JP3819563B2 - FM multiplex broadcast data reception method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an FM multiplex broadcast data receiving method, and more particularly to an FM multiplex broadcast data receiving method in which DGPS information and VICS information are received by a single receiver.
[0002]
[Prior art]
In a navigation system that guides a car toward a destination, it is important to accurately grasp the position of the car and correctly recognize road traffic information (such as traffic jams, accidents, and regulations).
Currently, (1) self-contained navigation using a distance sensor (for example, a vehicle speed sensor) and direction sensor (for example, a gyro) and (2) GPS (Global Positioning System) navigation that receives position information from satellites are used in combination. ing. The position accuracy of GPS is bad and may be over 100 m. For this reason, it is required to improve the positional accuracy of GPS, and a DGPS (Differential Global Positioning System) has been proposed and put into practical use. DGPS (1) GPS satellite radio waves are received at a location where the exact position is known, and (2) the error between the known location and the positioning location is determined. (3) The same positioning system in the same area. By transmitting the determined error or correction coefficient to the user, the position accuracy and reliability of the positioning system are improved and ensured. (4) FM multiple broadcast radio waves are used as means for transmitting the above information to the user. Has been.
[0003]
Road traffic information (congestion, accidents, regulations, etc.) is provided by the road traffic information communication system (VICS). The in-vehicle navigation system receives the road traffic information (VICS information) and displays it on the map in real time. It is supposed to be displayed. Level 1 to level 3 can be used as the display method of VICS information, and road traffic information can be displayed at a desired level according to the situation and purpose. Level 1 is a character information display mode in which section travel time information, failure information, service information, general FM character information, and the like are displayed in the upper area of the display screen. Level 2 is a simple graphic display mode in which a simple graphic of a congestion monitoring road is drawn and traffic jam / fault information is displayed on the simple graphic. Level 3 is a map information display mode in which information such as traffic jams, accidents and regulations is displayed on the map in real time. By using the VICS road traffic information, the driver can reach the destination in a short time while avoiding the traffic jam road, the traffic restriction road, and the accident occurrence road. Currently, optical beacons, radio beacons and FM multiplex broadcast radio waves are used as means for communicating such VICS information. The communication area of each communication means is 10 to 50 km per FM multiplex broadcast, 60 to 70 m per radio beacon, and 3.5 m per optical beacon. For this reason, FM multiplex broadcasting with a wide communication area flows high-frequency traffic information, and radio wave beacons and optical beacons flow traffic information in limited areas.
[0004]
FIG. 4 is a block diagram of FM multiplexed data multiplexed in FM broadcasting. 272 blocks (packets) per frame, 190 blocks out of 272 blocks are data blocks, and 82 blocks are parity blocks that transmit only parity. The parity block is distributed in the data block. One frame is 4.896 seconds and one block is 18 msec.
Each data block includes a 16-bit block identification code (BIC), 176-bit data, a 14-bit CRC code, and a 82-bit parity for error detection and correction (horizontal code). . The parity block is composed of a 16-bit block identification code BIC, a 190-bit parity (vertical code), and a 82-bit parity for error detection and correction (horizontal code). Among the first 13 blocks, the data block identification code is BIC1, among the next 123 blocks the data block identification code is BIC3, and among the next 13 blocks, the data block identification code is BIC2, and the last Of the 123 blocks, the identification code of the data block is BIC3, and the identification code of the parity block is BIC4.
[0005]
Block synchronization can be achieved by detecting the block identification code for each block, and frame synchronization can be achieved for every 272 blocks (by detecting BIC1 next to the block identification code BIC4). Further, since parity (vertical code, horizontal code) for error detection and correction is included, error detection and error correction processing (vertical correction, horizontal correction) can be performed using these parities. Further, since the CRC code is included in the data block, a CRC check can be performed for each block.
The VICS information is transmitted using all blocks of the frame, while the DGPS information is transmitted using two blocks at the head of the frame.
[0006]
FIG. 5A shows a block configuration of DGPS data, which shows a format of a 176-bit data block (a data block obtained by excluding a 14-bit CRC block from the 190-bit data block in FIG. 4), and a 16-bit prefix. It consists of 51 and 160-bit or 144-bit DGPS segments 52 and 53 and a 16-bit CRC 54. The prefix 51 is as shown in FIG.
(1) A service identification unit 51a for indicating the content of a program and a transmission mode and designating a data packet configuration;
(2) Decoding identification flag (“1” is decoded only in the horizontal direction, “0” horizontal / vertical / horizontal decoding) 51b for designating the decoding method of the error correction circuit;
(3) An information end flag ("1" is ended) 51c indicating the end of the data group transmitted with a certain data group number;
(4) An update flag 51d indicating that a data group transmitted with a certain data group number is updated;
(5) A data group number part 51e for designating a data group number;
(6) It is composed of a data packet number part 51f.
[0007]
The DGPS information prefix 51 is
(1) Service identification: 1011
(2) Decryption identification flag: 1
(3) Data group number: 1100
It is.
FIG. 6 shows the segment structure of DGPS information. The DGPS segment is composed of 304 bits of 160 + 144 bits, and the first 16 bits are the following contents
(1) Segment identification: 1101 (D)
(2) Segment length: 1111 (F)
(3) Extended segment length: 00100100
It has become.
As described above, the DGPS information can be identified by referring to the prefix 51 and the next 16 bits.
[0008]
[Problems to be solved by the invention]
At present, the DGPS information is transmitted by the JFN-series FM multiplex station, and the VICS information is transmitted by the NHK-series FM multiplex station. For this reason, as the FM multiplex broadcast receiver, a configuration using two receivers and a configuration using one receiver by switching are considered.
However, using two receivers to receive VICS information and DGPS information is problematic in terms of cost and space. For this reason, one receiver is switched and used. However, in the method of switching reception of VICS information and DGPS information for each frame, since one frame is about 5 seconds, VICS information for at least 5 seconds ( There is a problem that VICS information for one frame is lost.
In addition, the frame synchronization timing is consistent between NHK sequence FM multiple stations, but the frame synchronization timing is not consistent between JFN sequence FM multiple stations. For this reason, when switching to a well-received JFN series FM station according to the driving of the vehicle, the frame synchronization timing of the JFN series FM station does not change, so synchronization is necessary, and at least 5 seconds of VICS information is lost. There is a problem.
[0009]
Accordingly, an object of the present invention is to provide an FM multiplex broadcast receiving method capable of receiving DGPS information without losing VICS information.
Another object of the present invention is to provide an FM multiplex broadcast receiving method that does not lose VICS information even when the currently receiving JFN sequence FM multiplex station is switched to another JFN sequence FM multiplex station. is there.
[0010]
[Means for Solving the Problems]
According to the present invention, (1) the frame synchronization timing of FM multiplex broadcast data is detected in one or more FM multiplex broadcast stations with good reception status among FM multiplex broadcast stations that broadcast DGPS information every predetermined time. And store the frame synchronization timing of the FM multiplex broadcast data corresponding to the FM multiplex broadcast station, and (2) When the operation of storing the frame synchronization timing of the FM multiplex broadcast data is completed , FM multiplex broadcast data from an FM multiplex broadcast station that broadcasts VICS information is received, and DGPS information is broadcast while the FM multiplex broadcast is being received. When the reception state of the FM multiplex broadcast station is a predetermined time before the frame synchronization timing of the best FM multiplex broadcast station, the reception station is switched to an FM multiplex broadcast station that broadcasts DGPS information. (3) After the reception is completed, the operation is switched to the FM multiplex broadcasting station that broadcasts the VICS information. Thereafter, the above operation is repeated, and (4) This is accomplished by switching to another stored FM multiplex broadcast station.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
(A) Configuration of FM multiplex broadcast receiver of embodiment FIG. 1 is a block diagram of an FM multiplex broadcast receiver of an embodiment of the present invention. The FM multiplex broadcast receiver receives the FM broadcast signal, separates and demodulates the FM multiplex broadcast data such as VICS information, DGPS information, and character information that are multiplexed and sent to the FM broadcast signal, and passes them to the navigation system. Or displayed on a display device.
In the figure, reference numeral 1 denotes an antenna, and 4 denotes a front end (F / E), which includes an antenna tuning circuit, a high-frequency amplifier circuit, a local oscillator, a mixer, and the like (not shown). Reference numeral 5 is a PLL circuit, 6 is a low-pass filter, and 7 is an intermediate frequency amplifier / FM detector (IF / DET). The PLL circuit 5, the low-pass filter 6, and the local oscillator built in the front end 4 constitute an electronic channel selection device, and the local oscillator oscillates at a frequency corresponding to the reception frequency (the frequency of the FM broadcast station selected by the channel selection operation). The intermediate frequency signal is output by a mixer in the front end 4. 8 is a noise canceller / stereo demodulation circuit (NC / MPX) that performs noise cancellation and stereo demodulation, 9 is a filter circuit that extracts an L-MSK modulation signal component from the FM detection signal, and 10 is input with an intermediate frequency signal to obtain the received electric field strength. It is an S meter that outputs a corresponding signal. Thus, a tuner is formed.
[0012]
21 is a multiplex decoder provided in common for DGPS information and VICS information, 51 is an L-MSK demodulator circuit that performs delay detection on the L-MSK modulated signal, regenerates the bit clock, and demodulates the bit data string, 52 A synchronization circuit that detects block synchronization and frame synchronization, 53 is a correction processing unit, 54 is a VICS RAM for one frame that stores VICS information, and 55 is a DGPS RAM for one frame that stores DGPS information. The correction processing unit 53 includes a CRC check unit 53a and an error detection / correction unit 53b that performs horizontal correction / vertical correction on VICS information and horizontal correction on DGPS information. The CRC check unit 53a performs a CRC check for each block, and the error detection / correction unit 53b temporarily stores the VICS information in the RAM 54 and the DGPS information in the RAM 55 based on the block synchronization and frame synchronization detection signals input from the synchronization circuit. After that, using the parity code, the VICS information is subjected to horizontal correction → vertical correction → horizontal correction, and the DGPS information is subjected to horizontal correction.
[0013]
A processor (CPU) 23 performs reception control of VICS information / DGPS information, character information display control, channel selection control, and the like, and stores a synchronization list SLT in a built-in RAM. The synchronization list SLT shows the correspondence between one or more FM multiplex broadcast stations (frequency fi) in a good reception state among FM multiplex broadcast stations that broadcast DGPS information and the frame synchronization timing (Si).
24 is a synchronization counter that counts to 0 at the DGPS frame synchronization timing of one FM multiplex broadcasting station that broadcasts DGPS information, and thereafter counts the clock and repeatedly counts one frame period (= 4.896 seconds). It is. That is, the frame synchronization timing of FM multiplex broadcast data from an FM broadcast multiplex station that broadcasts DGPS information is detected in advance, the count value of the synchronization counter 24 is set to 0 at this timing, and thereafter, the clock is counted, and one frame period To keep time.
Reference numeral 25 denotes a memory for storing the received FM multiplexed data (VICS information, DGPS information, teletext program information, etc.), 26 is an operation unit for the user to select a channel or select a desired teletext program, 27 Is a display device that displays text information (news, weather forecast, etc.) on the screen.
[0014]
(B) Setting the synchronization timing Every predetermined time, for example, every 15 minutes, the CPU 23 performs seek control, and stores the frequency f ₁ of the JFN series FM multiplex station whose received electric field strength is equal to or higher than the set level. Thereafter, FM multiplex broadcast data from the FM multiplex station is received in order to detect the synchronization timing. Thus, the synchronization circuit 52 of the decoder 21 notifies the CPU23 detects the frame synchronization timing S ₁ of the FM multiplex data, CPU stores the corresponding FM frequency f ₁ and the frame synchronization timing S ₁ in a built-in RAM.
The reference of the time is the synchronization timing of the VICS information. The synchronization timing of the VICS information is set to time 0, and thereafter, the reference clock is counted to make one frame period (= 4.896 seconds) one cycle. Therefore, the frame synchronization timing S ₁ means a time S ₁ between the reference times 0 and 4.896 seconds.
[0015]
Thereafter, similarly, seek control is performed to create a synchronization list that is a correspondence relationship between the FM frequency fi (i = 1, 2, 3,...) Of the JFN series FM multiplex broadcasting station having a good reception electric field strength and the synchronization timing Si. And stored in the RAM. Since the NHK series FM multiplex station broadcasts VICS information for about 2.5 minutes, that is, 30 frames, the VICS information is not lost by setting the synchronization timing of the DGPS information.
As described above, when the creation of the synchronization list of the FM multiplex broadcasting station that broadcasts the DGPS information is completed, the CPU 23 sets the content of the synchronization counter 24 to 0 at the frame synchronization timing time Sj of the FM multiplex broadcasting station having the best received electric field strength. After that, a clock (not shown) is counted and one frame period (= 4.896 seconds) is repeatedly counted.
[0016]
(C) Receiving DGPS Information and VICS Information FIG. 2 is a flowchart for receiving DGPS information and VICS information. Since the synchronization list SLT is updated every predetermined time (for example, every 15 minutes), the CPU 23 checks whether the current time is the synchronization list creation timing (step 101). If it is the synchronization list creation timing, the synchronization list is created by the method described in (b) (step 102). However, if it is not the synchronization list creation timing, it is checked whether the reception level of the currently receiving JFN series FM multiplex station is equal to or higher than the set level (step 103).
[0017]
If it is equal to or higher than the set level, VICS information and DGPS information are received according to the flow of FIG. 3 described later (step 104). However, if it is below the set level, another JFN sequence FM multiplex station in the synchronization list is searched (step 105), and the synchronization timing Si of the JFN sequence FM multiplex station is obtained (step 106). The contents of the synchronization counter 24 are cleared, and thereafter the clock is counted (step 107). In step 104, VICS information and DGPS information are received.
In the step of receiving VICS and DGPS information in step 104, the tuner first receives the VICS information from the NHK series FM multiplex station under the control of the CPU 23 and inputs it to the multiplex decoder 21. The multiplex decoder 21 contains the received data of each block. (Step 201).
Next, the CPU 23 monitors the count value of the synchronous counter 24 and checks whether or not the DGPS information reception time has come (step 202). If not, the VICS information reception process of step 201 is continued.
[0018]
By switching the receiving station to be able to receive DGPS information,
(1) About 10 msec until the PLL of the electronic tuning circuit is locked after switching the receiving station from the NHK series FM multiplex station to the JFN series multiplex station
(2) 9msec for several bits for BIC detection (block synchronization)
A total of 19msec is required. Therefore, it is assumed that the DGPS information reception time is reached when the count value of the synchronization counter 24 reaches a value corresponding to the time 19 msec before the synchronization timing.
[0019]
When the DGPS information reception time comes, the CPU 23 controls the electronic channel selection device to switch the receiving station from the NHK series FM multiplex station to the JFN series multiplex station. Further, the CPU 23 instructs the synchronization circuit 52 to maintain synchronization. Thereby, the synchronization circuit 52 holds the block synchronization and the frame synchronization of the VICS information (step 203).
Thereafter, the tuner inputs the information received from the JFN series FM multiplex station to the multiplex decoder 21 (step 204), and the CPU 23 waits for a DGPS information reception completion notification from the multiplex decoder 21 (step 205). The multiplex decoder 21 starts receiving DGPS information after detecting the BIC, stores two blocks of DGPS information in the built-in RAM 55, and then notifies the CPU 23 of the completion of reception of the DGPS information.
Upon completion of reception of this DGPS information, the CPU 23 switches the receiving station from the JFN series FM multiplex station to the NHK series FM multiplex station (step 206), and the tuner receives the VICS information from the NHK series FM multiplex station and inputs it to the multiplex decoder 21. The multiplex decoder 21 writes the received VICS information in the RAM 54 based on the stored block synchronization (without synchronization supplement).
[0020]
As described above, when the VICS information for one frame is captured, the error detection / correction unit 53b of the decoder 21 first performs lateral correction on the DGPS information for two blocks stored in the RAM 55, and sends the correction result to the CPU 23. Send. Next, the error correction unit 53b performs horizontal correction → vertical correction → horizontal correction for one frame of VICS information stored in the RAM 54, and VICS information of some blocks that could not be received during reception of DGPS information. And VICS information is transmitted to the CPU 23. The CPU 23 stores the VICS information and the DGPS information received from the decoder 21 in the memory 25, and appropriately transmits these information to the navigation controller.
[0021]
In this embodiment, when VICS information lost due to reception of DGPS information is estimated, the total time of (1) to (4) below is obtained. That is,
(1) About 10 msec until the PLL of the electronic tuning circuit is locked after switching the receiving station from the NHK series FM multiplex station to the JFN series multiplex station
(2) 9msec for several bits for BIC detection (block synchronization)
(3) 36 msec for receiving 2 blocks of DGPS information,
(4) About 10 msec until the PLL of the electronic tuning circuit is locked by switching the receiving station from the JFN series FM multiplex station to the NHK series multiplex station.
65msec is required. This time is 1.3% of the time of 4896 msec for one frame. Due to the parity correction capability, the VICS information lost due to the reception of the DGPS information can be restored with a margin.
[0022]
Further, even when switching the receiving JFN sequence FM multiplex station to another JFN sequence FM multiplex station, since the synchronization timing of the FM multiplex station is known, there is no need to re-adjust the synchronization timing. The DGPS information can be immediately received through steps 105 to 107, and the VICS information lost due to the reception of the DGPS information can be restored.
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.
[0023]
【The invention's effect】
As described above, according to the present invention, since the amount of VICS information lost due to reception of DGPS information can be reduced, VICS information lost by error correction processing (horizontal correction / vertical correction / horizontal correction processing) can be restored with sufficient margin. Can do.
Even when switching JFN series FM multiplex stations, the synchronization timing of the FM multiplex station is already known, so there is no need to reset the synchronization timing, and DGPS information is immediately received from the switched FM multiplex station. Thus, the VICS information lost due to the reception of the DGPS information can be restored with a sufficient margin.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an FM multiplex broadcast receiver according to the present invention.
FIG. 2 is a reception processing flow.
FIG. 3 is a flowchart of reception control of VICS information and DGPS information.
FIG. 4 is a frame configuration diagram of FM multiplexed data.
FIG. 5 is a configuration diagram of DGPS data.
FIG. 6 is an explanatory diagram of DGPS segment contents.
[Explanation of symbols]
4. Front end (F / E)
5. ・ PLL circuit ・ ・ Intermediate frequency amplification / FM detector (IF / DET)
9. Filter circuit 10 S meter 21 Multiple decoder 23 Processor (CPU)
24. Synchronous counter

Claims (1)

In an FM multiplex broadcast data receiving method for receiving DGPS information and VICS information broadcast by FM multiplex from different broadcast stations with one receiver,
Frame synchronization timing of FM multiplex broadcast data in one or more FM multiplex broadcast stations with good reception status among FM multiplex broadcast stations that broadcast DGPS information every predetermined time is detected, and the FM multiplex broadcast station is associated with the FM multiplex broadcast station. Save the frame synchronization timing of FM multiplex broadcast data,
When the operation of storing the frame synchronization timing of the FM multiplex broadcast data is completed , FM multiplex broadcast data from an FM multiplex broadcast station that broadcasts VICS information is received, and DGPS information is broadcast while the FM multiplex broadcast is being received. When the reception state of the FM multiplex broadcast station is a predetermined time before the frame synchronization timing of the best FM multiplex broadcast station, the reception station is switched to an FM multiplex broadcast station that broadcasts DGPS information, and after reception of DGPS information is completed. , Switch to FM multiplex broadcasting station that broadcasts VICS information, and then repeat the above operation,
When the reception level of the current FM multiplex broadcast station that broadcasts DGPS information becomes equal to or lower than the set level, switching to another FM multiplex broadcast station that has been stored,
A method of receiving FM multiplex broadcast data.

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