Improving multi-channel operations in VANETs by leveraging stopped vehicles

Multiple channels have been allocated in the 5 GHz spectrum for vehicular communications in USA and in Europe. Due to the limited spectrum, simultaneous communications may occur over nearby channels and be affected by adjacent channel interference (ACI). To protect safety messages delivered on the control channel (CCH), the most likely approach is to prevent the use of adjacent channels with the consequence of spectrum resources wasting. In this paper we identify temporarily stopped vehicles (e.g., at the gas station for refuelling) as users that are potentially allowed to transmit on a channel that is adjacent to the CCH. A simulation study has been conducted to evaluate the viability of our proposal. Achieved results show that the two conflicting objectives of improving spectrum utilization and not penalizing safety messages can be successfully met, provided that the transmission power on the adjacent channel is adequately tuned and the stopped vehicle is at a sufficient distance from the vehicle that is using the CCH.