Roadside transmitter
First Claim
1. A road transmission equipment used for a communication system between a road and a vehicle, which communicates between a road communication station arranged in a cell and a vehicle-mounted mobile station within the cell, comprising:
- a first transmitting antenna having a directivity in a running direction of a vehicle, a second transmitting antenna having a directivity in the opposite direction to the running direction of the vehicle, a first transmitting section and a second transmitting section respectively connected to the first transmitting antenna and the second transmitting antenna to output signals of the same frequency, and a frequency correction section, wherein;
the frequency correction section provides the first transmitting section with a positive frequency offset for increasing the frequency of a signal supplied to the first transmitting antenna, and provides the second transmitting section with a negative frequency offset for lowering the frequency of a signal supplied to the second transmitting antenna.
1 Assignment
0 Petitions
Accused Products
Abstract
In a communication system between a road and a vehicle, communicating between a plurality of road communication stations arranged in a cell and a vehicle-mounted mobile station within the cell, a vehicle-mounted transmitting equipment, in which communication is not interrupted even when a received frequency varies due to the Doppler effect and which performs stable communication, is realized. A transmitting antenna 36a having a directivity in the running direction of the vehicle and a transmitting antenna 36b having a directivity opposite to the running direction of the vehicle are arranged. An offset for increasing a frequency is provided for a radio wave emitted from the antenna 36a while an offset for lowering a frequency is provided for a radio wave emitted from the antenna 36b. The variation in the received frequency depending on the Doppler shift is reduced for the vehicle-mounted receiving device to facilitate automatic frequency control (AFC), thereby reducing degradation in the quality of data after demodulation.
34 Citations
5 Claims
-
1. A road transmission equipment used for a communication system between a road and a vehicle, which communicates between a road communication station arranged in a cell and a vehicle-mounted mobile station within the cell, comprising:
-
a first transmitting antenna having a directivity in a running direction of a vehicle, a second transmitting antenna having a directivity in the opposite direction to the running direction of the vehicle, a first transmitting section and a second transmitting section respectively connected to the first transmitting antenna and the second transmitting antenna to output signals of the same frequency, and a frequency correction section, wherein;
the frequency correction section provides the first transmitting section with a positive frequency offset for increasing the frequency of a signal supplied to the first transmitting antenna, and provides the second transmitting section with a negative frequency offset for lowering the frequency of a signal supplied to the second transmitting antenna. - View Dependent Claims (2, 3, 4, 5)
the frequency correction section sets the amount of the frequency offset based on the detected speed of the vehicle. -
4. A road transmission equipment as set forth in claim 1, wherein
the amount of the frequency offset provided by the frequency correction section is set to a fixed value on the assumption that the vehicle is subjected to constant Doppler shift. -
5. A road transmission equipment according to any of claims 1 to 4, wherein each of the first transmitting section and the second transmitting section transmits an orthogonal frequency division multiplex (OFDM) modulated radio wave.
-
Specification