JP5030001B2 - Time synchronization apparatus and time synchronization method - Google Patents

Description

  The present invention relates to time synchronization, and more particularly to time synchronization of a base station using a time synchronization signal generated based on a time signal transmitted from a GPS satellite. Wireless communication systems that require synchronization include PHS (Personal Handy-Phone System), WiMAX (Worldwide Interoperability for Microwave Access), LTE (Long Time Evolution), and next-generation PHS. In these wireless communication systems, when performing handover (switching between base stations connected for communication), it is necessary that the time timing inside each base station is synchronized with other base stations in absolute time.

  When this type of conventional time synchronizer can receive a time signal from a GPS communication satellite, it receives the GPS time signal, outputs a PPS (Pulse Per Second) signal, and generates a PPS clock based on this signal. When the time synchronization signal cannot be received from the GPS communication satellite, the clock synchronization is performed by the RTC (Real Time Clock) generated by the base station (for example, Patent Document 1). reference). The PPS signal is also generated when the time signal from the GPS communication satellite cannot be received. The RTC is monitored to see if it matches the PPS clock, and if not, it is corrected based on the PPS clock. When a time signal is received, a PSC (Pps Signal Counter) that counts RTC and PPS signals is initialized.

  FIG. 8 is a block diagram showing the above prior art. The GPS receiving unit 106 receives the time signal provided by the GPS communication satellite by the antenna 105 and outputs a PPS signal, and sends the PPS signal to the PPS receiving unit 107 through the line L1. The PPS receiving unit 107 generates a PPS clock based on the PPS signal and provides this to the CPU 101. The PPS signal is a signal generated based on a time signal substantially equal to the standard time signal, and is a signal provided every second.

  Therefore, as long as the time signal from the GPS communication satellite can be received, the CPU 101 is provided with the PPS clock at the correct timing, and the clock synchronization is accurately maintained. The local clock generating unit 102 generates an RTC, and the RTC matches the PPS clock or is monitored by the CPU 101. If the RTC does not match, the local clock generating unit 102 corrects the RTC by a correcting unit configured by the CPU 101, the ROM 103, and the RAM 104.

  However, in the above-described prior art, the time synchronization device using the GPS satellite can obtain a very accurate time, but once the GPS communication satellite cannot be captured for some reason, the system clock is generated by the RTC. Although correction is performed in units of seconds, since the RTC itself is a circuit that assumes an accuracy of about 1 second, such a correction method is a system synchronized with UTC (Coordinated Universal Time). Since it can be corrected only with an accuracy of about 1 second, there is a first problem that the correct time cannot be obtained.

  In addition, the PSC value obtained by counting 1 PPS signal output from the time synchronizer using a GPS satellite and the second information of the RTC clock are compared and the RTC is corrected. There is also a second problem that high accuracy cannot be maintained.

  In order to solve such a problem, the present applicant, when the GPS communication satellite cannot be acquired, receives the base station from the GPS communication satellite via the mobile station from another base station in the handover state. The time synchronization device that acquires the time information of the current time signal and that synchronizes itself with the acquired time information has been proposed. However, in this time synchronizer, since the presence of a mobile station to which communication is relayed by a base station is an essential component, time correction based on a time signal from a GPS communication satellite cannot be performed when there is no mobile station. It will be.

  In addition, the PHP base station that generates the first timing signal that defines the frame timing generates the second timing based on the received signal from the GPS satellite, and calibrates the first timing based on the second timing. On the other hand, a wireless communication apparatus that receives a control signal from an adjacent PHP base station, detects a frame timing, and determines an abnormality of the own station from a difference from the frame timing of the own station is known. However, in this wireless communication apparatus, control signals from adjacent PHP base stations are passively received, and the frame timings are compared with each other and are simply determined only by time. The element cannot be excluded. Furthermore, it is not possible to expect a highly accurate time synchronization accuracy of 1 usec level required in a wireless communication system such as WiMAX.

JP-A-11-154920 Japanese Patent Application No. 2008-162647 JP2007-228327A

  The problem to be solved is that the time synchronization between the base stations cannot be stably maintained for a long time with a predetermined accuracy when a GPS satellite cannot be captured in an existing base station without a mobile station. .

  When the GPS satellite cannot be acquired, the present invention receives the time deviation information between the own base station and the base station that has acquired the GPS satellite together with the information guaranteeing the fact, and synchronizes the time of the base station. The most important feature is signal correction.

  According to the present invention, even if the GPS satellite cannot be captured without changing the basic configuration of the conventional time synchronization apparatus using the GPS satellite, the system can be operated for a long time. There are advantages. This is because the UTC timing of the base station that can no longer capture the GPS satellite is obtained from another base station that can normally receive the GPS satellite, and it is determined whether it is within the reference accuracy.

  In addition, in the conventional time synchronizer using a GPS satellite, the oscillator inside the GPS receiver can be changed to a low-priced one. The reason for this is that, in the past, an expensive system was used so that the time required for the system when the holdover occurred was within the specified accuracy, but it was used to determine whether it was within the accuracy allowed from the UTC timing. This is because it is possible to cope with the actual value including the oscillator or the ambient temperature environment.

1 is a schematic diagram of a wireless communication system to which the present invention is applied. It is a block diagram of the base station which shows Example 1 of this invention. It is a timing chart of the data frame transmitted from a base station. It is a flowchart when a GPS satellite becomes impossible to capture. It is a flowchart which calculates the timing shift inside a base station. It is a block diagram of the base station which shows the form of Example 2 of this invention. It is a block diagram of the base station which shows the form of Example 3 of this invention. It is a block diagram which shows an example of a prior art.

  When the existing base station falls into a situation where GPS satellites cannot be captured, the purpose of maintaining stable time synchronization between base stations for a long time with a predetermined accuracy can be captured normally. This was realized by correcting the time difference between the base stations acquired at the base station.

  FIG. 1 is a schematic diagram of a wireless communication system to which the present invention is applied, in which a base station 100 performs wireless communication with each other via an antenna 91 and a base station 200 via an antenna 92. Indicates. The base station 100 receives the time signal from the GPS communication satellite (hereinafter referred to as “GPS satellite”) by the antenna 81 and the base station 200 by the antenna 82, respectively. Based on this, the base station 100 and the base station 200 Clock synchronization between the two. This time signal is synchronized with UTC with extremely high accuracy.

  It is assumed that the positions of the base station 100 and the base station 200 are fixed and have a positional relationship in which wireless communication can be performed directly. Therefore, the radio wave propagation delay time generated when performing wireless communication can also be regarded as fixed. In the following description, it is assumed that the base station 100 is a base station that can no longer capture GPS satellites, and the base station 200 is a base station that can normally capture GPS satellites.

  FIG. 2 is a block diagram showing the main parts of base stations 100 and 200. These base stations include a GPS receiver 1 with a built-in oscillator 11, a counter 2, a frame timing control unit 3, a frame generation unit 4, a radio wave input / output unit 5, a calculation unit 6, a frame timing detection unit 7, an antenna 8, an antenna 9 and a memory 10. The antenna 8 is for capturing GPS satellites, the antenna 9 is for wireless connection, and the memory 10 functions as a work memory for the arithmetic unit 6.

  The GPS receiver 1 receives a navigation message from a GPS satellite via the antenna 8 and obtains various information by receiving the navigation message. Various types of information are represented by almanac and ephemeris.

  The navigation message consists of 25 frames. Furthermore, one frame consists of 6 subframes. The period of one subframe is 6 seconds, and the period of one frame is 30 seconds. Therefore, since the navigation message cycle is 30 seconds * 25 frames = 12.5 minutes, it takes a minimum of 12.5 minutes to receive all the navigation messages.

  The ephemeris data is data indicating the exact position of the GPS satellite, and is detailed information specific to the transmitted GPS satellite. The ephemeris data is the precise orbit information of the satellite itself and is updated about every hour. Almanac data is data indicating the approximate position of each GPS satellite, and includes data other than the transmitted GPS satellite. Almanac data is updated about every week. The ephemeris data and almanac data are also stored in the GPS receiver 1 and used for calculation, but are also configured to be temporarily stored in the memory 10.

  The GPS receiver 1 can acquire base station position information, GPS satellite information, time information, and the like by internally processing navigation messages from a plurality of GPS satellites. After the internal processing, the GPS receiver 1 outputs a 10 MHz clock and a 1 PPS (1 Pulse Per Second) signal, which is a time synchronization signal, to the counter 2, the control unit 3 and the calculation unit 6.

  The 10 MHz clock and 1 PPS signal are output with very accurate timing because correction is performed based on information from the GPS satellite based on the 10 MHz output of the built-in oscillator 11. As the oscillator 11, a double oven type OCXO (Oven Controlled Xtal Oscillator) or the like is employed. As a result, the operation of the base station in the holdover state (HOLDOVER: GPS satellites cannot be supplemented and correction is not applied by the time signal from the GPS satellites) can be made as long as possible.

  The GPS receiver 1 distributes and outputs the 1PPS signal to the frame timing control unit 3, the calculation unit 6, and the counter 2. In addition, a 10 MHz clock is distributed and output to the frame timing control unit 3 and the counter 2. Further, when the time signal cannot be received, the position information is output to the calculation unit 6 and the alarm information is output to the frame timing control unit 3 as a control signal. When the correction information (correction phase amount) is received from the frame timing control unit 3, the 1PPS signal is corrected.

  The counter 2 counts a 10 MHz clock from the rising edge of the 1PPS signal from the GPS receiver 1 and outputs the number of clocks to the arithmetic unit 6 sequentially. This count value is cleared by the arithmetic unit 6 as will be described later. Since the counter 2 always counts an accurate 10 MHz clock, the accuracy of the count result is kept at 0.1 usec.

  On the other hand, the radio wave input / output unit 5 wirelessly outputs the frame input from the frame generation unit 4 to the other base station from the antenna 9, and is wirelessly output from the other base station (referred to as the base station 200). The frame received at 9 is sent to the frame timing detection unit 7 via the radio wave input / output unit 5. In this way, communication is performed between the base station 100 and the base station 200.

  The frame timing detection unit 7 detects timing information and position information in the frame and sends them to the calculation unit 6. The timing information may include alarm data. If alarm data is not included, the frame can be assumed to have been received from a base station that has been successfully acquired by a GPS satellite.

  The arithmetic unit 6 transfers the 1PPS signal and the position information from the GPS receiver 1 to the frame timing control unit 3 in a normal state. However, when a timer operation start request is received from the frame timing control unit 3 that has received the alarm information, the base station that can be handed over waits for timing information and position information from the frame timing detection unit 7 within a predetermined time. Determine if it exists. As a result, if not found, the fact is notified to the frame timing control unit 3.

  On the other hand, when the base station 200 that can be handed over is found, the timing information and position information of the base station 200 are input from the frame timing detection unit 7, so that the base station 100 and the base station The timing shift of the base station 100 is obtained by subtracting the radio wave propagation delay time between 200. The deviation information is the apparent time difference between the 1PPS signal of the base station 100 and the 1PPS signal of the base station 200, and the timing deviation is the 1PPS signal of the base station 100 in which the radio wave propagation delay time is corrected to the deviation information and the 1PPS signal of the base station 200. The actual time difference of

  Here, it should be noted that the alarm information is naturally not included in the timing information from the base station 200. For this reason, the timing information is reliable and accurate time synchronization can be guaranteed by the obtained timing deviation. It is temporarily stored in the memory 10 together with the timing of the 1PPS signal from the GPS receiver 1.

  When the calculation unit 6 sends the timing deviation to the frame timing control unit 3 as correction information of the 1PPS signal and receives a notification from the frame timing control unit 3 that the corrected 1PPS signal can be output to the frame generation unit 4, the counter 6 2 is reset. The functions of the calculation unit 6 so far are those in the base station 100.

  When the arithmetic unit 6 in the base station 200 receives the alarm data from the frame timing detection unit 7, the arithmetic unit 6 acquires the deviation information between the base station 100 and the base station 200. For this purpose, the timing of the 1PPS signal in the base station 200 is determined from the timing information received from the frame timing detection unit 7, and the count result from the counter 2 at this timing is used as deviation information.

  The frame timing control unit 3 receives various status information and alarm information (control signal) from the GPS receiver 1 by serial communication via the RS-232C or the like. In addition, in order to change the state and status of the GPS receiver 1, it is configured to be able to change the setting or the like by serial communication. In a normal state, the 1PPS signal and position information from the calculation unit 6 are configured. Is output to the frame generation unit 4.

  However, when alarm information is received from the GPS receiver 1, a timer operation start request is made to the calculation unit 6. Then, based on the correction information from the calculation unit 6, it is determined whether the timing shift inside the base station 100 is within a predetermined accuracy. As a result of this determination, if there is no input of correction information within a predetermined accuracy within a predetermined time from the timer operation start request, the frame generation unit 4 stops the wireless output. The same applies when there is a notification that a base station capable of handover cannot be found.

  When the timing shift within the base station 100 is within a predetermined accuracy, correction information (correction phase amount) is sent to the GPS receiver 1. Further, when the corrected 1PPS signal from the GPS receiver 1 is received, it is output to the frame generation unit 4 and the fact is notified to the calculation unit 6.

  The frame generation unit 4 generates a frame based on the 1PPS signal from the frame timing control unit 3. At this time, timing information (including alarm information in some cases) and position information of the 1PPS signal are included in the frame. The generated frame is sent to the radio wave input / output unit 5.

  The radio wave input / output unit 5 outputs the frame input from the frame generation unit 4 by radio from the antenna 9 toward another base station. Communication with other base stations is performed by this frame. As a result, even if the base station 100 can no longer capture GPS satellites, the timing information is supplied from the base station 200 that can capture GPS satellites, and the timing from the UTC is corrected by correcting the timing of the 1PPS signal. The accuracy can be maintained.

  The GPS satellite capturing antenna 8 and the radio antenna 9 shown in FIG. 1 are well known to those skilled in the art and are not directly related to the present invention, and thus detailed configurations thereof are omitted.

  Next, the operation of this embodiment will be described with reference to the time chart of FIG. 3 and the flowcharts of FIGS.

  FIG. 3 shows data frames wirelessly communicated between base stations in time series. The data frame 301 transmitted from the base station 100 is synchronized with UTC, and has a common time timing which is effective for synchronization even when viewed from other base stations. By considering the difference between the time timing of the data frame 302 received by another base station and the time timing inside the base station as a time difference from UTC, it is possible to share the time timing between different base stations. it can.

  A data frame 301 transmitted from the base station 100 is transmitted to the base station 200. Since the base station 100 and the base station 200 are physically separated, a radio wave propagation delay occurs. A data frame 302 arrives at the base station 200 after the radio wave propagation delay time Ld1 has elapsed. The data frame 302 is processed in the base station 200. The data processing time Md in the base station 200 is unique to the apparatus and does not change with time. At this time, the data frame 302 is compared with the internal timing of the base station 200, and the degree of delay from the timing at which the base station 100 transmits the data frame 301 is measured and stored.

  Referring to FIG. 2, the arithmetic unit 6 of the base station 200 performs the period from the timing of the 1PPS signal from the GPS receiver 1 to the timing of the 1PPS signal calculated from the timing information included in the data frame 302. The number of 10 MHz clocks counted by counter 2 is used as the deviation information.

  After receiving the data frame 301 transmitted from the base station 100, data is transmitted to the base station 100 immediately after performing a predetermined treatment in the base station 200. The reason why the data is sent back immediately is to reflect the time timing shift at that time as soon as possible.

  Since the data frame 303 transmitted from the base station 2 is transmitted every predetermined time from the base station 200, a little waiting time occurs. The waiting time (= Fadj) at this time may always vary. Since the radio wave propagation delay from the base station 200 to the base station 100 is Ld2 = Ld1 because the spatial distance has not changed, the data frame 303 reaches the base station 100 as the data frame 304 after being delayed by Ld2 hours. . As a result, when data is exchanged from the base station 100 to the base station 200 and from the base station 200 to the base station 100, a temporally varying element is a waiting time Fadj.

  Therefore, in order to eliminate the time variation factor, it is important to perform processing so as not to include the waiting time Fadj. For this purpose, in the base station 200, the above-described deviation information is included in the data frame 303 as time difference information and sent back to the base station 100. As a result, in the base station 100, the time at the base station 100 is not based on the timing at which the data frame 304 is received, but on the deviation information in the timing information included in the data frame 304 and detected by the frame timing detection unit 7. Since the synchronization shift is determined, there is no need to consider Fadj.

  FIG. 4 shows a process when a GPS satellite cannot be captured. When a GPS satellite supplement impossible state occurs in the base station 100 (step S1 in FIG. 4), alarm data is transmitted from the base station 100 to the base station 200 which is another nearby base station (step S2). At this time, in the data frame to be transmitted to the base station 200, timing information of the 1PPS signal and possibly alarm information are placed. At the same time, the data frame number at which the data frame transmitted by the base station 100 is commonly recognized by other base stations is also placed.

  For example, a method of identifying the commonly recognized data frame number by an elapsed time from January 6, 1980, which is a GPS-TIME start time, can be considered. Employing the association with GPS-TIME is beneficial in time synchronization systems using other GPS. This is because of a common process of using a navigation message from a GPS satellite when considering the application of the system.

  When the alarm data arrives at the base station 200 (step S3), the calculation unit 6 of the base station 200 acquires the deviation information from the base station 100 (step S4), and obtains the deviation information and the position information of the base station 200. Transmit to the base station 100 (step S5). When deviation information and position information data arrive at the base station 100 (step S6), the calculation unit 6 calculates a time difference from the base station 200 (step S7).

  And the calculating part 6 determines whether this calculation result is less than predetermined precision (step S8). As a result, if it is within the predetermined accuracy, the operation is continued as usual (step S9). On the other hand, if it is out of the predetermined accuracy, the operation is stopped (step S10), and at the same time, an operation stop alarm is notified to the upper network or the like (step S11).

  FIG. 5 shows the details of the time difference calculation (step 4). How much the internal timing of the base station 100 is different from the internal timing of the normally operating base station 200 that normally receives other GPS satellites. This is to calculate whether the timing is shifted.

  In the base station 200, first, the position of the base station 100 is confirmed from the position information from the frame timing detector 7 (LCT1), and the position (LCT2) of the base station 200 is confirmed from the position information from the GPS receiver 1 (step T2). ) Next, a straight line distance D1 between the base station 100 and the base station 200 is calculated from LCT1 and LCT2 (step T3), and a radio wave propagation delay time is calculated (step T4).

  For example, when the radio wave propagation speed is simply c = 30,000 km / sec, if the spatial distance between the base station 100 and the base station 200 is 2 km, 2 km ÷ 30,000 km / sec≈6.7 usec, that is, the distance of 2 km It can be seen that about 6.7usec is required to transmit radio waves. Similarly, if the distance between base stations is known, the radio wave propagation delay time can be calculated. At this time, an error occurs depending on the surrounding environment (temperature, humidity, atmospheric pressure), etc., but it is not considered in the calculation because it is a negligible level if it is determined at 1 usec level. Therefore, the circuit can be simplified. In addition, since the ambient environmental conditions are not taken into consideration, the circuit can be simplified, and the application to other time synchronization systems can be simplified.

  Finally, by subtracting the calculated (step T4) radio wave propagation delay time from the deviation information of the arrival (step S6 in FIG. 4) (step T5), the timing deviation of the base station 100 is determined (step T6). .

  As described above, according to the present embodiment, even when the base station 100 cannot acquire a GPS satellite for some reason, if there is the base station 200 in a positional relationship capable of wireless communication with each other, It is possible to determine whether the internal timing of the base station 100 is within a predetermined accuracy. By making this determination possible, the ability performance of the oscillator 11 built in the GPS receiver 1 can be utilized to the maximum. As a result, it is not necessary to mount a very expensive oscillator employed for safety reasons, and the cost can be reduced.

  At the same time, even if a base station is equipped with an oscillator with the same performance, the time until operation stop determined based on the worst value of the oscillator can be continued on an actual value basis. Can take longer. Further, since the operation can be continued on the basis of the capability value, a lower-priced oscillator can be mounted if the same operation time is sufficient, and the cost can be reduced.

  Moreover, according to the present Example, since it is almost unnecessary to change the structure of the conventional base station apparatus, additional cost can also be suppressed low.

  In the above embodiment, the internal time timing level of the base station 100 is set to 1 usec level with respect to UTC. However, depending on the radio communication system employed, for example, it may be set to 10 usec level, and absolute time accuracy may be used. In systems where there is a margin due to misalignment, 10 usec is acceptable.

  In the above embodiment, only one base station 200 is able to capture GPS satellites, but a plurality of base stations may be used.

  In the above embodiment, a GPS receiver is used. However, GLONASS (Global Navigation Satellite System), Galileo (European version of satellite positioning system), a combination of GPS and GLONASS, or a combination of GPS and Galileo. It may be used, a combination of GLONASS and Galileo, or a combination of GPS, GLONASS, and Galileo.

  Moreover, in the said Example, although the double oven type OCXO is applied to the oscillator 100, if a single oven type oscillator is applied, cost can be reduced. However, the time until the deviation from UTC that the system can tolerate is shortened. Further, if an ovenless type oscillator such as TCXO (Temperature Compensated Crysal Oscillator) is applied, the cost can be further reduced. However, the time until the deviation from the UTC allowable by the system is exceeded is shorter than that when the single oven type OCXO is applied. It is also possible to use Rb oscillators, Cs oscillators, and more precise oscillators such as Rb oscillators (Rubidium) and Cs oscillators (Caesium), in which case the time allowed by the system is longer. can do. However, the cost increases.

  Moreover, in the said Example, although the communication system with a GPS receiver is RS-232C, the thing using RS-422, the thing using GP-IB, the thing using IrDA, or IEEE1394 is used. It is also possible to use a serial ATA (Serial AT Attachment), a PCI Express, a USB (Universal Serial Byus), or another parallel communication method.

  The basic configuration of the second embodiment of the present invention is as described above, but the GPS receiver 1 is further devised. The configuration is shown in FIG. In this figure, the GPS receiver 1 is a main operating unit, the GPS receiver 1-1 is a sub-operating unit, and a 1PPS signal and a 10 MHz clock from the GPS receivers 1 and 1-1 are selectively output by a selector 12.

  With this configuration, if the GPS receiver 1 fails for some reason, timing information synchronized with UTC can be obtained from another base station, the GPS receiver 1-1, which is a sub-operation device, performs a backup operation, and the time synchronization device Long-term operation is possible. In this configuration, when further device stability is required in the event of a failure, the number of GPS receivers that perform a backup operation may be three or more.

  Further, the basic configuration of the third embodiment of the present invention is as described above, but the antenna 8 for supplementing the GPS satellite is further devised. The configuration is shown in FIG. In this figure, the GPS satellite supplementing antenna 8 and the GPS satellite supplementing antenna 8-1 operate independently of each other.

  In this embodiment, when the antenna 8 fails for some reason (for example, failure due to induced lightning), the antenna 8-1 operates independently, so the GPS receiver 1-1 performs a backup operation and time synchronization. Equipment can be operated continuously. Similarly, when the GPS receiver 1 fails for some reason, the GPS receiver 1-1 performs a backup operation alone, and the time synchronization apparatus can be continuously operated.

DESCRIPTION OF SYMBOLS 1 GPS receiver 2 Counter 3 Frame timing control part 4 Frame generation part 5 Radio wave input / output part 6 Calculation part 7 Frame timing detection part 8 Antenna 9 Antenna 10 Memory 11 Oscillator 12 Selector 8-1 Antenna 1-1 GPS receiver 11-1 Oscillator 100 Base station 200 Base station

Claims (8)

In a base station time synchronization device using a time synchronization signal generated based on a time signal transmitted from a GPS satellite,
When the GPS satellite cannot be acquired, alarm information is included in a radio frame together with timing information of the time synchronization signal and transmitted to another base station. The other base station uses the timing information to indicate time shift information between its own base stations. send be included in the radio frame with the position information of the base station seeking, in the base station having received the radio frame to confirm that there are no alarm information, determined by the time shift information and the position information A time synchronization apparatus that corrects the time synchronization signal based on a timing shift. In a base station time synchronization device using a time synchronization signal generated based on a time signal transmitted from a GPS satellite,
A GPS receiver that outputs the time synchronization signal together with a high-accuracy clock and outputs alarm information when the time signal cannot be received;
A counter that counts and outputs the number of high-precision clocks from the rising edge of the time synchronization signal;
A frame generation unit that generates a radio frame including timing information of the time synchronization signal ;
A radio wave input / output unit that transmits and receives the radio frame to and from other base stations;
When there is the alarm information in the timing information, a calculation unit that calculates a timing shift between the base station and another base station receiving a time signal from the GPS satellite,
Frame timing for outputting timing information of the time synchronization signal to the frame generator when there is no alarm signal, and timing information of the time synchronization signal corrected by the GPS receiver based on the timing deviation when there is the alarm signal The other base station obtains time shift information from the timing information received by the radio wave input / output unit and the timing information of the own base station, and includes it in the radio frame together with the position information of the base station. Transmitting to the base station, and used for calculating the timing deviation from the base station . When the arithmetic unit of the other base station detects the alarm signal in the received radio frame, it obtains the count value of the time determined by the timing information included in the radio frame as the time shift information,
The frame timing control unit of the other base station outputs the time shift information to the frame generation unit,
When the arithmetic unit of the base station does not detect the alarm signal in the received radio frame, the arithmetic unit of the base station calculates the timing deviation by subtracting the radio wave propagation delay time between its own and other base stations from the timing based on the time deviation information. The time synchronizer according to claim 2. When the frame timing control unit receives alarm information from the GPS receiver, the frame timing control unit requests the calculation unit to start a timer operation, and determines whether the correction information due to the timing shift from the calculation unit is within a predetermined accuracy. , when the request for starting timer operation there is no input of the correction information within a predetermined accuracy within a predetermined time period, according to claim 2 or claim 3, characterized in that to stop the wireless output to the frame generation unit The time synchronizer described in 1. In a time synchronization method of a base station using a time synchronization signal generated based on a time signal transmitted from a GPS satellite,
When the GPS satellite cannot be captured, the alarm information is included in a radio frame together with the timing information of the time synchronization signal, and transmitted to another base station.
In the other base station, a procedure for obtaining time shift information between the base stations based on the timing information and transmitting it in a radio frame together with the position information of the base station ;
Characterized in that it has the steps in the base station having received the radio frame to confirm that there are no alarm information, corrects the time synchronization signal based on the timing deviation determined by the time shift information and the position information Time synchronization method. In a time synchronization method of a base station using a time synchronization signal generated based on a time signal transmitted from a GPS satellite,
Outputting the time synchronization signal together with a high-precision clock;
A procedure for outputting alarm information when the time signal cannot be received;
A procedure for counting and outputting the number of high-precision clocks from the rising edge of the time synchronization signal;
Generating a radio frame including timing information of the time synchronization signal ;
A procedure for transmitting and receiving the radio frame to and from another base station;
When there is the alarm information in the timing information, a procedure for calculating a timing shift between the base station and another base station receiving a time signal from the GPS satellite;
A procedure for outputting timing information of the time synchronization signal when there is no alarm signal, and outputting timing information of the time synchronization signal corrected based on the timing shift when there is the alarm signal ;
The other base station obtains time deviation information from the timing information received by the radio wave input / output unit and the timing information of the own base station, and transmits it to the base station by including it in the radio frame together with the base station position information. And a time synchronization method characterized by having a procedure for calculating the timing deviation from the base station . In the other base station, upon detecting the alarm signal in the received radio frame, a procedure for acquiring the count value of the time determined by the timing information included in the radio frame as the time shift information;
Including the procedure of transmitting the time offset information by including it in a radio frame,
In the base station, when the alarm signal is not detected in the received radio frame, the base station has a procedure for calculating the timing deviation by subtracting the radio wave propagation delay time between its own and other base stations from the timing based on the time deviation information. The time synchronization method according to claim 6. A procedure for making a timer operation start request upon receiving the alarm information;
A procedure for determining whether correction information due to the timing shift of the base station is within a predetermined accuracy;
8. The time according to claim 6, further comprising a step of stopping wireless output when correction information within a predetermined accuracy is not input within a predetermined time from the timer operation start request. Synchronizer.

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