Proxy cooperative awareness message: an infrastructure-assisted V2V messaging

Cooperative Intelligent Transportation Systems (CITS) are being developed to make road traffic safer and more efficient. Vehicle to vehicle (V2V) communication plays an important role for the cooperative awareness of vehicles in all the CITS standards in EU, US, and Japan. Essentially the CITS application relies on the exchanged data by V2V messages (called Cooperative Awareness Message (CAM) in EU). However, the V2V communication suffers from two significant problems: 1) mixed environment and 2) obstacle interference. First, the CITS application cannot be aware of a non-CAM-aware vehicle because of low market penetration ratio of the V2V message transmitter in the early deployment phase. Second, the V2V messages may not reach the receivers because of interference by the obstacle between the vehicles. To solve these problems, the proposed system called Proxy CAM generates the necessary V2V messages in the roadside unit on behalf of sender vehicles (or non-CAM-aware vehicle) by sensing the vehicle. We design the system based on the ITS Station architecture standardized in ISO/ETSI, working with any vehicle sensing technology. Moreover, we implement the prototype system with a stereo vision for the vehicle sensing. The prototype system is evaluated in an indoor test and also validated in a field test in Tokyo with some modifications in the link layer to adapt the Japanese regulation. The results show that Proxy CAM significantly improves the coverage of V2V messaging while the system overhead is limited.