Implementation of the IEEE 802.11p protocol on embedded systems

In this master degree thesis, an implementation and integration of the IEEE 802.11p protocol in two different models of PC Engines boards is investigated. The focus is put on the physical and MAC layers. PC Engines is a Swiss producer that makes and sells embedded boards, typically based on AMD x86 processors. These boards are specifically targeted to networking applications and always include at least one mini PCI or mini PCIe slot to accommodate a proper WNIC (Wireless Network Interface Controller), providing a quite customizable architecture, as already investigated in literature. Systems like the one which is investigated in this work actually represent an important part of the ITS applications, which are becoming more and more of interest both in the industrial and academic world. This work focuses in particular on open source solutions, since they are important for the investigation of V2X (Vehicle To Everything) protocols, allowing to implement new features and patch existing ones with much more ease than commercial products which are starting to emerge nowadays on the market. In both cases, an embedded Linux operating system (OpenWrt) is used, providing all the proper tools needed to develop the work and giving a high degree of flexibility, being completely open source. The integration of other WAVE (Wireless Access in Vehicular Environment) important features are also investigated, such as the different traffic classes defined in the MAC layer of 802.11. The final goal is to test our implementation and analyze the system performance using the collected data, highlighting strength and possible problems that could arise. Part of this work is also related to the analysis of the ITS frequency spectrum used by the boards, by means of a proper analyzer hardware, eventually finding out few PHY layer problems affecting the older boards (ALIX 3d2); this motivated us to move to the newer boards (APU 1d), which also provide a more updated hardware system with a better overall performance. We were able to test the connectivity writing few basic C programs for broadcast transmissions over the wireless medium, showing that the communication can correctly happen. Then we performed measurements of packet loss and reachable throughput under various conditions, using OCB mode and the UDP protocol, which seemed to be the best choice to simulate the transmission of WSMs (WAVE Short Messages) when a proper stack will be implemented (UDP messages are also foreseen by the IEEE 802.11p standard, when IP frames are sent). These measurements were performed also thanks to the iPerf tool. It is also possible to highlight how these boards can be used to sniff traffic over the 802.11p frequencies (5.850-5.950 GHz), showing three different methods that can be used to capture packets travelling over the air inside the aforementioned spectrum. In conclusion, this work highlighted the importance of open source solutions for V2X experimentation, showing how the platform we studied and developed, also thanks to the very important work of the CCS Labs team of University of Paderborn on the OpenC2X platform, can be used as a skeleton to build more complex V2X applications and research about new protocols and features.