# A Novel Cloud Approach for Connected Vehicles
## 2 Related Works
### ETSI Standards for C-ITS  
ETSI defined different layers used by the intelligent transport systems (ITSs) to communicate [4] (Figure 1). In the figure, the access is composed of the physical layer [5; 6; 7] and the MAC layer [8; 9]. The networking and transport layer is ensured by the geometworking (GN) protocol for the routing and basic transport protocol (BTP) for the transport. Then, the facilities layer specifies the messages exchanged on the channel: CAM (cooperative awareness message) [10], DENM (decentralized environmental notification message) [11], SPAT (signal phase and time), and MAP (map data) [12]. Finally, we find the applications layer (e.g., Android, cloud). As a vertical layer, there are the security [13] and the management layers. These are the standards currently used for the deployment of C-ITSs in Europe and our approach will be based on these ones.  
Figure 1, extracted from [9], presents the ETSI layers architecture explained above. The bubbles MA, FA, SA, etc., refer to the protocols and access points to associated services that we will not detail here. The G5 technology is based on the standard IEEE 802.11p, a kind of Wi-Fi (IEEE 802.11) dedicated to short-range communications, considering high-speed mobility. In the current study, we will focus on three types of communications: V2V (vehicle to vehicle), V2I (vehicle to infrastructure), and I2V (infrastructure to vehicle). ITS-G5 is another name for the access layer composed of the physical layer 802.11p and the MAC layer. The geometworking protocol, associated with BTP, is used to route and transport the data. The geometworking protocol is a geographical routing protocol, which means a packet is not destined for a specific node but for a region, usually called a destination area. There  
are three kinds of routing algorithms: the simple one, contention base forwarding (CBF), and the advanced one. The three algorithms use the same process to forward the packet to the destination area: they all select the closest neighbor to the area (greedy process). When the packet is received in the destination area, it is broadcast again to everyone. In the current study, we will consider simple geonetworking, since it is the one currently used for ITS.  
Security data, used to verify the integrity and authenticity of the message, are included in geometworking headers. Certificates are provided by a public key infrastructure (PKI) and a turnover in a pool of certificates guarantees the privacy of the user. In our study, we focus on CAM (cooperative awareness message) and DENM (decentralized event notification message), which are the most common messages. CAMs are a kind of super beacon emitted by the vehicle and give its speed, location, heading, path history, etc. They are emitted in a single hop (i.e., only to the neighbors). These messages are sent at a frequency varying between 1 Hz and 10 Hz (10 Hz most of the time).  
Its structure is defined as being extensible, allowing it to include proprietary content without changing the nature of the message. Thus, we will take advantage of the CAM's structure in order to include additional information, such as interests and data.