Vehicular ad hoc network (VANET) is an emerging technology for the future intelligent transportation systems (ITS). How to design an efficient routing protocol for VANET is a challenging task due to the high mobility and uneven distribution of vehicles in urban areas. This paper proposes a backbone-based approach to providing the optimal inner-street relaying strategy. The virtual backbone is created distributively in each road segment based on the newly introduced stability index, which considers the link stability between vehicles and the mobility of vehicles. We also deploy the roadside unit (RSU) at intersections to determine the next path for forwarding data. The RSU gathers a global view of backbone vehicles on each road connected to the junction and analyzes the performance of the backbone as a basis of routing path selection. Simulation results show that the proposed protocol outperforms the conventional protocols in terms of packet delivery ratio and end-to-end delay.

Regression testing is essential for assuring the quality of a software product. Because rerunning all test cases in regression testing may be impractical under limited resources, test case prioritization is a feasible solution to optimize regression testing by reordering test cases for the current testing version. In this paper, we propose a novel test case prioritization approach that combines the clustering algorithm and the scheduling algorithm for improving the effectiveness of regression testing. By using the clustering algorithm, test cases with same or similar properties are merged into a cluster, and the scheduling algorithm helps allocate an execution priority for each test case by incorporating fault detection rates with the waiting time of test cases in candidate set. We have conducted several experiments on 12 C programs to validate the effectiveness of our proposed approach. Experimental results show that our approach is more effective than some well studied test case prioritization techniques in terms of average percentage of fault detected (APFD) values.