In the context of growing demand for mobile data and the emergence of ve hicular applications, heterogeneous networks will become a necessity to meet the various requirements of future Intelligent Transport Systems. The aim of this research work is to investigate the use of heterogeneous vehicular wireless net works with multiple independent Radio Access Technologies (RATs). A Multiple Interface Scheduling System (MISS) is proposed, based on a user perspective, where the vehicle has visibility of all the available RATs, with no modification to the fixed infrastructure, operator independent, to improve the performance of vehicular networks. Multi RAT solutions have been reported previously where the packets are scheduled at different layers of the OSI seven-layered architecture but they require modifying the routing protocols, have one IP address per RAT or involve designing specific solution for each RAT. To overcome these limita tions, the proposed approach is to schedule the packets at an intermediate layer located between the network layer and the MAC layer. This solution avoids any changes to the RAT standards, and maintains a single IP address.
An adaptive scheduling algorithm has been devised which is comprised of automatic wireless access interface selection, intelligent bandwidth aggregation and allocation, seamless Quality of Service (QoS) support, and context-aware packet scheduling. The system dynamically selects the most suitable wireless technology in a given space and time, or it may use the technologies j ointly to maximise the throughput, or improve the reliability that can be achieved with a single radio technology. This work focusses on the uplink, and it addresses the scenario where the vehicle is treated as a data source. The evaluated wireless technologies include cellular (4G) and Wi-Fi (802.llp and 802.lln).
The proposed scheme has been simulated and implemented in hardware to validate the performance of the proposed packet scheduler. The results and hardware implementation demonstrate that the scheduling algorithm is able to transfer packets transparently over multiple RATs to provide higher availabil ity and/or throughput together with prioritization of selected services, without requiring any change to existing wireless standards. In terms of scalability, the intermediate layer approach is shown to be suitable for supporting connectivity by increasing the availability of uplink connection with the current infrastruc ture. Such an approach is not only valid for heterogeneous vehicular networks but can be used by mobile devices and the future internet of things where the goal is to upload information from different devices anywhere and at any time
