Telecommunications – Transmitter and receiver at separate stations – Short range rf communication
Reexamination Certificate
1998-11-09
2001-09-04
Maung, Nay (Department: 2681)
Telecommunications
Transmitter and receiver at separate stations
Short range rf communication
C340S928000, C342S042000, C343S719000
Reexamination Certificate
active
06285858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improved techniques for establishing radio communications between a vehicle and a roadside network, and more specifically to such techniques for use in ITS (Intelligent transportation systems). Still more specifically, the present invention is well suited for effectively establishing radio communication links between an in-vehicle unit and a roadside unit in an ETC (electronic toll collection) system.
2. Description of the Related Art
In an effort to solve a variety of transportation problems, a broad range of diverse technologies, known collectively as ITS, have been proposed. Among others, the ETC system has been found extremely preferable to eliminate traffic congestion and backups on toll booths.
Before turning to the present invention, it is deemed advantageous to briefly describe, with reference to
FIG. 1
, a conventional technique that may be relevant to the present invention.
As shown in
FIG. 1
, an antenna
10
is provided high on a pole
12
that is located on a roadside. When a moving vehicle approaches a toll facility or booth (not shown), the vehicle is detected using an approaching vehicle detecting unit
14
that is usually comprised of two devices located on each side of a lane (as best shown in FIG.
3
). In
FIG. 1
, two vehicles
16
and
18
are schematically illustrated, which carry respectively in-vehicle units
20
and
22
for establishing a two-way communication with roadside network through the antenna
10
. Each of the units
20
and
22
is located on a dashboard and includes an antenna (not shown). However, the above-mentioned conventional technique suffers from the following problem. That is, if the vehicle
16
, which is a usual sedan in this case, approaches the pole
12
(viz., toll booth) immediately following the vehicle
18
(viz., a truck with a tall cargo room), the radio communication between the in-vehicle unit
20
and the antenna
10
is undesirably blocked. Since the radio communication is made via a direct wave, the quality of data to be transmitted is deteriorated to such an extent that the data is not correctly exchanged.
Accordingly, what is desired is to establish radio communication links which are not blocked by a tall vehicle.
SUMMARY OF THE INVENTION
It is therefore an object of the present to provide a technique via which a radio communication path is not blocked by a preceding tall vehicle.
Another object of the present invention is to provide a technique via which a radio communication can be established using an extremely small electromagnetic power.
In brief, these objects are achieved by techniques wherein in order to establish radio communications between an in-vehicle unit mounted on a vehicle and a roadside unit, a unique antenna arrangement is provided. That is, an on-board antenna is operatively coupled to the in-vehicle unit and has directivity toward a road surface. Further, a stationary antenna means is operatively coupled to the roadside unit. The stationary antenna is provided at approximately a center portion of a vehicle lane in such a manner as to have directivity toward an upward direction. Thus, a very short distance of radio communication can be formed thereby to eliminate radio wave interference caused by a big vehicle.
One aspect of the present invention resides in a system for establishing radio communications between an in-vehicle unit mounted on a vehicle and a roadside unit, comprising: an on-board antenna mounted on the vehicle, the on-board antenna being operatively coupled to the in-vehicle unit and having directivity toward a road surface; and stationary antenna means operatively coupled to the roadside unit, the stationary antenna being provided at approximately center portion of a vehicle lane in a manner to have directivity toward an upward direction.
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Maung Nay
McGinn & Gibb PLLC
NEC Corporation
Vuong Quochien B.
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