Enhancements to IEEE 802.15.4 MAC Protocol to Support Vehicle-to-Roadside Communications in VANETs

The Internet of Things (IoT) paradigm and its applications have been gaining popularity recently. The Intelligent Transportation System (ITS) is a major area of IoT applications. With ITS the transportation infrastructure is supported with advanced networking and computing technologies to better manage traffics on the roads. The Vehicular Ad-Hoc Network (VANET) stands out as an important technology under the ITS. The VANET technology supports different architectures for data communication, namely, vehicle-to-vehicle (V2V), vehicle-to-road-side (V2R), vehicle-to-infrastructure (V2I), and infrastructure-toinfrastructure (I2I). In V2R communication, data flow between vehicles and roadside units (RSUs) to convey important information about the road traffic and emergency situations. This data should be transferred with high probability of successful delivery. Also, the sensitivity of this data requires reducing the end-to-end communication delay. The IEEE 802.15.4 standard is one of the important candidate standards that supports the V2R communications. In this paper, we propose the Dynamic Window Algorithm (DWA); a backoff algorithm that targets improving the performance of V2R communications in terms of throughput and delay. This is attained by proposing changes to the operation of the standard Binary Exponent Backoff (BEB) algorithm (in IEEE 802.15.4 MAC). A Java-based simulation tool has been developed to simulate both BEB and DWA algorithms and conduct a comparison study between them. Our results show that in clusters of 20 nodes, the performance in terms of throughput and delay is improved by 32% and 88%, respectively, with DWA.