Joint time-frequency DMRS design for high mobility LTE-A V2V communication systems

The purpose of the paper is to research and modify the existing LTE-A device-to-device (D2D) physical layer design for the application of the high mobility vehicle-to-vehicle (V2V) communication scenario. To achieve the goal, the training sequence assignment of the demodulation reference signal (DMRS) of the D2D specification is modified and the two possible assignments are proposed in this paper. One modification is the time-domain DMRS assignment. It is designed to extend two DMRS symbols to three or four DMRS symbols during one subframe period. Another modification is the frequency-domain DMRS assignment. It is designed to increase the subcarrier spacing 15KHz to 30KHz or 60KHz. In the above modifications, the signal bandwidth is retained to be the same as the D2D specification. Based on the previous design, we have multiple DMRS assignments to provide the low, medium, high density training sequences, which can be useful for the different mobility V2V communication systems. Simulation results confirm that the proposed DMRS assignments with MODEM and CODEC processing can provide better quality and the efficient data rate performances for the different high mobility scenarios.