JP2012164222A - Time synchronization method and computer system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a time synchronization method and a computer system for promptly detecting time deviation at a base station as a time synchronization source.SOLUTION: In a time synchronization method, a communication controller for controlling plural base stations synchronizes time with any of the plural base stations in a computer system including the plural base stations and the communication controller. The method includes: a step in which each of the plural base stations transmits a message with time information on the base station added thereto to the communication controller; a step in which the communication controller calculates a difference value between the time information on the base station and time information on the communication controller for each base station on the basis of the message received from each of the plural base stations, and stores the calculated difference value in a time difference table; and a step in which, when the calculated difference value is larger than a predetermined threshold, the communication controller calculates an average value of the difference values of the plural base stations stored in the time difference table, and determines that the base station having a difference value whose difference from the calculated average value is the largest is abnormal.

Description

  The present invention relates to a time synchronization method and a computer system.

  In a computer system including a plurality of base stations and a communication control device that controls the plurality of base stations, when the communication control device is time-synchronized with one specific base station, there are the following problems: .

  The problem is that when a time lag (time irregularity due to GPS failure) occurs in the time synchronization destination base station, the communication control device cannot detect this time lag and is affected by the time synchronization destination base station. Was to be set to an incorrect time. Furthermore, the communication control device set at an incorrect time originally recognizes another base station at the correct time as an illegal base station.

  As a technique for solving the above problem, a technique described in Patent Document 1 is known. In Patent Literature 1, “the time information of the own station (communication control device), that is, the time information transmitted from the own station to the reference station (base station) 1 and the time information received by the own station from the reference station 1 are compared. As a result of the comparison, it is determined whether the difference between them is smaller or larger than a certain time, and the above determination is repeated for the reference stations 2 to N. After that, based on the ratio of the reference stations whose difference is smaller than the certain time to all the reference stations. "It is determined whether the time information of the own station is correct or abnormal."

  Further, in Patent Document 1, as a method for selecting a new reference station, “a reference station that has notified itself as being abnormal and a reference station that has been determined to be abnormal by 50% or more of the reference stations among all the reference stations” are disclosed. It is regarded as abnormal, and other base stations are regarded as normal.After that, the local station receives time information from the base station with the smallest serial number among the base stations regarded as normal and uses it as its own time information. Is disclosed.

Japanese Patent Laid-Open No. 5-108198

  However, in the method disclosed in Patent Document 1, since it is necessary to repeat the above determination for all the reference stations, there is a problem that it is not possible to quickly detect the time lag of the time synchronization destination reference station. For example, when there is even one reference station whose difference from the time of its own station is greater than a certain time, the reference station is immediately identified, and if the reference station is a time synchronization destination, a new time synchronization destination reference station is selected. Although it is desirable to select, such a process could not be realized.

  Further, in the method for selecting a reference station disclosed in Patent Document 1, even a reference station determined to be abnormal by 40% of all reference stations can be regarded as normal (to a new time synchronization destination reference station). Can be). Also, since the reference station with the smallest serial number among the reference stations regarded as normal is used as a new time synchronization destination reference station, it cannot be said that the optimum reference station has been selected.

  An object of the present invention is to provide a time synchronization method and a computer system for quickly detecting a time lag of a time synchronization destination base station in consideration of the above-described problems.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present application includes a plurality of means for solving the above-described problems. For example, in a computer system including a plurality of base stations and a communication control apparatus that controls the plurality of base stations, the communication control is performed. A time synchronization method in which a device synchronizes time with any of the plurality of base stations, each of the plurality of base stations transmitting a message with time information of the base station to the communication control device; The communication control device calculates a difference value between the time information of the base station and the time information of the communication control device for each base station based on a message received from each of the plurality of base stations, and calculates The stored difference value in the time difference table, and the communication control device, when the calculated difference value is greater than a predetermined threshold, the plurality of bases stored in the time difference table Calculates an average value of the difference value of the station, the procedure for determining the difference between the calculated average value is abnormal base station having the largest difference value, characterized in that it comprises a.

  ADVANTAGE OF THE INVENTION According to this invention, the time shift of the base station of a time synchronization destination can be detected rapidly.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a figure which shows the structural example of the computer system of embodiment of this invention. It is a figure which shows the operation | movement sequence in the computer system of embodiment of this invention. It is a reference figure for demonstrating the computer system of embodiment of this invention. It is a flowchart which shows the reference operation of the computer system of embodiment of this invention. It is a block diagram which shows the function structural example of PCF-SC of embodiment of this invention. It is a figure explaining the example of a change of the time synchronization destination of PCF-SC of embodiment of this invention. It is a flowchart which shows the control logic when PCF-SC of embodiment of this invention receives an ICMP message from each AP. It is a figure which shows an example of the time difference table before the change of embodiment of this invention. It is a figure which shows an example of the time difference table after the change of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of a computer system 1 according to the embodiment of this invention. A computer system 1 shown in FIG. 1 includes an IP-NW 101, a PDSN (Packet Data Service Node) 102, an OMS (Operation and Maintenance System) 105, a RAN (Radio Access Network) 106, and a plurality of ATs (Access Terminals) 107- 1-107-8 (hereinafter collectively referred to as "AT107") and AN-AAA (Access Network-Authentication Authorization Accounting) 108.

  The IP-NW 101 is an IP network (computer network) interconnected using Internet protocol technology. The PDSN 102 is an IP packet terminating device. The OMS 105 is a device that controls and monitors each AP 104-1 to 104-4 (hereinafter collectively referred to as “AP 104”) and the PCF-SC 103 in the RAN 106.

  The RAN 106 includes a PCF-SC (Packet Call Function Session Control, communication control device) 103 and a plurality of APs (Access Points, base stations) 104 and is a wirelessly accessible network.

  The PCF-SC 103 is a communication control device that performs session management of each AT 107 and transfer control of packets received from each AP 104 and PDSN 102. A plurality of APs 104 are connected to the PCF-SC 103 and periodically receive ICMP (Internet Control Message Protocol) messages 109-1 to 109-4 from each AP 104. The PCF-SC 103 designates one of the plurality of APs 104 as a time synchronization destination, and performs time synchronization with the designated AP 104.

  AP 104 is a base station for transmitting and receiving radio signals between RAN 106 and AT 107. The AT 107 is a terminal device (computer device) used by a user of the computer system 1. For example, a wireless terminal such as a mobile phone. AN-AAA 108 is a device for authenticating AT 107.

  As described above, the computer system 1 according to the embodiment of this invention is a 1xEVDO RAN system in which one PCF-SC 103 and a plurality of APs 104 are arranged in a RAN 106.

  FIG. 2 is a diagram showing an operation sequence in the computer system 1 according to the embodiment of this invention. Various operations when the AT 107 uses a voice call or web browsing service provided by a service providing apparatus (not shown, the same applies hereinafter) connected via the PDSN 102 will be described with reference to FIG.

(Connection establishment processing 209)
First, the connection establishment process 209 will be described. The connection establishment process 209 is a process in which the AT 107 establishes a connection with the service providing apparatus.

  The AT 107 transmits an identifier request 201 to the PCF-SC 103 via the AP 104. The PCF-SC 103 transmits an authentication request 202 to the AN-AAA 108. The AN-AAA 108 executes an authentication process in response to the authentication request 202 and transmits an authentication response 203 as an authentication result to the PCF-SC 103. The PCF-SC 103 transmits an identifier response 204 to the AT 107.

  Thereafter, the AT 107 transmits a connection request 205 to the PCF-SC 103 via the AP 104. The PCF-SC 103 transmits a connection request 206 corresponding to the connection request 205 to the PDSN 102. The PDSN 102 establishes a connection in response to the connection request 206 and transmits a connection response 207 indicating that the connection has been established to the PCF-SC 103. The PCF-SC 103 transmits a connection response 208 corresponding to the connection response 207 to the AT 107.

(Packet reception processing 212)
Next, the packet reception process 212 will be described. The packet reception process 212 is a process in which the AT 107 receives a packet from the service providing apparatus.

  The PCF-SC 103 receives the packet 210 from the PDSN 102. Thereafter, the AT 107 receives a packet 211 corresponding to the packet 210 from the PCF-SC 103.

(Packet transfer waiting process 217)
Next, the packet transfer waiting process 217 will be described. The packet transfer waiting process 217 is a process in which the AT 107 temporarily stops using the service provided by the service providing apparatus.

  The AT 107 transmits a Dormant request 213 to the PCF-SC 103. The Dormant request 213 is a request to stop connection to the service providing apparatus. The PCF-SC 103 transmits a Dormant request 214 corresponding to the Dormant request 213 to the PDSN 102.

  The PDSN 102 stops the connection to the service providing apparatus in response to the Dormant request 214 and transmits a Dormant response 215 indicating that the connection has stopped to the PCF-SC 103. The PCF-SC 103 transmits a Dormant response 216 corresponding to the Dormant response 215 to the AT 107.

(Packet transfer start process 222)
Next, the packet transfer start process 222 will be described. The packet transfer start process 222 is a process for resuming the use of the service once stopped by the AT 107.

  The AT 107 transmits an Active request 218 to the PCF-SC 103. The Active request 218 is a reconnection request to the service providing apparatus. The PCF-SC 103 transmits an Active request 219 corresponding to the Active request 218 to the PDSN 102.

  The PDSN 102 executes reconnection to the service providing apparatus in response to the Active request 219 and transmits an Active response 220 indicating that the connection has been established to the PCF-SC 103. The PCF-SC 103 transmits an Active response 221 corresponding to the Active response 220 to the AT 107.

(Packet transmission processing 225)
Next, the packet transmission process 225 will be described. The packet transmission process 225 is a process in which the AT 107 transmits a packet to the service providing apparatus.

  The AT 107 transmits a packet 223 to the PCF-SC 103. Thereafter, the PCF-SC 103 transmits a packet 224 corresponding to the packet 223 to the PDSN 102.

(Connection disconnection process 230)
Next, the connection disconnection process 230 will be described. The connection disconnection process 230 is a process of disconnecting the connection with the service providing apparatus when the AT 107 ends the packet transfer.

  The AT 107 transmits a disconnection request 226 to the PCF-SC 103 via the AP 104. The PCF-SC 103 transmits a disconnection request 227 corresponding to the disconnection request 226 to the PDSN 102. The PDSN 102 disconnects the connection in response to the disconnect request 227 and transmits a disconnect response 228 indicating that the connection has been disconnected to the PCF-SC 103. The PCF-SC 103 transmits a disconnection response 229 corresponding to the disconnection response 228 to the AT 107.

  FIG. 3 is a reference diagram for explaining the computer system 1 according to the embodiment of this invention. The time synchronization method of PCF-SC103 in the conventional computer system 1 is demonstrated using FIG.

  Consider a case where the PCF-SC 103 is time-synchronized with a specific base station APb 104-2. In this case, even if a time lag occurs in the base station APb 104-2, the PCF-SC 103 cannot detect this time lag. For this reason, the time of the PCF-SC 103 is also set to an incorrect time due to the influence of the base station APb 104-2 where the time difference has occurred. In addition, the PCF-SC 103 set at an incorrect time recognizes other base stations APa104-1, APc104-3, and APd104-4 that are originally at the correct time as unauthorized base stations.

  As a result, in the conventional time synchronization method, when the condition 1 (the base station APb 104-2 is the time synchronization destination of the PCF-SC 103 and the time of the APb 104-2 is an invalid time) is satisfied, the PCF-SC 103 And the times of the base stations APa104-1, APc104-3, and APd104-4 are not matched.

  FIG. 4 is a flowchart showing the reference operation of the computer system 1 according to the embodiment of this invention. The operation of the PCF-SC 103 in the conventional computer system 1 will be described with reference to FIG. Reference is made to FIG. 2 as appropriate.

  First, in step 401, the PCF-SC 103 receives a request from the AP 104 (401). In step 401, strictly speaking, a request regarding the use of a voice call or web browsing service is received from the AT 107 via the AP 104. Next, in step 402, it is determined whether or not the request received in step 401 is a connection request 205 (or active request 218) (402).

  If the received request is the connection request 205 (or Active request 218) (YES in 402), the process proceeds to step 403. On the other hand, if the received request is not the connection request 205 (or the Active request 218) (NO in 402), the process ends here.

  In step 403, the PCF-SC 103 acquires TimeStamp added to the connection request 205 (or active request 218) received in step 401 (403). The TimeStamp here is time information of the AP 104 that is the source of the request. Thereafter, in step 404, time information of the own node (PCF-SC 103) is acquired (404). Thereafter, in step 405, a difference value between the time indicated in TimeStamp acquired in step 403 and the time indicated in the time information acquired in step 404 is calculated (405). Thereafter, in step 406, it is determined whether or not the time difference value calculated in step 405 is equal to or smaller than a certain value (406).

  When the time difference value is equal to or smaller than a certain value (YES in 406), the process proceeds to step 407, and the PCF-SC 103 allows the connection request 205 (or Active request 218) and the corresponding connection request 206 (or Active request 219). Is transmitted to the PDSN 102 (407). Thereby, the AT 107 under the control of the AP 104 whose time difference value is equal to or smaller than a certain value can use the service.

  On the other hand, if the time difference value exceeds a certain value (NO in 406), the process proceeds to step 408, and the PCF-SC 103 rejects the connection request 205 (or Active request 218) as an invalid request, and notifies that. Respond to the AP 104 (408). As a result, the AT 107 under the control of the AP 104 whose time difference value exceeds a certain value cannot use the service.

  In the following description, the PCF-SC 103 according to the embodiment of the present invention holds the time difference value between each AP 104 and its own node in the time difference table 531 (see FIG. 5), and sets each time difference value as a constant value. A method of detecting a time lag of the AP 104 that is the time synchronization destination by comparison and further selecting the AP 104 that is the optimal time synchronization destination based on the average value of the time difference values will be described.

  FIG. 5 is a block diagram illustrating a configuration example of the PCF-SC 103 according to the embodiment of this invention. The PCF-SC 103 illustrated in FIG. 5 includes a reception unit 510, a time acquisition unit 520, a storage unit 530, a determination unit 540, a control unit 550, and a transmission unit 560.

  A receiving unit 510 receives a NTP (Network Time Protocol) message according to the type of the received message, a receiving source discriminating unit 511 that discriminates a receiving source of a message received from the opposite device such as the AP 104 or the PDSN 102. 512, an ICMP message receiving unit 513 for receiving an ICMP message, and a call processing message receiving unit 514 for receiving a call processing message such as a connection request 205 or an Active request 218 (see FIG. 2).

  Note that time information (TimeStamp) of the transmission source AP 104 is added to the ICMP message (Ping or the like) periodically transmitted to the PCF-SC 103 by each AP 104. Thereby, PCF-SC103 can acquire the newest time information of each AP104 regularly.

  The time acquisition unit 520 acquires the time information of the own node (PCF-SC 103 itself), the time information of the own node, the time information of the own node, and the time information added to the ICMP message (or call processing message). Based on this, a time difference calculation unit 522 that calculates a time difference value between the AP 104 and the own node for each AP 104 is provided.

  The storage unit 530 stores a time difference table (time difference storage unit) 531 for storing the time difference value of each AP 104 calculated by the time difference calculation unit 522, registration of the time difference value in the time difference table 531, and time difference An AP address registration / deletion unit 532 that deletes the time difference value from the table 531 is provided. The storage unit 530 manages the time difference value of each AP 104.

  The discriminating unit 540 compares the time difference value of each AP 104 calculated by the time difference calculating unit 522 with a certain threshold value to determine whether the time difference value is larger than the certain threshold value for each AP 104. The time difference of any AP 104 is determined by the synchronization determination unit 542 and the time difference determination unit 541 that determine whether the AP 104 to be determined by the difference determination unit 541 and the time difference determination unit 541 is the time synchronization destination of the PCF-SC 103. When it is determined that the value is greater than a certain threshold value, a failure determination unit 543 is provided that determines a faulty AP 104 (which AP 104 has a time lag).

  Note that the time difference determination unit 541 in this case particularly executes a determination process related to the time difference value calculated based on the call processing message (a message corresponding to the call processing message (such as a connection request in step 407 in FIG. 4). The response of step 408) is transmitted to the transmission destination determination unit 561.

  Further, when the failed AP 104 is an AP 104 other than the time synchronization destination, the failure determination unit 543 notifies the OMS 105 of the failure of the AP 104. On the other hand, when the failed AP 104 is the time synchronization destination AP 104, the time synchronization destination changing unit 552 is notified of the fact. Further, the failure determination unit 543 instructs the AP address registration deletion unit 532 to delete the time difference value of the failed AP 104. Then, the AP address registration deletion unit 532 deletes the time difference value of the failed AP 104 from the time difference table 531.

  Based on the NTP message received by the NTP message receiving unit 512 from the AP 104 that is the time synchronization destination, the control unit 550 performs the time synchronization destination based on the notification from the time synchronization unit 551 and the failure determination unit 543 that are time synchronized with the AP 104. A time synchronization destination changing unit 552 for changing the AP 104 of the mobile phone is provided.

  The transmission unit 560 includes a transmission destination determination unit 561 that determines a transmission destination of a message corresponding to the call processing message. The transmission unit 560 transmits a message to the determined transmission destination (opposite device such as the AP 104 or the PDSN 102).

  FIG. 6 is a diagram illustrating an example of changing the time synchronization destination of the PCF-SC 103 according to the embodiment of this invention.

  In FIG. 6, the time synchronization destination before the change is APb 104-2. Each AP 104-1 to 104-4 transmits ICMP messages 109-1 to 109-4 to which each time information is periodically added to the PCF-SC 103.

  Here, when a time lag occurs in the APb 104-2, the PCF-SC 103 quickly detects the time lag of the APb 104-2 based on the ICMP messages 109-1 to 109-4. Also, the APc 104-3 that is the optimal time synchronization destination base station is selected, and the time synchronization destination is changed to the APc 104-3. These processes will be described with reference to FIGS.

  FIG. 7 is a flowchart illustrating a control logic when the PCF-SC 103 according to the embodiment of this invention receives the ICMP message 109 from each AP 104. FIG. 8A is a diagram illustrating an example of the time difference table 531 before the change according to the embodiment of this invention. FIG. 8B is a diagram illustrating an example of the time difference table 531 after the change according to the embodiment of this invention.

  As a premise, the time synchronization destination of the PCF-SC 103 is APb 104-2, and a time difference is generated between the PCF-SC 103 and the other APa 104-1, APc 104-3, and APd 104-4 (FIG. 8A). reference). Further, when the PCF-SC 103 receives a connection request message, the constant threshold value of the time difference for rejecting the connection request is set to ± 10 sec. That is, the threshold value used for determination by the time difference determination unit 541 (see FIG. 5) is ± 10 seconds.

  In this case, as shown in FIG. 8A, in the time difference table 531, the time difference values of APa104-1, APb104-2, APc104-3, and APd104-4 are -9.82 sec, 0.00 sec, -9.79 sec,- 9.73 sec.

  First, in step 701, the PCF-SC 103 receives an ICMP message to which a TimeStamp is added from the AP 104 (701).

  Next, in Step 702, the PCF-SC 103 acquires time information of the own node (PCF-SC 103) (702). Thereafter, in step 703, a difference value between the time indicated in TimeStamp acquired in step 701 and the time indicated in the time information acquired in step 702 is calculated (703). Thereafter, in step 704, it is determined whether or not the source of the ICMP message received in step 701 is the time synchronization destination AP 104 (704).

  When the reception source is the AP 104 that is the time synchronization destination (YES in 704), the process proceeds to step 705, and the PCF-SC 103 uses the time difference value calculated in step 703 to store the time synchronization destination in the time difference table 531. The time difference values of all the APs 104 including “” are updated (705). The reason why the time difference values of all APs 104 are updated is that when the time difference values of the time synchronization destination AP 104 are updated, the time difference values of all other APs 104 are also updated in the same manner.

  On the other hand, when the receiving source is the AP 104 other than the time synchronization destination (NO in 704), the process proceeds to step 706, and the PCF-SC 103 uses the time difference value calculated in step 703, Only the time difference value of the receiving AP 104 is updated (706). The reason why the time difference value of the AP 104 as the reception source is updated is that the time difference value of the AP 104 other than the time synchronization destination does not affect the time difference value of the other AP 104.

  The processing in steps 701 to 706 will be specifically described with reference to FIG. 8A. In step 701, the PCF-SC 103 receives an ICMP message from the APb 104-2 as the time synchronization destination (701), and then calculates a difference value (−0.2 sec) in step 703 (703).

  Then, since the reception source is the time synchronization destination in Step 704 (YES in 704), the process proceeds to Step 705, and the PCF-SC 103 uses the time difference value (−0.2 sec) to use the APa 104 in the time difference table 531. −1, APb 104-2, APc 104-3, APd 104-4, the time difference values are −9.82 sec + (− 0.2 sec) = − 10.02 sec, 0.00 sec, −9.79 sec + (− 0.2 sec) = − 9.99 sec, Update to -9.73 sec + (-0.2 sec) = -9.93 sec. Note that the time difference value of the APb 104-2 that is the time synchronization destination is not changed.

  Returning to FIG. 7, in step 707, the PCF-SC 103 determines whether or not the time difference value of one or more APs 104 in the time difference table 531 updated in step 705 or 706 is equal to or less than a certain value. (707). If the time difference value is equal to or less than a certain value (YES in 707), the process ends here.

  On the other hand, if the time difference value exceeds a certain value (NO in 707), the process proceeds to step 708. The case where the time difference value exceeds a certain value means that the time difference value in the time difference table 531 exceeds a certain value as a result of updating the time difference table 531 in step 705 or 706. This is a case where any one or more of 1 to APd104-4 is considered to be set at an illegal time.

  In step 708, the PCF-SC 103 obtains the average value of the time difference values of the APs 104 in the time difference table 531, and specifies the AP 104 set at an incorrect time (708). Note that the AP 104 set at an illegal time here is an AP 104 having a time difference value farthest from the obtained average value.

  Thereafter, in step 709, the PCF-SC 103 notifies the OMS 105 that the AP 104 that received the ICMP message is an AP 104 set at an illegal time (709). Thereafter, in step 710, the time difference value of the AP 104 set at an illegal time is deleted from the time difference table 531 (710).

  The processing in steps 707 to 710 will be specifically described with reference to FIG. 8A (after being updated in step 705). In step 707, since the time difference value (-10.02 sec) of the APa 104-1 exceeds the fixed value (-10.0 sec) (NO in 707), the process proceeds to step 708, and the PCF-SC 103 stores the time difference table 531. An average value of time difference values of each AP 104 in the center is obtained (708).

  The average value obtained here is (−10.02 sec) + (0.00 sec) + (− 9.99 sec) + (− 9.93 sec) / 4AP = (− 29.94 sec) / 4AP = (− 7.485 sec). In step 708, the PCF-SC 103 sets the APb 104-2 (time difference value 0.00 sec) of the time difference value having the largest difference from the obtained average value (-7.485 sec) to the AP 104 set to the incorrect time. As specified.

  Thereafter, in step 709, the PCF-SC 103 notifies that the APb 104-2 is the AP 104 set at an invalid time (709), and the time difference value of the faulty APb 104-2 is obtained from the time difference table 531. It is deleted (710).

  Returning to FIG. 7, in step 711, the PCF-SC 103 determines whether or not the faulty AP 104 is the AP 104 that is the time synchronization destination (711).

  If the faulty AP 104 is not the time synchronization destination AP 104 (NO in 711), the process ends here. On the other hand, when the faulty AP 104 is the time synchronization destination AP 104 (YES in 711), the PCF-SC 103 determines the average value of the time difference values of the APs 104 other than the faulty AP 104 in the time difference table 531. The AP 104 having the value closest to the calculated average value is changed to the AP 104 that is the time synchronization destination (712).

  Thereafter, in step 713, the PCF-SC 103 updates the time difference value of each AP 104 in the time difference table 531 based on the time synchronization destination AP 104 changed in step 712 (713). Specifically, the time difference table 531 is updated by adding an offset amount for setting the time difference value of the newly set time synchronization destination AP 104 to 0 to the time difference values of all APs 104.

  The processing in steps 711 to 713 will be specifically described with reference to FIG. 8A (after being updated in step 710). In step 711, since the faulty APb 104-2 is the AP 104 that is the time synchronization destination (YES in 711), the process proceeds to step 712, and the PCF-SC 103 determines that the faulty APb 104-2 in the time difference table 531. The average value of the time difference values of each AP 104 other than is calculated (712).

  The average value calculated here is (−10.02 sec) + (− 9.99 sec) + (− 9.93 sec) / 3AP = (− 29.94 sec) / 3AP = (− 9.98 sec). In step 712, the PCF-SC 103 changes the APc 104-3 (time difference value-9.99 sec) having the time difference value closest to the calculated average value (-9.98 sec) to the AP 104 that is the time synchronization destination.

  Thereafter, in step 713, the PCF-SC 103 sets the offset amount (+9.99 sec) in which the time difference value of the time synchronization destination APc 104-3 newly set in step 712 is 0 as the time difference value of all APs 104. The time difference table 531 is updated by adding (713).

  As a result, as shown in FIG. 8B, in the time difference table 531, the time difference values of APa 104-1, APc 104-3, and APd 104-4 are −0.02 sec + (+ 9.99 sec) = − 0.03 sec, −9.99 sec + (+9.99 sec) = 0.00 sec, −9.93 sec + (+ 9.99 sec) = + 0.06 sec.

  Through the processing described above, the PCF-SC 103 quickly detects a time lag that has occurred in the APb 104-2 that is the time synchronization destination, based on the ICMP messages 109-1 to 109-4. Further, APc 104-3 which is the optimum base station for time synchronization is selected, and the time synchronization destination is changed to APc 104-3.

  According to the computer system 1 of the embodiment of the present invention described above, the PCF-SC 103 manages the time difference value with each AP 104 by using the time difference table 531, so that the time lag (GPS failure) of the AP 104 that is the time synchronization destination. It is possible to immediately detect (such as time fraud due to, etc.).

  Further, when the failed AP 104 is the time synchronization destination of the PCF-SC 103, the optimum time synchronization destination AP 104 is selected by calculating the average value of the time difference values of each AP 104 in the time difference table 531. Can do. Further, by updating the time difference table 531 according to the time difference value of the new time synchronization destination AP 104 (time difference value offset amount), the relationship of the time difference values is inherited and the failure of the AP 104 is continued. Can be detected.

  As mentioned above, although embodiment of this invention was described, the said embodiment showed one of the application examples of this invention, and in the meaning which limits the technical scope of this invention to the specific structure of the said embodiment. Absent. Various modifications can be made without departing from the scope of the present invention.

  For example, in the description of FIG. 7 described above, the processing in which the PCF-SC 103 executes the control logic illustrated in FIG. 7 based on the ICMP message 109 received from each AP 104 has been described as an example. For example, the same control logic as in FIG. 7 may be executed based on the call processing message received from each AP 104.

1 Computer system 101 IP-NW
102 PDSN
103 PCF-SC
104 AP
104-1 APa
104-2 APb
104-3 APc
104-4 APd
105 OMS
106 RAN
107 AT
108 AN-AAA
510 Reception unit 511 Reception source determination unit 512 NTP message reception unit 513 ICMP message reception unit 514 Call processing message reception unit 520 Time acquisition unit 521 Local node time acquisition unit 522 Time difference calculation unit 530 Storage unit 531 Time difference table 532 AP address registration Deletion unit 540 Determination unit 541 Time difference determination unit 542 Synchronization destination determination unit 543 Failure determination unit 550 Control unit 551 Time synchronization unit 552 Time synchronization destination change unit 560 Transmission unit 561 Transmission destination determination unit

Claims (8)

In a computer system comprising a plurality of base stations and a communication control device that controls the plurality of base stations, the communication control device is a time synchronization method in which time synchronization is performed with any of the plurality of base stations,
A procedure in which each of the plurality of base stations transmits a message with time information of the base station to the communication control device;
The communication control device calculates a difference value between the time information of the base station and the time information of the communication control device for each base station based on a message received from each of the plurality of base stations, and calculates The stored difference value in the time difference table;
If the calculated difference value is greater than a predetermined threshold, the communication control device calculates an average value of the difference values of the plurality of base stations stored in the time difference table, and the calculated average value A procedure for determining that the base station having the largest difference value is abnormal,
Including a time synchronization method.   When the base station determined to be abnormal by the communication control device is a time synchronization destination of the communication control device, the abnormality among the difference values of the plurality of base stations stored in the time difference table Calculating the average value of the difference values of the base stations excluding the base station determined to be, and changing the base station having the smallest difference from the calculated average value to a new time synchronization destination The time synchronization method according to claim 1, further comprising:   The time synchronization method according to claim 2, further comprising a step of updating the difference value of each base station in the time difference table based on the new time synchronization destination by the communication control device.   In the storing procedure, the communication control device obtains a difference value between the time information of the base station and the time information of the communication control device based on a message received from the time synchronization destination base station of the communication control device. The time synchronization according to claim 1, wherein the difference value of all base stations including the base station of the time synchronization destination in the time difference table is updated using the calculated difference value. Method. A computer system comprising a plurality of base stations and a communication control device for controlling the plurality of base stations, wherein the communication control device is time-synchronized with any of the plurality of base stations,
Each of the plurality of base stations transmits a message with time information of the base station to the communication control device,
The communication control device calculates, for each base station, a difference value between the time information of the base station and the time information of the communication control device based on a message received from each of the plurality of base stations. Stored difference value in the time difference table,
When the calculated difference value is greater than a predetermined threshold, the communication control apparatus calculates an average value of the difference values of the plurality of base stations stored in the time difference table, and calculates the calculated average value. A computer system characterized in that a base station having a difference value having the largest difference is determined to be abnormal.   When the base station determined to be abnormal is the time synchronization destination of the communication control apparatus, the communication control apparatus is configured to use the abnormality among the difference values of the plurality of base stations stored in the time difference table. Calculating the average value of the difference values of the base stations excluding the base station determined to be, and changing the base station having the smallest difference from the calculated average value to a new time synchronization destination. The computer system according to claim 5, wherein the computer system is characterized.   The computer system according to claim 6, wherein the communication control device updates a difference value of each base station in the time difference table based on the new time synchronization destination.   The communication control device calculates a difference value between the time information of the base station and the time information of the communication control device based on a message received from the time synchronization destination base station of the communication control device. 6. The computer system according to claim 5, wherein difference values of all base stations including the time synchronization destination base station in the time difference table are updated using a difference value.