JP2013153242A - Base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station capable of keeping accuracy of synchronization even under s hold-over state.SOLUTION: A base station 1 for processing synchronization signals for synchronizing with other base stations comprises: a selector 12 for selecting any of signals received from a GPS satellite and other carrier synchronization signals; and a synchronization section 10 for providing a reference pulse based on the signals selected by the selector 12. The selector 12 is configured to select the signals received from the other base stations under a hold-over state.

Description

  The present invention relates to a base station that performs synchronization.

  Generally, as means for establishing synchronization between base stations, high-precision clock information transmitted from GPS satellites is received by a GPS module and input to the base station as a 1 pps signal to synchronize the base stations in the same carrier. By doing so, synchronization between base stations is performed. By continuously acquiring clock information from GPS satellites and correcting the clock synchronization circuit within the base station, synchronization between base stations of the entire system is performed.

  A GPS satellite used as a synchronization source for performing synchronization between base stations is assumed to be unable to be captured at all times due to the base station installation environment and the positional variation between the earth and the GPS satellite. Actually, there may occur a time when high-accuracy clock information from the GPS satellite of each base station is not captured. A function to continue the communication service is required even during this time (holdover). At the time of holdover, synchronization accuracy (frequency accuracy) is maintained by 1PPS signal based on clock information from GPS satellite before it can not be captured and high precision XTAL (crystal) provided in the base station, etc. When GPS capture is lost Will continue to communicate with terminals.

  In the holdover state, the base station must keep the accuracy of the internal pulse and the internal frequency signal within a predetermined range. In order to realize this, in the holdover state, a method for maintaining the accuracy of the internal pulse and the internal frequency signal within a predetermined range by using an oscillator having high frequency stability in the base station has been proposed (for example, Patent Document 1).

JP 2001-339373 A

  However, since the synchronization network between base stations is constructed based on high-accuracy clock information from GPS satellites, when the clock information from GPS satellites stops or is interrupted, the synchronization circuit provided in the base station When the synchronization holding time (holdover time) is exceeded, synchronization between base stations cannot be maintained. When synchronization between base stations cannot be maintained, when a terminal connected to a call synchronizes with another base station due to movement or the like (base station switching: handover), the call service cannot be continued.

  It is conceivable to improve the accuracy of the synchronization XTAL (crystal) mounted in the base station and extend the holdover possible time, but XTAL (crystal) for improving accuracy and maintaining accuracy for a long period of time is considered. Such devices are very expensive, large in size, and difficult to mount on commonly used base stations.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a base station capable of maintaining the accuracy of synchronization.

  The base station of the present invention is a base station that processes a synchronization signal for synchronizing with another base station, and includes a GPS receiver that receives a signal received from a GPS satellite and another carrier that receives another carrier synchronization signal. A synchronization signal transmission / reception unit; a selector that selects one of a signal received from a GPS satellite and another carrier synchronization signal; and a synchronization unit that provides a reference pulse based on the signal selected by the selector. doing.

  The base station of the present invention has a configuration in which the selector selects a signal received from another base station in a holdover state.

  The base station of the present invention can maintain synchronization accuracy.

It is a block diagram of the base station which concerns on embodiment of this invention. It is a block diagram of the synchronizing part which concerns on embodiment of this invention. It is a block diagram of the conventional base station. It is a block diagram of the conventional synchronizer.

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

  FIG. 1 is a block diagram of a base station according to an embodiment of the present invention. The base station 1 includes a synchronization unit 10, an RF unit 20, a modem unit 30, and a control unit 40. For example, the base station 1 is used in a time division multiplexing communication system.

  The synchronization unit 10 receives a GPS signal from a GPS satellite through the GPS antenna 2 and provides the base station 1 with an internal pulse (GPS — 1PPS) and an internal frequency signal that are signals synchronized with the GPS synchronization pulse. The synchronization unit 10 also receives a synchronization signal through the other carrier antenna 3 and provides the synchronization signal to the base station 1.

  The RF unit 20 receives a radio signal transmitted from another base station or a communication terminal via an antenna. The RF unit 20 transmits a transmission signal to be transmitted to the communication terminal via the antenna. Further, the RF unit 20 performs transmission / reception according to the synchronization signal provided by the synchronization unit 10.

  The modem unit 30 demodulates the signal received by the RF unit 20 and converts it into received data. In addition, the modem unit 30 modulates transmission data to be transmitted to the communication terminal and transmits a transmission signal to the communication terminal.

  The control unit 40 controls the components of the base station 1 together with the reception data and transmission data.

  FIG. 2 is a block diagram of a synchronization unit according to an embodiment of the present invention. The synchronization unit 10 includes a GPS reception unit 11, a selector 12, a frequency divider 13, a phase comparison unit 14, a filter 15, a DAC unit 16, an oscillator 17, and another carrier synchronization signal transmission / reception unit 18.

  The GPS receiver 11 receives a GPS signal from a GPS satellite through the GPS antenna 2.

  The selector 12 receives the other carrier synchronization signal from the GPS_1PPS and the other carrier synchronization signal transmission / reception unit 18, selects one of them, and outputs the selected reference pulse (Ref_1PPS) to the phase comparison unit 14.

The frequency divider 13 divides the internal frequency signal received from the oscillator 17 by a factor of 10 × 10 ⁶ to generate an internal pulse that is a 1 PPS signal, and the generated internal pulse is used as the phase comparison unit 14 and the control unit 40. To output.

  The phase comparison unit 14 compares the phase of the internal pulse received from Ref — 1PPS and the frequency divider 13 and outputs a signal obtained by multiplying the phase difference by the proportionality coefficient to the oscillator 17 via the filter 15 and the DAC unit 16.

  The filter 15 filters a signal, and the DAC unit 16 converts a digital signal into an analog signal.

  The oscillator 17 is adapted to provide a 10 MHz (megahertz) pulse. The oscillator 17 generates a 10 MHz (megahertz) pulse based on the above-described phase difference signal.

  A conventional base station is shown in FIG. The base station 1 includes a synchronization unit 90, an RF unit 20, a modem unit 30, and a control unit 40. A synchronization unit 90 of a conventional base station is shown in FIG. In addition, the same code | symbol is attached | subjected to the component similar to the base station 1. FIG.

  As shown in FIG. 4, the synchronization unit 90 does not have the selector 12 that selects another carrier synchronization signal.

  An operation of the base station 1 configured as described above will be described.

  First, the selector 12 receives the GPS_1PPS and the other carrier synchronization signal transmitted from the control unit 40, and selects GPS_1PPS.

  Next, the base station 1 cannot capture the GPS satellite, and the synchronization unit 10 (FPGA, MPU, etc.) recognizes that the holdover state has been reached, and instructs the selector 12 to switch to another carrier synchronization signal. Do it.

  When the GPS satellite can be captured and the normal state is restored, the synchronization unit 10 (FPGA, MPU, etc.) instructs the selector 12 to switch to GPS_1PPS.

  As described above, the base station according to an embodiment of the present invention obtains timing information from another carrier synchronization signal transmitted by another base station in a holdover state, and synchronizes with the timing information. By operating, it is possible to improve the accuracy of the 1PPS signal and the frequency accuracy of 10 MHz during a long-term holdover.

  Further, the base stations of other carriers are also synchronized between base stations based on clock information from GPS satellites. However, the PHS base station and base stations of other carriers are not synchronized between base stations. However, the clock information source from the GPS satellite that is the clock synchronization reference is the same, and the terminal module of the other carrier incorporated in the PHS base station that operates based on the clock information received and synchronized by the base station of the other carrier is Synchronized with base stations of other carriers. The PHS base station can synchronize with the clock information from the GPS satellite by having the function of obtaining the clock information from the GPS satellite from the terminal module of the other carrier incorporated therein. The clock synchronization signal can be extracted by processing such as performing time offset processing on the clock synchronization signal extracted from the transmission / reception signal from IEEE 1588 or another carrier base station.

DESCRIPTION OF SYMBOLS 1 Base station 2 GPS antenna 3 Other carrier antenna 10, 90 Synchronization part 11 GPS receiving part 12 Selector 13 Frequency divider 14 Phase comparison part 15 Filter 16 DAC part 17 Oscillator 18 Other carrier synchronous signal transmission / reception part 20 RF part 30 Modulation / demodulation part 40 Control unit

Claims (2)

A base station that processes a synchronization signal for synchronizing with other base stations,
A GPS receiver for receiving signals received from GPS satellites;
Other carrier synchronization signal transmission / reception unit for receiving another carrier synchronization signal;
A selector for selecting either a signal received from a GPS satellite or another carrier synchronization signal;
And a synchronization unit that provides a reference pulse based on the signal selected by the selector.   The base station according to claim 1, wherein the selector selects a signal received from another base station in a holdover state.

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