KR19990003118A - Reference Clock Transfer and Recovery Method for Network Synchronizer of Mobile Communication Switch - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Network Synchronizer of Mobile Communication Switching System (MSC)

2. The technical problem to be solved by the invention

This is to solve the problem of destabilization of the reference clock for the synchronization in the switching station caused by frequent switching and restoration in case the abnormal reference clock frequently occurs.

3. Summary of Solution to Invention

The first process of selecting a higher reference clock (reference clock A) from among a plurality of received reference clocks (A, B, C) and searching whether frame alarm and carrier loss alarm occur in each reference clock at regular intervals during system operation. and; A second step of switching to a next reference clock when a failure occurs in the upper reference clock and searching whether the upper reference clock is normal; When the upper reference clock maintains a stable state for a predetermined recovery time, a third process of restoring a clock to the upper reference clock and recovering the reference clock is performed.

4. Important uses of the invention

It is applied to transfer and recovery of reference clock for network synchronizer in mobile switching center.

Description

Reference Clock Transfer and Recovery Method for Network Synchronizer of Mobile Communication Switch

According to the present invention, when an abnormality occurs in the upper reference clock received from the upper switching station in the mobile communication exchange, the mobile terminal switches to the next higher reference clock and monitors the state of the upper reference clock for a predetermined time so as to restore the previous upper reference clock only when stabilized. The purpose of the present invention is to provide a reference clock switching and recovery method for a network synchronizer of a mobile communication exchange to prevent frequent switching of the reference clock.

In general, a mobile communication switch (MSN) in a CDMA mobile communication system is a mobile communication switch that is developed to be flexibly applied in various network types such as a public switched telephotione network (PSTN) and a packet switched data network (PSDN). B. It is modularized to make it easy to add and change the functions of the software. It is easy to modify and expand according to performance improvement or capacity expansion, and is open structure to facilitate various network access.

Such a general mobile communication switch operates a system by selecting a higher clock among the clocks received in a switching center receiving a plurality of reference clocks for a network synchronizer from a higher switching center (network) as a reference clock for system synchronization. If an error occurs in the clock, the system operates by stalling to the next higher reference clock.

In other words, when receiving a plurality of reference clocks for the network synchronizer from a higher switching center (network), the reference clock of the highest priority is used as the reference clock of the switching station, and when an abnormality occurs in this reference clock, the system is switched to the next higher clock. To operate. After switching to the next higher reference clock, the state of the upper reference clock is periodically checked and if there is no abnormality, the switch is immediately made to the upper reference clock again. Likewise, if an abnormality occurs in the reference clock on the back in the state of restoring to the upper reference clock, transfer to the next reference clock again, monitor the upper reference clock, and if the upper reference clock normalizes during monitoring, the upper reference clock immediately. Change the system to operate the system. In other words, the upper reference clock is given priority, and if a failure occurs in the upper reference clock, it is transferred to the next higher reference clock.If the upper reference clock is normal again, the upper reference clock is unconditionally regardless of whether the next reference clock is normal. You will be transferred.

Therefore, in the case of a general mobile communication switch as described above, if an abnormality occurs frequently in the upper reference clock, switching and restoration are performed at any time. Therefore, the synchronization clock used as a reference in the switching center is frequently changed. Adversely affected.

Therefore, the present invention has been proposed to solve various problems that occur when switching and restoring a reference clock for a network synchronizer of a general mobile communication switch as described above, and an object of the present invention is that an abnormality occurs in an upper reference clock received from an upper switching center. In the case of switching to the reference clock of the next phase and monitoring the status of the upper reference clock for a certain period of time, it is possible to recover to the previous upper reference clock only when it is stabilized so as to prevent frequent clock switching of the upper reference clock. And a recovery method.

Method for achieving the object of the present invention,

The first process of selecting a higher reference clock (reference clock A) from among a plurality of received reference clocks (A, B, C) and searching whether frame alarm and carrier loss alarm occur in each reference clock at regular intervals during system operation. and; A second step of performing a transfer to a next higher reference clock and searching whether the upper reference clock is normal when a failure occurs in the reference clock of the phase; When the upper reference clock maintains a stable state for a predetermined recovery time, a third process is performed to recover the reference clock by switching a clock to the upper reference clock.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

1 is a system configuration diagram of a mobile communication switch to which the present invention is applied;

2 is a flowchart illustrating a reference clock congestion and recovery method for a network synchronizer of a mobile communication switch according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: digital relay line interface unit, 2: external clock receiving unit, 3: network synchronizer control processor, 4: clock generating unit, 5: clock distribution unit

1 is a system configuration diagram of a mobile communication switch to which the present invention is applied.

As shown therein, among the digital relay line interface unit 1 for receiving a plurality of synchronization reference clocks transmitted from an upper switching center (network), and a plurality of network synchronizer reference clocks received by the digital relay line interface unit 1. Selects and outputs one of the external clock receivers 2 for switching the reference clocks for the starter according to the control of the starter control processor 3, and the reference clocks for the plurality of the starters received by the external clock receiver 2 A system reference clock for generating the system reference clock required by the system by monitoring the state and controlling the switching of the reference clock for the motor starter (3) and the motor starter reference clock selected and output from the external clock receiver (2) The clock generator 4 and the clock divider 5 for distributing the reference clock generated by the clock generator 4 to the clock required by the system.

2 is a flowchart illustrating a reference clock transfer and recovery method for a network synchronizer of a mobile communication switch according to the present invention.

As shown therein, a step (ST1) of operating the system by selecting the highest reference clock (A) having the highest priority among the plurality of received reference clocks (A, B, C; clock priority ABC); Searching for a frame alarm and a carrier loss alarm for each of the reference clocks A, B, and C during system operation (ST2); checking whether or not an alarm occurs for the reference clock A, the upper upper reference clock (ST3); Checking whether or not the reference clock B, which is the next higher reference clock, has failed when the upper reference clock A has a failure (ST4); and performing a transfer to the reference clock B when the next higher reference clock B is normal (ST5); Retrieving a frame alarm and a carrier loss alarm for each of the reference clocks A, B, and C after the transfer of the reference clock (ST6), checking whether the upper reference clock A is inferior (ST7), and the upper reference clock If A is normal, the recovery count time is Checking whether it is excessive (ST8), if the normal state of the upper reference clock A continues during the recovery count time, restoring to the upper reference clock A (ST9), and in the step, the upper reference clock A and the next higher reference clock Searching for an alarm of the next higher reference clock C (ST10) when all failures occur in B; and switching to the reference clock C if the reference clock C is normal (ST12), and after the step Checking whether the upper reference clock A has an alarm (ST13); if the upper reference clock A is normal as a result of the check, checking whether the normal state is maintained for a recovery count time (ST14); and the upper reference clock A Restoring to the upper reference clock A if the steady state of the recovery count time elapses (ST15), and if the reference clock A fails in the state of switching to the reference clock C, Searching whether there is a fault (ST16), if the reference clock B is normally maintained during the recovery count time, performing a clock switching to the reference clock B (ST18), and performing the reference clock A, after switching to the reference clock C, After checking whether the clock has failed for each of B and C, if all the reference clocks have failed, the alarms are checked in the order of reference clock priority (ABC) to switch to the current normal reference clock (ST19-ST21). .

1 and 2 with reference to the reference clock transfer and recovery method for the network synchronizer of the mobile communication switch according to the present invention as described above is as follows.

Before describing an embodiment of the present invention, the overall concept of the present invention is briefly described. The system is operated by receiving a plurality of reference clocks for the network synchronizer from the upper exchange (network) and using the double most significant clock as the reference clock for the network synchronizer. If an abnormality is detected in the operating clock during the operation, after switching to the next higher clock, it monitors the existing clock (higher clock) and recovers to the upper reference clock only if the clock does not occur at least once for a certain period. If a failure occurs even once, the clock is switched in such a manner as to maintain the current reference clock.

This does not create a new monitoring timer job (Job), but uses a timer job Job that was run on an existing manipulator control processor. The fault / alarm detection timer job (hereinafter referred to as fault-check process) which runs every 128 msec is used without change, and the reference clock change timer job (hereinafter referred to as monitor process) which is performed every 1 sec is called reliability and fault = check. Run it every 256msec to synchronize with the process. The fault-check process checks the alarm status of the synchronous clocks, and the monitor process reads it, switches over to the next higher clock if an error occurs in the current clock, and starts monitoring the reference clock. If the alarm does not occur once in the existing clock for a certain time, it is determined that the clock is intact and recover. Taking the recovery time of the clock as a condition that an alarm does not occur even once in a certain period of time is to attempt the recovery to a stable clock.

The operation of the preferred embodiment according to the present invention will be described below with reference to this concept.

First, the digital relay line interface unit 1 of FIG. 1 transmits a plurality of reference clocks for the network synchronizer, which are connected to the digital relay line and transmitted from an upper switching center (network), to the external clock receiver 2, and the external clock receiver 2. Transmits a plurality (up to three) reference clocks to the network controller 3.

Accordingly, the synchronizer control processor 3 is driven every 128 msec in the internal fault-check process to detect faults and alarm conditions of the entire synchronizer equipment. The frame clock (hereinafter referred to as FA) and the carrier loss alarm (hereinafter referred to as CA) are read from the external clock receiver 2 and used as a basis for switching the reference clock. The monitor processor checks the alarm status of the clock every 256 msec periodically after every 128 msec. When a failure is detected, the monitor processor switches to the next higher clock from the highest clock currently in operation. Read the alarm status of the highest clock in order to recover to the highest clock if there is no alarm during recovery count (R-CNT).

Where the value for the recovery count is as follows:

R-CNT: = M-CNT / Job-CNT

R-CNT: Recovery Count

M-CNT: Monitoring Count

(Monitoring time to be recovered if alarm never occurs [msec] / msec)

Job-CNT: Monitoring job process cycle time [msec] / msec --- 128

C-CNT: comparison count (initialization value: 0)

In the case of the monitoring count, the monitoring time to be restored is set as the count when the alarm does not occur at the time of restoring to the existing clock again after switching, and Job-CNT sets the periodic time for the monitoring process to be performed. This is represented by the count 128.

Therefore, the master synchronizer control processor 3 receives the frame alarms for the reference clocks A, B, and C while the reference clocks A, B, and C are received and are operating as the reference clock A (clock priority; ABC) (ST1). And carrier loss alarm are read from the external clock receiver 2 (ST2). Thereafter, by checking whether or not an alarm occurs in the reference clock A, the upper reference clock (ST3), and if a failure occurs in the upper reference clock A, it is determined whether the reference clock B, the next higher reference clock, has failed (ST4). At this time, if the next higher reference clock B is normal, the transfer is performed to the reference clock B (ST5), and after the reference clock changeover, the frame alarm and the carrier loss alarm are searched again for each of the reference clocks A, B, and C (ST6). Check whether clock A is normal (ST7). At this time, if a failure occurs in the upper reference clock A, after initializing the value of the C-CNT-a, and checks the alarm state of the next higher reference clock B (ST10). On the contrary, if the upper reference clock A is normal while the system is operated by switching to the next higher reference clock B, it is checked whether the recovery count time R-CNT is equal to the preset time C-CNT-a (ST8), If the recovery count time is the same as the preset time, that is, if the normal state of the upper reference clock A remains constant during the recovery count time (that is, no failure has occurred in the reference clock A during the recovery count time). The reference clock is transferred to A to recover the reference clock (ST9).

If a failure occurs in the upper reference clock A in the step ST3, the state of the next higher reference clock B is checked, and if the failure occurs in the reference clock B, the next higher reference clock C is searched for an alarm. (ST10) (ST11). At this time, if the reference clock C is normal, the transfer is performed to the reference clock C (ST12), and the alarm state of the reference clocks A, B, and C is read again, and the upper reference clock A is checked for alarm (ST13). Thereafter, if the upper reference clock A is normal, the recovery count time (R-CNT) and the preset recovery count time (C-CNT-a) are the same, that is, if the normal state of the reference clock A is maintained for the recovery count time (ST14). Then, the reference clock is restored by switching to the upper reference clock A again (ST15). On the contrary, if the reference clock A has failed while being transferred to the reference clock C, the reference clock B is searched for failure after the recovery count time is initialized (ST16), and the reference clock B is normally maintained during the recovery count time. When the clock is changed, the clock is switched to the reference clock B (ST18).

In addition, if a failure is detected in the reference clock C before the transfer to the reference clock C (when a clock failure occurs for each of the reference clocks A, B, and C), the states of the reference clocks A, B, and C are prioritized (ABC). In this case, the clock is switched to the clock whose current state is normal (ST19-ST21). At this time, C-CNT-a and C-CNT-b are initialized.

In this way, the master synchronizer control processor 3 controls the switching and recovery of the reference clock, and the clock generator 4 processes the reference clock, which is transferred from the external clock receiver 2, by the internal firmware. It will generate a reference clock of 32.768MHz for system delivery.

Accordingly, the clock divider 5 multiplies the generated 32.768 MHz reference clock to generate 65.536 MHz, which is the system's base clock, and distributes the generated 65,536 MHz base clock to various clocks required in the system. Will be supplied to the system.

As described above, the present invention operates the system with the upper reference clock among the plurality of reference clocks transmitted from the upper exchange station, and if a failure occurs in the upper reference clock during system operation, performs the clock switching to the next higher reference clock and then the higher reference. Checking the status of the clock and recovering to the previous higher reference clock only when there is no failure for a certain period of time (recovery count time). It is effective to prevent frequent change of the reference clock for synchronization.

In addition, restoring the reference clock in the same manner as the present invention can stabilize the reference clock for the network synchronizer, thereby improving overall performance and stabilizing the system.

Claims (6)

In the mobile communication switch which transfers a plurality of reference clocks for network synchronizers transmitted from a higher level switching station and uses them as a system reference clock, A first step of selecting a higher reference clock (reference clock A) of the plurality of received reference clocks (A, B, C) to search for the frame alarm and the carrier loss alarm of each reference clock at regular intervals during the operation of the system. Process; A second step of performing a transfer to a next higher reference clock and searching whether the upper reference clock is normal when a failure occurs in the upper reference clock; When the upper reference clock maintains a stable state for a predetermined recovery time, a third process of recovering the reference clock by switching a clock to the upper reference clock is performed. Recovery method. The method of claim 1, wherein the second process, Checking whether or not an alarm occurs in the reference clock A, the upper reference clock (ST3); and checking the failure of the reference clock B, the next higher reference clock (ST4) when a failure occurs in the upper reference clock A, and If the next higher reference clock B is normal, the step of performing the transfer to the reference clock B (ST5) characterized in that the transfer of the reference clock for the starter for the mobile communication switch. The method of claim 1, wherein the third process, Retrieving a frame alarm and a carrier loss alarm for each of the reference clocks A, B, and C after the transfer of the reference clock (ST6), checking whether the upper reference clock A is normal (ST7), and the upper reference clock If A is normal, checking whether the recovery count time has elapsed (ST8); and if the normal state of the upper reference clock A continues during the recovery count time, recovering to the upper reference clock A (ST9). A reference clock transfer and recovery method for a network synchronizer of a mobile switching center. The method of claim 1, wherein if a failure occurs in the next higher reference clock B while the upper reference clock A has failed, searching for an alarm of the next higher reference clock C (ST10) (ST11), and the reference clock C If normal, transfer to the reference clock C (ST12), and after the step of checking whether or not the alarm of the upper reference clock A (ST13), and if the upper reference clock A is normal as the check result, the normal state is a recovery count Checking whether it is maintained for a period of time (ST14), if the normal state of the upper reference clock A is maintained such that the recovery count time elapses, recovering to an upper reference clock A (ST15), and switching to the reference clock C If a failure occurs in the reference clock A in one state, detecting whether the reference clock B has failed (ST16), and checking whether the reference clock B is normally maintained during the recovery count time. And a step (ST18) of performing a clock switching to the reference clock B when the reference clock B is normally maintained during the recovery count time. Recovery method. The method according to claim 4, wherein after switching to the reference clock C and checking the clock failure for each of the reference clocks A, B, and C as a result, if all the reference clock has a failure, the alarm state according to the reference clock priority (ABC) And checking the current state to perform clock switching to a normal clock (ST19-ST21). The method of claim 1, wherein the frame alarm and the carrier loss alarm check of each reference clock of the first step, A reference clock transfer and recovery method for a starter of a mobile communication exchange, characterized in that the monitor process checks the alarm information (frame alarm and carrier loss alarm) read by the fault-checking process every 128 msec.