [2], [3]. With the expansion of wireless communication networks and the maturity of Intelligent Transportation Systems (ITS) technologies, the limited battery life and limited computing power of mobile devices pose considerable challenges for developing smart applications [4]. Especially in ITS, the traditional technology represented by cloud computing has been difficult to ensure the Quality of Service (QoS) of such a huge device [5], [6]. Aiming at the issue of inefficient use of computing, communication, and storage resources in wireless communication systems and the challenges posed by iIoT, the Multi-tier Computing Network (MTCN) architecture [7] provides an effective solution for ITS. It efficiently migrates computing-intensive tasks to the cloud, fog, edge, etc., with sufficient resources, realizes energy-efficient cloud-fog-edge collaborative computing and multi-dimensional resource sharing, and is utilized to achieve different levels of requirements for various devices [8]. Specifically, the multi-tier computing network is a high-speed, mobile, secure, and ubiquitous network connection [9]. It integrates multi-tier computing resources such as cloud, fog, and edge, and provides digital information infrastructure with integrated services such as data perception, transmission, storage, and computing.