Integrating Spectrum Database and Cooperative Sensing for Cognitive Vehicular Networks

Recent rules from FCC and OFCOM foresee the utilization of spectrum database as the main solution to provide accurate spectrum information about TV white spaces for secondary users in cognitive vehicular networks. Spectrum database provides maximum protection to licensed users, however, its implementation is not straight-forward in vehicular environments, due to the significant query overhead generated by mobile vehicles in congested urban scenarios. For this reason, in this paper we investigate possible solutions to integrate cooperative sensing and spectrum database querying, with the goal to minimize the primary users detection overhead while guaranteeing maximum protection for these primary users. We propose both theoretical and practical contributions in this field. First, we introduce a topological study to determine the optimal ratio between cooperation and spectrum database querying (referred to as ModeI, ModeII, cooperative Sensing-only devices according to FCC terminology) in order to minimize the network utilization for white space detection. We investigate various system parameters such as spectrum database query frequency, broadcast frequency (for cooperative sensing) and vehicles' velocity, and study their impact on system performance. Then, we propose a distributed (bio-inspired) protocol for network deployment that enables multi-interfaces vehicles to dynamically decide the detection mode to use, in order to minimize the database load, while providing high enough protection or licensed users.