JP2015207883A - Base station and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station and a radio communication system, preventing the incapability of maintaining the synchronization of a communication frame, and making the prompt restoration of air synchronization in an original base station.SOLUTION: A base station synchronous with another base station through radio to perform frame synchronization includes: an acquisition unit 13 for acquiring an identifier of the other base station capable of synchronization; a detection unit 17 for detecting that synchronization fails during synchronization with the other base station; and a synchronous control unit 16 for switching the destination of synchronization when the synchronization fails during synchronization with the other base station, and for confirming whether or not the synchronization is restored. When the base station on which whether or not restoration is made is confirmed restores, the synchronous control unit 16 switches synchronization to the restored base station.

Description

  The present invention relates to a base station and a wireless communication system that communicate between base stations.

  In PHS (Personal Handy phone System), which is one of wireless communication systems, frame synchronization for aligning frame timing, line synchronization for maintaining frame timing, GPS synchronization, or air synchronization is performed. Frame synchronization is a process in which reference base stations serving as frame timing references are interspersed for each predetermined area, and neighboring base stations receive control signals sequentially around the reference base station to match the frame timings. The number of stages indicating the number of stages synchronized with the reference base station as the 0th order is called the order. The reference base station determines the frame timing by referring to the coordinated universal time (UTC) of the GPS satellite, and maintains the frame timing by line synchronization after the frame timing is determined.

  The synchronization for maintaining the frame timing is performed by adjusting (acceleration / deceleration) the basic clock of the base station so as to maintain the shift of the frame timing with respect to a predetermined reference clock. In line synchronization, synchronization is performed using an ISDN line clock, an optical line DSU (Digital Service Unit), or an ONU (Optical Network Unit) as a reference clock. In GPS synchronization, synchronization is performed using a 1 PPS signal transmitted from a GPS satellite as a reference clock (for example, Patent Document 1).

  When a GPS satellite becomes invisible in a base station that performs GPS synchronization (hereinafter referred to as a GPS synchronized base station), it cannot receive a 1PPS signal. In such a case, a pseudo 1PPS signal is generated by the holdover circuit. However, since the pseudo 1PPS signal is less accurate than the 1PPS signal, air synchronization is performed after a predetermined time has passed in the holdover state. In air synchronization, a control signal (CCH: Control CHannel) transmitted from a neighboring base station is received, and the base station's frame timing is used as a reference clock to correct (accelerate / decelerate) its own reference clock (for example, Patent Documents). 2).

  Here, a base station that requests air synchronization is called a synchronization request base station (SBU), and a base station that provides air synchronization is called a synchronization providing base station (NBU).

  FIG. 4 shows a conventional air synchronization procedure. First, SBU and NBU perform frame synchronization. The SBU monitors whether there is another base station within the reception range, and acquires an identifier (CSID) of a base station that can be received. Next, the SBU selects one CSID of a base station (NBU) capable of air synchronization. NBU distributes notification information confirmation for searching for synchronization destination candidates. If the SBU is an air-synchronizable base station, the SBU transmits a BH-LCH response request to the NBU. When the NBU returns a BH-LCH response in response to the BH-LCH response request, air synchronization is started.

  The backhaul link channel LCH (Link CHannel) is a channel used between base stations in the service channel establishment phase.

JP 2001-339373 A JP 2010-118726 A

  However, conventionally, the synchronization requesting base station (SBU) has only one synchronization providing base station (NBU) for air synchronization, and does not perform air synchronization with other synchronization providing base stations.

  As shown in FIG. 5, since NBU CCH may not be received, air synchronization fails and the clock accuracy of SBU cannot be maintained. For this reason, it is necessary to restart the air synchronization processing after the air synchronization failure, but since the air synchronization sequence is started again and the frame synchronization is started again, a long time is generated until the resynchronization is completed, and the synchronization cannot be maintained.

  Therefore, the present invention has been made to solve the conventional problems, and prevents the base station and the radio from quickly returning the air synchronization to the original base station while preventing the synchronization of the communication frame from being lost. An object is to provide a communication system.

  The base station of the present invention includes: an acquisition unit that acquires an identifier of another base station that can be synchronized in a base station that synchronizes wirelessly with another base station in order to perform frame synchronization; and the other base station A detection unit that detects that synchronization cannot be performed during synchronization, and a synchronization control unit that switches a synchronization destination and confirms whether or not the synchronization has been restored when synchronization cannot be performed during synchronization with the other base station. It has the composition provided with.

  The synchronization control unit of the base station of the present invention switches the synchronization to the restored base station when the base station that has confirmed whether or not the restoration is restored.

  The wireless communication system of the present invention is a wireless communication system in which the first base station synchronizes wirelessly with the second base station in order for the first base station to perform frame synchronization. An acquisition unit that acquires an identifier of a base station, a detection unit that detects that synchronization is lost during synchronization with the second base station, and synchronization that cannot be performed during synchronization with the second base station And a synchronization control unit for switching the synchronization destination to another base station and confirming whether or not the first base station has returned.

  The present invention provides a base station and a wireless communication system that prevent the synchronization of communication frames from being lost and quickly return air synchronization to the original base station.

It is a block diagram of the base station which concerns on embodiment of this invention. It is a sequence diagram which shows the air synchronization procedure which concerns on embodiment of this invention. It is a flowchart which shows the air synchronization procedure of the synchronous request | requirement base station (SBU) which concerns on embodiment of this invention. It is a figure which shows the conventional air synchronous procedure. It is a figure which shows the procedure when the conventional air synchronization is interrupted.

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

  FIG. 1 is a configuration diagram of a base station according to an embodiment of the present invention. The base station shown in FIG. 1 includes a transmission unit 11, a reception unit 12, a BS information acquisition unit 13, a BS information storage unit 14, a CSID selection unit 15, an air synchronization control unit 16, an NBU detection unit 17, and an air synchronization switching determination. The unit 18 is configured.

  The base station shown in FIG. 1 communicates in units of frames by time division multiplexing and complies with, for example, a PHS communication system.

  The transmission unit 11 is configured to transmit a radio signal, and the reception unit 12 is configured to transmit a radio signal.

  The BS information acquisition unit 13 is configured to monitor whether there is another base station within the reception range, and to acquire an identifier (CSID) of each base station that can be received. The BS information storage unit 14 is configured to store the acquired CSID.

  The CSID selection unit 15 is configured to select the most appropriate CSID among the acquired CSIDs. An appropriate CSID is, for example, the CSID of a base station having the best reception sensitivity among neighboring base stations.

  The air synchronization control unit 16 is configured to perform air synchronization with the CSID base station stored in the BS information storage unit 14.

  The NBU detection unit 17 is configured to detect that the NBU CCH cannot be received during air synchronization.

  The air synchronization switching determination unit 18 is configured to determine whether or not to switch the air synchronization destination NBU based on detection by the NBU detection unit 17.

  The air synchronization control unit 16 is configured to switch the synchronization destination and confirm whether or not the synchronization has been restored when synchronization becomes impossible during synchronization with another base station. Further, the air synchronization control unit 16 is configured to switch the air synchronization to the restored base station when it returns.

  FIG. 2 is a sequence diagram showing an air synchronization procedure according to the embodiment of the present invention.

  First, frame synchronization is performed between the SBU and the NBU, and when the NBU detection unit 17 detects that the CBU transmission of the NBU is stopped during the air synchronization, the SBU selects another air-synchronizable base station. If there is another air-synchronizable base station, the air-synchronization is switched to this base station.

  Meanwhile, the SBU monitors whether or not the NBU for which CCH transmission has been stopped has recovered, and when the base station recovers, the SBU receives the broadcast information confirmation and transmits a BH-LCH response request to the NBU. The NBU returns a BH-LCH response in response to the BH-LCH response request. When the SBU receives this BH-LCH response, the SBU switches based on air synchronization.

  FIG. 3 is a flowchart showing an air synchronization procedure of the synchronization request base station (SBU) according to the embodiment of the present invention. FIG. 3A is a flowchart showing an air synchronization procedure, and FIG. 3B is a flowchart showing a procedure when an NBU is interrupted during air synchronization.

First, the SBU performs frame synchronization (S1). The SBU monitors whether there is another base station within the reception range (S2), and acquires and holds identifiers (CSIDs) of all base stations that can be received (S3). Next, the SBU selects one CSID of the base station (NBU) capable of air synchronization (S4).
When the NBU distributes notification information confirmation for searching for synchronization destination candidates, the SBU receives the notification information confirmation (S5).

  If the SBU is a base station capable of air synchronization, the SBU transmits a BH-LCH response request to the NBU, and the NBU returns a BH-LCH response in response to the BH-LCH response request (S6). When the SBU receives this BH-LCH response (S7), it starts air synchronization (S8).

  Next, when the NBU detection unit 17 detects that the CBU transmission of the NBU is stopped during the air synchronization, the SBU checks whether there is a CSID of another base station (NBU) capable of air synchronization (NBU) ( S11). When there is another CSID (for example, the ID of the base station having the second best reception sensitivity), the SBU switches the air synchronization to this NBU when receiving the notification information confirmation of the NBU of the other CSID (S12). .

At the same time, the SBU monitors whether or not the base station that has stopped transmitting CCH has returned (S13). When the base station recovers (S14), the SBU receives the broadcast information confirmation and receives a BH-LCH response request. To the NBU, and the NBU returns a BH-LCH response in response to the BH-LCH response request (S15). When the SBU receives this BH-LCH response, the SBU switches based on air synchronization (S16).

  As described above, the base station according to the embodiment of the present invention acquires the identifier of an NBU that can be synchronized, and when synchronization cannot be performed during synchronization with the NBU, the synchronization destination is switched to another NBU. When the base station that has confirmed whether or not has returned, the synchronization is switched to the recovered base station, so that the synchronization of the communication frame is prevented from being lost, and air synchronization is performed with the original base station. To return quickly.

  When the SBU cannot synchronize with the NBU, the SBU maintains the clock accuracy of the SBU by performing air synchronization with other NBUs. Thereby, “frame synchronization” which is one of the air synchronization procedures can be omitted. Also, by holding the CSID of the NBU that was previously air-synchronized, the “notification information confirmation” procedure can be omitted.

DESCRIPTION OF SYMBOLS 11 Transmission part 12 Reception part 13 BS information acquisition part 14 BS information storage part 15 CSID selection part 16 Air synchronization control part 17 NBU detection part 18 Air synchronization switching determination part

Claims (3)

In the base station that synchronizes wirelessly with other base stations to perform frame synchronization,
An acquisition unit that acquires identifiers of other base stations that can be synchronized;
A detection unit for detecting that synchronization cannot be performed during synchronization with the other base station;
A base station comprising: a synchronization control unit that switches a synchronization destination and confirms whether or not the synchronization is restored when synchronization becomes impossible during synchronization with the other base station.   The base station according to claim 1, wherein the synchronization control unit switches synchronization to the restored base station when the base station that has confirmed whether or not the restoration is restored. In a wireless communication system in which a first base station synchronizes wirelessly with a second base station in order to perform frame synchronization,
The first base station is
An acquisition unit that acquires identifiers of other base stations that can be synchronized;
A detection unit for detecting that synchronization cannot be performed during synchronization with the second base station;
A radio comprising: a synchronization control unit that switches a synchronization destination to another base station and confirms whether or not the first base station has returned when synchronization becomes impossible during synchronization with the second base station Communications system.

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