A Decentralized Coexistence Protocol for V2X and Wi-Fi in Unlicensed Bands

The Federal Communications Commission (FCC) in the United States has reallocated 45 MHz from the 75 MHz spectrum previously reserved for ITS, for the use of unlicensed devices such as Wi-Fi. On the other hand, as V2X deployment and the number of V2X applications are expected to gradually increase, the remaining 30 MHz may not be sufficient for ITS communication, resulting in options seeking to share unlicensed spectrum with Wi-Fi. This paper introduces an analytical model and decentralized spectrum sharing protocol for V2X sidelink to coexist with standardized IEEE 802.11 Wi-Fi in the 5.9 GHz unlicensed spectrum. The protocol uses both theoretical projection and historical channel usage information to ensure fair coexistence between Wi-Fi and V2X sidelink. Simulation based evaluation indicates that this protocol improves the performance of both types of communications when sharing unlicensed bands.