On Scheduling Real-Time Multi-item Query with Network Coding in Multi-RSU Vehicular Networks

Road Side Units (RSUs) installed alongside the road in Vehicular Ad Hoc Networks (VANETs) act as buffer points and alleviate the frequent vehicle-to-vehicle connectivity problem. In VANETs, submitting multi-item query is a common phenomenon, for instance, a query with required traffic information of multiple routes. Unlike the single item query, a multi-item query only be satisfied successfully if all the required data items are served within the stipulated deadline. In serving multi-item query, the system also needs to address the query starvation problem which causes due to the presence of less popular data items in the same query with the high popular data items. In this paper, for serving multi-item queries efficiently, we have proposed an approach which integrates network coding with on-demand broadcasting in multi-RSU VANETs. The traditional on-demand broadcast only disseminates a single data item in a broadcast tick which restricts the maximum channel bandwidth utilization. On the contrary, our proposed approach uses network coding through which multiple data items can be broadcast in a single broadcast. Again, our proposed network coding based approach learns the cache information of vehicles intrinsically which cuts the overhead of network coding, namely avoids uploading cache information of vehicles to the RSU server explicitly. In addition, the proposed approach is equally good to integrate both with the item-level and query-level on-demand scheduling algorithms for maximizing the system performance. Finally, we have performed an extensive simulation experiment to demonstrate the superiority of our proposed approach against the traditional broadcasting system for a number of on-demand scheduling algorithms.