JP2573761B2 - Performance test equipment for roadside beacon utilization system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a performance test apparatus in a road-to-vehicle communication system using a roadside beacon.

[0002]

2. Description of the Related Art Various navigation devices have been proposed and put into practical use for assisting a vehicle to travel on unfamiliar land. Conventional navigation devices are generally
A position detection unit for detecting the current position of the vehicle based on outputs from the distance sensor and the direction sensor, a map memory constituted by a CD-ROM, a display device, and a current position of the vehicle detected by the position detection unit And a control unit for reading a road map including the above from the map memory and displaying the read road map on the display device.

[0003] In such a navigation device, the current position of the vehicle on the display device is largely deviated from the actual position with an increase in the traveling distance due to errors inherent in the vehicle speed sensor and the direction sensor. There is a possibility that it will shift. In addition, when traveling near a railway line or the like, a large error is likely to occur in the direction sensor due to magnetic action.

[0004] For the purpose of solving such a problem, installation of a roadside beacon has been proposed. The roadside beacon includes beacon antennas arranged at predetermined distances in a road traffic network, and emits a signal including position data and road direction data from the beacon antenna to a relatively narrow range. A vehicle traveling on the road can receive this signal and take it into the navigation device, and calibrate the current position and orientation of the vehicle to the correct one.

[0005]

By the way, the service area of the roadside beacon is limited, the signal radiated from the beacon antenna is liable to cause fading, and the reception level of the signal in the onboard receiver fluctuates. The traveling range of a vehicle in which a receiver that receives a radiated signal can accurately receive a signal radiated from a beacon antenna is limited to a certain range around the beacon. Therefore, it is necessary for the receiver to receive the beacon signal with the highest possible probability within this range and reproduce it as a data frame. Therefore, how to evaluate the radio wave propagation characteristics and the reception characteristics of the receiver becomes a problem.

Conventionally, a bit error rate (BER) has been mainly used for evaluating the radio wave propagation characteristics and the characteristics of a receiver. This BER is defined by (the number of bits received incorrectly) / (the total number of received bits) for each bit constituting the beacon signal. The percentage increases.

However, the BER is an evaluation method that focuses on whether or not each bit has been correctly received, and cannot determine the reception rate in a frame unit composed of bits. For this reason, even if the value of the BER is known, it is not always clear whether or not the receiver actually mounted on the vehicle has the frame receiving performance sufficient to constitute the navigation device. For example, BER is measured over a certain period of time, and even if it is found that the BER takes a certain value, bit errors occur sporadically in that time period or bit errors are concentrated in a part of the time period. I don't know what's going on. If it happens sporadically, each frame contains an error,
Each frame is affected by the error, and the signal may not be received correctly, but if it is concentrated, only the frame at that time is not correctly reproduced due to the effect of the error. The frame is likely to have been received correctly.

Further, in order to measure BER, it is necessary to add a random signal for BER measurement such as a PN signal to a beacon signal, and there is a disadvantage that measurement cannot be performed based on a normal beacon signal. Accordingly, an object of the present invention is to provide a performance test apparatus that can correctly evaluate signal reception performance, signal propagation state, and the like in a road-to-vehicle communication system using a roadside beacon.

[0009]

SUMMARY OF THE INVENTION The present invention evaluates, in a road-to-vehicle communication system using a roadside beacon, the propagation state of a signal radiated from the roadside beacon and the receiving performance of an on-board receiver for receiving the signal. A roadside beacon comprising a plurality of fixed length frames.
That repeatedly transmits the same information consisting of
Frame number prediction means for predicting the number of frames included in the signal radiated from the roadside beacon antenna in a certain period , and the number of normally received frames included in the roadside beacon reception output signal of the on-vehicle receiver to be evaluated. And a ratio of the number of frames counted by the frame check unit during the same period to the number of frames predicted by the frame number prediction unit is calculated. Control means for evaluating the reception performance of the roadside beacon signal of the receiver.

In the above-mentioned performance testing apparatus, the frame check means performs a cyclic redundancy check on the roadside beacon reception output signal of the on-vehicle receiver under evaluation to determine whether the frame has been normally received. The determination may be made. In addition,
Display the evaluation result by the control means on the performance test equipment
The display means may further include a display means for performing
Is the data obtained by running the vehicle at almost constant speed.
It may be displayed in units of separation.

[0011]

The above-mentioned frame number predicting means can predict the number of frames contained in the signal emitted from the roadside beacon antenna for a predetermined period from vehicle speed information and the like. It is possible to count the number of frames that can be normally received among the frames included in, so that the frame reception rate can be obtained from these ratios, including the radio wave propagation characteristics of the roadside beacon signal of the in-vehicle receiver. It becomes possible to evaluate the reception performance.

[0012]

[0013]

FIG. 4 is a diagram for explaining an outline of position detection and direction identification using a roadside beacon. As shown in FIG. 4A, a beacon antenna 12
Is installed. A signal is radiated from the beacon antenna 12 toward the road 11.

As shown in FIG. 4C, a signal radiated from the beacon antenna 12 is a first signal for modulating various data.
Modulation method (GMSK, PSK, FSK, ASK modulation, etc.)
Is divided into two, and the two-divided signals are subjected to amplitude modulation of, for example, 1 kHz in opposite phases to each other as position data.
There is a signal. The position data is 1 kHz
It may be superimposed by other AM signals. Alternatively, they may be superimposed using another modulation method.

Therefore, the emission zone of the AM signal is shown in FIG.
For example, an in-phase signal is emitted from the beacon antenna 12 in the right direction, and an out-of-phase signal is emitted in the left direction. A signal radiated from the beacon antenna 12 is received by a receiver mounted on a vehicle traveling on the road 11. The signal reception level is, for example, as shown in FIG. 4B. That is, for the data signal component of the received signal, a reception level of a predetermined electric field intensity distribution spreading around the beacon antenna 12 is obtained. On the other hand, A
As for the M signal component, the reception level of the electric field distribution that causes a sharp drop in the main radiation direction boundary line between the in-phase signal and the out-of-phase signal is obtained. Therefore, in the vehicle traveling on the road 11, when the reception level of the received AM signal component changes and the level drops sharply, it can be determined that the vehicle is just below the beacon antenna 12.
That is, it can be determined that the position of the received position data has been reached.

In FIG. 4A, when the traveling direction of the vehicle is “a”, the AM signal is first received in-phase, and after an abrupt level decrease, the AM signal is received in the opposite phase. On the other hand, when the traveling direction of the vehicle is b, first, the AM signal of the opposite phase is received, and after the level decreases sharply, the A signal of the same phase is received.
An M signal is received. Therefore, in receiving the AM signal, the traveling direction of the vehicle can be identified based on whether the phase of the received signal has changed from the same phase to the opposite phase or from the opposite phase to the same phase.

Whether the AM signal is in phase or out of phase, as shown in FIG.
It is determined whether the AM signal is synchronized at the rising edge or synchronized at the falling edge. FIG. 1 is a block diagram illustrating a configuration example of a road-side beacon signal reception performance testing apparatus according to the embodiment. A signal radiated from the beacon antenna 12 is received by the on-vehicle antenna 8, and detection and amplification are performed in the receiver 1. The output of the receiver 1 is usually provided to a navigation device, where demodulation of beacon data, phase detection, phase determination, and the like are performed, and the current position and direction of the vehicle are calibrated to correct ones. When testing the reception performance of the roadside beacon according to the present invention, the output of the receiver 1 is supplied to the frame check circuit 2 and the electric field strength measuring device 3 which constitute the roadside beacon signal reception performance testing device.

The output of the frame check circuit 2 is supplied to a personal computer 4, and the output of the electric field strength measuring device 3 is A / D converted and supplied to the personal computer 4. The personal computer 4 also includes an on / off signal of a switch 5 directly below the antenna and a vehicle speed sensor 6 which are manually operated by a measurer when the vehicle comes directly below the beacon antenna.
From the vehicle speed signal.

The display 7 displays a test result by the personal computer 4. Hereinafter, the function of each unit of the roadside beacon signal reception performance test apparatus will be described in detail. The frame check circuit 2 determines the number of normally received frames (Cyclic) among the frames received within a predetermined section based on the signal radiated from the beacon antenna 12.
It is determined by Redundancy Check (CRC). In the following, if there is no error in the CRC,
COK) and the number of frames that could not be received normally (displayed as CRCNG) are counted.

The personal computer 4 functions as a frame number estimating means and a control means. Based on the vehicle speed signal from the vehicle speed sensor 6, the number of frames included in the signal radiated from the roadside beacon antenna 12 for each fixed traveling section is determined. (Expressed as EXPECT), and based on the following formula, the number of frames that could not be received in the section, that is, the number of frames that could not be synchronized (LOST)
Is displayed).

LOST = EXPECT− (CRCOK + CRCNG) The personal computer 4 further calculates the number of normally received frames CRCOK calculated as described above.
And the number of frames EXPECT included in the beacon signal, the ratio CRCOK / EXPECT is determined.

Next, referring to FIG. 2, generally, information of the same content composed of a plurality of frames is repeatedly transmitted from antenna 12. Therefore, the probability of successfully receiving a frame in the i-th cycle of the signal radiated from the beacon antenna 12 is defined as a frame reception rate PFi. Assuming that the receiver 1 repeatedly receives the same information R times and also performs error detection, the frame reception rate becomes

[0023]

(Equation 1)

Is improved. Therefore, if a series of information is composed of n frames, the reception rate of the series of information is

[0025]

(Equation 2)

## EQU1 ## Now, it is assumed that the vehicle is driven at a substantially constant speed using a test beacon signal having a 40-frame configuration in one cycle, and data is collected. Vehicle speed 50km / h
In this case, the traveling distance required to obtain one cycle of data is about 10 m. So, every 10m
The ratio CRCOC / EXPECT of the number of normally received frames CRCOK to the number of frames EXPECT is calculated. CRCO acquired in the first 10m
Regarding K / EXPECT, CRCOK / EXPECT = {1- (1-PF1)} can be set to ⁴⁰ . For the next 10 m, CRCOK / EXPECT = {1- (1-PF1) (1-PF2)} ⁴⁰ . For the next 10 m, CRCOK / EXPECT = {1- (1-PF1) (1-PF2) (1-PF3)} ⁴⁰ . In this way, by continuing the 4, 5, 6,... Cycle, the frame reception rate in each cycle can be obtained, and it can be directly evaluated whether or not the reception has been correctly performed in each cycle unit.

Table 1 shows examples of numerical values counted or calculated as a result of the actual measurement.

[0028]

[Table 1]

Further, when the data in Table 1 is obtained, the received electric field strength, the cumulative number of normal received frames, the frame reception rate (the same data as the data in Table 1), the result of carrier level judgment (CD), and the phase judgment The results are shown in FIG. In Table 1 and FIG. 3, the vehicle speed is determined based on the vehicle speed signal from the vehicle speed sensor 6, and the point where the distance (running distance) = 0 is manually measured by the tester when the vehicle is directly below the antenna. This is determined based on the fact that the switch 5 is turned on. By performing the above test, the number of correctly received frames CR
The ratio CRCOC / EXPECT of COK to the number of frames EXPECT can be actually measured.

Further, as a result of the above-described test, it is possible to directly know how many frames have been correctly received within a predetermined distance before and after the beacon. For this purpose, as shown in the upper graph of FIG. 3, a cumulative count of the number of normally received frames may be obtained. Further, as shown in FIG. 3, according to the apparatus of this embodiment, the distance is taken on the horizontal axis,
Each measurement data can be displayed as a graph and evaluated. That is, when the road-to-vehicle communication is performed in a spot within a short predetermined distance range around the installation position of the roadside beacon, the signal reception state, the signal propagation state, and the like within the distance range. Has the advantage that it can be correctly evaluated based on the distance.

According to the general beacon signal reception standard, 1
As a 50-70 frame cycle, information for three cycles within ± 60 m around the beacon (that is, 15 frames)
It is considered that practical use will be sufficient if 0 to 210 frames can be obtained. To explain based on the example of Table 1, 55 + 80 + 109 + 97 + 106 = 447 frames can be correctly received within ± 50 m around the beacon. Therefore, Table 1
In the case, the receiving performance of the roadside beacon signal of the on-vehicle receiver can be made sufficient.

[0032]

As described above, according to the present invention, the number of frames included in the signal emitted from the roadside beacon antenna in a certain period predicted by the number-of-frames predicting means is counted by the frame checking means within the same period. The ratio of the number of transmitted frames is obtained, and based on this ratio, it is possible to know how much of the transmitted frames the frame was correctly received. Therefore, you can directly know the frame reception rate,
Compared with the conventional method, the reception performance of the roadside beacon signal including the propagation state of the radio wave and the performance of the receiver can be directly and accurately evaluated. Also, the propagation state of the roadside beacon signal can be confirmed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a roadside beacon signal reception performance testing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing a series of frames repeatedly transmitted.

FIG. 3 is a graph showing a specific example of received data in the embodiment.

FIG. 4 is a diagram for explaining an outline of position detection and direction identification using a roadside beacon, where A indicates a state of installation of a beacon antenna and a state of an emitted radio wave, and B indicates a demodulated received signal level. , C indicate the phase difference of the received data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Onboard receiver 2 Frame check circuit 4 Personal computer 6 Vehicle speed sensor

Claims (4)

(57) [Claims] In a road-vehicle communication system using a roadside beacon, a test apparatus capable of evaluating a propagation state of a signal radiated from the roadside beacon, a receiving performance of a vehicle-mounted receiver for receiving the signal, and the like. The roadside beacon is composed of a plurality of fixed-length frames.
Frame number prediction means for predicting the number of frames included in a signal radiated from a roadside beacon antenna for a predetermined period of time, and a roadside beacon reception output signal of an on-vehicle receiver to be evaluated. Frame checking means for counting the number of normally received frames included in, the ratio of the number of frames counted by the frame checking means during the same period with respect to the number of frames predicted by the frame number prediction means, Control means for evaluating the reception performance of the roadside beacon signal of the on-vehicle receiver under evaluation based on the ratio, a performance test apparatus for a roadside beacon utilization system, comprising: 2. The frame check means performs a cyclic redundancy check on a roadside beacon reception output signal of the on-vehicle receiver under evaluation to determine whether or not the frame has been normally received. Is the thing
The performance for the roadside beacon utilization system according to claim 1.
Testing equipment. 3. A table for displaying an evaluation result by said control means.
2. The roadside beacon use system according to claim 1, further comprising an indicating means.
Performance test equipment for stems. 4. The display means causes the vehicle to travel at a substantially constant speed.
The data collected and displayed in units of mileage
The performance for the roadside beacon utilization system according to claim 3.
Testing equipment.