LAUSR

The vehicle-to-vehicle (V2V) communications channel is highly time-varying, making reliable communication difficult. This problem is particularly challenging because the de facto standard for V2V communications, the IEEE 802.11p standard, is based on the IEEE 802.11a standard, which was designed for the indoor and relatively stationary wireless LAN channel. In particular, the frame structure, which allows large packets and has low pilot density makes channel estimation difficult. In this paper, we propose several semi-blind channel estimation and tracking algorithms that are suitable for highly time-varying channels using the 802.11p frame structure. Two of the proposed schemes utilize the finite alphabet property of the transmitted symbols and utilize pilot information. A third scheme is a variant of decision-directed channel estimation that utilizes knowledge of the preamble. All schemes apply time-domain channel impulse response truncation for improved performance. We compare the performance of the proposed schemes using six different V2V channel models. The proposed schemes realize huge performance gains over previously proposed ones, reaching 20 dB in some cases, where previously proposed schemes are unusable. These performance gains are realized for all the V2V channel models, at different vehicle velocities, and for all modulation schemes and packet sizes. Two of the proposed schemes are low-complexity schemes that avoid expensive search operations, yet offer significantly improved performance.