# Fog-Based Two-Phase Event Monitoring and Data Gathering in Vehicular Sensor Networks
## 2 Related Work
### VANETs and Fog Computing  
Within the concept of edge computing and fog computing, more and more fog nodes would be deployed at the edge of networks for various applications. [PERSON] et al. (2018) proposed a mobility-enhanced small-scale cloud data center that is located at the edge of the Internet. A cloudlet is a trusted, resource-rich computer or cluster of computers that is well-connected to the Internet and available for use by nearby mobile devices. [PERSON] et al. (2018) proposed a framework for coordinated processing between edge and cloud computing/processing by integrating the advantages from both platforms. The proposed framework can exploit the network-wide knowledge and historical information available at the cloud center to guide edge computing units towards satisfying various performance requirements of heterogeneous wireless IoT networks. Similarly, [PERSON] et al. (2018) proposed a hierarchical distributed fog computing architecture for big data analysis in smart cities. It distributes intelligence at the edge of a layered fog computing network. [PERSON] et al. (2018) for the first time coined the term of autonomous vehicular clouds (AVC), where a group of largely autonomous vehicles whose corporate computing, sensing, communication and physical resources can be coordinated and dynamically allocated to authorized users. [PERSON] et al. (2018) took a step forward to broaden the idea of VANET clouds by defining a communication paradigm for VANET clouds and then put forth the potential cloud services from the VANET standpoint. [PERSON] and [PERSON] (2018) proposed a system where cloud computing services are hosted by vehicles that have sufficient resources to act as mobile cloud servers and vehicles could search the mobile cloud servers that are moving nearby and discover their services and resources. The concept of VANET cloud, indeed, is highly related to the fog computing, which extends the traditional cloud computing paradigm to the edge. Edge nodes are able to provide computation, storage and networking services between the end nodes and traditional clouds. Fog reduces service latency and improves QoS, resulting in superior user experience. [PERSON] et al. (2018) defined the characteristics of fog computing and its role in the Internet of Things. They emphasized the fact that fog computing brings new elements to the realm of the Internet of Things through a reduction of service latency and improvement of QoS (quality of service). [PERSON] et al. (2018) gave a border and integrated view of the fog, and they argued that the fog will dramatically shift many current practices at almost every layer of the IT stack, like app development, network traffic management, network/service provision, accounting, app collaboration mechanisms, etc. [PERSON] et al. (2018) elaborated previous scenarios and further expanded this concept on a series of real scenarios, such as the smart grid, smart traffic lights in vehicular networks and software-defined networks. More recently, [PERSON] et al. (2018) gave a survey about some opportunitiesand challenges related to the context of fog computing in VANETs; and [PERSON] et al. (2012) proposed a three-layer framework based on a fog structure for uploading data from sensor readings to the cloud. Static sensor nodes can forward their data to their nearby mobile fog nodes, so that the data transmission latency to the cloud center can be greatly reduced. [PERSON] et al. (2013) gave a detailed description of fog computing and proposed a flexible software architecture to incorporate different design choices and user-specified polices. The challenge of fog computing lies in that the nodes are ubiquitously connected at the edge of network, and there should be a careful design of scheduling and cooperation schemes among the fog nodes, as well as collaboration between vehicular nodes and the cloud. [PERSON] et al. (2014) presented smart gateway-based communication, along with fog computing, for the purpose of smart communication and helping lessen the burden on the cloud.