JP2002040119A - Detecting method for position immediately below radio beacon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a position immediately below a beacon, taking into consideration the receiving state and phase decision in many frames. SOLUTION: A beacon emits AM signals with mutually different phases in both directions to the forward side and to the backward side of a beacon passing, while emitting the same traffic information signal in both the directions. An electric field strength detecting part 16 detects received electric field strength E and a phase detecting part 15 detects a phase of an AM signal SAM for every frame. A processing part 18 increments or decrements a phase count value θ, corresponding to whether the AM signal phases are the same phases or opposite phases and monitors a peak value θp of the phase output value (1), when the received electric field strength E is larger than a set strength Es1; it decides that a moving terminal exists at the position immediately below the beacon; and when (2) the peak value θp is larger than a set peak value and the difference between the peak value θp and the phase count value θ is a set value or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a position directly under a radio beacon in a mobile terminal such as a navigation device for receiving and outputting traffic information from a radio beacon provided near a road. About the method.

[0002]

2. Description of the Related Art An on-vehicle navigation device (1) detects a vehicle position, reads map data around the vehicle position from a map storage medium such as a DVD, draws a map on a display screen, and draws a map on the display screen. The function to draw the vehicle position mark on the own vehicle position, (2) The function to display the vehicle position mark fixedly at a predetermined position on the display screen, and to scroll the map as the vehicle moves, (3) From the starting point It has a function of searching for a route with the minimum cost (for example, the shortest time or the shortest distance) to the destination and displaying the route on the screen.

In addition to the above functions, the on-vehicle navigation device receives road traffic information such as traffic congestion, accidents and regulations provided by a road traffic information communication system (VICS (registered trademark)) and maps the information in real time. It has the function of displaying on the top. Levels 1 to 3 can be used as a display method of road traffic information in VICS, and road traffic information can be displayed at a desired level according to a situation or purpose. Level 1 is a text information display mode in which characters are displayed in the upper area of the display screen, section travel time information,
It displays fault information, service information, general FM character information, and the like. Level 2 is the simple figure display mode,
A simple figure of a traffic congestion monitoring road is drawn, and information on traffic congestion and obstacles is displayed on the simple figure. Level 3 is a map information display mode for displaying information such as traffic congestion, accidents and regulations on a map in real time.

As means for communicating VICS information,
Optical beacons, radio beacons and FM multiplex broadcast radio waves are used. The communication area of each communication means is 10 to 50 km per FM multiplex broadcast, 60 to 70 m per radio beacon,
Each optical beacon is 3.5m. For this reason, FM multiplex broadcasting with a wide communication area flows wide area traffic information, and radio beacons and optical beacons flow more detailed traffic information in a limited area.

FIG. 4A shows an example of VICS information related to traffic congestion, which includes a link number constituting a road, a traffic congestion head position, a traffic congestion length, a congestion degree, and the like. Fig. 4 (b)
, The distance from the end B of the link LK, the length of the congestion indicates the distance of the congested section, and the degree of congestion indicates the degree of congestion.
Unknown / No traffic / Congestion / Congestion FIG.
Is a conventional traffic jam display example at level 3, in which red-line arrows A and B indicating traffic jam are displayed on a map along a road over a traffic jam range, and the traffic jam is displayed separately for up and down. By using such VICS road traffic information, the driver can avoid a congested road, a traffic-restricted road, and an accident-causing road and reach the destination in a short time.

Among the above three communication means, as shown in FIG. 6, traffic information is cyclically transmitted from the radio beacon at one cycle / N frame, and T1 (= 2 ms +
α) is inserted. Each frame has a size of 128 bytes / 16 ms (= 64 kbps) as shown in FIG.
Byte synchronization section SYNC, 19-byte frame header section, 10
It consists of a 3-byte real data section and a 2-byte CRC section, and large pieces of data (variable length) are composed of some real data. The synchronization unit SYNC detects the head of the frame.
The frame header section includes various header information such as a header identifier, a beacon number, and an information format. The information form specifies the direction in which information is to be provided, and specifies whether the traffic information is a main direction, a sub direction, or both directions. The actual data section includes various information for performing display based on the levels 1 to 3 in VICS.

As shown in FIGS. 8 (a) to 8 (c), radio beacons include a one-way lane beacon and a two-way lane beacon, each of which cyclically transmits information to a car. In the case of a one-lane beacon ((a), (b)), the direction in which traffic information is provided is the main direction, and in the case of a two-lane beacon ((c)), traffic on the side of the road where the beacon is installed The direction is the main direction. The one-lane beacon transmits information only for the main direction of the road, and the two-lane beacon transmits information for both the main direction and the slave direction.

In order to identify the main direction using the information provided from the radio wave beacon BCN, the determination is made based on the phase of the AM modulated signal. As shown in FIG. 9 (a), the radio beacon BCN radiates the same traffic information signal before and after passing the beacon for traffic information, but has a different phase between the AM signal before and after the beacon passes. Emit AM signal. In this case, the phase of the AM signal from the beacon BCN is set so as to change from “the same phase” to “opposite phase” with respect to the traffic flow in the main direction. As a result, the mobile terminal (not shown) detects the phase (same phase, opposite phase) of the AM signal received from the beacon BCN, and determines the main direction / slave direction based on the detected phase. For example, as shown in FIG. 9B, if the phase of the AM signal from the beacon BCN changes from “in phase” to “opposite phase”, it is determined that the signal is traveling in the main direction. If the phase changes from “phase” to “same phase”, it is determined that the vehicle is traveling in the slave direction.

FIG. 10 shows A before and after passing a radio beacon and at 1 KHz.
FIG. 4 is a phase relationship diagram of an M signal. The radio wave beacon BCN radiates traffic information at a rate of 64 kbps for each frame in both directions before and after passing the beacon, and radiates 1 KHz AM signals having phases different from each other before and after passing the beacon. That is, radio wave beacon, the beacon passes through the front side generates an AM signal S _AM which becomes frame head (synchronizer SYNC) frame in phase I rise, in the frame top beacon passes the rear (synchronization section SYNC) standing An AM signal S _AM which goes down in phase with the frame is generated.

FIG. 11 is a block diagram of a conventional direction judging circuit. A synchronous detecting section 1 detects a synchronous section SYNC from frame data, and a 1 KHz signal generating section 2 detects a synchronous section SYNC when the synchronous section SYNC is detected. 1 KHz signal S _INT is internally generated.
AM signal S _AM and internal 1K of 1KHz is exclusive logical sum circuit (EXOR circuit) 3 demodulated from the beacon radio wave operates as a comparison unit
The exclusive OR operation with the Hz signal _SINT is executed and output. Internal 1KHz phase of the EXOR circuit 3 1KHz of AM signal S _AM is
If the phase matches the phase of the signal S _INT , “0” is output,
If they are different, "1" is output. The direction determination unit 4 monitors “0” and “1” for each frame, and keeps “0” for four consecutive frames.
If so, it is determined that the phase is the same, and if it is "1" for four consecutive frames, it is the opposite phase, and the others are undefined. The direction determination unit 4 continues the above-described phase detection, and determines that the mobile terminal is traveling in the main direction if the detected phase changes from “same phase” to “opposite phase” when the mobile terminal passes immediately below the beacon. Conversely, if the mobile terminal passes just below the beacon and the detected phase changes from “opposite phase” to “in-phase”, it is determined that the mobile terminal is traveling in the slave direction. If it is determined as the main direction, traffic information in the main direction or both directions transmitted from the beacon is displayed.If it is determined as the slave direction, only traffic information in both directions transmitted from the beacon is displayed. Does not display traffic information. The conventional direction determination circuit shown in FIG. 11 is configured such that when the phase of the AM signal is inverted or the phase is delayed or advanced due to multipath or fading, the phase determination is erroneous and the mobile terminal must not display the opposite direction. There is a problem that the traffic information is displayed or the traffic information to be displayed is not displayed.

FIG. 12 is a block diagram of another direction judging circuit which has already been proposed by the present applicant. The synchronization detecting section 1 detects the synchronization section SYNC from the frame data, and the 1 KHz signal generation section 2 detects the 1 KHz signal S in phase with the frame when the synchronization section SYNC is detected.
Generates _INT internally. The exclusive OR circuit (EXOR circuit) 3 that operates as a comparison unit is 1K demodulated from a beacon radio wave.
The exclusive OR operation of the AM signal S _AM of 1 Hz and the internal 1 KHz signal S _INT is executed and output. The EXOR circuit 3 outputs “0” if the phase of the 1 kHz AM signal S _AM matches the phase of the internal 1 kHz signal S _INT , and outputs “1” if different. The sampling unit 5 samples the output signal of the EXOR circuit 3 at 10 KHz, the counter 6 counts up if the sampling signal is "1", and the direction determination unit 7 in-phase / out-phase for each frame based on the count value. / Judge indefinite.

[0012] EXOR circuit 3 FIG. 13 (a), the (b), the long phase of 1KHz of the AM signal S _AM is consistent with the phase of the internal 1KHz signal S _INT (same phase), the low level "0" is output, and if different (opposite phase), a high level "1" is output. Since one frame is 16 ms, sampling at 10 KHz yields 160 sampling signals per frame. At the same phase of (a), the EXOR circuit output is "0", so the count value of the counter 6 is "0". At the opposite phase of (b), the EXOR circuit output is "1", so the count value of the counter 6 is It becomes “160”. In practice, or the phase is inverted for AM signal S _AM of 1KHz as shown by multipath and fading (c), the phase lag, because proceeds occurs, the direction determining circuit 7 count value 0
If it is 1010, it is determined that the phase is the same. If the count value is 150〜160, it is determined that the phase is opposite. If the count value is 11〜149, it is determined that the phase is indefinite.

[0013]

According to the direction judging circuit of FIG. 12, it is possible to judge whether the direction is the main direction or the subordinate direction more accurately than the direction judging circuit of FIG. However, FIG.
The second direction determination circuit performs the phase determination without considering the reception state (reception electric field strength) from the radio beacon. For this reason, it may be erroneous to determine the phase at a point away from the radio wave beacon and where the received electric field strength is weak. Further, the direction determination circuit in FIG. 12 determines the phase in a short frame unit of 16 ms (same phase, opposite phase, indeterminate phase), and determines the immediate lower position based on the change in the phase determined in one frame unit. Like this one
If the phase is determined on a frame basis, it is likely to be affected by phase disturbance due to multipath, fading, and running along with the track, and the phase determination is often erroneous. If the phase determination is erroneous, the position immediately below the beacon will be erroneously detected, causing a problem that traffic information to be displayed is not displayed or traffic information in the opposite direction which should not be displayed is displayed. That is, it is not sufficient to determine the phase in units of one frame without considering the received electric field strength. As described above, it is an object of the present invention to accurately detect a position directly below by considering a reception state (reception electric field strength) and a phase determination in a large number of frames.

[0014]

SUMMARY OF THE INVENTION The present invention is a method for detecting a position directly below a radio beacon of a mobile terminal which receives and outputs traffic information from a radio beacon provided near a road. According to the present invention, (1) the same traffic information signal is emitted from the radio beacon in both directions before and after passing the beacon, and AM signals having different phases are emitted from the radio beacon to the front and rear sides of the beacon. The terminal detects the received electric field strength from the beacon and detects the phase of the AM signal received from the beacon for each frame.
Is greater than the set intensity, the phase count value is counted up or down depending on whether the phase of the AM signal is the first phase (same phase) or the second phase (opposite phase), and Monitor the peak value of the count value,
(4) When the peak value is larger than the set value and the difference between the peak value and the phase count value exceeds the set value, it is determined that the mobile terminal is located immediately below the beacon. In addition, in addition to the above-described immediately below position determination condition, when the received electric field intensity is larger than the second set intensity (> first set intensity) and the peak value of the received electric field intensity is equal to or more than the set peak value, the moving is performed. The terminal determines that the terminal exists immediately below the beacon. In this way, it is possible to accurately detect immediately below the antenna in consideration of the reception state (reception electric field strength) and the phase determination in many frames, and to correctly display traffic information. it can.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (A) Directly-underlying position detecting condition First first-underlying position detecting condition The phase determination for each frame is performed in the same manner as in FIG. 12, and when the phase is the same, the phase count value θ is counted up, Count down when In this manner, the phase count value θ increases to the position directly below the beacon as shown by the solid line in FIG. 1A, and decreases after passing through the position directly below the beacon. Therefore, the time when the phase count value starts decreasing from the peak value can be estimated as the position immediately below the beacon. However, as indicated by the dotted line, the phase count value decreases and increases at the point where the reception condition deteriorates, even if it does not pass through the position directly below the beacon, as shown by the dotted line when affected by phase disturbance due to multipath, fading, and running along with the track. There is. In such a case, the phase count value takes the peak value θp ′ and decreases from the peak value θp ′. Therefore, it is necessary to distinguish between a decrease in the phase count value from the peak value due to the passage immediately below and a decrease in the phase count value from the peak value due to the deterioration of the reception environment.

Therefore, according to the present invention, (1) the reception state is improved when approaching the position directly below the beacon, and the peak value becomes larger than the set peak value θps. (2) If the reception state deteriorates, the phase count value θ determines that the set value theta not decrease _TH above (in decreasing theta _TH has to continue 16 · theta _TH (ms) worsening state), it was considered a beacon position directly below as follows . That is, the phase count value θ
Is monitored, the peak value θp is larger than the set peak value θps, and the phase count value θ decreases from the peak value, and the difference | θp−θ | from the peak value θp becomes the set value θ _TH
When the number exceeds the threshold, the mobile terminal determines that the mobile terminal is located immediately below the antenna.

In the above description, the received electric field strength was not considered, but the received electric field strength E is the same as the phase count value θ in FIG.
As shown by the solid line in (b), it increases to the position directly below the beacon, and decreases after passing through the position directly below the beacon. In addition, when receiving the influence of phase disturbance due to multipath, fading, and parallel running with a track, the reception electric field strength decreases as shown by a dotted line. Therefore, in order to eliminate the phase determination result at the point where the reception state is poor, when the received electric field strength E is equal to or less than the _first set value Es ₁ (for example, 0.9 V), the phase count value θ is counted based on the phase determination result for each frame. Instead, the phase determination result is counted only when the reception state where the reception electric field strength E is equal to or more than the _first set value Es ₁ (= 0.9v) is good.

Second Second Direction Position Detecting Condition When approaching the position directly below the beacon, the reception state is improved, the received electric field strength E is large, and the peak value Ep of the received electric field strength is also large. Therefore, according to the present invention, when the above-mentioned first direct position detection condition is satisfied, (1) the received electric field strength E is larger than the _second set strength Es ₂ (for example, 1.1 V), and (2) When the peak value Ep of the received electric field strength E is equal to or larger than the set peak value Esp (for example, 1.5 V), it is determined that the mobile terminal is located immediately below the antenna. In this way, it is possible to accurately determine the position directly below. In the above description, the position directly below is detected while traveling in the main direction. However, the case where the position immediately below is detected while traveling in the subordinate direction can be similarly performed. However, when traveling in the slave direction, the phase count value θ increases in the negative direction, and decreases toward zero after passing just below the beacon.

(B) Configuration for detecting the position directly below FIG. 2 is a diagram showing the configuration for detecting the position directly below according to the present invention. The radio receiving unit 11 frequency-converts a radio signal from the beacon received by the antenna ATN into an intermediate frequency signal, and performs an AM demodulation unit 12,
Input to the FM demodulation unit 13. The AM demodulator 12 demodulates the 1 KHz AM signal S _AM (see FIG. 10) transmitted from the beacon, the FM demodulator 13 demodulates the FM modulated signal transmitted from the beacon, and the AD converter 14 modulates the FM demodulated signal. Is converted to 64 kbps digital data DATA and output. Phase detector 1
5 has the configuration shown in FIG. 12, and determines and outputs the phase (same phase / opposite phase / undefined) of the detected AM signal _SAM for each frame. The electric field intensity detector 16 detects the received electric field intensity E from the S meter terminal of the wireless receiver, and the electric field intensity peak monitor 17 monitors the peak value of the received electric field intensity E for each frame. The processing unit 18 receives an input from the phase detection unit 15
(1) Phase (in-phase / opposite-phase / indefinite), (2) Receive electric field strength E, (3) Perform direct position detection processing using the peak value Ep of the received electric field strength. The traffic information display process is performed based on the traffic information.

FIG. 3 is a flowchart of the processing performed by the processing unit 18 to determine the position immediately below the present invention. Frame header of data DATA
When it is detected that the beacon No. has changed based on the beacon number included in FIG. 7 (see FIG. 7), or when the received electric field strength exceeds the set level and an area-in is detected (step 101), the processing unit 18 clears the internally held phase count value θ, phase peak value θp, and electric field strength peak value Ep (step 102).

The phase detector 15 outputs an AM signal S for each frame.
The phase of _AM is detected and input to the processing unit 18 (step 1).
03). When the phase is detected, the processing unit 18 checks whether the received electric field intensity E is equal to or higher than the _first set intensity Es ₁ (= 0.9v) (step 104), and if E <Es ₁ (= 0.9v). , Ignore the input detection phase and wait for the input of the detection phase of the next frame. If E ≧ Es ₁ (= 0.9v), it is checked whether the detected phase is the same phase, opposite phase, or indeterminate (step 105). If undetermined, the detected phase of the next frame is determined. Wait for input. If the detected phase is the same phase, the phase count value θ (initial value is 0) is counted up (θ + 1 → θ) (Step 106), and if the detected phase is the opposite phase, the phase count value θ is counted down (θ (-1 → θ) (step 107).

Thereafter, it is checked that the absolute value of the difference between the previous peak value θp of the phase count value and the current phase count value θ is equal to or greater than the set value θ _TH (for example, 10) (step 10).
8). | θp-θ | if <theta _TH, and update processing of the peak value theta] p of the phase count value (step 109), thereafter, step
The processing after 103 is performed. The peak value θp is updated by comparing the current peak value θp with the current phase count value θ. If θp ≧ θ, the peak value θp is not changed, and θp <θ
If so, the current phase count value θ is newly set as the peak value θp (θ → θp).

[0023] In step 108, | θp-θ | if ≧ theta _TH, the current received field strength E is the second set value Es ₂ (= 1.1V)
It is checked whether it is the above (step 110), and E <Es ₂ (= 1.1
If v), the processing after step 103 is repeated. E ≧
If Es ₂ (= 1.1v), the peak value Ep becomes the set peak value Esp
(= 1.5v) or more is checked (step 111). Ep
If <Esp (= 1.5v), the processing after step 103 is repeated, and if Ep ≧ Esp (= 1.5v), it is determined that the position is immediately below the beacon (step 112), and the processing ends.

[0024] In the above, although the position immediately below determination is satisfied second position immediately below the detection conditions described in (A), in step 108 | θp-θ | when he became ≧ theta _TH, immediately beacon immediately below The position can also be determined. That is, when the first directly-underlying position detection condition is satisfied, it can be determined that the vehicle is immediately below. As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0025]

As described above, according to the present invention, when the received electric field strength is larger than the first set strength, the phase of the AM signal is changed to the first phase.
The phase count value is counted up or down depending on whether the phase is the same (in phase) or the second phase (opposite phase), and the peak value of the phase count value is monitored. When the difference is large and the difference between the peak value and the phase count value exceeds a set value, it is determined that the mobile terminal is present at a position immediately below the beacon. In the present invention,
When the above-described immediately below position detection condition is satisfied, further, when the (1) received electric field strength is larger than the second set intensity, and (2) the peak value of the received electric field strength is equal to or more than the set peak value, the mobile terminal It is determined that it exists immediately below the beacon. As a result, according to the present invention, the position directly below the beacon can be accurately detected in consideration of the reception state (reception electric field strength) and the phase determination in many frames, and the traffic information is correctly displayed. can do.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a directly-underlying position detection condition.

FIG. 2 is a configuration diagram of detecting a position directly below.

FIG. 3 is a flowchart of a position determination process immediately below.

FIG. 4 is an example of VICS information.

FIG. 5 is an example of road congestion display at level 3;

FIG. 6 is an explanatory diagram of transmission of traffic information.

FIG. 7 is a frame configuration diagram.

FIG. 8 is an explanatory diagram of a main direction and a sub direction.

FIG. 9 is an explanatory diagram of main direction and sub direction determination.

FIG. 10 is a phase relationship diagram of a 1 KHz AM signal before and after passing a beacon.

FIG. 11 is a conventional direction determination circuit.

FIG. 12 shows a direction determination circuit already proposed.

FIG. 13 is a time chart.

[Explanation of symbols]

 11. Radio receiving unit 12. AM demodulation unit 13. FM demodulation unit 15. Phase detection unit 16. Electric field intensity detection unit 17. Electric field intensity peak monitoring unit 18. Processing unit

Claims (2)

[Claims] 1. A method for detecting a position directly below a radio beacon of a mobile terminal, which receives and outputs traffic information from a radio beacon provided near a road, comprising: It emits an information signal and has different phases A before and after the beacon.
The mobile terminal detects the phase of the AM signal received from the radio beacon and detects the phase of the AM signal at the mobile terminal. The phase count value is counted up or down according to whether it is the first phase or the second phase, and the peak value of the phase count value is monitored, and the peak value is larger than a set value, and When the difference between the peak value and the phase count value exceeds a set value, the mobile terminal determines that the mobile terminal is located immediately below the radio beacon. 2. When the above condition is satisfied, if the received electric field intensity is larger than the second set intensity and the peak value of the received electric field intensity is equal to or more than the set peak value, the mobile terminal moves to the position immediately below the radio beacon. The method according to claim 1, wherein it is determined that the radio wave beacon exists.