An 802.11p cross-layered pilot scheme for time- and frequency-varying channels and its hardware implementation

Robust channel estimation in IEEE 802.11p systems in highly time- and frequency-varying vehicular channels, in combination with long data packets, is a challenging task due to the ill-suited pilot pattern. Solutions of increased receiver complexity that use decision feedback and iterative decoding have been proposed to overcome the difficulty in robust channel estimation. In this paper, a cross-layered method to introduce complementary training symbols into an 802.11p frame is proposed. In the proposed approach, known bits are multiplexed with the data in higher layers, and a modified receiver can utilize these bits as training data for improved channel estimation. A standard receiver treats these bits as data and passes them to the higher layers, where they can be removed, making the method compatible with standard 802.11p transceivers. A software/firmware update of the higher layers is needed in a standard receiver to remove the multiplexed bits.