Supporting real-time multiple data items query in multi-RSU vehicular ad hoc networks (VANETs)

• Explores the real-time multi-item query problem in the context of a multi-RUS infrastructure based VANETs.
• Addresses the bandwidth utilization and starvation problem using an efficient Cooperative Query Serving approach.
• CQS considers item-level and query-level scheduling as well as intelligent deferral of service to neighboring RSUs.
• CQS is able to efficiently optimize the overall query servicing.
• Extensive simulation demonstrates the proposed CQS approach outperforms existing strategies in the literature.

There has been increasing interest in the issue of multi-item queries in wireless broadcasting systems recently. Query starvation and bandwidth utilization have been identified as key issues for improved performance. In this paper, we examine this problem in the context of VANETs with multiple cooperating Road Side Units (RSUs). We characterize a query with two deadlines: Query Total Deadline (QTD) which is the actual deadline of a query and Query Local Deadline (QLD) which is the duration a query is valid for serving in an RSU. By considering these two deadlines together with vehicle speed, RSU range and inter-RSU distance, we formulate a Cooperative Query Serving (CQS) scheme which allows multiple RSUs to share residual bandwidth and effectively address the query starvation as well as the bandwidth utilization problems, hence maximizing the chance of serving multiple items queries. Extensive simulation results confirm that CQS outperforms other existing scheduling algorithms.