## 2 Internet of Vehicles and Smart Cities
### Architecture
#### 2.2.5 Comparison  
It is possible to conclude that the four architectures share some similarities between themselves. All the architectures have the following characteristics: layers responsible for sensors, vehicles, and data collection (sensor, end-point, perception, and data acquisition layers); layers that handle and manage communications between entities (communication, infrastructure, perception, and coordination, and communication layers); the data processing, service, artificial intelligence and application, and the processing layers which are all responsible for data processing and decision making, among other services, usually provided by the cloud infrastructure. The management of network providers is only present in the four, five, and seven-layered architectures in the operation, coordination, and control and management layers. Only the five and seven-layered architectures have layers responsible for or help in the development of business models: the business and processing layers, respectively. Finally, only the seven-layered architecture has layers that handle data pre-processing and, most importantly, security. While the five-layer architecture does not present a security layer, they mention the secure transmission of information between layers through the usage of protocols to achieve a safe exchange of data. Each architecture presented has benefits and downsides, as the increasing complexity maybe be useful for some research and not so much for others. Given this, the choice of what architecture framework should be followed is in the researcher's hands, which must make their decision based on what their project requires from the IoV architecture and what aspects are relevant to consider to fulfill the needs of the work in question. [PERSON] et al. [3] state that the three and five-layer architectures do not consider the security challenges of IoV. It is also possible to add the four-layer architecture to this affirmation, giving the analysis above. The authors further noticed that even the most complete one, i.e., seven-layered architecture, does not take advantage of new paradigms and technologies, such as using 4G/5G communications to deal with high latencies and low bandwidth or even using computing paradigms, such as edge and fog computing, for pre-processing and data management. They then present a three-layered generic architecture, which is presented in Figure 3, and is organized as follows:  
* _Terminal layer_ (or _IoV layer_) that is responsible for gathering information on the road through millimeter-wave (_mm-wave_) _V2X_ communication modes (_mm-wave_ is a new 5G network technique that can promise multigigabit communication services [17]). * _Edge computing layer_ that has:
* _Fog infrastructure sublayer_ that is responsible for data processing, analysis, computing storing, networking, and security. * _Fog virtualization sublayer_, which is further divided in:
* _the upper level_ has two planes that manage the network (_control plane_ that manages the local and global data planes and provides programmability and flexible management, and _global data plane_ that contains forwarding and data processing devices). * _the lower level_ contains the local data plane, which has nodes that forward and receive data to and from fog and cloud computing. * _Fog service sublayer_ which offers traditional fog services adapted to IoV, such as:
* _Fog Vehicular Infrastructure as a Service_ (offers data processing, storage, and analysis while having the capability of adopting another infrastructure to serve other needs). * _Fog Vehicular Platform as a Service_ (offers different operational systems and computational environments to ensure the fulfillment of the heterogeneous needs of drivers and vehicles). * _Fog Vehicular Software as a Service_ (offers fog-based software divided into user applications and safety applications, which is be explained below).