# Analysis of Low Cost Communication Technologies for V2I Applications
## 3 Materials and Methods
### Communication Technology  
To achieve the overall goal, which was described in the previous section, it was necessary to have different communication technologies and microprocessors. The technology created the network with adequate performance (in terms of latency, data rate, and data payload) and the microprocessor carried out its control, although it needed the right algorithm.  
With the goal of taking the best relationship between cost and performance, Arduino and Raspberry microprocessors were tested. They are widely used for home automation, robotics, and Internet of Things (IoT). Some solutions checked in Section 2 were used for the same microprocessor for its solution regardless of its work role. In this work, both were used because we wanted to take advantage of the faster response of the Raspberry for a better response in the vehicle, and take advantage of the robustness of the Arduino in the RSU for ensuring the right delivery of the message with the best performance available.  
Three microprocessors were used depending on the communication technology needed:  
* Arduino UNO R3: It is a robust microprocessor and it ensures the right operation of any algorithm. The technical specifications are in [20]. It was used for all the technological solutions, excluding Wi-Fi option, because using a microprocessor with the Wi-Fi integrated was preferred.
* Raspberry Pi 3B+: Last release of Raspberry in the selection time, its technical specifications can be found in [21]. It was used for all the technological solutions, taking advantage of its faster operation and the embedded Wi-Fi 802.11 b/g/n/ac.
* Arduino UNO WIFI REV2: Last version of Arduino in the selection time, its technical specifications are in [22]. This microprocessor integrated the Wi-Fi 802.11 b/g/n.  
Following the microprocessors' selection, the next step was the choice of communication technologies. There is a wide range of technologies in the market, as it can be seen in Figure 3. Particularly, the desired technology must have a short/middle range. In other words, it has to cover a minimum distance of 100 m, in accordance with the specifications of Section 1.  
Figure 3: Communication technologies.  
Inside the short/middle range technologies, which were available in the market, it was selected the following technologies, which have been collected inTable 1.  
Following Table 1, three technologies were chosen: ZigBee, nRF24L01, and Wi-Fi:  
* DIGI XBEE S2C: Radiofrequency module from DIGI XBee, whose operation protocol is ZigBee, which is inside 802.15.4 radiofrequency protocol. Its technical specifications are in [23].
* nRF24L01+: Radiofrequency module with an integrated antenna amplifier. It operates inside 802.15.4 radiofrequency protocol. Its technical specifications can be found in [24].
* Wi-Fi IEEE 802.11 b/g/n: Wi-Fi module embedded in the Arduino Uno WiFi REV2. The technical specifications of the Wi-Fi module are in [25].
* Wi-Fi IEEE 802.11 b/g/n/ac: Wi-Fi module embedded in the Raspberry Pi 3B+. The technical specifications of the Wi-Fi module are in [26].  
The obvious choice for Wi-Fi technology could have been the standard 802.11p. Nevertheless, these modules required a high investment, which was out of our selection criteria. In this way, with the last version of both microprocessors, it was achieved two Wi-Fi technologies with a low cost.