JP2006217359A - Synchronizing device and method of mobile communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synchronizing device and a synchronizing method of a mobile communication system, which are capable of accurately keeping timing synchronization between respective base stations to maintain synchronous communication even in the case that a GPS time broadcast signal cannot be received and line signals of only independent wired transmission lines can be obtained. <P>SOLUTION: A terrestrial digital reception part 15 and a clock extraction part 16 for receiving a terrestrial digital broadcast signal and extracting a clock from the reception signal are provided in addition to a line interface 13 for extracting a clock from a line signal of a wired transmission line and a GPS reception part 11 as well as a PPS reception part 12 for generating a clock from a time signal from a GPS communication satellite. Thus timing synchronization between respective base stations can be accurately kept to maintain synchronous communication even in the case that the GPS time signal cannot be received and line signals of only independent wired transmission lines can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a synchronization device and a synchronization method suitable for use in a mobile communication system such as a mobile phone system.

  Conventionally, in a mobile communication system employing a CDMA (Code Division Multiple Access) system, in order to obtain accurate timing synchronization between base stations, a clock extracted from a wired transmission path (a line provided by a communication carrier) or A time signal received from a GPS (Global Positioning System) communication satellite is used. Also, a GPS receiver that receives a time signal from the GPS communication satellite and a local clock generator are provided. When the time signal from the GPS communication satellite cannot be received, the RTC (Real Some devices use Time Clock (for example, see Patent Document 1).

  In particular, the system disclosed in Patent Document 1 generates a PPS (Pulse Per Second) clock based on a received time signal from a GPS communication satellite, performs timing synchronization with the PPS clock, and generates a PPS clock. The PSC (PPS Signal Counter) value obtained by counting the PPS signal to be compared is compared with the second information of the RTC clock. If the PSC value and the second information of the RTC clock do not match, the second information of the RTC clock is corrected. Thus, when the time signal from the GPS communication satellite cannot be received, the RTC is used for synchronization.

Japanese Patent Laid-Open No. 11-154920

  However, in the synchronization method in the conventional mobile communication system, when the GPS time signal cannot be received, the clock extracted from the line signal of the wired transmission path or the RTC generated by the local clock generator should be used. However, since the RTC generated by the local clock generator is low in accuracy, some of the wired transmission lines other than the wired transmission line provided by a major telecommunications carrier are inaccurate. There is a possibility that the timing synchronization between them may lack accuracy, and it may be difficult to maintain synchronous communication.

  The present invention has been made in view of the above points, and even when the GPS time signal cannot be received and the line signal of the wired transmission path can only be obtained from the independent wired transmission path, It is an object of the present invention to provide a synchronization apparatus and a synchronization method for a mobile communication system that can maintain timing communication accurately and maintain synchronous communication.

The object is achieved by the following configuration or method.
(1) In a synchronization device that synchronizes timing between base stations of a mobile communication system, a first clock acquisition unit that acquires a clock from a line signal of a wired transmission path, and a time signal transmitted from a communication satellite for positioning Second clock acquisition means for acquiring a clock based on a signal; third clock acquisition means for receiving a terrestrial digital broadcast and acquiring a clock from the terrestrial digital broadcast signal; and the first clock acquisition means; Of the second clock acquisition unit and the third clock acquisition unit, a clock selection unit that selectively selects a clock that can be acquired according to a predetermined priority order due to a difference in accuracy; A reference clock generator for generating a reference clock for synchronizing the timing between the base stations from the clock selected by the clock selection means And a step.

  (2) In the synchronization device of the mobile communication system according to (1), the clock selection unit is configured such that the clock acquired by the first clock acquisition unit is a wired transmission path provided by a major communication carrier. If it is not derived from the line signal, the next priority clock is selected.

  (3) In a synchronization method for timing synchronization between base stations of a mobile communication system, a clock is extracted from a line signal of a wired transmission path, and a PPS clock is extracted from a time signal transmitted from a communication satellite for positioning. Generate and extract the clock from the terrestrial digital broadcasting signal, and select one of these clocks according to the priority determined in advance according to the difference in accuracy. A reference clock is generated for timing synchronization between the base stations.

  (4) In the synchronization method of the mobile communication system according to (3) above, the clock extracted from the line signal of the wired transmission path is obtained from the line signal of the wired transmission path provided by a major communication carrier Otherwise, the next priority clock is selected.

  In the synchronization device for a mobile communication system described in (1) above, a clock is acquired from a line signal of a wired transmission path, a PPS clock is acquired from a time signal transmitted from a communication satellite for positioning, and terrestrial digital broadcasting The clock is acquired from the signal, and one of these clocks that can be acquired is selected according to the priority order determined in advance by the difference in accuracy, and the timing synchronization between the base stations is selected from the selected clock. The timing clock between the base stations can be accurately synchronized even when the time signal cannot be received and the line signal of the wired transmission line can only be obtained from an independent wired transmission line. It is possible to maintain synchronous communication.

  In the synchronization device of the mobile communication system described in (2) above, when the line signal of the wired transmission path can be obtained only as an independent one other than the wired transmission path provided by a major communication carrier, Since the clock is selected, the reliability can be improved because the clock from the wired transmission line with unknown clock accuracy is not selected.

  In the synchronization method of the mobile communication system described in (3) above, even when the time signal cannot be received and the line signal of the wired transmission path can only be obtained from the independent wired transmission path, It becomes possible to maintain timing synchronization accurately and maintain synchronous communication.

  In the synchronization method of the mobile communication system described in (4) above, when the line signal of the wired transmission path can be obtained only as an independent signal other than the wired transmission path provided by the major communication carrier, Since the clock is selected, the reliability can be improved because the clock from the wired transmission line with unknown clock accuracy is not selected.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a synchronization device of a mobile communication system according to an embodiment of the present invention. In this figure, the synchronization device 100 of the present embodiment includes a GPS antenna 10, a GPS receiver 11, a PPS receiver 12, a line interface 13, a UHF antenna 14, a terrestrial digital receiver 15, a clock extractor 16, and a clock selection. A unit 17 and a digital PLL (Phase Locked Loop) 18 are provided. Although not shown, the synchronization device 100 of the present embodiment includes a control unit (CPU: central processing unit), and each unit of the device is controlled by the control unit.

  The GPS receiver 11 receives a time signal provided by a GPS communication satellite (positioning communication satellite) (not shown) by the GPS antenna 10 and outputs a PPS signal. The PPS receiver 12 generates and outputs a PPS clock based on the PPS signal. The line interface 13 connects to the wired transmission path 30 provided by the communication carrier, extracts a clock from the line signal of the wired transmission path 30, and outputs it. In this case, the clock extraction in the line interface 13 is performed by a clock extraction unit 13A provided in the line interface 13.

  The terrestrial digital receiver 15 receives a digital broadcast signal transmitted from a terrestrial digital broadcast station (not shown). FIG. 2 is a block diagram showing a schematic configuration of the terrestrial digital receiving unit 15. The RFIF (high frequency amplification, intermediate frequency conversion) unit 151, the ADC (analog / digital conversion) unit 152, and the synchronization detection / OFDM demodulation unit 153. And. The modulated wave signal captured by the antenna 14 is input to the RFIF unit 151, and only the selected channel is extracted, then converted to digital by the ADC unit 152, and input to the synchronization detection / OFDM demodulation unit 153. .

  Synchronization detection / OFDM demodulation section 153 performs synchronization processing, detection processing, etc., and outputs a transport stream signal (TS signal). This transport stream signal is input to the clock extraction unit 16. The clock extraction unit 16 performs clock extraction from the transport stream signal input from the terrestrial digital reception unit 15 and reproduces a clock according to the rubidium oscillator accuracy.

  The clock selection unit 17 selects any one of a PPS clock obtained from a time signal from a GPS communication satellite, a clock obtained from a line signal of the wired transmission path 30, and a clock obtained from terrestrial digital broadcasting. When these clocks are selected, first, the presence or absence of the clock is determined, and if there is only one, it is selected, and if there are a plurality of clocks, one that matches according to the accuracy (variation) of the frequency is selected.

  Selection when there are a plurality is performed based on a preset priority order. In the present embodiment, (1) a line signal of a wired transmission path, (2) a GPS time signal, and (3) a terrestrial digital broadcast signal as priorities. The clock selection unit 17 is provided with a priority table 17A for determining the selection order, and the clock selection unit 17 performs selection using the priority table 17A.

  The reason why the line signal of the wired transmission path is given the highest priority is that the GPS receiving unit 11 cannot receive the time signal of the GPS communication satellite or is located in an area where it is difficult to receive, or the packet by the interrupt or polling method. This is because there is a case where it is difficult to perform transmission and reception, and there is a case where the terrestrial digital reception unit 15 is also located in an area where reception is difficult. On the other hand, for wired transmission lines, infrastructure development is progressing so that communication is possible in almost all areas in the current environment where people live, and the clock accuracy of the line signals of large telecommunications carriers is very high. It is expensive. Therefore, the wired transmission line is given top priority. However, in the case of an original wired transmission line (line) other than a major telecommunications carrier, it is unknown whether the clock accuracy is high, and if it is low, another means is selected.

  The clocks obtained from the GPS time signal and the terrestrial digital broadcast signal have substantially the same accuracy, but at present, the terrestrial digital broadcast infrastructure is not established nationwide. The priority was set lower than the GPS time signal.

  In FIG. 1, a digital PLL 18 detects a phase difference between an input digital signal and an output digital signal and controls a VCO and a circuit loop to transmit a signal having a precisely synchronized frequency. A high-accuracy reference clock is generated using the clock selected in step 1 as an input digital signal.

  The clock extraction unit 13A corresponds to the first clock acquisition unit. The GPS receiving unit 11 and the PPS receiving unit 12 constitute a second clock acquisition unit. The terrestrial digital reception unit 15 and the clock extraction unit 16 constitute a third clock acquisition unit. The clock selection unit 17 and the priority order table 17A constitute clock selection means. The digital PLL 18 corresponds to reference clock generation means.

  Next, the operation of the synchronization device 100 configured as described above will be described. When a time signal from the GPS communication satellite is received, a PPS signal is generated from the received time signal, and a PPS clock is generated based on the generated PPS signal. If there is a line signal of the wired transmission path 30, a clock is extracted from the line signal. When terrestrial digital broadcasting is received, a clock is extracted from the transport stream signal.

  When there is only one of a time signal, a line signal, and a terrestrial digital broadcast signal, timing synchronization is taken based on the clock. When there are a plurality, the frequency is selected with accuracy. That is, the selection is performed with a predetermined priority. For example, when there are all, the clock from the wired transmission line 30 having the highest priority is selected. However, if the wired transmission path 30 is not that of a major communication carrier and is an original wired transmission path, the PPS clock generated from the time signal from the GPS communication satellite with the next highest priority is selected.

  If there is a PPS clock generated from the time signal from the GPS communication satellite and a clock extracted from the terrestrial digital broadcast signal of the terrestrial digital broadcast, the PPS clock generated from the time signal from the GPS communication satellite is selected. Is done. For the selected clock, a high-precision reference clock is generated by the digital PLL 18, and timing synchronization is achieved by this clock.

  As described above, according to the synchronization device 100 of the mobile communication system of the present embodiment, the clock extraction unit 13A of the line interface 13 that extracts the clock from the line signal of the wired transmission path 30 and the time signal from the GPS communication satellite. In addition to the GPS receiver 11 and the PPS receiver 12 that generate the clock, the terrestrial digital receiver 15 and the clock extractor 16 that receive the terrestrial digital broadcast signal and extract the clock from the received signal, Even when the GPS time signal cannot be received and the line signal of the wired transmission path can only be obtained from an independent wired transmission path, it is possible to maintain synchronized communication by accurately maintaining timing synchronization between the base stations. It becomes possible.

  In addition, if the line signal of the wired transmission path can be obtained only as an independent one other than the wired transmission path provided by a major carrier, the next priority clock is selected, so the wired transmission path with unknown clock accuracy. The reliability can be improved by not selecting the clock from

  In the above embodiment, when the terrestrial digital broadcasting has become widespread and infrastructure has been improved, the priorities described above may be reversed. That is, (1) a wire transmission line signal, (2) a terrestrial digital broadcast signal, and (3) a GPS time signal.

  Also, when terrestrial digital broadcasting has become widespread, it can be obtained more reliably than when a clock is obtained from a GPS communication satellite, and therefore the GPS receiver 11 and the PPS receiver 12 can be omitted. If these are omitted, the cost can be greatly reduced. In addition, since an existing antenna cable can be used in the building, work costs such as cable installation can be reduced.

  Further, in the above embodiment, a local clock generator is added so that the second information of the RTC clock is compensated with a clock periodically obtained from a time signal from a GPS communication satellite or a terrestrial digital broadcast signal. good.

  Even when the GPS time signal cannot be received and the line signal of the wired transmission path can only be obtained from an independent wired transmission path, the present invention can maintain synchronous timing synchronization between base stations accurately. And can be applied to mobile communication systems such as mobile phone systems.

1 is a block diagram showing a schematic configuration of a synchronization device of a mobile communication system according to an embodiment of the present invention. The block diagram which shows schematic structure of the terrestrial digital receiver which comprises the synchronizer of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 GPS antenna 11 GPS receiving part 12 PPS receiving part 13 Line interface 13A Clock extracting part 14 UHF antenna 15 Terrestrial digital receiving part 16 Clock extracting part 17 Clock selecting part 17A Priority order table 18 Digital PLL
30 Wired Transmission Line 100 Synchronizer 151 RFIF Unit 152 ADC Unit 153 Synchronization Detection / OFDM Demodulation Unit

Claims (4)

In a synchronization device that synchronizes timing between base stations of a mobile communication system,
First clock acquisition means for acquiring a clock from a line signal of a wired transmission path;
Second clock acquisition means for acquiring a clock based on a time signal transmitted from a communication satellite for positioning;
Third clock acquisition means for receiving terrestrial digital broadcast and acquiring a clock from the terrestrial digital broadcast signal;
Of the first clock acquisition unit, the second clock acquisition unit, and the third clock acquisition unit, one that can acquire a clock is selected according to a predetermined priority order due to a difference in accuracy. Clock selection means to select,
Reference clock generation means for generating a reference clock for timing synchronization between the base stations from the clock selected by the clock selection means;
A synchronization device for a mobile communication system comprising:   If the clock acquired by the first clock acquisition unit is not obtained from a line signal of a wired transmission line provided by a major telecommunications carrier, the clock selection unit selects a clock having the next priority. The synchronization device for a mobile communication system according to claim 1. In a synchronization method for synchronizing timing between base stations of a mobile communication system,
The clock was extracted from the line signal of the wired transmission path, the PPS clock was generated from the time signal transmitted from the positioning communication satellite, the clock was extracted from the terrestrial digital broadcast signal, and the clock could be obtained. Synchronization method for a mobile communication system in which a clock is alternatively selected according to a predetermined priority order according to a difference in accuracy, and a reference clock for generating timing synchronization between base stations is generated from the selected clock .   The clock of the next priority is selected if the clock extracted from the line signal of the wired transmission path is not obtained from the line signal of the wired transmission path provided by a major communication carrier. A synchronization method for a mobile communication system.

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