JP2013153241A - Base station - Google Patents

Abstract

To provide a base station capable of maintaining synchronization accuracy even in a holdover state.
A base station 1 for processing a synchronization signal for synchronizing with another base station, wherein a selector 12 selects either a signal received from a GPS satellite or a signal received from another base station; And a synchronizer 10 that provides a reference pulse based on the signal selected by the selector 12, and in the holdover state, the selector 12 is configured to select a signal received from another base station.
[Selection] Figure 1

Description

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

  A base station that performs wireless communication generally uses a GPS satellite when establishing synchronization between base stations. All base stations are operated based on highly accurate clock information that can be acquired from GPS satellites. Furthermore, as a signal generated from clock information that can be acquired from a GPS satellite, there is generally a “1PPS signal” (GPS synchronization signal) that can be handled as a timing signal for operation of the apparatus.

  However, in the base station for PHS, the accuracy of the 1PPS signal timing signal is important. On the other hand, in the WiMAX base station and the LTE base station, since the radio frequency accuracy is also strictly regulated, a high-accuracy and maintenance-free oscillator that is the basis of the radio frequency accuracy is mounted in the base station. There is a need.

  Therefore, another way to use high-accuracy clock information from GPS satellites is to use the high-accuracy clock information as a reference, and by combining the oscillator output and PLL, eliminating the need for oscillator frequency calibration, Accurate frequency accuracy can be maintained.

  However, it is not guaranteed that clock information from GPS satellites can always be captured for the convenience of the base station installation environment. Therefore, even when the supply of high-accuracy clock information from the GPS satellite is stopped (this state is referred to as “holdover”), in order to continue the communication service by the base station, It is necessary to maintain the accuracy and the frequency accuracy of the oscillator output (hereinafter referred to as 10 MHz) as long as the communication service is not affected.

  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

  In order to maintain the accuracy of the 1PPS signal and the frequency accuracy of 10 MHz in the holdover state, an oscillator such as OCXO or rubidium (hereinafter referred to as OCXO) having a high frequency accuracy is generally used. Are expensive and large in size.

  In addition, since there is no high-accuracy clock information acquired from the GPS satellite that is the reference of the PLL in the holdover state, the control voltage to the OCXO is constant and the free-run state is entered. And the frequency accuracy of 10 MHz depend on the specification of the OCXO to be used. For this reason, the OCXO to be used is highly accurate as the accuracy required for maintaining the holdover is increased, the time required for maintaining the performance is increased, or the both are required simultaneously. Become expensive.

  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 a selector that selects either a signal received from a GPS satellite or a signal received from another base station; And a synchronizer that provides a reference pulse based on the signal selected by the selector.

  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.

  Further, the synchronization unit 10 receives the control channel (CCH) received from the control unit 40 via the RF unit 20, and provides the base station 1 with a control pulse (CCH_1PPS) that is a signal synchronized with the CCH. .

  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. After the control channel (CCH) is received and demodulated, the control unit 40 generates a CCH_1PPS signal and outputs the CCH_1PPS signal to the synchronization unit 10.

  For example, the PHS control channel (CCH) includes timing information that can be acquired from the CCH, and the control unit 40 can reference the timing information.

  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, and an oscillator 17.

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

  The selector 12 receives the GPS_1PPS and the CCH_1PPS transmitted from the control unit 40, selects one, 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 illustrated in FIG. 4, the synchronization unit 90 does not include the selector 12 that selects the CCH_1PPS signal.

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

  First, the selector 12 receives GPS_1PPS and CCH_1PPS transmitted from the control unit 40, and selects GPS_1PPS.

  Next, the base station 1 becomes unable to 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 CCH_1PPS.

  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 the CCH transmitted by another base station in the holdover state, and uses CCH_1PPS to synchronize with the timing information. Thus, the accuracy of the 1PPS signal at the time of holdover and the frequency accuracy of 10 MHz can be improved over a long period of time.

DESCRIPTION OF SYMBOLS 1 Base station 2 GPS antenna 10, 90 Synchronizing part 11 GPS receiving part 12 Selector 13 Frequency divider 14 Phase comparison part 15 Filter 16 DAC part 17 Oscillator 20 RF part 30 Modulation / demodulation part 40 Control part

Claims (2)

A base station that processes a synchronization signal for synchronizing with other base stations,
A selector for selecting either a signal received from a GPS satellite or a signal received from another base station;
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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