Physical layer simulations of IEEE802.11a for vehicle-to-vehicle communications

Results of system simulations on link level for vehicle-to-vehicle (v2v) communications are presented in this paper. The corresponding system model complies with the IEEE802.11a wireless LAN standard, which is expected to play a major role in future inter-vehicle communications (IVC) systems. Only the physical (PHY) layer is considered for the simulations. A realistic channel model is integrated in the system model. Different characteristic road traffic scenarios, such as a motorway and an urban road are investigated. Both, line-of-sight (LOS) and non-line-of-sight (NLOS) situations are taken into account. For the simulations only the link between two vehicles is considered. Interference resulting from other vehicles is neglected. The results are characteristic curves of the bit error rate (BER) and packet error rate (PER) over the signal to noise ratio (SNR) at the receiver. I. INTRODUCTION The road traffic density is continuously increasing. The re- sulting large number of vehicles on the streets leads to congestion and accidents, which cause delays, costs, injuries and sometimes death. It is therefore a challenging task to cope with all the upcoming traffic. A necessary step to solve the problem is to provide the driver in time with specific route dependent information. This includes mobility-relevant information (e.g. the actual traffic conditions on the whole route) as well as safety-relevant information (e.g. detailed information about the road and traffic conditions in the vicinity of the vehicle). Thereby, the primary goal is to improve the traffic flow, avoid accidents and shorten journey lengths. Moreover, the increasing demand for mobile computing will have the future automobiles being equipped with high data rate access to the internet. Various multimedia applications, such as video on demand, games, email, etc. will be available. To provide automobiles with this large amount of informa- tion, inter-vehicle communications will be one necessary tool (1), (2). It is expected that in the future all vehicles on a road are able to communicate with each other and to share data. As the number of participants in such a dynamic communication scenario is fluctuating rapidly, IVC will be organised in an ad-hoc network manner (3). North American authorities allocated 75MHz of spectrum in the 5GHz band for dedicated short-range communications (DSRC). DSRC is expected to enable delivery of large amount of data to vehicles at short ranges via v2v and vehicle-to- roadside (v2r) wireless links (3). The Federal Communications Commission (FCC) report and order 03-324 is adopting licen- sing and service rules for the DSRC standard, especially focu- sed on v2v and v2r communication (4). Currently, the Ameri- can Society for Testing and Materials (ASTM) and the Institute of Electrical and Electronics Engineers (IEEE) are working on an evolution of the IEEE802.11a wireless LAN standard for v2v and v2r communications termed IEEE802.11p (Wireless Access in Vehicular Environments, WAVE) (5), (6). The PHY layer of IEEE802.11p will be similar to that of IEEE802.11a. Results of IVC link level simulations, which are performed on the basis of IEEE802.11a (7), are presented in this paper. For the investigations a base-band model of IEEE802.11a is implemented in the development environment "System Studio" (8). The model contains solely the PHY layer of the system. In order to get reasonable results a realistic model of the inter-vehicle transmission channel is used for the system simulations (9). Different characteristic road traffic scenarios, such as a motorway and an urban road are investigated. Both, LOS and NLOS situations are taken into account. For the simulations only the link between two vehicles is considered. Interference resulting form other vehicles is neglected. For each scenario the BER and PER over the SNR at the receiver are determined. The 6Mbit/s and 12Mbit/s transmission mode of IEEE802.11a are analysed. The channel model and the system model are described in the following two sections. Subsequently, the results of the simulations are presented.