Cooperative information services based on predictable trajectories in bus-VANETs

As a special yet important part of vehicular ad hoc networks (VANETs), Bus-VANETs have attracted much research attention in recent years. Most of existing studies focused on developing routing protocols in Bus-VANETs based on the predictable bus route. In this work, we embark a study on information services in Bus-VANETs, where bus information is provided via the hybrid of infrastructure-to-vehicle (I2V) and vehicle-to-vehicle (V2V) communications. In particular, we consider the scenario where buses on different routes request different information from roadside units (RSUs), which are the static infrastructures installed along the road, and provide information services to passing buses via I2V communication. Furthermore, buses are also able to share information with each other via V2V communications. On this basis, we formulate the cooperative data sharing problem by considering the requested information and the encounter probability of buses. Then, we put forward an offline Integer Linear Programming (ILP) solution based on the knowledge of bus traces to obtain the optimal performance. Moreover, we propose an on-line Prediction-based Data Sharing (PDS) algorithm by analyzing the encounter probability of buses. Based on the analysis, each RSU computes the utility of broadcasting data items and makes the scheduling decision with the cooperation of other RSUs. Finally, we build the simulation model and implement the proposed solution for performance comparison. The experiment results demonstrate that PDS can achieve near-optimal performance with much lower computational overhead, and it can outperform other alternative on-line scheduling algorithms significantly.