We propose a vehicle-to-infrastructure (V2I) communication system that utilizes a smart antenna technology to increase service coverage and system throughput. During contention-based channel access, a collision occurs when more than one vehicle selects the same minislot to transmit an access signal to an infrastructure. To solve this problem, we propose a group-based channel access scheme. Numerical analysis and simulation results show that the proposed scheme can help to reduce the number of collisions that occur during channel access.