Transmission Protocol of Emergency Messages in VANET Based on the Trust Level of Nodes

Vehicle Ad Hoc Networks (VANETs) can help reduce traffic accidents and improve road safety by broadcasting Emergency Messages (EMs) between vehicles in advance so that the vehicle can take action to avoid accidents. However, its advantages are often compromised by factors such as high mobility, uneven nodes distribution, and signal attenuation, resulting in lower reliability and higher delay in the delivery of EMs. Besides, because of its open and mobility, VANETs are vulnerable to cyber security threats and are prone to multiple malicious attacks in the network. Malicious nodes can join the set of candidate forwarding nodes through collusion and identity forgery, which poses a serious challenge to EMs forwarding. In order to resolve the problems above, this paper proposes a geographic routing strategy to deliver EMs based on trusted nodes, focusing on measuring the reliability of link quality and node quality. The link quality between nodes is evaluated by measuring the actual transmission cost and the link signal-to-noise ratio to minimize the possible link interruption; at the same time, the node trust value is introduced to measure the credibility of the node and filter out the possible malicious nodes in the network. The research results show that the protocol is suitable for dense and sparse traffic conditions, can detect and identify malicious nodes, and has significant performance improvements in message delivery rate, end-to-end delay, and network throughput.