## 4 Evaluation
### Car Sharing Experiment  
#### 4.2.1 Car Sharing Case Description  
The car sharing case has been visualized in Figure 20. The system has been built to provide real-time car sharing services such as e.g., monitoring the status and location of the cars _etc._ In the experimental system, a car is connected via 3G/GPRS to a Car-sharing web application that shows real time the relevant data that comes from the car. The data is collected by some sensors that can be placed in the car, in the parking spot, or in any other provider of the car sharing scenario. Also the data that manages the application can come from any other external provider of the car sharing business as the car maintenance provider, cleaning company _etc._  
For example, if the car sharing company wants to know the state of the doors, while the customer is using the car, we click on the button doors in the web application, this application sends (in a standard format) to the car the request of the state of the doors via the M2M gateway, and the car returns the data via standard XML-format. Or a Car-sharing customer wants to make a reservation, a code is sent to the customer for reserving a determinate car, after this the customer will be able to open the car with his mobile phone (NFC system). The idea is that the car is managed and monitored by the car sharing company, providing many services to the customer in order to rent the car whenever is necessary with the maximum flexibility. Figure 20: Car sharing case. A key novel component of the system is the A2 Nets Gateway functions executed within the on-board computer of the car. The gateway has three different connections to devices: CANBUS gets car values such as speed, fuel status, status of doors and windows, _etc._; The GPS sensor provides the car localization; The NFC Sensor authenticates the user's from NFC tag or mobile device to allow open or close the door. In the car also there are wireless devices (IR and RADIO) that communicate with wireless sensors of the parking, so that they know the location of the vehicle inside the parking house. The A2 Nets gateway connects the sensors into the back-office server. The Server contains the general database system and a range of services to interact with other actors. From the car collects data in real time and historical of localization, speed, fuel, _etc._ From Parking gets the position of the place where is the vehicle to offer the customer who wants to rent it. Sends a customer keys to the car in order to client can open the door by NFC authentication. Also, allows client to make the reservation of a vehicle and know the basic statistics of client trip. When parking a wireless sensor detects the vehicle that is parked in a particular position. The Computer Parking automatically sends the data to the Car-Sharing company. Similarly, when the car leaves the parking, also sends information to the server. An UML deployment diagram for car sharing scenario is shown in Figure 21.  
The A2 Nets gateway consist of components for both M2M service gateway and M2M overlay communication gateway as is shown in Figure 22. The M2M Service Gateway acts as an application level translator of messages between M2M capillary Networks to Overlay Communications protocol. For example, the messages from CANBUS and USB modules (NFC, GPS) needs to be translated to application level messages in formats applied by the back-office server. The M2M overlay communication gateway facilitates communication with all the devices of the system in a virtual network. For this purpose, the Communications Gateway establishes a  
Figure 21: UMP deployment diagram of the car sharing scenario. Layer2 Tunnel to a Virtual switch through IP/SSL, similarly to OpenVPN Layer2 [74] and studies and definitions of L2 VPN Working Group [75]. One of basics functions of the Communications Gateway is to establish the WAN connection (GPRS, 3G, xDSL, Satellite), maintain the connection, and change automatically the connection if the active is in failure or constrained.