Novel BER improvement method for OFDM simulcast road vehicle communication system

When road to vehicle communication (RVC) is applied to an intelligent transport system (ITS), we sometimes need a larger or more complicated shaped radio zone than the usual dedicated short range communication (DSRC) system. One solution for extending the zone is to place another transmitter that sends the identical data to the original one. The OFDM capability of combining a number of delayed signals from each transmitter enables to adopt the same carrier frequency for every transmitter. However, in the overlap of two radio zones in such a single frequency system, the received power at a vehicle could drop sharply due to the interference of direct waves resulting in the occurrence of severe transmission errors. We propose a technique to control the constellation of each subcarrier to avoid this problem. We show, by computer simulations, that this technique is effective.