JPH11353586A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce retransmission of data and to stably perform data communication. SOLUTION: An antenna 20, a reception part 1, a level detection part 2 which detects the input level from the reception part 1 and outputs a DC voltage 14 corresponding to this input level, a comparator 3 which compares the DC voltage 14 with a prescribed reference voltage and generates and outputs a data string 15 based on the comparison result, a data reproducing part 4 which detects the frame constitution from the data string 15 to perform a frame synchronism establishing operation and outputs a data reproducing detection signal 10 after reproducing communication control information transmitted from a machine on the road side, an A/D conversion part 8 which converts the DC voltage 14 transmitted from the level detection part 2 into a digital signal and outputs this signal, and a control part 5 which periodically takes in the digital signal to always monitor the reception level of a reception signal and takes in communication control information 13 held in the data reproducing part 4 to analyze its contents at the time of exceeding this reception level over a prescribed value and generates and outputs link connection request data 16 if it is decided from the analysis result that communication is permitted are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-range wireless communication system, and more particularly to an intelligent transportation system (ITS: Intelligent).
Nonstop automated toll collection system (ETC: Electronic Toll Collec) which is one application example of Transport Systems
Short Range Wireless Communication (DSRC: Dedic)
ated Short Range Communication) wireless communication is performed between a wireless device installed at a toll booth (hereinafter referred to as a roadside device) and a wireless device mounted on a vehicle (hereinafter referred to as an onboard device). It is about.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned ETC has been put to practical use in order to eliminate congestion at tollgates on toll roads, improve user services, and reduce management costs. In this type of communication, a vehicle traveling on the main line of a toll road need not always perform data communication, and only needs to perform spot communication mainly at a tollgate.

[0003] Therefore, during a period in which the on-vehicle device does not communicate with the opposing roadside device, only a necessary portion of the receiving system function needs to be operated to be in a standby state for the purpose of reducing power consumption. Therefore, only when the vehicle in the standby state enters the communication range of the roadside device, the function of the vehicle-mounted device is activated and the state shifts to the activation state.

FIG. 3 is a block diagram showing the configuration of a conventional vehicle-mounted device. As shown in FIG. 1, the receiving unit 1 receives a carrier transmitted from a roadside device via an antenna 20.
The received carrier is amplified and frequency down-converted by the receiving unit 1 and then transmitted to the level detecting unit 2.
Level detector 2 outputs DC voltage 14 corresponding to the reception level of the received carrier.

[0005] The comparator 3 compares the DC voltage 14 output from the level detector 2 with a reference voltage preset in the inside, and generates and outputs a data string 15 transmitted from the roadside device.

[0006] Upon receiving the data sequence 15, the data reproducing unit 4 generates a reception clock based on the data sequence 15, and further, based on the frame format defined by DSRC, the communication control transmitted from the roadside device. Play information. Further, when reproducing the communication control information, the data reproducing unit 4 sends a data reproduction detection signal 10 to the control unit 5.

When receiving the data reproduction detection signal 10, the control unit 5 fetches the communication control information 13 held in the data reproduction unit 4 and analyzes the contents. As a result of this content analysis, if the transmission of the vehicle-mounted device is permitted from the roadside device,
The control unit 5 performs a process for transmission to the data reproduction unit 4 and the data conversion unit 6. That is, the control unit 5 generates the link connection request data 16 and passes it to the data conversion unit 6.

The data converter 6 modulates the received link connection request data 16, and the transmitter 7 transmits a carrier to the roadside device via the antenna 21. As a result, when the link connection request is correctly received by the 16 roadside unit, the link connection processing and the data exchange are started.

As described above, conventionally, in order to reduce power consumption, when the roadside device is out of the communication range, only the reception system function is operated, and the roadside device enters the communication range and performs reception. If successful, the receiving system, the transmitting system, and the control system were all activated to make a link connection request.

[0010]

Road-to-vehicle wireless communication supplied as a DSRC system requires communication before a vehicle passes through a very narrow area near a tollgate on a toll road. It is necessary to complete the communication within a very short time. Therefore, in the DSRC system, it is important to secure the line quality of the wireless communication path and maintain a high throughput during road-to-vehicle communication. Conventionally, in order to start communication as soon as possible, communication has been started in a state in which the quality of the wireless communication path has not yet been good, shortly after the vehicle started to enter the communicable range. However, if communication is started in such a state, an error occurs in the content of data transmitted and received between the road and the vehicle, and retransmission processing on the wireless communication path may be frequently performed. As a result, the processing time required for one vehicle increases, and for a roadside device that is required to perform wireless communication with a plurality of vehicles simultaneously,
On the contrary, there has been a problem that the throughput is reduced and the number of vehicles that can communicate at the same time is limited. Furthermore, when vehicles exceeding the number of vehicles that can communicate at a certain point exist in the narrow area communication range, the roadside unit cannot perform good wireless communication with the following vehicle, and the vehicle completes processing such as toll collection. There is also a problem that the user passes through the communication range without doing so. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a narrow-area wireless communication system capable of reducing data retransmission and stably performing data communication.

[0011]

In order to achieve the above object, a narrow-area wireless communication system according to claim 1 is mounted on a roadside device which is a roadside wireless device and a vehicle on the road. A non-stop automatic toll collection system configured to perform toll collection by performing wireless communication between the roadside unit and the on-board unit. An antenna for receiving a carrier wave transmitted from the roadside device, and a receiving unit connected to the subsequent stage of the antenna and amplifying the carrier wave, converting the frequency of the received signal to a desired frequency and outputting the signal, A level detection unit that detects an input level from the receiving unit and outputs a DC voltage corresponding to the input level, compares the DC voltage with a predetermined reference voltage, and, based on the result, A comparator that generates and outputs a data sequence, detects a frame configuration from the data sequence, performs a frame synchronization operation, reproduces communication control information transmitted from the roadside device, and outputs a data reproduction detection signal A data reproducing section, an A / D converting section for converting a DC voltage transmitted from the level detecting section into a digital signal, and outputting the digital signal. When the reception level exceeds a predetermined value, the communication control information held in the data reproducing unit is fetched and analyzed, and if it is determined from the result of the analysis that communication is permitted, further link connection is performed. A control unit that generates and outputs request data, the vehicle-mounted device and the roadside device by transmitting the link connection request data to the roadside device. It is obtained so as to implement the wireless communication. The narrow-area wireless communication system according to claim 2 comprises a roadside device that is a roadside wireless device and an on-board device that is a wireless device mounted on a vehicle on the road, and the roadside device and the vehicle In a short-range wireless communication system in a non-stop automatic toll collection system that performs toll collection by performing wireless communication with the on-vehicle unit, the on-vehicle unit receives an antenna that receives a carrier wave transmitted from the roadside unit, A receiver connected to the subsequent stage of the antenna and amplifying the carrier, converting the frequency of the received signal to a desired frequency and outputting the signal, and detecting an input level from the receiver, corresponding to the input level A level detector that outputs a DC voltage, a comparator that compares the DC voltage with a predetermined reference voltage, generates and outputs a data string based on the result, A data reproducing unit that detects a frame configuration, performs a frame synchronization operation, reproduces communication control information transmitted from the roadside device, and then outputs a data reproduction detection signal, and counts the number of times the data reproduction detection signal is received. Counts up and outputs a count end signal when a result of the count is larger than a predetermined value. Upon receiving the count end signal, fetches communication control information held in the data reproducing unit and reads the contents. And a control unit that further generates and outputs link connection request data when it is determined that communication is permitted from the result of the analysis, and transmits the link connection request data to the roadside device by transmitting the link connection request data to the roadside device. The wireless communication is carried out between the on-vehicle device and the roadside device. With this configuration, according to the present invention, communication can be started after the line state is stabilized, so that retransmission of data can be reduced and stable data communication can be performed.

[0012]

Next, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG.
In the drawings, the same reference numerals indicate the same or equivalent parts. The present embodiment is characterized in that not only the communication control information but also the reception level is monitored to start communication. That is, the DC voltage 14 output from the level detector 2 is converted into a digital signal by the A / D converter 8 and then supplied to the controller 5 to monitor the reception level.

Here, the operation of the present embodiment will be described. The operation in the ETC system from when the vehicle-mounted device enters the communication range to when the permission to start communication is checked is the same as in the above-described conventional example. That is, in the conventional example,
Whether or not the OBE starts communication is determined only by the communication control information transmitted from the roadside device.In this embodiment, however, the communication channel is stabilized by monitoring the reception level in addition to this condition. Determine if it is. That is, if the reception level is equal to or greater than a certain threshold, it is determined that the communication path is sufficiently stable and communication is started.

More specifically, the analog signal from the level detector 2 is converted into a digital signal by the A / D converter 8 and then supplied to the controller 5. Then, the control unit 5 periodically determines whether the reception level is equal to or higher than the threshold by comparing the digital signal with a predetermined threshold. As a result, when the reception level is equal to or higher than the threshold, when the data reproduction detection signal 10 is received, the data reproduction unit 4
The communication control information 13 is fetched from the server and the contents thereof are analyzed to determine whether or not communication is permitted. Of course, when the reception level is less than the threshold value, the communication cannot be started yet, so the control unit 5 sends the data reproduction detection signal 10
The communication control information 13 is not fetched even if the communication control information 13 is received.

As a result, the reception level is equal to or higher than the threshold,
When it is determined that the communication is permitted based on the analysis result of the communication control information, the control unit 5 generates the link connection request data 16 and passes it to the data conversion unit 6 to start processing for transmission. I do. The subsequent operation is the same as in the conventional example. Note that these series of operations are controlled by software incorporated in the control unit 5.

Next, another embodiment of the present invention will be described. FIG. 3 is a block diagram showing another embodiment of the present invention. In the figure, the same or equivalent components in FIG. 1 are denoted by the same reference numerals. The embodiment shown in FIG. 3 is characterized in that a counter unit 9 is provided between the data reproduction unit 4 and the control unit 5 instead of the A / D conversion unit 8 in FIG.

The counter section 9 counts up the number of receptions of the data reproduction detection signal 10 sent from the data reproduction section 4. And the counter unit 9
When the count value exceeds a preset count value, a count end signal 11 is sent to the control unit 5.

Control unit 5 receiving count end signal 11
Starts the communication after checking the communication control information held in the data reproducing unit 4. The process for starting the communication is the same as in the conventional example. Thereafter, when the communication is completed, the control unit 5 resets the reset signal 1 to prepare for the next communication.
2 is output to reset the count value of the counter unit 9.

The structure of the present invention is not limited to the above embodiment. For example, in the above description, the receiving antenna 20 and the transmitting antenna 21 are separately provided.
Obviously, two antennas may be used.

[0020]

As described above, according to the present invention, in addition to the condition that communication control information is successfully received and communication start is permitted as in the conventional example, communication is started, and the reception level at the vehicle-mounted device is monitored. Then, the communication is started when a line state is reached in which a sufficiently stable communication path can be obtained. Therefore, unnecessary retransmission is not performed until the line path becomes stable, and real-time processing can be reliably performed by performing stable communication.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reception part, 2 ... Level detection part, 3 ... Comparator, 4 ... Data reproduction part, 5 ... Control part, 6 ... Data conversion part, 7 ... Transmission part, 8 ... A / D conversion part, 10 ... Data reproduction Detection signal, 1
1 ... Count signal, 12 ... Reset signal, 13 ... Communication control information, 14 ... DC voltage, 15 ... Data string, 16 ... Link connection request data, 20, 21 ... Antenna.

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[Procedure amendment]

[Submission date] September 6, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Wireless communication system

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

The present invention relates to relates to radio communications systems, in particular Intelligent Transport System (ITS: Intelligent Tran
non-stop automatic toll collection system (ETC: Electronic Toll Collection)
No line communication that are used in the System) (DSRC: Dedicated Sho
rt Range Communication) system, and relates to wireless communication performed between a wireless device (hereinafter referred to as a roadside device) installed at a tollgate or the like and a wireless device (hereinafter referred to as an onboard device) mounted on a vehicle side. Things.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010]

Road-to-vehicle wireless communication supplied as a DSRC system requires communication before a vehicle passes through a very narrow area near a tollgate on a toll road. It is necessary to complete the communication within a very short time. Therefore, in the DSRC system, it is important to secure the line quality of the wireless communication path and maintain a high throughput during road-to-vehicle communication. Conventionally, in order to start communication as soon as possible, communication has been started in a state in which the quality of the wireless communication path has not yet been good, shortly after the vehicle started to enter the communicable range. However, if communication is started in such a state, an error occurs in the content of data transmitted and received between the road and the vehicle, and retransmission processing on the wireless communication path may be frequently performed. As a result, the processing time required for one vehicle increases, and for a roadside device that is required to perform wireless communication with a plurality of vehicles simultaneously,
On the contrary, there has been a problem that the throughput is reduced and the number of vehicles that can communicate at the same time is limited. Furthermore, if the vehicle exceeded the number of vehicles that can communicate at a certain time exists in the communication range, the roadside device becomes impossible good wireless communication with the following vehicle, the vehicle does not complete the processing, such as toll collection There is also a problem that the vehicle passes through the communication range as it is. The present invention is intended to solve such problems, reducing the retransmission of data is to provide a radio communications scheme to allow data communication stably.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

[0011]

Means for Solving the Problems] To achieve the above object, radio communications system Ru engaging in claim 1, the roadside device is a wireless device of a road side, it is mounted on a vehicle on the road is composed of a vehicle-mounted device is a wireless device, the radio communications system that put the non-stop automatic toll collection system for toll collection by performing wireless communication with the roadside device and the vehicle-mounted device, the vehicle The device is an antenna that receives a carrier wave transmitted from the roadside device, and a receiving unit that is connected to the subsequent stage of the antenna and amplifies the carrier wave, and converts the frequency of a received signal to a desired frequency and outputs the converted signal. A level detector that detects an input level from the receiving unit and outputs a DC voltage corresponding to the input level, compares the DC voltage with a predetermined reference voltage, and outputs data based on the result. And a comparator for generating and outputting the data, detecting a frame configuration from the data sequence, performing a frame synchronization establishing operation, reproducing communication control information transmitted from the roadside device, and then outputting a data reproduction detection signal. A reproduction unit, an A / D conversion unit that converts a DC voltage transmitted from the level detection unit into a digital signal and outputs the digital signal, and constantly monitors the reception level of the reception signal by periodically taking in the digital signal. When the reception level exceeds a predetermined value, the communication control information held in the data reproducing unit is fetched and analyzed, and if it is determined from the analysis result that the communication is permitted, the link connection request data is further transmitted. And a control unit for generating and outputting the link connection request data, and transmitting the link connection request data to the roadside device so that a wireless connection is established between the on-board unit and the roadside device. It is obtained so as to implement the communication. Also, radio communications system Ru engaging in claim 2, the roadside device is a wireless device of a road side, is composed of a vehicle-mounted device is a wireless device mounted on a vehicle on the road, the roadside device and the in radio communications systems that put the non-stop automatic toll collection system for toll collection by performing wireless communication with the vehicle-mounted device, the vehicle-mounted device,
An antenna for receiving a carrier wave transmitted from the roadside device, a receiving unit connected to a stage subsequent to the antenna and amplifying the carrier wave, converting the frequency of a received signal to a desired frequency, and outputting the converted signal; A level detector that detects an input level from the unit and outputs a DC voltage corresponding to the input level, compares the DC voltage with a predetermined reference voltage, and generates and outputs a data string based on the result. A data reproducing unit that detects a frame configuration from the data sequence, performs a frame synchronization establishing operation, reproduces communication control information transmitted from the roadside device, and then outputs a data reproduction detection signal; A counter that counts up the number of times a data reproduction detection signal is received, and outputs a count end signal when the result of the counting is greater than a predetermined value. When the count end signal is received, the communication control information held in the data reproducing unit is fetched and analyzed, and when it is determined that communication is permitted from the result of the analysis, the link connection request data is further transmitted. And a controller that generates and outputs the link connection request data to the roadside device to perform wireless communication between the vehicle-mounted device and the roadside device. With this configuration, according to the present invention, communication can be started after the line state is stabilized, so that retransmission of data can be reduced and stable data communication can be performed.

Claims (2)

[Claims] 1. A roadside device, which is a wireless device on the roadside, and a vehicle-mounted device, which is a wireless device mounted on a vehicle on the road, and wirelessly communicates between the roadside device and the vehicle-mounted device. In the short-range wireless communication system in the non-stop automatic toll collection system that performs toll collection by performing, the on-vehicle device, an antenna for receiving a carrier wave transmitted from the roadside device, and connected to the subsequent stage of the antenna and the carrier Amplifying the received signal, a receiving unit that converts the frequency of the received signal to a desired frequency and outputs the converted signal, a level detecting unit that detects an input level from the receiving unit and outputs a DC voltage corresponding to the input level. A comparator that compares the DC voltage with a predetermined reference voltage, generates and outputs a data sequence based on the result, and detects a frame configuration from the data sequence and outputs a frame. A frame synchronization establishing operation, a data reproduction unit that reproduces the communication control information transmitted from the roadside device and then outputs a data reproduction detection signal, and converts a DC voltage transmitted from the level detection unit into a digital signal. An A / D conversion unit that constantly monitors the reception level of the reception signal by periodically taking in the digital signal, and when the reception level exceeds a predetermined value, a communication held in the data reproduction unit. A control unit that fetches the control information, analyzes the content thereof, and determines that the communication is permitted based on the result of the analysis, and further generates and outputs link connection request data, and outputs the link connection request data to the roadside. Wireless communication between the on-vehicle device and the roadside device by transmitting to the device. 2. A roadside device which is a roadside wireless device and an onboard device which is a wireless device mounted on a vehicle on the road, and wireless communication is performed between the roadside device and the onboard device. In the short-range wireless communication system in the non-stop automatic toll collection system that performs toll collection by performing, the on-vehicle device, an antenna for receiving a carrier wave transmitted from the roadside device, and connected to the subsequent stage of the antenna and the carrier Amplifying the received signal, a receiving unit that converts the frequency of the received signal to a desired frequency and outputs the converted signal, a level detecting unit that detects an input level from the receiving unit and outputs a DC voltage corresponding to the input level. A comparator that compares the DC voltage with a predetermined reference voltage, generates and outputs a data sequence based on the result, and detects a frame configuration from the data sequence and outputs a frame. A data reproducing unit that performs a frame synchronization establishing operation, reproduces the communication control information transmitted from the roadside device, and then outputs a data reproduction detection signal; and counts up the number of times that the data reproduction detection signal is received. A counter section that outputs a count end signal when the result of the increase is larger than a predetermined value; and receiving the count end signal, captures communication control information held in the data reproducing section and analyzes the contents thereof. And a controller for generating and outputting link connection request data when it is determined that the communication is permitted from the result of the on-board unit and the roadside unit by transmitting the link connection request data to the roadside unit. A short-range wireless communication system characterized in that wireless communication is performed between the wireless communication system and the mobile terminal.