Evaluation of Space-Time Diversity Techniques in Car-to-Car Communications

Car-to-car (C2C) communications requires reliable connectivity at moderate data rates. This is essential for safety-related applications. The development of such communications systems needs to cope with time-variant propagation channels including shadowing by other vehicles, high Doppler shifts and rich multipath environments. Moreover, the choice of the antennas and their position in/on the car highly influences the overall propagation channel. This paper elaborates on different antenna configurations and diversity techniques to overcome these issues. Especially, Alamouti space-time coding is applied to the 802.11p standard in order to exploit diversity by using two transmit antennas on a car. This configuration as well as maximum ratio and selection combining are then evaluated in terms of frame error rate in an urban car-to-car scenario. With these parameters, the reliable communication range between two cars is derived.