Abstract
Embedding information messages in radar signals through index modulation is a promising approach for dual function radar and communication in automotive systems. In this paper, we optimize the index modulation order to maximize the communication performance without compromising the radar operation. We derive novel expressions for the number of successfully transmitted bits per symbol and the target detection probability as functions of the road layout, traffic conditions and index modulation order. Results show that in light traffic conditions, index modulation can achieve up to 12 bits/symbol when line of sight is present between the transmit and receive vehicles with up to 140% improvement compared to the case with absent line of sight. Finally, we show that the received radar signal can be used, at the receive vehicle, to estimate the location of the transmitting vehicle via a maximum-likelihood estimator.