JP7762022B2 - Synchronous signal conversion device - Google Patents

Description

The present invention relates to a synchronization signal conversion device installed in the base station of a mobile communication system, and in particular to a synchronization signal conversion device that can build a system synchronized with GPS even in an environment where GPS signals cannot be received, provides a pseudo GPS reception signal that is precisely synchronized with the GPS reception signal by reflecting offset values that differ for each base station, and prevents a decrease in processing power at the base station.

Description of the Prior Art
In conventional TDD (Time Division Duplex) wireless systems (existing wireless communication systems), it is necessary to synchronize the timing of communication between terminals and base stations throughout the entire system. To achieve this, base stations generate synchronization signals synchronized with the GPS (Global Positioning System) reference time to control the timing of uplink and downlink communications, thereby achieving a system synchronized with the GPS reference time.

GPS and other GNSS (Global Navigation Satellite Systems) are commonly used for inter-base station synchronization. GNSS is a general term for satellite positioning systems, and is synchronized with UTC (Coordinated Universal Time), making it easy to establish network consistency.

[Base station device equipped with a GPS receiver: Figure 6]
Here, a base station device equipped with a GPS receiver will be described with reference to Fig. 6. Fig. 6 is an explanatory diagram showing the schematic configuration of a base station device equipped with a GPS receiver.
As shown in FIG. 6, the base station device 20 includes a GPS antenna 22 and a GPS receiver 21 .
The GPS antenna 22 receives GPS signals from GPS satellites and outputs GPS received signals.
The GPS receiver 21 extracts a reference time expressed in UTC from the GPS reception signal from the GPS antenna 21, and generates a synchronization signal that is synchronized with the reference time (time synchronization).
The conventional base station device 20 then operates in accordance with the synchronization signal, thereby performing communication synchronized with the GPS reference time.

Herein, in this specification, the signal transmitted from each GPS satellite (satellite) is referred to as a "GPS signal," and the signal in which GPS signals from multiple satellites are superimposed and received by a GPS antenna is referred to as a "GPS received signal."
In other words, the GPS reception signal is a signal that is input to the GPS receiver 21, and the GPS receiver 21 acquires (calculates) time information synchronized with UTC and current location information based on the input GPS reception signal.

However, GNSS has problems with interference from other radio signals, and there are dead zones indoors, underground, and between buildings, and cable wiring is also a major obstacle.
In recent years, many indoor base stations have been installed, but GPS antennas must be installed outdoors for synchronization, which is costly.
Furthermore, with the expansion of IoT (Internet of Things) use, there is an increasing demand for inter-base station synchronization methods that do not rely on GNSS.

[System synchronization signal of wireless communication system]
Therefore, in the past, there was a synchronization signal conversion device that generates synchronization time information synchronized with the GPS reference time based on the time information of the broadcast wave and the system synchronization signal of a wireless communication system synchronized with the GPS reference time, and generates a pseudo GPS reception signal that calculates the time and outputs it to a base station device (Patent Document 1).
The system synchronization signal may be, for example, a frame number obtained from an LTE signal output from a base station.

[Base station frame offset value]
The system synchronization signal included in the LTE signal output from the base station may have a certain deviation from the 1 PPS signal extracted from the GPS received signal.
This is called a frame time offset value (base station signal offset information, base station offset value).
The frame time offset value may differ depending on the type of base station.
However, in conventional synchronization signal conversion devices, the offset of the system synchronization signal is corrected by treating it as a fixed value.

[Related Technology]
Incidentally, a conventional technology for a synchronization signal conversion device is disclosed in Japanese Patent Laid-Open Publication No. 2019-204999, "Wireless selective calling receiver" (Patent Document 1).
Patent Document 1 describes the above-mentioned synchronization signal conversion device.

Japanese Patent Application Laid-Open No. 2019-204999

As mentioned above, conventional synchronization signal conversion devices have the problem that the accuracy of the pseudo GPS reception signal can be reduced due to base station offsets that differ for each base station that transmits the LTE signal, resulting in reduced throughput at the base station to which the pseudo GPS reception signal is output.

Note that Patent Document 1 does not describe extracting base station identification information that identifies a base station from a received LTE signal, performing timing correction using a base station offset value that has been pre-stored in accordance with the base station identification information, outputting the time information of the broadcast wave at the corrected timing, and generating a pseudo GPS reception signal.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a synchronization signal conversion device that corrects the timing of a system synchronization signal obtained from an LTE signal in accordance with the transmitting base station, generates a highly accurate pseudo GPS reception signal, and prevents a decrease in throughput of the receiving device (e.g., a base station device) of the pseudo GPS reception signal.

The present invention, which solves the problems of the above-mentioned conventional example, is a synchronization signal conversion device connected to a receiver of a base station of a wireless communication system, comprising: a synchronization signal acquisition unit that receives a signal of the wireless communication system and acquires a system synchronization signal synchronized with GPS reference time and base station identification information that identifies a source base station that is a sender of the signal; a time information acquisition unit that receives broadcast waves and acquires time information from the broadcast waves; an offset control unit that stores a plurality of pairs of base station offset information corresponding to the base station identification information, the offset control unit using the output base station offset information to correct the timing of the system synchronization signal and output the time information to the correct timing, thereby The system comprises a time information synchronization unit that generates synchronized time information synchronized with the PS reference time, a GPS time information conversion unit that generates a pseudo GPS reception signal including orbital information of a plurality of satellites and time information corresponding to the transmission time from each satellite based on the synchronized time information so that the base station can calculate a time that matches the synchronized time information, and a pseudo GPS reception signal transmission unit that outputs the pseudo GPS reception signal to the base station , and is characterized in that the offset control unit sets base station identification information acquired from a signal of the wireless communication system and its corresponding base station offset information as source base station information, and when the base station identification information and its corresponding base station offset information acquired from a newly received signal of the wireless communication system differ from the source base station information, updates and sets the source base station information with the newly acquired base station identification information and its corresponding base station offset information .

Furthermore, in the above-mentioned synchronization signal conversion device, the present invention is characterized in that, if the offset control unit does not store base station offset information corresponding to the base station identification information acquired from the signal of the wireless communication system, it inquires of the connected upper-level device about base station offset information corresponding to the base station identification information, and outputs the base station offset information acquired from the upper-level device to the time information synchronization unit.

According to the present invention, a synchronization signal conversion device connected to a receiver of a base station of a wireless communication system includes a synchronization signal acquisition unit that receives a wireless communication system signal and acquires a system synchronization signal synchronized with GPS reference time and base station identification information that identifies a source base station that is a sender of the signal, a time information acquisition unit that receives broadcast waves and acquires time information from the broadcast waves, an offset control unit that stores a plurality of pairs of base station offset information corresponding to the base station identification information, the offset control unit using the deviation between the system synchronization signal and the GPS reference signal generated by the source base station as base station offset information, and outputs the base station offset information corresponding to the base station identification information acquired from the received wireless communication system signal, a time information synchronization unit that uses the output base station offset information to correct the timing of the system synchronization signal and output time information at that timing, thereby generating synchronized time information synchronized with GPS reference time, and a time information synchronization unit that calculates a time that matches the synchronized time information at the base station based on the synchronized time information. To achieve this, the synchronization signal conversion device is equipped with a GPS time information conversion unit that generates a pseudo GPS reception signal including orbital information for a plurality of satellites and time information corresponding to the transmission time from each of the satellites, and a pseudo GPS reception signal transmission unit that outputs the pseudo GPS reception signal to a base station, and the offset control unit sets base station identification information obtained from a wireless communication system signal and its corresponding base station offset information as source base station information, and when the base station identification information and its corresponding base station offset information obtained from a newly received wireless communication system signal differ from the source base station information, the synchronization signal conversion device updates and sets the source base station information with the newly obtained base station identification information and its corresponding base station offset information , so that the offset can be corrected in accordance with the source base station of the actually received wireless communication system signal, and a pseudo GPS reception signal that is precisely synchronized with the GPS reference time can be generated and output, thereby preventing a decrease in the throughput of the output destination base station.

Furthermore, according to the present invention, in the synchronization signal conversion device, if the offset control unit does not store base station offset information corresponding to the base station identification information obtained from the wireless communication system signal, it inquires of the connected upper device about base station offset information corresponding to the base station identification information, and outputs the base station offset information obtained from the upper device to the time information synchronization unit.Therefore, even when a wireless communication system signal is received from a source base station that has not been received before, it is possible to obtain the corresponding offset information from the upper device and perform timing correction, resulting in the effect of being applicable to various base stations and generating highly accurate pseudo GPS reception signals.

1 is an explanatory diagram showing the configuration of a synchronous signal conversion device. FIG. 2 is a schematic diagram of an offset control unit 30. FIG. 2 is a configuration block diagram of a time information synchronization unit. FIG. 10 is a schematic explanatory diagram of a base station offset information table. 10 is a flowchart showing the process of an offset control unit 30. FIG. 1 is an explanatory diagram showing a schematic configuration of a base station device equipped with a GPS receiver.

An embodiment of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
A synchronization signal conversion device according to an embodiment of the present invention (the present synchronization signal conversion device) generates and outputs a pseudo GPS reception signal from which time information synchronized with GPS is calculated using time information from broadcast waves and a system synchronization signal included in an LTE signal of a wireless communication system. The synchronization signal conversion device stores a plurality of pairs of base station identification information that identifies the base station (source base station) that is the source of the LTE signal, and a base station offset value that indicates the deviation from the timing of the GPS signal. The synchronization signal conversion device extracts the base station identification information from the received LTE signal, corrects the timing of the system synchronization signal using the base station offset value stored in correspondence with the base station identification information, outputs the time information from the broadcast waves at the corrected timing, and generates and outputs a pseudo GPS reception signal so that the time information is calculated. Even if the base station that is the source of the LTE signal changes, the timing can be corrected using the base station offset value of the new source base station, and the synchronization signal can always be generated that is synchronized with the GPS reference time with high accuracy, preventing a decrease in throughput at the receiving device.

In addition, if the base station identification information extracted from the received LTE signal is not stored internally, this synchronization signal conversion device queries the higher-level device to obtain the base station offset value corresponding to the base station identification information, stores the base station offset value, and uses the base station offset value to correct the timing, thereby enabling the generation of highly accurate GPS reception signals corresponding to various transmitting base stations.

[Configuration of the present synchronous signal conversion device: Figure 1]
The configuration of this synchronous signal conversion device will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram showing the configuration of this synchronous signal conversion device.
Before describing the specific configuration of the synchronous signal conversion device, an outline will be given.
As shown in Figure 1, this synchronization signal conversion device 1 generates time information synchronized with the GPS reference time based on the LTE signal from the LTE station 3 and the broadcast wave from the broadcast relay station 4, and further generates a pseudo GPS reception signal including information for allowing the receiving device (here, the base station 2) to obtain the time information synchronized with the GPS reference time, and outputs it to the base station device 2.

Furthermore, the LTE signal from the LTE station 3 is transmitted from any base station, and since the LTE signal with the highest reception level is usually used, the source of the LTE signal is the base station 2 to which the pseudo GPS reception signal is output.
However, since the source base station may be a different device (a base station not connected to this synchronization signal conversion device) from the destination base station 2, here the device that transmits the LTE signal received by this synchronization signal conversion device 1 will be referred to as the "source base station."

Base station 2 is equipped with a GPS receiver 21, but is not equipped with a GPS antenna. Instead of a GPS reception signal, the GPS receiver 21 inputs a pseudo GPS reception signal from the synchronization signal conversion device 1, obtains time information synchronized with the GPS reference time, and generates a synchronization signal based on this information.

Here, the pseudo GPS reception signal generated by this synchronization signal conversion device is a signal generated so that the GPS receiver 21 of the connected base station 2 can obtain accurate time information synchronized with UTC and correct location information, and is a signal that includes orbital information corresponding to multiple satellites and time information corresponding to the transmission time of each satellite, just as when receiving GPS signals from multiple satellites.
In other words, when the GPS receiver 21 of the base station 2 receives a pseudo GPS reception signal, it recognizes it as a superimposed GPS signal from multiple satellites and performs the same operation as if it had received an original GPS reception signal.
It should be noted that "time information synchronized with the GPS reference time" is used here as a synonym for "time information synchronized with UTC."

As shown in Figure 1, the synchronization signal conversion device 1 includes an LTE signal receiving antenna 16a, a broadcast wave receiving antenna 16b, a synchronization signal acquisition unit 11, a time information acquisition unit 12, a time information synchronization unit 13, a GPS time information conversion unit 14, a pseudo GPS received signal transmission unit 15, and an offset control unit 30, which is a characteristic part of the synchronization signal conversion device.

Each part of the synchronous signal conversion device 1 will now be described.
The LTE signal receiving antenna 16 a receives an LTE signal transmitted from a base station (source base station) of an LTE wireless communication system (mobile communication system) and relayed by the LTE station 3 .
Note that, although LTE will be used as an example here, the present invention is not limited to LTE and can be applied to systems that do not include time information in the system synchronization signal, such as LTE-Advanced or 5G (fifth generation communication system).
The broadcast wave receiving antenna 16 b is an antenna that receives broadcast waves from the broadcast relay station 4 .

In addition, here, the antenna for the wireless communication system and the antenna for broadcast waves are provided independently, but they may also be configured to be shared, with a single receiving antenna receiving both LTE signals and broadcast waves, and connected to the synchronization signal acquisition unit 11 and the time information acquisition unit 12.

The synchronization signal acquisition unit 11 demodulates the received LTE signal, extracts a system synchronization signal from the broadcast information, and outputs the system synchronization signal to the time information synchronization unit 13. The system synchronization signal may be, for example, a signal indicating a specific frame number. The system synchronization signal is synchronized with the timing of the GPS reference time.
The LTE signal receiving antenna 16a may receive LTE signals from a plurality of source base stations, and the synchronization signal acquisition unit 11 demodulates the LTE signal with the highest reception level among them.

Furthermore, the synchronization signal acquisition unit 11 of the synchronization signal conversion device 1 acquires base station identification information for identifying the source base station of the LTE signal from the demodulated information, and outputs the information to the offset control unit 30 .
As described above, the system synchronization signal from the transmitting base station has a deviation from the 1PPS signal contained in the GPS signal depending on the type of transmitting base station, and the frame time offset value (base station offset value) indicating this deviation differs for each base station.

The synchronization signal conversion device 1 corrects the base station offset in accordance with the transmitting base station, thereby generating a highly accurate pseudo GPS reception signal synchronized with the GPS signal.
The operation using the base station identification information will be described later.

The time information acquisition unit 12 extracts time information contained in the received broadcast waves (terrestrial digital broadcast waves). The time information contained in the broadcast waves contains errors due to differences in clock accuracy and fluctuations in reception timing caused by radio wave propagation, and is not synchronized with the GPS reference time.

The offset control unit 30 is a characteristic part of the present synchronization signal conversion device 1, and outputs a base station offset value corresponding to the base station that transmitted the LTE signal to the time information synchronization unit 13 based on the base station identification information from the synchronization signal acquisition unit 11.
Specifically, the offset control unit 30 stores the base station identification information of various source base stations in association with the base station offset values, and outputs the base station offset value corresponding to the base station identification information extracted from the input LTE signal.
The base station offset information described in the claims corresponds to the base station offset value.

Furthermore, if the base station identification information obtained from the received LTE signal is not stored internally, the offset control unit 30 inquires of the higher-level device 5 about the base station offset value corresponding to the base station identification information.
The configuration and operation of the offset control unit 30 will be described later.

The time information synchronization unit 13 corrects the time information based on the system synchronization information from the synchronization signal acquisition unit 11 and the time information from the time information acquisition unit 12, and generates time information (synchronized time information) synchronized with the GPS reference time.
At this time, the time information synchronizer 13 corrects the timing of the system synchronization information using the base station offset value input from the offset controller 30 .
The configuration and operation of the time information synchronization unit 13 will be described later.

The GPS time information conversion unit 14 generates a pseudo GPS reception signal based on the synchronized time information input from the time information synchronization unit 13 .
Specifically, the GPS time information conversion unit 14 calculates pseudo GPS signals from multiple satellites to correspond to the synchronized time information, and generates a GPS reception signal (pseudo GPS reception signal) that looks as if multiple GPS signals are overlapping.

As described above, the pseudo GPS reception signal contains orbital information for multiple satellites and time information corresponding to the transmission time from each satellite, which is generated so that the receiving device (here, base station 2) can calculate the synchronized time information.The GPS receiver 21 of base station 2 can calculate time information identical to the synchronized time information based on the received pseudo GPS reception signal, generate a synchronized signal, and calculate the position.

The pseudo GPS reception signal is similar to the signal generated by a GPS simulator used to test GPS receivers, and is described, for example, in "Keysight Technologies GPS Receiver Test," published by Keysight Technologies, Inc. on January 6, 2015.

The pseudo GPS reception signal transmitter 15 outputs the pseudo GPS reception signal output from the GPS time information converter 14 to the connected base station 2.

[Configuration of offset control unit 30: FIG. 2]
Next, the configuration of the offset control section 30, which is a characteristic part of the present synchronization signal conversion device, will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the offset control section 30.
The offset control unit 30 is a characteristic part of this synchronization signal conversion device, and outputs the base station offset value to the synchronization correction unit 31 (described later) of the time information synchronization unit 13 in order to correct the base station offset, which differs depending on the type of source base station that transmits the LTE signal.

As shown in Figure 2, the offset control unit 30 has a base station offset information table 301 that stores multiple frame time offset values (base station offset values) that differ for each source base station, and associates them with base station identification information that identifies the source base station.

The base station offset information table 301 stores base station offset values associated with base station identification information for identifying the type of base station for multiple types of base stations that are expected to be applied to the wireless communication system (expected to become source base stations).

When the offset control unit 30 receives the base station identification information acquired by the synchronization signal acquisition unit 11, it refers to the base station offset information table 301, reads out the corresponding base station offset value, and outputs it to the synchronization correction unit 31.
The base station offset value may be output to the time information synchronizer 13 each time base station identification information is input, or may be output when the base station offset value is updated.

Further, the offset control unit 30 stores, as source base station information 302, base station identification information and a base station offset value for the source base station of the currently received LTE signal.
The offset control unit 30 then compares the base station identification information obtained from the received LTE signal with the source base station information 302 it holds, and monitors the base station identification information to see if there has been any change in the source base station.
This makes it possible to immediately output an appropriate base station offset value to the synchronization correction unit 31 when the source base station changes.

Furthermore, if the input base station identification information is not stored in the base station offset information table 301, the offset control unit 30 attaches the base station identification information to the higher-level device 5 and queries the base station offset value.

When a base station offset value is received in response to an inquiry from the higher-level device 5, the offset control unit 30 outputs the base station offset value to the synchronization correction unit 31 and adds the base station identification information and base station offset value to the base station offset information table 301.
As a result, even if a base station that has not been stored in advance becomes the source base station, it is possible to obtain an appropriate base station offset value from the higher-level device 5 and perform timing correction.
The offset control unit 30 may be configured as an integral part of the time information synchronization unit 13 .

[Configuration of the time information synchronization unit 13: FIG. 3]
Next, the configuration of the time information synchronization unit 13 of the present synchronization signal conversion device will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration of the time information synchronization unit.
As shown in FIG. 3, the time information synchronization unit 13 of the present synchronization signal conversion device includes a synchronization correction unit 31, a time information correction unit 32, and a synchronization time generation unit 33.
The time information synchronization unit 13 basically operates independently based on an internal clock, and the synchronized time generation unit 33 outputs the time information from the time information correction unit 32 according to the timing from the synchronization correction unit 31, thereby generating time information (synchronized time information) synchronized with the GPS reference time.

In the time information synchronization unit 13, when a system synchronization signal is input from the synchronization signal acquisition unit 11, the synchronization timing correction unit 311 corrects the timing, and when time information of the broadcast wave is input from the time information acquisition unit 12, the time correction unit 321 corrects the internal time information.
The synchronization timing correction unit 311 corrects the base station offset according to the source base station in accordance with instructions from the offset control unit 30 .

The self-sustaining operation of the time information synchronization unit 13 allows the unit 13 to output synchronized time information without interruption, even when radio waves from the transmitting base station or broadcast waves from a broadcast relay station are not sufficiently received, or when radio wave transmission is suspended due to maintenance, etc.

Each part of the time information synchronization unit 13 will now be described in detail.
The synchronization correction unit 31 includes a synchronization timing correction unit 311 and a synchronization counter 312 .
The synchronization timing correction unit 311 performs timing correction on the synchronization counter 312 based on the 1 PPS (Pulse Per Second) system synchronization signal input from the synchronization signal acquisition unit 11, and instructs the synchronization counter 312 on timing when the system synchronization signal is input.

Specifically, the synchronization timing correction unit 311 determines whether the system synchronization signal is being received normally, and if it is being received normally, updates the timing of the synchronization counter 312 in accordance with the system synchronization signal.
At this time, the synchronization timing correction unit 311 issues a timing instruction with the offset corrected based on the base station offset value input from the offset control unit 30. This allows for accurate correction using an offset value according to the transmitting base station, compared to the conventional method of performing offset correction using a fixed value, and enables the generation of a highly accurate pseudo GPS reception signal.

The synchronous counter 312 is a frequency generating circuit equipped with a VCXO (Voltage Controlled Crystal Oscillator) or a TCXO (Temperature Compensated Crystal Oscillator), and generates a free-running signal (free-running clock) that counts timing.
Here, the synchronization counter 312 outputs synchronization timing (timing signal) every second based on a free-running clock. When a timing instruction is input from the timing correction unit 311, the synchronization counter 312 generates synchronization timing every second, starting from the timing instruction.

This allows the timing to be corrected even if the system synchronization signal has an offset originating from the transmitting base station relative to the GPS reference time, and also allows correction even if the free-running state is prolonged and the synchronization timing generated by the synchronization counter 312 becomes out of sync.
That is, when the system synchronization signal is input normally, the synchronization counter 312 outputs a 1 PPS timing signal synchronized with the GPS reference time.

The time information correction unit 32 includes a time correction unit 321 and a time counter 322 .
The time correction unit 321 determines whether the item information extracted from the broadcast wave is being received normally from the time information acquisition unit 12, and if it is being received normally, updates the counter value (internal time information) of the time counter 322 to the acquired time information.

The time counter 322 is a frequency generation circuit equipped with a VCXO or TCXO, which generates a free-running clock to generate independent time information (internal time information), and outputs corrected time information by adding a specific time to the internal time information. The specific time will be described later.

Furthermore, when an instruction to update the time information is input from the time correction unit 321, the time counter 322 updates the internal time information with the input time information (time information acquired from the broadcast wave).
As a result, if the time information obtained from the broadcast wave is input correctly, the time counter 322 outputs corrected time information in which a specific time has been added to the time information of the broadcast wave.

Here, the specific time added by the time counter 322 will be described.
The specific time is the time added in order to perform processing to generate synchronized time information synchronized with GPS reference time from the internal time information.
Specifically, the specific time is set to a time greater than the maximum time expected as the difference between the time information extracted from the broadcast wave and the GPS reference time, and is set to 0.5 seconds in this example.
Although the internal time information may be slightly ahead or behind the broadcast time information when the watch is running independently, if the broadcast time information is received correctly, the internal time information will be updated to match the broadcast time information, so there is no need to consider the discrepancy caused by running independently.

The synchronized time generation unit 33 holds the corrected time information input from the time information correction unit 32, and when a 1 PPS timing signal synchronized with GPS reference time is input from the synchronization correction unit 31, it outputs the held corrected time information according to that timing.

That is, the synchronization time generation unit 33 outputs corrected time information that is ahead of the actual GPS reference time by adding a specific time, according to the timing corrected by the synchronization timing correction unit 311 .
As a result, the synchronized time generating unit 33 outputs time information synchronized with the GPS reference time (synchronized time information) every second.
The method for generating the synchronized time information is the same as the method described in Patent Document 1, and therefore a detailed description thereof will be omitted here.

[Base Station Offset Information Table: Figure 4]
The base station offset information table 301 in the offset control unit 30 will be described with reference to Fig. 4. Fig. 4 is a schematic explanatory diagram of the base station offset information table.
4, the base station offset information table 301 stores, for multiple types of base stations (source base stations), base station identification information and base station offset values specific to the base station in association with each other. The base station identification information is, for example, the model number of the base station device.

Normally, the transmitting base station and the base station 2 to which the pseudo GPS reception signal is output are the same device, so the base station offset information table 301 stores (registers) information on multiple base stations 2 that are expected to be connected to the synchronization signal conversion device 1.

In addition, when the offset control unit 30 receives base station identification information that is not stored in the base station offset information table 301, it queries the higher-level device 5 and adds the information to the base station offset information table 301 together with the obtained base station offset value.
As a result, even if an LTE signal is received from an unregistered base station, a single inquiry will result in registration in the base station offset information table 301, and subsequent inquiries will not be necessary.

[Processing of the offset control unit 30: FIG. 5]
Next, the control of the base station offset value in the offset control unit 30 will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the process of the offset control unit 30.
In this synchronization signal conversion device 1, when an LTE signal is received by the LTE signal receiving antenna 16a, the synchronization signal acquisition unit 11 demodulates the signal and outputs the system synchronization signal to the synchronization timing correction unit 311 of the time information synchronization unit 13, and also outputs base station identification information to the offset control unit 30.

As shown in Figure 5, when base station identification information is input from the synchronization signal acquisition unit 11 (104), the offset control unit 30 determines whether the input base station identification information matches the base station identification information of the source base station information, which is information about the source base station that has been receiving the LTE signal up until that point (106).

If there is a match (Yes), the offset control unit 30 determines that the currently set source base station has not changed, proceeds to process 130, and outputs the base station offset value set in the source base station information 302 (130).

Also, if there is no match with the source base station information in process 106 (No), the offset control unit 30 determines whether the input base station identification information is registered in the base station offset information table (108).

In process 106, if the input base station identification information is registered in the base station offset information table 301 (if Yes), the offset control unit 30 notifies the input base station identification information to the higher-level device 5 and reports that the source base station of the LTE signal has changed (110).
Then, the offset control unit 30 updates the source base station information 302 with the currently received base station identification information and the corresponding base station offset value (112), and proceeds to process 130 to output the base station offset value.

In other words, when there is a change in the source base station, the offset control unit 30 not only updates the internal source base station information 302, but also notifies the higher-level device 5, making it available for use in managing the entire system.

Also, in process 108, if the input base station identification information is not registered in the base station offset information table (No), the offset control unit 30 attaches the base station identification information and queries the higher-level device 5 for the base station offset value (120).

Then, when the base station offset value is received from the higher-level device 5, the offset control unit 30 associates the base station identification information with the base station offset value, adds the association to the base station offset information table 301 (122), and proceeds to process 112, where the source base station information 302 is updated and the base station offset value is output.
In this manner, the processing in the offset control unit 30 is carried out.

[Effects of the embodiment]
According to this synchronization signal conversion device, a pseudo GPS reception signal is generated from which time information synchronized with GPS is calculated based on time information from broadcast waves and a system synchronization signal included in the LTE signal of a wireless communication system, and the pseudo GPS reception signal is output. The synchronization signal acquisition unit 11 extracts the system synchronization signal and base station identification information that identifies the transmitting base station from the LTE signal. The offset control unit 30 refers to a pre-stored base station offset information table 301, reads out and outputs a base station offset value corresponding to the base station identification information. The time information synchronization unit 13 corrects the timing of the system synchronization signal based on the base station offset value and outputs broadcast wave time information at the corrected timing, thereby generating synchronized time information synchronized with GPS reference time. The GPS time information conversion unit 14 generates a pseudo GPS reception signal from which the synchronized time information is calculated. Therefore, the frame time offset, which differs depending on the transmitting base station, is corrected in accordance with the actual transmitting base station of the LTE signal, and a pseudo GPS reception signal that is accurately synchronized with GPS reference time is generated, thereby enabling the receiving device to generate an accurate synchronization signal and preventing a decrease in throughput.

Furthermore, according to this synchronization signal conversion device, if the base station identification information obtained from the LTE signal is not registered in the base station offset information table 301, the offset control unit 30 queries the higher-level device 5, and upon receiving the base station offset value, stores it in the base station offset information table 301 in association with the base station identification information, and outputs the base station offset value to the time information synchronization unit 13. Therefore, even when an LTE signal is received from an unregistered base station and a system synchronization signal is used, the offset can be corrected according to the transmitting base station, and a pseudo GPS reception signal that is always synchronized with GPS reference time with high precision can be generated.

The present invention is suitable for a synchronization signal conversion device that can correct the timing of a system synchronization signal obtained from an LTE signal in accordance with the transmitting base station, generate a highly accurate pseudo GPS reception signal, and prevent a decrease in throughput in the receiving device (e.g., a base station device) of the pseudo GPS reception signal.

1...Synchronization signal conversion device, 2, 20...Base station, 3...LTE station, 4...Broadcast relay station, 5...High-level device, 11...Synchronization signal acquisition unit, 12...Time information acquisition unit, 13...Time information synchronization unit, 14...GPS time information conversion unit, 15...Pseudo GPS received signal transmission unit, 16...Receiving antenna, 21...GPS receiver, 22...GPS receiving antenna, 30...Offset control unit, 31...Synchronization correction unit, 32...Time information correction unit, 33...Synchronization time generation unit, 301...Base station offset information table, 302...Source base station information, 311...Timing correction unit, 312...Synchronization counter, 321...Time correction unit, 322...Time counter

Claims (2)

A synchronization signal conversion device connected to a receiver of a base station of a wireless communication system, comprising:
a synchronization signal acquisition unit that receives a signal from the wireless communication system and acquires a system synchronization signal synchronized with a GPS reference time and base station identification information that identifies a source base station that is a source of the signal;
a time information acquisition unit that receives a broadcast wave and acquires time information from the broadcast wave;
an offset control unit that stores a plurality of pairs of base station offset information, each pair corresponding to a base station identification information, and outputs the base station offset information corresponding to the base station identification information acquired from the received signal of the wireless communication system; and
a time information synchronization unit that uses the output base station offset information to correct the timing of the system synchronization signal and outputs the time information at the correct timing, thereby generating synchronized time information synchronized with GPS reference time;
a GPS time information conversion unit that generates a pseudo GPS reception signal including orbital information of a plurality of satellites and time information corresponding to the transmission time from each satellite, based on the synchronized time information, so that the base station can calculate a time that coincides with the synchronized time information;
a pseudo GPS reception signal transmitter that outputs the pseudo GPS reception signal to the base station ,
The offset control unit sets base station identification information acquired from a signal of the wireless communication system and its corresponding base station offset information as source base station information, and when the base station identification information acquired from a newly received signal of the wireless communication system and its corresponding base station offset information differ from the source base station information, updates and sets the source base station information with the newly acquired base station identification information and its corresponding base station offset information. The synchronization signal conversion device according to claim 1 , characterized in that, when the offset control unit does not store base station offset information corresponding to the base station identification information acquired from the signal of the wireless communication system, it inquires of the connected higher-level device about base station offset information corresponding to the base station identification information, and outputs the base station offset information obtained from the higher-level device to the time information synchronization unit.