Priority-Based Multi-carrier Access Schemes for Safety Message Transmission in Vehicular Networks

With the explosive growth of vehicles, current vehicular networks, based on CSMA/CA, are unable to guarantee the low latency and high reliability for safety message transmission under heavy traffic condition. In this paper, we propose a Priority-based Multi-carrier Random Access with Carrier Switching (PMRA/CS) scheme, which is designed for OFDMA-based vehicular networks to support massive concurrent access of large number of vehicles. Compared to CSMA/CA, PMRA/CS utilizes a special short detecting frame to resolve the alarm message collision with less cost. Moreover, the scheme provides more opportunities for vehicles to access the channel in one period by allowing the loser of one sub-carrier to switch to another idle one and continue to access contention. Use of vehicle priority assignment makes the proposed strategy more applicable to realistic scenarios. Furthermore, we provide some theoretical analysis of the proposed scheme combined with derived formula derivation. Simulation results are provided to demonstrate the improvements of message sending success rate and average delay reduction of our proposed scheme.