# Analysis of Low Cost Communication Technologies for V2I Applications
## 2 Related Work  
To fix the base on which our solution was developed, a preliminary state of the art was established. On the one hand, we reviewed different technologies which have been used and those which could be used. While on the other hand, we reviewed the different applications for V2I which have been developed. Many studies have focused efforts on alternatives for the two tendencies (802.11p and 5G). More specifically, [8] has contrasted ZigBee technology against Bluetooth and UWB (ultra-wide band), highlighting that ZigBee was the most stable technology sending messages. The same authors made in [9] a laboratory test where they tested a V2I prototype with ZigBee, reaching the conclusion that is an adequate technology for V2I, although it has disadvantages. The most important one is that its data rate is slower than Wi-Fi or Bluetooth. In [10], they used ZigBee, too. They demonstrated that at high speed (80 km/h), ZigBee modules covered 500-700 m. It took 21-30 s to transmit the data. Another emergent technology was analyzed in [11], where ZigBee was compared with nRF24L01 modules. The conclusion was that nRF24L01 had better performance than ZigBee, however they consumed more energy. Another technology studied is the VLC (visible light communication). In [12], they worked with Li-Fi (Light Fidelity) (standard IEEE802.15.7) for short range V2I communication, although it could be used for V2V. In [13], they demonstrated that VLC could offer a good performance for V2I up to 50 m, achieving lower latencies (below 10 ms) and higher reliability (packet error rate below \(10^{-5}\)). In addition, their VLC system was integrable with 5G systems. It is a promising technology, but its problem are the really short range, only a few meters, and its low network capacity. A comparison between Li-Fi and Wi-Fi can be found in [14]. Finally, [15] sought for an alternative to mmWave. They carried out simulations, where they contrasted LTE with mmWave. They considered that devices with high frequency bands are a promising technology because they can carry much more data, although they cover much smaller areas. Regarding the applications, urban cases were mainly studied. The aim was to optimize the urban traffic density by means of adaptive traffic lights, cutting down pollutant vehicle emissions and improving driving efficiency. In [16] there was a simulation of an algorithm to control traffic lights through communication technology 802.11p. They claimed that it is possible to reduce CO\({}_{2}\) emissions. In [17], it was carried out a proof of concept with a low cost microprocessor, Raspberry Pi, which took control of a camera to detect the number of vehicles in the intersection. Similarly, in [18] a Raspberry Pi, a radar, and an 802.11p module were used to detect vehicles which were approaching the intersection and warning the vehicles in the transversal road. Another interesting study is [19], where it is described the proof of concept of the architecture for communication V2I. Its goal was to increase the available information for the driver in intersections and traffic lights, searching for a change in driver behavior so that the driver carried out a safe and efficient drive. Once the main tendencies were reviewed, it was exposed the conclusion which put together the starting point:  
* Applications for V2I communication for managing traffic flow with traffic lights are a priority, which will be able to reduce congestion and fuel consumption. * Most studies were focused only on urban cases. * Using low cost microprocessors for V2I communications is an option in a proof of concept. * There is not a methodology for analyzing the performance of the different communications' technologies. In conclusion, the goal was to search for a technological alternative for V2I communication in a short/middle range. After ensuring the features of the technology by means of an own validation methodology for V2I communication, proofs of concept for two specific applications are planned.