This section provides information required to troubleshoot specific transmission synchronization faults. The information includes fault descriptions, background information, possible causes, fault handling method and procedure, and typical cases.
12.1 Definitions of Transmission Synchronization Faults
This section describes the classification and definitions of transmission synchronization faults.
The following defines common transmission synchronization faults:
l Clock reference problem
This fault occurs in the case of external clock reference loss, external clock reference unavailability due to unacceptable quality, or excessive phase (or frequency) deviation between the local oscillator and external clock references.
l IP clock link fault
This fault occurs when the IP clock link between the eNodeB and the clock server malfunctions.
l System clock unlocked fault
This fault occurs when a phase-locked loop in a board is unlocked.
l Base station synchronization frame number error
This error occurs when a synchronization frame number provided to a board is incorrect.
For example, a frame number jump occurs when the pps signals provided by the GPS are abnormal.
l Time synchronization failure
This failure occurs when the eNodeB fails to synchronize with the time synchronization server (for example, the NTP server).
12.2 Background Information
For details about IP clock and non-IP clock, see eRAN Synchronization Feature Parameter Description.
12.3 Troubleshooting Specific Transmission Synchronization Faults
This section provides information required to troubleshoot specific transmission synchronization faults. The information includes fault descriptions, background information, possible causes, fault handling method and procedure, and typical cases.
Fault Description
External reference clocks for eNodeBs include GPS, synchronous Ethernet, clock over IP, BITS, E1/T1, and TOD clocks. Any abnormality in a reference clock will cause the eNodeB incapable of locking the reference clock. The clock status can be checked by running the DSP
CLKSTAT command.
l The value of Current Clock Source State indicates an unknown status.
l The value of Current Clock Source State indicates that the reference clock is abnormal, for example, the reference clock is lost.
l The value of PLL Status indicates that the PLL status is abnormal, for example, the reference clock is in free-run mode or there is excessive frequency deviation.
l The value of Clock Synchronization Mode indicates that the clock synchronization mode is not set to a specified mode.
If one of the previous conditions is met, there is a transmission security problem.
Background Information
l The following describes how to perform a clock quality test:
1. Start a clock quality test by running the STR CLKTST command.
2. Several hours later, stop the clock quality check by running the STP CLKTST command.
3. Check the clock quality test result by running the DSP CLKTST command.
Possible Causes
l The clock mode is incorrectly set.
l The clock source is incorrectly added.
l The clock working mode is incorrectly set for the eNodeB.
l The external reference clock is abnormal, for example, there is excessive frequency deviation.
l The clock source is incorrectly selected, which leads to a clock lock failure.
Troubleshooting Flowchart
None
Troubleshooting Procedure
1. Check the clock configuration for the eNodeB.
a. Check whether the clock synchronization mode is set to a specified mode.
Check whether the mode is set to the required one, for example, frequency
synchronization or phase synchronization. If the configuration is incorrect, change the mode to the required one.
b. Check whether the clock sources are correctly added.
Use different query commands for different clock sources. For details, see eNodeB MML Command Reference.
c. Check whether the work mode of the clock is correctly set.
If the eNodeB needs to lock an external clock source, set the clock working mode to AUTO or MANUAL. The difference between the two settings are:
l AUTO indicates that the eNodeB automatically selects a reference clock based on the status, priorities, and link available status of reference clocks.
l MANUAL indicates that the eNodeB is forced to select a user-defined reference clock.
Set the clock working mode based on actual requirements.
2. Check whether the external clock resources of the eNodeB work properly.
To check the status of an external clock source, run the DSP CLKSRC command. Pay attention to the following two parameters:
l License Authorized
Generally, the value of this parameter indicates that the clock source can be used. If the value indicates that the clock source cannot be used, enable the eNodeB synchronization function.
To check whether the eNodeB synchronization function is enabled, run the DSP LICENSE command. If the Allocated, Config, and Actual Used fields of the Enhanced Synchronization control item are all 1, the function is enabled.
l Clock Source State
The link available status (Link Available State) of a reference clock can be checked by running a command such as DSP IPCLKLINK, DSP SYNCETH, or DSP TOD.
The value of Clock Source State is Available when the external reference clock of the eNodeB meets either of the following conditions:
–Non-IP clock
The physical connection between the reference clock and the eNodeB is normal, and the eNodeB can properly receive clock signals sent by the reference clock.
–IP clock
The route from the eNodeB to the IP clock server is correct, and the eNodeB can properly receive clock signals sent by the IP clock server.
If the clock source state or the link available state is unavailable, investigate the reason.
–Check whether the physical connection and communication are normal between the eNodeB and the clock source. For the GPS, the number of satellites must be greater than or equal to 4; the related command is DSP GPS.
–Check whether the eNodeB can properly receive clock signals. For a non-IP clock, clock signals are generated at the physical layer, and therefore you can check only on the equipment that sends the clock signals whether they are correctly sent. For an IP clock, you can check whether clock packets are correctly received by performing a trace task on the M2000 or by analyzing packet headers on the nearest transmission equipment. The clock source state and link available state of an IP clock can be determined based on the characteristics of received clock packets. For details about the analysis, see the PTP clock packet analysis procedure in the next step.
3. Check whether the eNodeB correctly selects a clock source.
When multiple external clock sources are added and work properly, the output of the DSP CLKSRC command indicates that the status of these clock sources is Available. In addition, the output of the corresponding link query command (DSP IPCLKLINK, DSP SYNCETH, DSP GPS, or DSP TOD) indicates that the status of the clock link is also Available. Note that only the link activation status (Link Active State) of the clock source selected as the reference clock is Activated. The link activation status of other clock sources is Unactivated.
The reference clock is explained as follows:
l If the clock working mode is set to MANUAL using the SET CLKMODE command, the reference clock is the manually selected clock source.
l If the clock working mode is set to AUTO using the SET CLKMODE command, the reference clock is the one automatically selected. The query command is DSP CLKSTAT.
l If the link availability status of the selected clock source is Available but the link activation status is Unactivated, the reference clock is the one manually selected after the clock working mode is set to MANUAL using the SET CLKMODE command.
4. Check whether the eNodeB correctly locks an external clock source.
To check the lock status, run the DSP CLKSTAT command. The following describes the parameters in this command:
l Current Clock Source: It indicates the clock source to be traced by the eNodeB.
l Current Clock Source State: The value should be Normal.
l PLL Status: The initial status should be Fast Tracking, and then Locked.
l Clock Synchronization Mode: It indicates the configured clock synchronization mode.
–Non-IP clock
For a non-IP clock source, if the link available state is available and the link active state is activated in step 3, the states queried by running DSP CLKSTAT must be normal.
The only risk is that the eNodeB enters free-run mode (instead of locked mode) after a period of fast tracking. The eNodeB adjusts the local oscillator during fast tracking, but the difference between the local oscillator and external clock sources is still above the locking threshold. Therefore, the eNodeB cannot lock an external clock source and enters free-run mode.
In this case, perform a clock quality test to check the frequency deviation values, and report them to Huawei technical support.
–IP clock
For an IP clock, even if the clock link is available and activated, it cannot be guaranteed that all check items are normal. The query command is DSP CLKSTAT. The reason is that whether the eNodeB can lock an external clock source depends on two packets (Sync and Delay_Resp) as well as the clock information the packets carry.
In this situation, take two actions: (1) Collect clock packets received by the eNodeB on the M2000 or collect headers of the packets on the nearest transmission
equipment; (2) Perform a clock quality test on the IP clock in the same way as that for a non-IP clock. Then, send the packets (or packet headers) and quality test result to Huawei technical support.
5. If the transmission synchronization fault persists, contact Huawei technical support.
Typical Cases
None
13 Troubleshooting Transmission Security Faults
About This Chapter
This chapter describes how to troubleshoot transmission security faults.