Importance

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Abstract

The present invention realizes a communication system between a road and a vehicle which performs communication between a road communication station and a vehicle-mounted mobile station in a cell, utilizing an OFDM modulation method, in which interference between carriers does not occur even when a vehicle runs at high speed and Doppler shift increases, which prevents occurrence of the degradation in communication quality. After detecting the velocity of a vehicle in the cell, the space between frequencies of subcarriers of OFDM is increased as the detected velocity of the vehicle becomes higher. Assuming that an occupied bandwidth of frequency assigned according to the Radio Law is fixed in a radio wave, the number of subcarriers within the occupied bandwidth of 1 frequency is reduced (thinned out). Even when the vehicle runs at high speed, the interference between carriers does not occur, thereby allowing high-quality data communication. Moreover, since the number of vehicles present in the cell is small, a drop in the data transmission rate due to a phenomenon related to the number of subcarriers can be coped with by the present invention.

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First Claim