| dc.description.abstract | There are many people die or hurt because of car accident every year in the world. Therefore, automotive industry, government, and organization are trying to find a solution to improve it. The technique of wireless made grate progress, so the framework of Vehicle Ad-hoc Network (VANET) is developed. It can exchange data between vehicles without the help of base station or it can communicates with outside by base station for VANET. The characteristic produces many applications, such as the vehicular Cooperative Collision Avoidance (CCA). Many proposals provide some solution for CCA. Although they improve the bandwidth of usage and reduce the end to end delay time, they don’t to confer with driver reactive time and braking distance.
This thesis proposes the using of Warning Message and Emergency Message; Warning Message provide the early warning ability, and Emergency Message confirm that the emergency brake occurred. This thesis utilizes CTB-to-itself scheme, hence it can reduce the number of collision packets, avoid Hidden node problem and reduce waiting time before sending message.
The Early Warning scheme based on CCA (EWCCA) that this thesis proposes does not require vehicular position by other device, and it can determine driving direction and the direction of message propagation. EWCCA can solve broadcast storm problem. It utilizes the ranging technique of RSSI and TOA which transform the measuring data into waiting time. Therefore, it can avoid a solution that all receiving vehicles forward this message at the same time. Finally, the thesis uses QualNet simulation software to simulate, and it differentiates between EWCCA for RSSI form and EWCCA for TOA, and comparing itself with Simple Flooding. By the simulating results, in fading model experiments, it improves 60% for end-to-end delay time, it improves 86% for collision packets and it improves 56% for receiving failure rate. It proves that EWCCA can provide lower delay time, less number of collision packets and lower receiving failure rate. Hence, it can achieve the purpose of increasing reactive time for driver. | en_US |