Vehicular wireless channels are highly time-varying and the pilot pattern inthe 802.11p orthogonal frequency-division multiplexing frame has been shown tobe ill suited for long data packets. The high frame error rate in off-the-shelfchipsets with noniterative receiver configurations is mostly due to the use ofoutdated channel estimates for equalization. This paper deals with improvingthe channel estimation in 802.11p systems using a cross layered approach, whereknown data bits are inserted in the higher layers and a modified receiver makesuse of these bits as training data for improved channel estimation. We alsodescribe a noniterative receiver configuration for utilizing the additionaltraining bits and show through simulations that frame error rates close to thecase with perfect channel knowledge can be achieved.
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