Vehicular Wi-Fi Offloading in Heterogeneous Vehicular Networks: Techniques and Challenges

The increasing use of smartphones, tablets, and other vehicular network applications with varied capabilities and the associated growth in the use of all types of data-hungry multimedia services pose a significant challenge to cellular infrastructure operators. Vehicular Wi-Fi offloading (VWO) is one of the potential solutions for offloading cellular traffic. Several offloading techniques through vehicular ad-hoc networks are proposed in the literature. Thus, this paper reviews several state-of-the-art VWO techniques. We categorize the techniques based on the application requirements and the medium used for offloading. Two groups of techniques are identified. All techniques that depend on the roadside unit as offloading media are classified as vehicle-to-infrastructure-based techniques and those that depend on the opportunistic vehicle-to-vehicle (V2 V) network are called V2 V-based techniques. We present a comprehensive VWO architecture and VWO performance metrics derived from mobile-data offloading metrics. We also elucidate the important issues to be incorporated in designing VWO techniques together with future research directions in this domain.