JP3384355B2 - Receiving device for car navigation device and frequency switching method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a car navigation system for receiving road traffic information from each information broadcasting station of a road traffic information system, the information broadcasting being receivable at the current vehicle position. The present invention relates to a receiving device that automatically selects an information broadcasting station that provides the most road traffic information around a vehicle position among stations, and a frequency switching method thereof.

[0002]

2. Description of the Related Art In recent years, the operation of a road traffic information system, which uses FM multiplex broadcasting or the like to provide road traffic information of a region to a running vehicle, has been started. A car navigation device that receives and displays information such as traffic jam information, accident information, construction information, etc. on a map for optimal guidance is being researched and developed.

In such a road traffic information system, the area on the map is divided into mesh areas, and the information broadcasting stations in each area provide information on the mesh areas belonging to the service area. Since each information broadcasting station broadcasts with a radio wave of a different frequency, in order to receive road traffic information with a moving car, a new information broadcasting station is selected each time the service area of the information broadcasting station changes. It is necessary to track it by re-doing it. In particular, when moving at high speed or when traveling near the boundary of the service area of each information broadcasting station, it is inconvenient for the user because it is necessary to perform frequent tracking. There is a demand for a receiving device of a car navigation device capable of automatically performing such tracking.

A conventional receiving device is disclosed in Japanese Patent Laid-Open No. 6-27.
Japanese Patent No. 4792 (hereinafter referred to as "A") describes "an automobile provided with receiving means for receiving information supplied from a predetermined information broadcasting station in each area within the receivable area in a divided manner. In the vehicle, a vehicle position detecting means for detecting a traveling position of the vehicle and a memory means for storing the area information near the traveling position detected by the vehicle position detecting means are provided. Information storage device "is disclosed.

In the information storage device for an automobile disclosed in the above publication (a), the information in the mesh area that has been run once is stored, and when traveling in the same mesh area again, the information stored in the past is used. It was that.

[0006]

However, the above-mentioned conventional receiving device cannot cope with the road traffic information which changes from moment to moment such as traffic jams and accidents, so that the provided road traffic information can be effectively utilized. I had the problem that I couldn't.

Therefore, in order to perform automatic tracking in response to such road traffic information that changes with time, the error rate at the time of receiving the information broadcasting signal being received at each time is detected, and the error rate is detected. If the time when a certain threshold is exceeded continues for a predetermined time or longer, it is determined that the vehicle has gone out of the service area of the information broadcasting station, and another information broadcasting station with a good reception state is automatically selected. Can be considered.

However, when performing such automatic tracking, there are the following problems.

(1) If the vehicle is traveling in a place where the reception of radio waves is poor, such as in the shadow of a tunnel or a shield while traveling, it is determined that the vehicle has accidentally gone out of the service area of the information broadcasting station,
The frequency of the information broadcasting station is switched. Road traffic information is provided at time intervals of 1 to 5 minutes, so once the frequency is switched, it takes time to store the information,
It will not be possible to effectively utilize road traffic information that changes over time.

(2) On the contrary, assuming that the frequency is not switched unless the error rate continues for a predetermined time or more for a certain threshold value or more, even if the user goes out of the service area of the information broadcasting station, If a situation occurs where the reception status improves intermittently, the frequency will not be switched easily, and the information from the information broadcasting station outside the service area will continue to be received, enabling effective use of road traffic information. Disappear.

(3) In the central part of the city, the service areas of the information broadcasting stations are often mixed, and in such a case, when the information broadcasting stations with good reception are automatically used for tuning, It takes time to search for a hit, and it becomes impossible to effectively utilize road traffic information that changes with time.

(4) When traveling on a bridge over the sea, the reception condition of the information broadcasting station on the opposite bank across the sea may be good, and the frequency is switched at such time. Then, since the information of the information broadcasting station outside the service area is received, it becomes impossible to effectively use the road traffic information.

(5) Near the boundary of the service area of each information broadcasting station, road traffic information provided by the information broadcasting station located in the forward direction of travel is necessary. For that purpose, the information broadcasting located in the forward direction of travel is required. It is necessary to select a station. However, if the reception status of the information broadcasting station located at the rear of the traveling direction that has continued to be received does not deteriorate, frequency switching is not performed, and useful road traffic information is provided from the receivable information broadcasting station. in spite of,
Road traffic information cannot be used effectively.

The present invention is to solve the above-mentioned conventional problems, and it is possible to switch the selection of the information broadcasting station according to the reception state of the broadcast at the own vehicle position, and further the information broadcasting which can be received at the own vehicle position. Among the stations, it is possible to automatically select the information broadcasting station that provides the largest amount of road traffic information near the vehicle position, and to effectively use the road traffic information provided by the information broadcasting station. An object of the present invention is to provide a receiving device for a car navigation device that can be utilized.

Further, the present invention is to solve the above-mentioned conventional problems, and it is possible to switch the selection of the information broadcasting station according to the reception state of the broadcast at the own vehicle position, and further it is possible to receive at the own vehicle position. Among the information broadcasting stations, it is possible to automatically select the information broadcasting station that provides the largest amount of information on road traffic information near the vehicle position, and to save the road traffic information provided by the information broadcasting station. It is an object of the present invention to provide a frequency switching method for a receiving device of a car navigation device that can be effectively utilized.

[0016]

In order to solve the above problems, a receiving device for a car navigation device of the present invention is a receiving device for a car navigation device that receives information from each information broadcasting station of a road traffic information system. A receiving means for receiving the information of each mesh area provided by radio waves from an information broadcasting station, a vehicle position detecting means for detecting a vehicle position, and an information storing means for storing the information of each mesh area. Information size storage means for storing an information size, which is the size of the information for each mesh area and each reception frequency, and the information for each mesh area provided from the information broadcasting station received by the reception means. Information storage means for storing and storing in the storage means, and the information of the information for each mesh area stored in the information storage means Information size registration means for acquiring the size and registering or updating it in the information size storage means, and each reception read from the information size storage means of the mesh area to which the vehicle position detected by the vehicle position detection means belongs. In front of the receiving means , information size comparing and switching means for comparing the information size of frequencies and switching the detection frequency of the receiving means to the receiving frequency of the largest information size.
If the error rate at the time of receiving the information exceeds the specified threshold
Of the receiving means when the state continues for a predetermined time or more.
Other than the information broadcasting station that has selected the detection frequency at that time
Error rate comparison switching to switch to the frequency of the information broadcasting station
Means and the error rate comparison switching means or the information service.
The noise comparison switching means switches the detection frequency of the receiving means.
If the receiving means has not received the information after
Switching signature for returning the detection frequency of the receiving means to the original frequency
It is composed of a disconnection means .

With this configuration, it is possible to switch the selection of the information broadcasting station according to the reception status of the broadcast at the own vehicle position, and among the information broadcasting stations which can be received at the own vehicle position, the one near the own vehicle position is selected. A car navigation system that can automatically select the information broadcasting station that provides the largest amount of road traffic information and effectively use the road traffic information provided by the information broadcasting station. A receiver of the device can be provided.

Further, the frequency switching method of the receiving device of the car navigation system according to the present invention comprises a receiving means for receiving information of each mesh area provided by radio waves from each information broadcasting station of the road traffic information system, and a vehicle position. A vehicle position detection means for detecting the information, an information storage means for storing information of each mesh area, and an information size storage means for storing an information size which is a size of information for each mesh area and each reception frequency. A method for switching frequency of a receiving device of a car navigation device, comprising: an information storing procedure for receiving information of each mesh area provided from an information broadcasting station by the receiving means and storing and storing the information in the information storing means; The information size of the accumulated information for each mesh area is acquired and registered or updated in the information size storage means. The procedure and the own vehicle position detection means detect the own vehicle position, read the information size of each reception frequency of the mesh area to which the own vehicle position belongs from the information size storage means, compare the information size of each reception frequency, and And an information size comparison switching procedure for switching the detection frequency to a frequency having the largest information size.

With this configuration, the selection of the information broadcasting station can be switched according to the reception status of the broadcast at the own vehicle position, and among the information broadcasting stations receivable at the own vehicle position, the one near the own vehicle position can be selected. A car navigation system that can automatically select the information broadcasting station that provides the largest amount of road traffic information and effectively use the road traffic information provided by the information broadcasting station. A frequency switching method for a receiver of a device can be provided.

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[Means for Solving the Problems] To achieve this object
Of the car navigation device according to claim 1 of the present invention.
The receiving device is from each information broadcasting station of the road traffic information system.
In the car navigation device receiving device that receives the information of
Therefore, each message provided by the information broadcasting station by radio waves
The receiving means for receiving the above information of the vehicle area and the vehicle position
Own vehicle position detecting means for detecting,
Information storage means for storing information, each mesh area and
Information size, which is the size of the information for each reception frequency
And an information size storage means for storing
Each mesh area provided by the received information broadcasting station
Information stored in the information storage means and stored.
Information storage means and each message stored in the information storage means.
The information size of the information for each area
Information size registration to be registered or updated in the information size storage means
Means and the vehicle position detected by the vehicle position detection means
The information size storage means of the mesh area to which the device belongs
Compare the information size of each received frequency read out
The detection frequency of the receiving means is set to the maximum of the information size.
Information size comparison switching means for switching to a high reception frequency,
The error rate when the receiving means receives the information is predetermined.
When the state of being equal to or more than the threshold of continues for a predetermined time or more
The detection frequency of the receiving means is selected at that time
Error that switches to the frequency of the information broadcasting station other than the information broadcasting station
-Rate comparison switching means and the error rate comparison switching means
Or the information size comparison / switching means detects the receiving means.
The receiving means receives the information after switching the wave frequency.
If not received, the frequency based on the detection frequency of the receiving means is used.
It is configured by a switching determination means for returning to the wave number.

With this configuration, the following effects can be obtained.

(1) The switching judgment means checks whether or not the receiving means receives information after the error rate comparison switching means or the information size comparison switching means switches the detection frequency of the receiving means. If the receiving means has not received the information, the detection frequency of the receiving means is returned to the original frequency.

(2) When the selected information broadcasting station has stopped broadcasting after the switching, it is prevented from selecting that broadcasting station.

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) A receiving apparatus according to the present embodiment is a VICS (Vehicle Information and Comm) transmitted from an FM broadcasting station which is an information broadcasting station by FM multiplex broadcasting.
unication Syatem (road traffic information communication system) A receiver equipped with a car navigation system that receives and reproduces information, and selects a broadcasting station that transmits optimal information at the position of the vehicle as the vehicle moves. The detection frequency is automatically switched by the frequency switching method.

In FM multiplex broadcasting, VICS information is transmitted as 1 to a plurality of data groups every 1 to 5 minutes. The data group is further composed of a plurality of data blocks, and the VICS information is carried as a data block in a data packet and transmitted as a multiplexed signal of FM radio waves. The receiving apparatus according to the present embodiment reproduces the data blocks after performing error correction on the received data packet, and further connects the data blocks in a predetermined order to construct a data group, and VIC
Although the S information is reproduced, the optimum FM broadcasting station is selected according to the error rate at the time of reception and the amount of information around the vehicle position included in the received VICS information at this time. is there.

FIG. 1 is a block diagram showing a device configuration of a receiving device according to the first embodiment of the present invention.

In FIG. 1, 1 is a receiver for receiving FM radio waves.
The signal antenna 2 detects the received FM reception signal and selects a channel.
Detection channel selection section 3 which outputs a detection signal
Phase synchronization is applied to and the frequency signal for detection of the detection tuning unit 2
Output PLL frequency demodulator (Phase-Locked Loop freq
uency demodulator Phase locked loop frequency demodulator), 4
Is the data obtained by decoding the FM reception signal output by the wave detection and selection unit 2.
Outputs packets and measures error rate during decoding
DARC (Data
 Radio Channel) decoder, 5 is a data group (later
Memory (Dynamic Random Access Memo)
ry dynamic constant speed call storage device), 6 is each mesh area
Stores the size of the data group corresponding to each frequency
SRAM (Static Random Access Memory)
Constant-speed call storage device), 7 of the DARC decoder 4
Create a data group from the data packet to output D
A data group stored in the RAM 5 or stored in the DRAM 5.
Data group construction unit for updating the group, 8 is the DARC data
Error rate P output by coder 4_errAccumulated for a certain period of time
Received time integrated value S_errIs a constant threshold S_maxWhen
Is the current frequency f stored in the SRAM 6._x,mesh
Area y (mesh code M_y) Corresponding to
Loop size (hereinafter referred to as information size) S₀(F_x，
M_y) And information size update request to output information size update
Part, 9 is the information size S from the information size updating part 8.₀(F_x，
M_y) And an information size update request are entered.
S₀(F_x, M_y) And the current stored in SRAM6
Current frequency f of mesh area y of_xInformation corresponding to
Size S₁(F_x, M_y) And S₁(F_x, M_y) <S
₀(F _x, M_y), The information stored in SRAM 6
Size S₁(F_x, M_i) The current information size S₀(F_x，
M_y) Update history processing unit 10 updates the frequency f_x, Me
Information size S corresponding to the cache area y₁(F_x, M_y)
When there is a read request, the previous time stored in SRAM6
Data group size S₁(F_x, M_y) And the last day
Data group size S₂(F_x, M_y) And compare
Whichever is larger, the information size S₃(F_x, M_y) As
The information size reading processing unit, 11 is an information size reading processing unit.
Information of the mesh area y at the current location input from the management unit 10
Report size S ₃(F_x, M_y) And the frequency f of the surrounding broadcasting stations
_iInformation size of the current area mesh area y of (i ≠ x)
S₃(F_i, M_y) And S₃(F_x, M_y) <S
₃(F_i, M_y), The frequency f_iRequest to switch to
Information size comparison switching unit to output, 12 is DARC decoding
Error rate P output by DA4_errIs the predetermined time T₂(Example
For example, if it is continuously smaller than the threshold ε for 6 minutes),
Frequency f of other broadcasting stations including the rush area y_i(I is free
Output switching request S1 to an appropriate broadcasting station other than station x
Error rate comparison switching unit, 13 indicates information size comparison switching
Switching request S1 from the unit 11 and the error rate comparison switching unit 12
Alternatively, when S2 is input, the setting frequency of the PLL frequency demodulator 3 is set.
Wave number is the current frequency f_xTo frequency f_iSwitch to
When the frequencies do not match (when phase synchronization is not possible)
Or a data packet is output from the DARC decoder 4.
If not, based on the set frequency of the PLL frequency demodulator 3,
Frequency f _xThe switching determination unit for returning to the
The clock that outputs the data, and 15 is the date and time that the clock 14 outputs.
If the date of the data is changed,
Information size S₂’(F_j, M_i) Value of the last day information
Is S₂(F_j, M_i) Information size
Table updating unit, 16 is input from the information size updating unit 8.
Information size S₀(F_x, M_y) Is 0 or PLL loop
If the tracking cannot be performed when the frequency of the wave number demodulator 3 is switched.
Information size S stored in SRAM 6₁(F_x，
M_y) Is cleared to zero, 17 is GP
GPS antenna that receives navigation radio waves from S satellites,
18 is a GPS for positioning and outputting the position of the own vehicle by GPS.
The receiver, 19 is the position information output from the GPS receiver 18.
Positioning the coordinates (latitude, longitude, etc.) of the vehicle position based on the signal
A vehicle position detection unit for detecting the vehicle position, 20 is a CD-R
Map composed of OM and CD-ROM drive etc.
It is a map information storage unit that stores information.

The PLL frequency demodulator 3 outputs the detection frequency signal of the set predetermined frequency to the detection channel selection unit 2. The detection channel selection unit 2 detects and outputs the FM radio wave transmitted from the FM broadcasting station received by the receiving antenna 1 by the FM multiplex broadcasting. The detection frequency setting at this time is P
This is performed by the detection frequency signal output from the LL frequency demodulator 3. The FM reception signal received by the detection channel selection unit 2 is demodulated by the DARC decoder 4, and the multiplexed signal is further separated / demodulated. Then, the DARC decoder 4
Detects block synchronization of this multiplex signal, corrects errors by CRC and parity code, etc., and outputs it as a packet to the data group construction unit 7.

The DARC decoder 4 measures a block synchronization error, a horizontal correction error and a vertical correction error when decoding the FM reception signal, and outputs it in response to a request. Here, the block synchronization error means an error when the DARC decoder 4 cannot detect the block identification codes BIC1 to BIC4 at the head of each packet. If a block sync error occurs, the contents of the packet cannot be replayed. In addition, the horizontal correction error is a cyclic code (C
(RC) is an error detected by error detection, and a vertical correction error is an error that occurs when an error correction is attempted using a parity packet for a frame that cannot be corrected due to a horizontal correction error.

The information size updating section 8, the information size comparison switching section 11, and the error rate comparison switching section 12 each have a timer for measuring time inside.

GPS antenna 17 and GPS receiver 18
Receives the navigation radio waves wirelessly transmitted from the four GPS satellites to the ground, and outputs them to the vehicle position detection unit 19. The own vehicle position detection unit 19 determines the GP from the radio wave transmission time included in the navigation radio wave, the orbit information of the earth orbit and the navigation radio wave arrival time.
The distance from the S satellite to the own vehicle is measured, and the position of the own vehicle is detected from the coordinates of the intersection of the spherical surface centered on each GPS satellite.

In the present embodiment, the receiving means is the receiving antenna 1, the detection and channel selection unit 2, the PLL frequency demodulator 3,
The DARC decoder 4 is used, and the vehicle position detecting means is constituted by the GPS antenna 17, the GPS receiver 18, the vehicle position detecting section 19, and the map information storage section 20, and the information storing means is constituted by the DRAM 5. The information size storage means is composed of the SRAM 6, the information storage means is composed of the data group construction part 7, and the information size registration means is composed of the information size update part 8 and the update history processing part 9. The information size comparison switching means is composed of the information size reading processing section 10 and the information size comparison switching section 11, the error rate comparison switching means is composed of the error rate comparison switching section 12, and the switching judgment means is switched. The information size table updating means is composed of a clock 14,
The information size table updating unit 15 is configured,
The zero clear processing means is composed of the zero clear processing unit 16.

Next, the structure of each data processed in the receiving apparatus of this embodiment will be described.

FIG. 2 is a diagram showing the data format of the data frame.

As shown in FIG. 2, the data frame is 1
A frame is composed of a packet for transmitting data of 190 blocks and a parity packet of 82 blocks. Packets for transmitting data are
16-bit block identification code BIC, 176-bit data packet, 14-bit CRC (Cyclic Redunda)
ncy Check), a horizontal parity code of 82 bits. The block identification code BIC is a code representing the type of each packet, the data packet is data carrying information to be transmitted such as VICS information, and CRC.
Is a code for error detection using a cyclic code,
The horizontal direction parity code is horizontal direction parity information within one frame. The parity packet is composed of a 16-bit block identification code BIC and a 190-bit parity from the beginning. The parity packets are distributed in the data frame to prevent burst errors. A parity packet is a packet in which vertical parity codes of a plurality of data frames are placed,
For example, for parity 1 in FIG.
Parity information of data packet 5 and CRC, and parity 2 is data of data packets 16 and 17 and parity information of CRC.

FIG. 3 is a diagram showing the data format of the data packet of FIG.

As shown in FIG. 3, the data packet is
It is composed of a 32-bit prefix and a 144-bit data block (in the case of character / graphic information data) or a 16-bit prefix and a 160-bit data block (in the case of data such as time information and broadcasting station name). Further, the prefix includes service identification, decoding identification, information end flag, update flag, data group number, and data packet number.

FIG. 4 is a diagram showing the data format of the data group.

The data group is restored data which is formed by joining the data blocks of the received data frame in a predetermined order. As shown in FIG. 4, the program number and the content are updated from the beginning. The flag, the page number, the mesh number, the upper 8 bits of the map coordinate X, the upper 8 bits of the map coordinate Y, and the remaining message data are arranged in this order. A mesh code is composed of two codes, the upper 8 bits of the map coordinate X and the upper 8 bits of the map coordinate Y.

FIG. 5 is a diagram showing the data structure stored in the SRAM.

The SRAM 6 stores the size (information size) of the data group restored from the received data frame.
Are categorized and stored for each reception frequency and each mesh code. Specifically, as shown in FIG. 5, the mesh code, the reception frequency, the previous information size, the last day information size, and the date on which the last day information size was updated are set as one unit of data set, A plurality of units of this data set are stored as an information size table. As will be described later, when a data frame is received and a data group is obtained, the reception frequency of that data group in the information size table and the information size of the last day corresponding to the mesh code are set to the information size of the obtained data group. Will be updated. When the date and time output by the clock 14 is changed, the previous information size of each reception frequency and each mesh code in the information size table is updated to the information size of the last day.

The frequency switching method of the receiving apparatus of this embodiment having the above configuration will be described below.

In the frequency switching method of the present embodiment, the data group construction unit 7 reproduces data by constructing a data group from the data packet output from the DARC decoder 4, and sequentially stores it in the DRAM 5.
Update. In addition, in parallel with this, the information size updating unit 8
And the update history processing unit 9 calculates the size of the data block stored in the DRAM 5, creates the information size table of each frequency and each mesh code, and
It is stored and updated in M6. On the other hand, in parallel with this, the error rate comparison switching unit 12 and the switching determination unit 13 cause the DA
When the error rate output from the RC decoder 4 exceeds a predetermined threshold value ε for a predetermined time (for example, 6 minutes),
The detection frequency of the PLL frequency demodulator 3 is switched to the frequency of the FM broadcasting station having the smallest error rate among the FM broadcasting stations adjacent to the FM broadcasting station currently selected. Further, in parallel with this, the information size comparison switching unit 1
1. The switching determination unit 13 compares the information size of each frequency of the mesh area to which the current vehicle position belongs stored in the SRAM 6, and switches the detection frequency of the PLL frequency demodulator 3 to the frequency having the largest information size. To be It should be noted that a zero clear process for clearing the size stored in the SRAM 6 to zero when the broadcasting station stops broadcasting, and S
A date changing process for sequentially updating old data among the data stored in the RAM 6 is also performed.

Details of data group construction and storage / update in DRAM, update of SRAM data, detection frequency switching request by error rate comparison, detection frequency switching request by information size comparison, detection frequency switching will be described in detail below. Explained.

First, the data group construction and the storage / update in the DRAM will be described. Construction of the data group and storage / update in the DRAM are performed by the data group construction unit in FIG.

FIG. 6 is a flowchart showing the operation of the data group construction unit.

First, when a packet as shown in FIGS. 2 and 3 is input from the DARC decoder 4 (S1), the data group construction unit 7 constructs a data frame according to the number of each received packet. Next, it is judged whether or not the construction of the data frame is completed (S2), and if the construction of the data frame is not completed, step S
It returns to 1 and waits for the input of a packet again.

When the construction of the data frame is completed in step S2, the data group construction unit 7 takes out the data packets included in the data frame and connects them to construct frame data (S3). Further, the data group having the same data group number in the frame data is set as one data group to construct a data group (S4). If the data group end code is included in the constructed data group and the data group end code indicates continuation of the data group (S5), the process returns to step S1 again to continue the construction of the data group. .

In step S5, if the data group end code indicates the end of the data group (S5), the data group construction unit 7 determines whether or not the same mesh code data group is stored in the DRAM 5. When it is checked (S6), and the data group of the same mesh code is not stored in the DRAM 5 (S6), the constructed data group is newly added to the DRAM 5
(S7). In step S6, the DRAM
If the data group of the same mesh code is stored in 5, the data group of the same mesh code stored in the DRAM 5 is updated to the constructed data group (S8).

When the above operation is completed, the data group construction unit 7 returns to the operation of step S1 again, and the DRAM 5
Data group storage / update processing is continued.

As described above, the data group construction unit 7
Builds a data group from the data frame output from the DARC decoder 4 and stores / updates the data group in the DRAM 5 to continue to store the latest data group in the DRAM 5.

Next, the SRAM data update process will be described. The data update process of the SRAM is performed in the information size update unit 8 of FIG.

FIG. 7 is a flow chart showing the processing operation of the information size updating unit.

First, the information size updating unit 8 resets the value of the reception time integrated value variable S _err stored therein to 0,
The clock value t ₁ of the internal timer is reset to 0 and clocking is started (S10).

Next, the information size updating unit 8 sends an error rate output request to the DARC decoder 4, and acquires the error rate P _err from the DARC decoder 4 (S1).
1). Next, if the error rate P _err is smaller than the constant threshold ε ₁ (S12), 1 is added to S _err (S1).
3). That is, the number of timings when the reception status is good (that is, the reception time when the reception status is good) is obtained as the reception time integrated value Serr.

Next, the measured value t of the timer₁Is a predetermined time
Interval T₁It is determined whether or not the value is equal to or less than, and the time value t ₁Is the predetermined time
T₁In the following cases, the process returns to step S11.

In step S14, when the measured value t ₁ is equal to or longer than the predetermined measured time T ₁ (for example, 2 minutes and 30 seconds),
Information size updating unit 8, receives the time integrated value S _err it is determined whether more than a predetermined threshold value S _{m ax} (S15), if the reception time integrated value S _err is equal to or less than the predetermined threshold value S _max, step S1
Return to 1.

As a result, when the reception sensitivity is poor (when the user picks up the antenna or enters the underground parking lot, etc.), it is determined that the information is sufficiently collected simply by the passage of time. Therefore, the information size table of the SRAM 6 is not updated. Also, if the information can be received even from time to time, it will be possible to have enough information to update the information size sometime. Thus, in step S15, by waiting for the reception time integrated value S _{er r} is greater than a predetermined value, the data group sufficiently DRAM
It will wait until it is stored in 5. Incidentally, step S
If the information size table of the SRAM 6 is updated when step 15 is not performed and the data group is not sufficiently stored in the DRAM 5, the updated information size of each mesh area becomes smaller than the broadcast information size. However, the information size comparison switching unit 11 may automatically track the frequency of another broadcasting station, which is not preferable.

In step S15, when the reception time integrated value S _err is greater than or equal to the predetermined threshold value S _max , the information size updating unit 8 outputs a request for updating the information size table of the SRAM 6 to the update history processing unit 9 and will be described later. The size of the data group stored in the SRAM 6 is updated to the latest size by the SRAM update history processing (S16), and the time value t ₁ of the internal timer is reset to 0 again (S17), and the step S
Return to 11.

Here, the predetermined time count T ₁ is 2.5 to
It is preferable to set it to 10 minutes. If it is shorter than 2.5 minutes, the error rate of the DARC decoder 4 cannot be detected with sufficient accuracy, so that the SRA can be performed with a small information size.
10 tends to update the information size table of M6
If it is longer than the minute, the detection time of the error rate of the DARC decoder 4 is too long, the information size table of the SRAM 6 is not easily updated, and the information size comparison switching unit 11 to be described later
This is because there is a tendency that the optimal FM broadcasting station is not selected by the above.

Further, it is preferable that the threshold value S _max of the reception time integrated value S _err is set to 2.5 to 10 minutes. If less than 2.5 minutes, DARC decoder 4
Since the reception time is too short, sufficient information is not stored in the DRAM 5, and it tends to be difficult for the information size comparison switching unit 11 described later to select the optimum FM broadcasting station. If the value is large, the reception time of the DARC decoder 4 is too long, and therefore the information size table of the SRAM 6 tends to be delayed to be updated while waiting for the same information many times.

Next, SR in step S16 of FIG.
The AM history update process will be described. The SRAM history update processing is performed by the update history processing unit 9 in FIG.

FIG. 8 is a flowchart showing the processing operation of the update history processing section, and FIG. 9 is a view showing the structure of the update information size table.

First, the update history processing unit 9 decodes the multiplexed signal transmitted from the broadcasting station x at the frequency f _x in the information size updating unit 8 to obtain each mesh code M _j (j
Is a subscript corresponding to all mesh areas in the service area of broadcasting station x. ) Information size S of the data group
_{When 0} (f _x , M _j ) is input, each mesh code M _j and information size S ₀ (f _x , M _j ) as shown in FIG. 9 are stored in the memory provided inside. An update information size table, which is a corresponding table, is created (S20). Next, the information size S ₀ (f _x , M _j ) of the mesh code M _j of the update information size table, the frequency f _x stored in the SRAM 6, and the information size S ₁ (f of the last day of the mesh code M _{j x} , M _j ) and S ₁ (f _x , M _j ) <S
_{In the case of 0} (f _x , M _j ), the information size S ₁ (f _x , M _j ) of the last day stored in the SRAM 6 is rewritten to S ₀ (f _x , M _j ) (S21). As a result, the update history processing unit 9
The update information size table stored in the above is reflected in the information size table stored in the SRAM 6.

Next, the zero clear processing unit 16 causes the DARC
It is detected whether or not the data block is output from the decoder 4 (S22), and if the data block is output, the SRAM history update process is ended. Step S2
In 2, if the data block is not output,
For the frequency f _{x of the} currently selected broadcasting station x and the mesh code M _{y of the} mesh area to which the current vehicle position belongs, the “previous information size” S ₂ (of the information size table stored in the SRAM 6 f _x, "information the size of the last day" M _y) the S ₁ (f _x, and updates to the M _y), "the last of the information size of the day" S ₁ (f _x, the M _y) is updated with 0 ,"date"
Is set as the current date (S23), and the SRAM history update process ends. By the processing of steps S22 and S23, automatic tracking for the frequency is cut off for the data having the same frequency information size with which the broadcasting stations cannot be distinguished and the broadcasting of the broadcasting station has disappeared.

Here, the update information size table creation processing in step S20 is performed by registering the mesh code and information size in the order read from the DRAM 5, or by performing a quick sort or bubble sort on the mesh code read from the DRAM 5. A method of registering the mesh code and information size while arranging them in order is used, but it is preferable to generate a hash table by the hash method using the mesh code as a key in view of memory efficiency and access speed.

As an example, a process of creating the update information size table by the hash method will be shown below.

Here, it is assumed that the number n of columns in the update information size table is 1024 and the hash address is 10 bits. Also, as the hash function key, the upper 8 bits of the map coordinate X at the beginning of the data group (X = x ₇ x ₆ x ₅ x ₄ x
₃ x ₂ x ₁ x ₀ ) and the upper 8 bits of the map coordinate Y (Y = y ₇
y ₆ y ₅ y ₄ y ₃ y ₂ y ₁ y ₀ ) is used (hereinafter, this (X, Y) is referred to as a key code of the data group and is represented by K). Further, the hash function is performed by the equation (1).

[0098]

[Equation 1]

In (Equation 1), "|" represents bit OR logic.

FIG. 10 is a flowchart showing the operation of creating the update information size table of the update history processing section.

First, the update information size table is initialized (S30). Here, the initialization of the update information size table is to invalidate all the mesh codes registered in the update information size table and set the information size of all the mesh codes to 0.

Next, the internal variable i representing the number of data groups read from the DRAM 5 is set to 0 (S21), and it is determined whether or not i has reached the number of all data groups stored in the DRAM 5 ( S22), i is DRAM
When the number of all the data groups stored in 5 is not reached, the i-th data group is read from the DRAM 5, and the hash function h _{0 is used} with the key code K (i) of the i-th read data group as a key. The hash address j = h ₀ (K (i)) is calculated (S33).
Next, it is determined whether or not the column of the j-th update information size table is empty (S34). If the column of the j-th update information size table is empty, the j-th update information size is determined. Mesh code Ms (j) in the size table column
Be the mesh code M (i) of the i-th read data group, and the information size S ₀ (i) of the i-th read data group in the information size S ₁ '(j) of the column of the j-th update information size table. i) is added (S35), i
Is incremented by 1 (S41), and the process returns to step S32.

In step S34, if the column of the j-th update information size table is not empty, the mesh code Ms of the column of the j-th update information size table
(J) is compared with the mesh code M (i) of the i-th read data group to determine whether they match (S36),
When Ms (j) = M (i), the mesh code Ms (j) in the column of the j-th update information size table is the mesh code M of the data group read i-th.
(I), add the information size S ₀ (i) of the i-th read data group to the information size S ₁ '(j) in the column of the j-th update information size table (S35), and increase i by 1. (S41), and returns to step S32.

In step S36, Ms (j) ≠ M
In the case of (i), it is determined whether or not j is the last number n in the update information size table (S37), and when j = n, j = 0 is set (S38), and when j ≠ n. Is incremented by 1 (S39).

Then, it is judged whether or not j and h ₀ (K (i)) are equal (S40), and if j and h ₀ (K (i)) are not equal, the process returns to step S34. j and h ₀ (K
If (i) is equal, i is incremented by 1 (S41),
It returns to step S32.

Further, in step S22, i is DR
If the number of all the data groups stored in the AM5 has been reached, it is determined that the processing has been completed for all the data groups stored in the DRAM 5, and the update information size table creation processing is terminated.

With the above operation, the update information size table, which is a table of the mesh code and the sum of the information sizes corresponding to the mesh code, is updated.
It is generated on the memory provided inside.

Next, the process of reflecting the update information size table of the update history processing unit in the above-mentioned step S21 in the SRAM will be described in more detail.

FIG. 11 is a flow chart showing the processing operation for reflecting the update information size table of the update history processing section in the SRAM.

In the process of reflecting the update information size table of the update history processing unit in the SRAM, the step of updating the data of each mesh code for the frequency already registered in the information size table (S50) and the registration in the information size table. The step (S51) of adding data of each mesh code to the frequency that has not been performed is performed.

At step S50, the currently selected channel is selected.
Frequency f_xRegistered in the update data group table
Each mesh code M_yData, update history processing
Part 9 is an information size table stored in SRAM 6.
If it is registered, check whether it is registered in
Is the information size S registered in the information size table.
₁(F_x, M_y) And the information size table for update registered
Information size S₁’(F_x, M_y) And S
₁(F_x, M_y) <S₁’(F_x, M_y), S
₁(F_x, M_y) To S₁’(F_x, M_y) To the process
U The concrete method is the information size table and update information.
Depending on the format of the size table, as an example,
The report size table uses the above key code K as a key.
The case where the hash table is used will be described below.

FIG. 12 is a flow chart showing the processing operation for updating the mesh data already in the information size table of the update history processing section.

First, the internal variable i representing the number of data groups read from the SRAM 6 is set to 0 (S60), and it is determined whether i has reached the number of all columns of the information size table stored in the SRAM 6. (S61), if i does not reach the number of all the columns of the information size table stored in the SRAM 6, the mesh code M ₁ (i) and the frequency f ₁ (i) of the i-th column are read from the SRAM 6. Read, i-th read mesh code M ₁ (i)
The hash address j = h ₀ (K (i)) is calculated by the hash function h ₀ using the key code K (i) of the key as a key (S
62). Next, it is determined whether or not the column of the j-th update information size table is empty (the mesh code in the column of the j-th update information size table is invalid) (S63).
If the column of the j-th update information size table is empty, i is incremented by 1 (S71), and the process returns to step S61.

In step S63, if data is recorded in the j-th updating information size table column, the mesh code M ₁ '(j) in the j-th updating information size table column is read, Mesh code M ₁
It is determined whether (i) is equal to the mesh code M ₁ '(j) and the frequency f ₁ (i) is equal to the currently selected frequency f _x (S64).

If the conditions of and are satisfied in step S64, the "information size of the last day" S in the i-th column of the information size table stored in the SRAM 6 is satisfied.
_It is determined whether ₁ (i) is smaller than the information size S ₁ '(j) in the column of the j-th update information size table (S
65), if S ₁ (i) <S ₁ '(j), update the “last day information size” S ₁ (i) in the i-th column of the information size table stored in SRAM 6 to the j-th Update the information size S ₁ '(j) in the column of the information size table, update the "date" in the i-th column of the information size table to the current date, and disable the mesh code M ₁ ' (j). As a value, the information size S ₁ '(j) is set to 0 (S66).

In step S64, when the conditions of and are not satisfied, it is determined whether or not j is the last number n of the update information size table (S67), and when j = n, j = 0 is set. (S68), j is 1 if j ≠ n
Increase (S69).

Then, it is judged whether or not j and h ₀ (K (i)) are equal (S70), and if j and h ₀ (K (i)) are not equal, the process returns to step S63. j and h ₀ (K
If (i) is equal, i is incremented by 1 (S71),
It returns to step S61.

Further, in step S61, i is SR
If the number of all the columns of the information size table stored in the AM6 has been reached, it is determined that the processing has been completed for all the columns of the information size table stored in the SRAM 6, and the information is already in the information size table. The process of updating the mesh data ends.

By the above operation, the update information size table of the update history processing section 9 is reflected in the data already registered in the information size table of the SRAM 6.

Step S51 is a process of adding, to the information size table, data of frequencies and mesh codes which are not registered in the information size table of the SRAM 6 in the update information size table. There is no problem if the memory size of SRAM 6 is large enough, but SRAM
When the memory size of 6 is limited, it is necessary to simultaneously perform a process of erasing unnecessary data when adding frequency and mesh code data to the information size table. In this case, the data of the mesh area far from the mesh area to which the current vehicle position belongs may be deleted. Hereinafter, an example of a process of adding mesh data that is not in SRAM will be described below.

FIG. 13 is a flow chart showing the processing operation for adding mesh data which is not in the SRAM of the update history processing section.

First, the update history processing section 9 sets the internal variable j representing the number of inspected columns in the update information size table to 0 (S80), and j is the update stored in the update history processing section 9. It is determined whether or not the number of all columns of the usage information size table is reached (S81), and j is the update history processing unit 9
If the number of all columns of the update information size table stored in is not reached, the mesh code M ₁ '(j) and frequency f ₁ ' (j) of the j-th column from the update information size table are set. Read (S82). Next, the j-th update information size table column is empty (mesh code in the j-th update information size table column is invalid)
It is determined whether or not (S83), and if the column of the j-th update information size table is empty, j is increased by 1 (S83).
87), and returns to step S81.

In step S83, if data is recorded in the j-th updating information size table column, the mesh code M ₁ '(j) in the j-th updating information size table column is read, Next, the update history processing unit 9 checks whether or not there is a free area in the memory area of the SRAM 6 (S84). If there is no free area in the memory area of the SRAM 6, the update history processing section 9 stores it in the information size table of the SRAM 6. Of the data, a process of deleting the data of the mesh area far from the mesh area to which the current vehicle position belongs is performed (S85). This process will be described later. Next, data is added to the empty area of the memory of the update history processing unit 9 in the column of the j-th update information size table (S8).
6), j is incremented by 1 (S87), and the process returns to step S81.

If j reaches the number of all columns of the update information size table in step S81, the process for all columns of the update information size table stored in the update history processing section 9 is performed. Is determined to have ended, and the process of adding mesh data not in SRAM ends.

Next, the SRA in the above step S85
A process of deleting mesh area information far from M will be described.

As a concrete method, when the empty area of the memory area of the SRAM 6 runs out, the data of the mesh area farthest from the mesh area to which the current vehicle position belongs is erased from the information size table stored in the SRAM 6. There is a method of deleting a certain proportion of data in the order of the mesh area farthest from the mesh area to which the current vehicle position belongs in the information size table stored in the SRAM 6, but the latter method is more preferable. Is preferable because it can shorten the overall processing time. In the following, as an example, when the empty area of the memory area of the SRAM 6 runs out, 10% of the data is stored in the information size table stored in the SRAM 6 in the order of the mesh area farthest from the mesh area to which the current vehicle position belongs. A method of erasing will be described.

FIG. 14 is a flow chart showing the processing operation for deleting the distant mesh area information in the SRAM of the update history processing section.

Here, the update history processing section 9 stores a variable D representing the distance to the mesh area closest to the mesh area to which the current vehicle position belongs in the internal memory area.
n, a variable Df representing the distance from the mesh area to which the current vehicle position belongs to the furthest mesh area, a variable D representing the distance from the mesh area to which the current vehicle position belongs to each mesh area, the current vehicle position Section counter table C (0) consisting of an array in which the distance from the mesh area closest to the mesh area to which the current vehicle belongs to the distance from the mesh area to which the current vehicle position belongs to the farthest mesh area is divided into 300 stages. C (29
9), a variable j representing the number of data read from the SRAM 6 is stored.

First, the update history processing section 9 acquires the current own vehicle position from the own vehicle position detecting section 19 and inspects the mesh code of the information size table stored in the SRAM 6,
The distance Dn to the mesh area closest to the mesh area to which the current vehicle position belongs and the distance Df to the farthest mesh area from the mesh area to which the current vehicle position belongs are acquired (S91). Actually, the mesh code is represented by the code of the reference area mesh of JIS X0410, and therefore the distance to each mesh area can be acquired by the mesh code.

Next, the update history processing section 9 initializes a variable D representing the distance from the mesh area to which the current vehicle position belongs to each mesh area to 0 (S92), and the section counter tables C (1) to C (1)- C (300) is initialized to 0 (S93). Next, the variable j representing the number of data read from the SRAM 6 is initialized to 0 (S94). Next, it is determined whether or not j has reached the total number N of columns of the information size table stored in the SRAM (S95), and j is S
If the total number N of columns of the information size table stored in RAM has not been reached, the mesh code M ₁ (j) of the jth column of the information size table is acquired and the mesh code M
_{When 1} (j) is an invalid value (S96), j is incremented by 1 (S100), and the process returns to step S95. If the mesh code M ₁ (j) is a valid value at step S96, the distance between the mesh code M _y and the mesh code M ₁ (j) of the mesh area to which the current vehicle position belongs is between both mesh areas. Is stored in the variable D. Next, it is checked whether or not the variable D is between the distance Dn and the distance Df (S98), and when the variable D is between the distance Dn and the distance Df, j = [(D-Dn) × ( 300-1) / (Df-
Dn)] is calculated and the counter C of the section counter table is calculated.
(J) is incremented by 1 (S100), and the process returns to step S95. When the variable D is not between the distance Dn and the distance Df in step S98, the counter C (j) of the section counter table is incremented by 1 (S100), and step S95.
Return to.

When j reaches the total number N of columns of the information size table stored in the SRAM in step S95, the counter C (j) is added from C (299) in descending order of the index, and the total sum Nk. = C (29
9) + C (298) + ... + C (k) is (N + 1) ×
The index when it exceeds 0.1 (10% of the total number of data) is k (S101), and Nk is (N + 1) × 0.
It is determined whether or not it exceeds 2 (20% of the total number of data) (S102). If Nk does not exceed (N + 1) × 0.2, the mesh area to which the current vehicle position belongs is determined. The data of the information size table of the mesh area located at a distance longer than the distance D (k) corresponding to the index k is erased from the memory area of the SRAM 6 (S103),
The process of deleting the distant mesh area information of the SRAM is ended.

In step S102, Nk is (N +
1) When it exceeds 0.2, the data of the information size table of the mesh area located at a distance farther than the distance D (k + 1) corresponding to the index k + 1 from the mesh area to which the current vehicle position belongs is stored in the SRAM 6. It is erased from the memory area (S104), Dn is set to D (k), Df is set to D (k + 1), and the process returns to step S93.

By the above operation, the frequency and mesh code data which are not registered in the information size table of the SRAM 6 in the update information size table are additionally registered in the information size table, and the update history processing section 9
If there is no free area in the memory, the data in the mesh area far from the mesh area to which the current vehicle position belongs is erased.

Next, the detection frequency switching request processing by error rate comparison will be described. The detection request switching request processing based on the error rate comparison is performed in the error rate comparison switching unit 12 in FIG. In this processing operation, the error rate comparison switching unit 12 causes the DAR
When the time when the error rate P _err output by the C decoder 4 is equal to or greater than the predetermined threshold value ε continues for the predetermined time T ₂ or longer, the vehicle is outside the service area of the broadcasting station of the frequency f _x currently selected. PLL frequency demodulator 3
Outputting a request for switching the detection frequency in the frequency f _x 'of the broadcasting stations neighboring to the broadcasting station of the frequency f _x to set.

FIG. 15 is a flow chart showing a detection frequency switching request processing operation by error rate comparison of the error rate comparison switching unit.

First, the error rate comparison switching unit 12 resets the clock value t ₂ of the timer provided therein to 0 (S110) and starts clocking (S111).

Next, the error rate comparison switching unit 12 outputs D
The error rate P _err is acquired from the ARC decoder 4 (S
112), it is determined whether the error rate P _err is smaller than a certain threshold value (S113), and if P _err <ε,
It returns to step S110. In step S113,
If P _err ≧ ε, it is determined whether or not the timer value t ₂ has reached a predetermined time T ₂ (for example, 6 minutes) (S11).
4), if t ₂ <T ₂ , the process returns to step S112 and t
_{If 2} ≧ T _2, the frequency f _x currently selected by the vehicle is f _x
It is judged that the broadcasting station is outside the service area of the broadcasting station, and the detection frequency switching request S1 to the frequency f _x 'of the adjacent broadcasting station is made.
Is output to the switching determination unit 13 (S115).

Here, the frequencies of the adjacent broadcasting stations are transmitted as supplementary data, which is supplementary data shorter than that of the broadcasting stations as additional data such as management data of the broadcasting stations and data for D-GPS. This additional information includes an alternative frequency table that is a list of frequency information that the receiver may switch to when the receiving broadcast station cannot receive it. Information about the frequency of the station can be obtained. The error rate comparison switching unit 12 receives each of these frequencies for 10 seconds and selects the frequency with the smallest error rate.

Next, the detection frequency switching request processing by comparing the information sizes will be described. The processing for requesting the switching of the detection frequency by the information size comparison is performed by the information size comparison switching unit 11 in FIG. In this processing operation, the information size comparison switching unit 11 compares the information sizes stored in the SRAMs with respect to all the broadcasting stations whose service area is the mesh area to which the current vehicle position belongs and compares the information size with the most information size. Outputs a request to switch to the frequency of a large broadcasting station.

FIG. 16 is a flow chart showing the detection frequency switching request processing operation by the information size comparison switching unit by information size comparison.

First, the information size comparison switching unit 11
Value t of the timer provided in₃Is reset to 0 (S
120), start timing (S121), and count the timer
Value t ₃Is the predetermined time T₃Wait until it reaches (eg 5 minutes)
Yes (S122). This is a certain amount of data in the DRAM5.
Data groups are accumulated, and the information size update unit 8 and
The information size table stored in the SRAM 6 by the history processing unit 9
Frequency f that the cable is currently selected_xUpdated regarding
This is to wait for it.

When the measured value t _{3 of the} timer reaches a predetermined time T ₃ , the information size comparison switching unit 11 causes the information size of all frequencies corresponding to the mesh code M _y of the mesh area to which the current vehicle position belongs. The information size reading processing unit 1
It is acquired from the information size table stored in the SRAM 6 by 0 (S123). At this time, the information size reading processing unit 10 is assigned from the information size table of the SRAM 6 for each frequency f _j of the mesh code M _y (j is corresponding to each broadcasting station including the mesh code M _y in the service area). "Last day information size" for subscript S ₁ (f _j , M
_y) and "previous information size" _{S 2 (f j, M y} ) and reads and outputs whichever is greater of the information size S ₃ (f _j, the information size comparison switching section 11 as M _y). This means that if the FM radio wave cannot be temporarily received because the vehicle is located behind a tunnel or a building when the update history processing unit 9 is updated, the “information size of the last day” S ₁ ( f _j ,
Although M _y ) is updated to 0, this is a process performed to prevent 0 from being output as the information size S ₃ (f _j , M _y ) due to such a temporary reception failure.

Next, the obtained information sizes are compared, and the frequency f corresponding to the largest information size among them is compared.
to get _x '(S124). Next, the obtained frequency f _x 'is compared with the frequency f _{x of the} currently selected broadcasting station (S125). If the frequency f _x and the frequency f _x ' are different, the PLL frequency demodulator 3 Set frequency to frequency f
_The switching signal S2 for switching to x'is output to the switching determination unit 13 (S126).

When the above operation is completed, step S
Returning to operation 123.

Next, the detection frequency switching processing will be described. The process of switching the detection frequency is performed by the switching determination unit 13 in FIG.

FIG. 17 is a flow chart showing the detection frequency switching processing.

First, upon receiving the detection frequency switching request S1 or S2 to the frequency f _x 'of the adjacent broadcasting station, the switching judgment unit 13 changes the frequency f _x from the frequency f _x currently set in the PLL frequency demodulator 3 to the frequency f _x. setting the _x '(S130).
Next, it is checked whether or not there is an output from the wave detection and selection unit 2 (S131).

Here, whether or not there is an output from the detection and channel selection unit 2 depends on the hardware specifications of the PLL frequency demodulator 3, but for example, lock detection of the PLL frequency demodulator 3 and PLL frequency SD signal detection from demodulator 3,
This is performed by determining the IF frequency of the PLL frequency demodulator 3.

When the output from the wave detection and selection unit 2 is detected in step S131, the switching judgment unit 13 determines that the DARC
It is checked whether or not there is a packet output from the decoder 4 (S132).

Here, the check whether or not the DARC decoder 4 outputs a packet depends on the hardware specifications of the DARC decoder 4, but, for example, that the output data packet is synchronized, This is performed by confirming that the output data packet is normal data (not parity data).

When a data packet is output from the DARC decoder 4 in step S132, the switching determination unit 13 causes the data group construction unit 7, the information size updating unit 8, the information size comparison switching unit 11, and the error rate comparison switching unit 12 to operate. A reset signal is output (S133). When the reset signal is input, the data group construction unit 7, the information size update unit 8, the information size comparison switching unit 11, and the error rate comparison switching unit 12 stop the operation up to that point and reset, and then from the beginning of each unit. Restart processing.

When the output from the wave detection and selection unit 2 is not detected in step S131, or in step S13
If the data packet from the DARC decoder 4 in 2 is not output (i.e., if a new automatic tracking fails), the frequency f _x 'and mesh code M _y of the current mesh area belongs vehicle position newly tuned respect, SRAM 6 to "previous information size" of the information size table stored _{S 2 (f x ', M} y) "information size of the last day" of _{S 1 (f x', M} y) in updated, "information the size of the last day" _{S 1 (f x ', M} y) was updated with 0, and the current date the "date" (S134). Then, return the set frequency of the PLL frequency demodulator 3 f _x (S135), and terminates the switching process of the detection frequency.

In addition to the above processing, when the date and time output by the clock 14 is changed, the information size table updating unit 15 sets the "previous information size" in all the columns of the information size table of the SRAM 6 to " Perform processing to update to "information size of last day". Thereby, the information about the old data information size is updated at least every day.

As described above, according to the present embodiment, (1) DARC decoder 4 and data group construction unit 7
The data group of VICS information generated from the multiplex signal is sequentially stored in the DRAM 5.

(2) The information size updating unit 8 outputs an information size table update request to the update history processing unit 9 when a data group is accumulated in the DRAM 5 for a certain time or longer, and the currently selected frequency is selected. The information size of each mesh code transmitted from the broadcasting station is updated. At this time,
If the information size to be updated is smaller than the information size already registered in the information size table, the information size is not updated. When the information size to be updated is 0, the information size of the mesh code to which the current frequency and the current vehicle position belong in the information size table is updated to 0.

(3) On the other hand, the error rate comparison switching unit 12
Is the error rate P output from the DARC decoder 4.
_{When the time when err} is equal to or greater than a predetermined threshold value ε continues for a predetermined time T ₂ or more, the current detection frequency is the detection frequency of the broadcasting area of the currently selected broadcasting station and the detection frequency of another broadcasting station adjacent to the broadcasting area. A switching request S1 for switching to is output.

(4) In parallel with this, the information size comparison switching unit 11 waits for a predetermined time T ₃ for the update of the information size table of the SRAM 6 and waits for the current time registered in the information size table. The information size of each frequency of the mesh code to which the vehicle position belongs is compared, and a switching request S2 for switching the detection frequency to the frequency of the largest size (large amount of information) of the information size is output.

(5) When the switching request S1 or S2 is input, the switching determination unit 13 sets the current detection frequency f _x set in the PLL frequency demodulator 3 to the detection requested frequency f _x ′. Switch. After that, if there is an output from the detection channel selection unit 2 and a data packet output from the DARC decoder 4, the data group construction unit 7, the information size updating unit 8, the information size comparison switching unit 11, the error rate comparison switching. A reset signal is output to the unit 12 to reset and restart the operation of each unit. Further, when there is no output from the wave detection and selection unit 2 or when there is no data packet output from the DARC decoder 4, the frequency f _x 'in the information size table and the information size of the mesh code to which the current vehicle position belongs are Updated with 0, PL
The set frequency of the L frequency demodulator 3 is returned to f _x . By a series of operations, among the broadcasting stations broadcasting the receivable VICS information at the current vehicle position, the broadcasting station having the largest amount of information around the current vehicle position is automatically tracked, and V
It becomes possible to obtain ICS information.

[0159]

As described above, according to the receiver of the car navigation system of the present invention, the following advantageous effects can be obtained.

[0160]

[0161]

[0162]

According to the invention described in claim 1 , when the information broadcasting station selected after the switching stops broadcasting, it is prevented that the broadcasting station is tuned in, and the information broadcasting station is provided by the information broadcasting station. It is possible to provide a receiving device of a car navigation device that enables effective use of road traffic information.

According to the second and fifth aspects of the present invention, the information size of the information received in a poor reception state due to the presence of a shield such as a building can be registered or updated in the information size storage means. By preventing or registering or updating a small information size, it is possible to prevent the information size comparison and switching means from mistakenly switching the frequency, and to effectively utilize the road traffic information provided by the information broadcasting station. It is possible to provide a receiving device of a car navigation device that enables the above.

According to the third and sixth aspects of the invention, the information broadcasting station temporarily stops broadcasting and 0 is registered in the information size of the last day corresponding to the frequency and mesh code in the information size table. In case of accident, or by accidentally driving in an area where reception is poor, even if a small value is registered in the information size of the last day corresponding to the frequency and mesh code, the information size comparison switching means will use the previous information. The size and the information size of the last day are compared, and the larger one is read as the information size, and the detection frequency of the receiving means is switched by comparing them and the accuracy of the selection of the information broadcasting station is improved. It is possible to provide a receiving device of a car navigation device that enables effective use of road traffic information provided by a broadcasting station.

According to the invention described in claim 4 , when the information broadcasting station stops broadcasting, the data size of the broadcasting station remains in the information size table forever by setting the information of the information size table to zero. Since the information size comparison switching means can prevent the information broadcasting station from erroneously continuing to select the broadcasting station even if the information broadcasting station has stopped broadcasting, it is provided by the information broadcasting station. It is possible to provide a receiving device of a car navigation device that enables effective use of road traffic information.

[0167]

[0168]

[0169]

[0170]

[Brief description of drawings]

FIG. 1 is a block diagram showing a device configuration of a receiving device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a data format of a data frame.

FIG. 3 is a diagram showing a data format of the data packet of FIG.

FIG. 4 is a diagram showing a data format of a data group.

FIG. 5 is a diagram showing a data structure stored in SRAM.

FIG. 6 is a flowchart showing the operation of the data group construction unit.

FIG. 7 is a flowchart showing a processing operation of an information size updating unit.

FIG. 8 is a flowchart showing a processing operation of an update history processing unit.

FIG. 9 is a diagram showing a configuration of an update information size table.

FIG. 10 is a flowchart showing an operation of creating an update information size table of an update history processing unit.

FIG. 11 is a flowchart showing a processing operation of reflecting the update information size table of the update history processing unit in the SRAM.

FIG. 12 is a flowchart showing a processing operation for updating mesh data already in the information size table of the update history processing unit.

FIG. 13 is a flowchart showing a processing operation of adding mesh data that is not in the SRAM of the update history processing unit.

FIG. 14 is a flowchart showing a processing operation of deleting distant mesh area information of SRAM of the update history processing unit.

FIG. 15 is a flowchart showing a detection frequency switching request processing operation by error rate comparison of an error rate comparison switching unit.

FIG. 16 is a flowchart showing a detection frequency switching request processing operation by information size comparison of an information size comparison switching unit.

FIG. 17 is a flowchart showing a detection frequency switching process.

[Explanation of symbols]

1 receiving antenna 2 Detection station 3 PLL frequency demodulator 4 DARC decoder 5 DRAM 6 SRAM 7 Data Group Construction Department 8 Information size update section 9 Update history processing section 10 Information size read processing unit 11 Information size comparison switching unit 12 Error rate comparison switching unit 13 Switching judgment section 14 clock 15 Information size table update section 16 Zero clear processing unit 17 GPS antenna 18 GPS receiver 19 Own vehicle position detector 20 Map information storage

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G08G 1/09-1/0969 G01C 21/00 H04B 7/26

Claims (6)

(57) [Claims] 1. A receiving device of a car navigation device for receiving information from each information broadcasting station of a road traffic information system, and a receiving means for receiving the information of each mesh area provided by radio waves from the information broadcasting station. A vehicle position detecting means for detecting the vehicle position; an information storage means for storing the information of each mesh area; and information for storing an information size which is a size of the information for each mesh area and each reception frequency. Size storage means, information storage means for storing and storing in the information storage means the information of each mesh area provided by the information broadcasting station and received by the receiving means, and each mesh stored in the information storage means Information size registration means for acquiring the information size of the information for each area and registering or updating it in the information size storage means; The detection frequency of the receiving means is compared with the information size of each reception frequency read from the information size storage means of the mesh area to which the vehicle position is detected by the position detection means, and the reception frequency with the largest information size is received. Information size comparison switching means for switching to
The error rate when the receiving means receives the information is predetermined.
When the state of being equal to or more than the threshold of continues for a predetermined time or more
The detection frequency of the receiving means is selected at that time
Error that switches to the frequency of the information broadcasting station other than the information broadcasting station
-Rate comparison switching means and the error rate comparison switching means
Or the information size comparison / switching means detects the receiving means.
The receiving means receives the information after switching the wave frequency.
If not received, the frequency based on the detection frequency of the receiving means is used.
A receiving device for a car navigation device, characterized in that it is provided with a switching judging means for returning to the wave number . 2. The information size registration means has an error rate at the time of receiving the information of the receiving means, which is equal to or less than a predetermined threshold, after the information storage means starts the storage of the information in the information storage means. When the reception time of the information in the state reaches a predetermined time, the information size of the information for each mesh area accumulated in the information storage means is acquired and registered or updated in the information size storage means. The receiving device of the car navigation system according to claim 1 . 3. An information size table in which a plurality of units of data, which are stored in the information size storage means and have a reception frequency, a mesh code of a mesh area, a previous information size and an information size of the last day as one unit, are registered. And an information size table updating unit that updates the previous information size of each of the information size tables to the information size of the last day when a predetermined time elapses. If the information size of the last day corresponding to the information size is registered in the information size table before registering or updating the size in the information size table, the information size is smaller than the information size of the last day. Is larger, the information size of the last day is updated to the information size, and the information size is set to the information size table. If the information size of the last day corresponding to the information size is not registered in the information size table before registration, the information size is newly registered in the information size table as the information size of the last day. The information size comparison switching means compares the previous information size with the information size of the last day when reading the information size from the information size storage means, and reads the larger one as the information size. The receiving device for a car navigation device according to claim 1 , wherein the receiving device is a car navigation device. 4. When the error rate comparison switching means or the information size comparison switching means switches the detection frequency of the receiving means and the receiving means does not receive the information, the information size table is received after the switching. Updating the information size of the previous time to the information size of the last day and updating the information size of the last day to 0 in a unit corresponding to the frequency and the mesh area to which the vehicle position at that time belongs, and / or If the receiving unit does not receive the information when the update history processing unit registers the information size in the information size table, the reception frequency at that time of the information size table and the vehicle position at that time belong In the unit corresponding to the mesh area, the previous information size is updated to the information size of the last day, and Receiving device of the car navigation device according to claim 3, the information size day characterized by comprising a zero clear processing means for updating the zero. 5. A receiving device of a car navigation device for receiving information from each information broadcasting station of a road traffic information system, and receiving means for receiving the information of each mesh area provided by radio waves from the information broadcasting station. A vehicle position detecting means for detecting the vehicle position; an information storage means for storing the information of each mesh area; and information for storing an information size which is a size of the information for each mesh area and each reception frequency. Size storage means, information storage means for storing and storing in the information storage means the information of each mesh area provided by the information broadcasting station and received by the receiving means, and each mesh stored in the information storage means Information size registration means for acquiring the information size of the information for each area and registering or updating it in the information size storage means; The detection frequency of the receiving means is compared with the information size of each reception frequency read from the information size storage means of the mesh area to which the vehicle position is detected by the position detection means, and the reception frequency with the largest information size is received. And an information size comparison switching means for switching the information size registering means to the information size registering means.
After starting the accumulation of the information in the information storage means,
The error rate at the time of receiving the information by the receiving means is a predetermined value.
When the reception time of the information in the state below the threshold value is a predetermined time
When the time is reached, each message stored in the information storage means is
Before obtaining the information size of the information for each sherrier
A receiving device for a car navigation device, characterized in that the receiving device is registered or updated in the information size storage means . 6. A receiving device of a car navigation device for receiving information from each information broadcasting station of a road traffic information system, and receiving means for receiving the information of each mesh area provided by radio waves from the information broadcasting station. A vehicle position detecting means for detecting the vehicle position; an information storage means for storing the information of each mesh area; and information for storing an information size which is a size of the information for each mesh area and each reception frequency. Size storage means, information storage means for storing and storing in the information storage means the information of each mesh area provided by the information broadcasting station and received by the receiving means, and each mesh stored in the information storage means Information size registration means for acquiring the information size of the information for each area and registering or updating it in the information size storage means; The detection frequency of the receiving means is compared with the information size of each reception frequency read from the information size storage means of the mesh area to which the vehicle position is detected by the position detection means, and the detection frequency of the reception means is the reception frequency with the largest information size. Information size comparison switching means for switching to
An information size table in which a plurality of units of data, which are stored in the information size storage means, the reception frequency, the mesh code of the mesh area, the previous information size, and the information size of the last day are registered as a unit, and a predetermined time And an information size table updating means for updating the previous information size of each of the information size tables to the information size of the last day, the information size registration means.
Registers the information size in the information size table or
Before updating that information in the information size table
The information size of the last day corresponding to the size is registered
If the above information size is the information size of the last day
If the information size of the last day is greater than
Information size and update the information size
Before registering in the table
The information size of the last day corresponding to the information size is registered.
If it is not recorded, it is newly added to the above information size table.
Register the information size as the information size of the last day
However, the information size comparison switching means is
When reading the information size from the storage means,
Compare the information size with the information size of the last day
The larger one is read as the information size
Receiving device of the car navigation device to.