A spectrum penetration assisted MAC protocol for vehicular communication networks

Wireless Access in Vehicular Environments (WAVE) is designed for VANETs to provide safety services and infotainment services through contention-based medium access control (MAC) mechanism. However, the collision probability may increase dramatically in the case of high density of vehicles, due to the contention-based MAC mechanism. To address this issue, we propose a spectrum penetration (i.e., transmit message between neighbored channels) assisted medium access control (SPA-MAC) protocol for VANETs by introducing a contention-free channel allocation mechanism with the coordination of road side units. The contention-free mechanism can decrease the collision probability and reduce the transmission delay, especially in dense traffic. Different from the mechanism for message sender to wait until the instant of a time interval in WAVE, spectrum penetration makes it possible to broadcast safety messages to all vehicles immediately. Theoretical analysis and simulation results are presented to evaluate the performance of SPA-MAC, which verify that SPA-MAC protocol can reduce transmission delay and enhance throughput in the environment with different traffic densities.