KR20090095323A - Electrical toll collection system with terminal limiting communication zone - Google Patents

Abstract

An electrical toll collection system with a terminal limiting communication zone is provided to prevent noise interfering with ETCS performance in a shadow area. In a electrical toll collection system with a terminal limiting communication zone, a reception ability restricting device(240) limits reception a vehicle mounted device. The reception ability restricting device is composed of a digital control block(242) and a RSSI control block(244). The RSSI control block generates RSSI(Received Signal Strength Indicator) output signal in proportion to the level of received signal. The RSSI control block is adjusted by the digital control block, and an output signal of an ASK demodulator(218) is adjusted according to a signal value of the adjusted RSSI threshold value or the reference sensitivity.

Description

Communication area limiting device of ETC terminal {ELECTRICAL TOLL COLLECTION SYSTEM WITH TERMINAL LIMITING COMMUNICATION ZONE}

The present invention relates to a communication area limiting apparatus of an ETCS terminal, and more particularly, to an ETCS terminal for increasing the communication success rate in the communication area of the ETCS terminal by precisely adjusting the reception performance of the ETCS terminal.

The Electric Toll Collection System (ETCS) is referred to as the high pass system, which is an uninterrupted toll collection system using a 5.8 GHZ wireless communication system, which reduces traffic, improves environmental pollution, and computerizes traffic systems. It is a basic configuration system that implements an Intelligent Transport System (ITS) that can achieve the effect.

The ETCS communication system uses an amplitude shift keying (ASK) method of the 5.8GHZ band, and there are two types of passive type and active type, and the active type has the advantage of easy implementation of ITS as well as ETCS. .

1 shows a general configuration of an electronic toll collection system (ETCS).

Referring to FIG. 1, an electric toll collection system (ETCS) includes an onboard unit (OBU) 110, a first vehicle detector 120, a second vehicle detector 125, A first roadside device (RSU1) 130 and a second roadside device (RSU2) 135 are provided.

The OBU 110 is a terminal mounted in a vehicle and transmits or receives a radio frequency (RF) with the RSUs 130 and 135 which are terminals installed on a roadside. The vehicle detectors 120 and 125 are merely devices for recognizing a vehicle type and are not related to RF (Radio Frequency) transmission or reception. The OBU 110 collects tolls while sequentially passing through the first vehicle detector 120, the second vehicle detector 125, the first roadside device RSU1 130, and the second roadside device RSU2 135. Perform the necessary procedures.

The section indicated by the arrow in FIG. 1 represents the communication area 150, which means a section that can be transmitted or received between the OBU 110 and the RSUs 130 and 135, and is optimized in consideration of road conditions. This item does not change after installing ETCS on the roadside.

The communication area 150 is strictly limited to be a certain distance to minimize the malfunction of the ETCS, but according to the needs of the user through the transmission power (power) adjustment of the RSU (130, 135) and the antenna ease of adjustment desired 150 may be formed. The communication area 150 should not exceed the position of the first vehicle detector 120, and for example, an area other than the communication area 150, for example, the OBU 110 and the RSU before the first vehicle detector 120. If transmission or reception occurs between 130 and 135, it is treated as a malfunction. That is, only the case where transmission or reception between the OBU 110 and the RSUs 130 and 135 is performed in the communication area 150 is processed as a normal operation. Therefore, in order to comply with the communication area 150 of the ETCS, the performance of the OBU 110 must be excellent, and as the transmission and reception performance of the OBU 110 decreases with respect to the determined communication area 150, the possibility of malfunction of the ETCS is reduced. It can be seen that increases.

2 illustrates an embodiment of a transmitter or a receiver for a conventional electronic billing system (ETCS).

Referring to FIG. 2, the conventional ETCS includes an antenna 100, an RF transmitter, a receiver 200, a baseband transmitter, and a receiver 300.

The RF transmitter / receiver 200 includes an RF receiver 210, an RF transmitter 220, and an RF switch 230. The RF receiver 210 includes a low noise amplifier 212, a down conversion mixer 214, a filter 216, and an ASK demodulator 218.

The low noise amplifier 212 amplifies the RF signal. The down conversion mixer 214 down converts the amplified RF signal to an intermediate frequency (IF) signal. The filter 216 filters noise of the down-converted signal. The ASK Demodulator 218 demodulates the received signal by an Amplitude Shift Keying (ASK) method and outputs a digital signal to the baseband transmitting and receiving unit 300.

The RF transmitter 220 includes an up conversion mixer 222 and a power amplifier 224. The up conversion mixer 222 up-converts the signal input from the baseband transmitting and receiving unit 300 into an RF signal, and the power amplifier 224 amplifies the RF signal into a signal having a desired output level.

In FIG. 2, the illustration of a voltage controlled oscillator (VCO) and a phase locked loop (PLL) is omitted.

FIG. 3 illustrates the communication success rate of the electronic toll collection system (ETCS) according to the performance of the on-vehicle device (OBU).

3 and 1, 350 is the minimum communication success rate in the communication area 150, 310 is the communication success rate when the transmission and reception performance of the OBU 110 exceeds the standard, 330 is the OBU 110 Communication success rate when the transmission and reception performance is insufficient compared to the reference, 320 represents the communication success rate when the transmission and reception performance of the OBU 110 is optimized in accordance with the standard.

The 350 indicates that the communication success rate of the ETCS terminal is less than or equal to the minimum communication success rate, and the ETCS terminal is malfunctioned. When the transmission and reception performance of the OBU 110 is high enough to exceed the standard, the 310 transmits and receives before a section other than the communication area, that is, the position of the vehicle detector 1 120.

The 330 is a case where the transmission and reception performance of the OBU 110 is insufficient compared to the reference. In this case, a section 340 is also generated in which the communication success rate is sharply reduced within the communication area. In this case, when the OBU 110 passes the ETCS section at high speed, a probability of malfunction occurs is increased.

The 320 has a stable performance even when the OBU 110 transmits and receives at high speed because the transmission and reception performance of the OBU 110 does not deviate from the communication region 150 and there is no communication success rate reduction section in the communication region 150 unlike the case 310. It can be maintained.

4 illustrates an OBU transmitter output signal obtained by deteriorating a transmitter performance of a conventional OBU.

4 and 1, the left figure of FIG. 4 illustrates a general OBU transmitter output signal, and the OBU 110 output signal is a signal modulated by an ASK method and output at a predetermined level or more. .

The quality of the output signal is represented by a Modulation Index 412, which is defined as the difference between the Carrier component 410 and the amplitude variation component 414. The smaller the difference between the Carrier component 410 and the amplitude variation component 414 is, the better the Modulation Index 412 is. It means excellent.

4 shows the output signal of the OBU 110 transmitter obtained by degrading the transmitter performance of the OBU 110. The amplitude of the amplitude shift component 424 is reduced while the carrier component 420 is maintained. It can be seen that the decrease. Degrading the OBU 110 transmission performance in a manner of lowering the Modulation Index 422 of the OBU 110 transmission signal may degrade the reception performance of the receivers of the RSUs 130 and 135, and thus the OBU 110 and the RSU. It can be seen that it is possible to limit the communication area 150 between (130, 135).

However, although the conventional technology can satisfy a desired communication area, it has the following problems.

That is, the OBU 110 for the ETCS operates in a manner that a transmission is always performed when it is received. As a result, since the performance of the receiver of the OBU 110 is not limited, the receiver of the OBU 110 may be recognized as a normal receiver even before entering the communication area 150, and there is a state in which the transmitter of the OBU 110 also outputs. Done. That is, the communication between the OBU 110 and the RSUs 130 and 135 is not only successful before the communication area, and generates an unnecessary operation state. As a result, the OBU 110 generates an ETCS in an area other than the communication area 150. In addition to generating noise that hinders performance, the OBU 110 has a problem of reducing the efficiency of reception and transmission switching when entering the communication area 150.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an apparatus for limiting a communication area of an ETCS terminal capable of precisely controlling the reception sensitivity of the ETCS terminal in a limited communication area.

The communication area limiting device of the ETCS terminal according to the present invention for achieving the above technical problem, in the electronic toll collection system (ETCS) of the vehicle-mounted device (OBU) equipped with an antenna, RF receiver, RF transmitter and baseband transmission, receiver Receiving the OBU comprising the Digital Control Block and the RSSI Control Block as a component to limit the reception performance of the OBU to the receiving end of the ASK Demodulator constituting one of the RF receivers so as to be transmitted or received only in a communication range of a certain range. Provided is a communication area limiting device of an ETCS terminal, further comprising a performance limiting device.

The present invention complies with the communication area of the ETCS and operates the transmitter of the terminal only above the reception standard sensitivity, thereby generating noise that hinders the performance of the ETCS in the area other than the communication area and at the same time receiving and transmitting the transmission when the OBU enters the communication area. There is a technical advantage that can solve the disadvantage of reducing the efficiency of.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

5 illustrates a configuration of a communication area limiting apparatus of an ETCS terminal according to the present invention.

5 and 2, the communication area limiting apparatus of the present invention is an on-vehicle device equipped with an antenna 100, RF transmission, receiving unit 200, baseband transmission, receiving unit 300 and OBU terminal memory 400 Configure the OBU Electronic Toll Collection System (ETCS). The RF transmitter and receiver 200 includes a conventional RF receiver 210, an RF transmitter 220, and an RF switch 230, in addition to a receiver performance limiter 240 of an on-vehicle device (OBU).

The reception performance limiter 240 serves as a configuration circuit corresponding to a feature of the present invention and restricts reception performance of an OBU, and includes a digital control block 242 and an RSSI control block 244. The RSSI Control Block 244 is a circuit for generating a Received Signal Strength Indicator (RSSI) output signal proportional to the magnitude of the received signal, and is controlled by the Digital Control Block 242.

The RSSI Control Block 244 may be adjusted by the Digital Control Block 242, and may adjust the output signal of the ASK Demodulator 218 according to the adjusted RSSI threshold or an optimal signal value of reference reception sensitivity. The output signal is sent to the baseband transmitter and receiver 300. In this case, the optimized digital control value of the RSSI threshold value or the reference reception sensitivity is stored in the OBU terminal memory 400.

Since each of the antenna 100, the RF transmission and reception unit 200, the baseband transmission and the reception unit 300 has already been described with reference to FIG. 2, a detailed description thereof will be omitted.

6 is a graph illustrating RSSI in order to explain a method of controlling reception performance of an OBU according to the present invention.

6 and 5, reference numeral 610 denotes a reference reception sensitivity of an OBU, 611 an RSSI, 620 an RSSI threshold value (RSI), and 613 an RSSI slope. The reference reception sensitivity 610 should have a very small variation in reception sensitivity when applied between individual OBUs. The RSSI threshold 620 serves as a reference value for determining whether the magnitude of the received signal of the OBU is larger or smaller than the RSSI threshold 620 and is adjusted by the RSSI control block 244.

7 is a graph illustrating RSSI and demodulated ASK output signals according to reception performance control of the OBU of the present invention.

7 and 5, reference numeral 610 denotes a reference reception sensitivity (Pref) of an OBU, 730 denotes an RSSI, and 740 denotes a demodulated ASK output signal.

The RSSI 730 is generated by the RSSI Control Block 244. When the received signal is larger than the RSSI threshold value RSSIth1 corresponding to the reference reception sensitivity 610, the RSSI 730 becomes Logic Level High and the size of the received signal. If is less than the RSSI threshold value RSSIth1, the Logic Level Low becomes.

The output signal 740 outputs only when the received signal size of the OBU is larger than the RSSI threshold value RSSIth2 corresponding to the reference reception sensitivity 610, and the size of the received signal is greater than the RSSI threshold value RSSIth2. If it is small, no output signal is generated.

Although the communication area limiting apparatus of the present invention has been applied to the OBU, it can be applied to the RSU as necessary. When the communication area limiting device is implemented by applying to the RSU, the method applied to the OBU described with reference to FIGS. 5 to 7, that is, a method of limiting the communication area of the RSU by adjusting the RSSI slope 611 or RSSI threshold (RSSIth) The detailed description is omitted since it can be implemented.

Based on the above description, the following conclusions can be summarized.

First, the user adjusts the RSSI slope 611 and the RSSI threshold RSSIth2 by the RSSI Control Block 244 adjusted by the Digital Control Block 242 to bring the reception sensitivity of the OBU to a desired level. Since it can be precisely adjusted, transmission and reception between the OBU and the RSU can be realized only in the communication area 150.

Second, the RSSI Control Block 244 does not generate a demodulated output signal at the receiver of the OBU for an input signal below the reference reception sensitivity 610 through the RSSI 630 function, and the reference reception sensitivity 610. In case of abnormality, it can be adjusted to generate the transmission output of the OBU.

Third, since the communication area limiting apparatus of the present invention is adjusted by a digital control method, it is possible to implement an auto-calibration function during the production of the OBU, and the RSSI threshold value or the reference reception obtained by the experiment during the production of the OBU. The digital control value optimized for the sensitivity is stored in the OBU terminal memory 400 so that it can be easily implemented.

Fourth, the communication area limiting device may be implemented by applying to the RSU as well as the OBU, and in this case, may be implemented by applying the same method applied to the above-described OBU.

In the above description, the technical idea of the present invention has been described with the accompanying drawings, which illustrate exemplary embodiments of the present invention by way of example and do not limit the present invention. In addition, it is apparent that any person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

1 shows a general configuration of an electronic toll collection system (ETCS).

2 illustrates an embodiment of a transmitter or a receiver for a conventional electronic billing system (ETCS).

FIG. 3 illustrates the communication success rate of the electronic toll collection system (ETCS) according to the performance of the on-vehicle device (OBU).

4 illustrates an OBU transmitter output signal obtained by deteriorating a transmitter performance of a conventional OBU.

5 illustrates a configuration of a communication area limiting apparatus of an ETCS terminal according to the present invention.

6 is a graph illustrating RSSI in order to explain a method of controlling reception performance of an OBU according to the present invention.

7 is a graph illustrating RSSI and demodulated ASK output signals according to reception performance control of the OBU of the present invention.

Claims (10)

In an electronic toll collection system (ETCS) of an onboard vehicle (OBU) equipped with an antenna, an RF receiver, an RF transmitter, and a baseband transmission and receiver, Receiving performance of the OBU comprising the Digital Control Block and the RSSI Control Block as a component to limit the receiving performance of the OBU to the receiving end of the ASK Demodulator constituting one of the RF receivers so as to be transmitted or received only in a communication range of a certain range. Communication area limiting device of the ETCS terminal, characterized in that it further comprises a limiting device. The method of claim 1, wherein the RSSI Control Block, And controlling an RSSI threshold value or an RSSI slope to control an ASK output signal generated by the ASK Demodulator. The ASK output signal of claim 2, wherein the ASK output signal comprises: And output only when the received signal input power of the OBU is greater than a reference reception sensitivity (Pref) corresponding to the RSSI threshold. The method of claim 1, wherein the RF transmitter, And a transmission signal is transmitted only when the reference reception sensitivity (Pref) corresponding to the RSSI threshold is equal to or greater than. The method of claim 1, And an OBU terminal memory for storing an RSSI threshold value or a digital control value of a reference reception sensitivity (Pref) at one end of the baseband transmitting and receiving unit. In an electronic toll collection system (ETCS) comprising an antenna, an RF receiver, an RF transmitter, and a baseband transmitter and receiver attached to each of a plurality of roadside devices (RSUs), The digital control block and the RSSI control block are configured to operate to transmit or receive only in a communication range of a limited range by limiting the reception performance of the roadside device (RSU) to the receiving end of the ASK demodulator constituting the RF receiver. Communication area limiting device of the ETCS terminal, characterized in that it further comprises a reception performance limiting device of the RSU. The method of claim 6, wherein the RSSI Control Block, And controlling an RSSI threshold value or an RSSI slope to control an ASK output signal generated by the ASK Demodulator. The method of claim 6, wherein the ASK output signal is And output only when the received signal input power of the RSU is greater than a reference reception sensitivity (Pref) corresponding to the RSSI threshold. The method of claim 6, wherein the RF transmitter, And a transmission signal is transmitted only when the reference reception sensitivity (Pref) corresponding to the RSSI threshold is equal to or greater than. The method of claim 6, And an RSU terminal memory for storing an RSSI threshold value or a digital control value of a reference reception sensitivity (Pref) at one end of the baseband transmitting and receiving unit.

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