J. Zheng et al. (Eds.): Adhocnets 2012, LNICST 111, pp. 289–301, 2013. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2013 Design Challenges and Solutions for Multi-channel Communications in Vehicular Ad Hoc NETworks Claudia Campolo and Antonella Molinaro Università Mediterranea di Reggio Calabria, Loc. Feo di Vito, 89060, Reggio Calabria, Italy {name.surname}@unirc.it Abstract. Vehicular Ad-Hoc Networks rely on a multi-channel architecture to support vehicle-to-vehicle and vehicle-to-infrastructure communications. Multiple service channels are assigned in the 5GHz spectrum for non-safety data transfer, while a unique control channel is used for broadcasting safety messages and service advertisements. Single-radio vehicular devices stay tuned on one radio channel at a time and alternately switch between channels to monitor safety messages and to access information and entertainment services; while dual-radio devices can simultaneously stay tuned on both types of channels. Multi-channel coordination, synchronization, and access are big challenges in VANETs; many design choices are still open issues in ETSI and IEEE standardization bodies. In this paper, counter-measures and recent trends in standardization bodies are discussed to cope with inefficiencies related to multi-channel operation for single-radio devices (e.g., inefficient spectrum utilization, synchronized frame collisions, bandwidth waste), and dual-radio devices (e.g., cross-channel interference, coexistence with single-radio devices). Keywords: VANET, 802.11p, WAVE, ETSI, IEEE, multi-channel. 1 Introduction Research activities in governmental, industrial and academy bodies have been underway to accelerate the deployment of Vehicular Ad Hoc Networks (VANETs) that provide wireless communications among moving vehicles (Vehicle-to-Vehicle, V2V) and between vehicles and roadside infrastructure (Vehicle-to-Infrastructure, V2I). Potential applications for VANETs are categorized based on their targets as: safety applications, geared primarily toward avoiding the risk of car accidents; transport efficiency applications, focusing on optimizing flows of vehicles; and commercial applications, aimed at providing the road traveller with information support and entertainment to make the journey more pleasant. The last two categories are also known with the generic term of non-safety applications. The history leading to the development of VANETs goes back in the early 1990s when the U.S. Department of Transportation (DOT) and the Intelligent Transportation Society of America (ISTA) developed a plan for Intelligent Transportation Systems (ITSs) to make road traffic safe, efficient, and environmentally friendly.