BTS3606 Troubleshooting

7/21/2019 BTS3606 Troubleshooting

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Maintenance ManualAirbridge BTS36 Series CDMA Base Station Table of Contents

Huawei Technologies Proprietary

i

Table of Contents

Chapter 3 Troubleshooting .......................................................................................................... 3-1

3.1 Troubleshooting Flow ........................................................................................................ 3-1

3.1.1 Power Failure Handling Flow .................................................................................. 3-1

3.1.2 BTS Start Failure Handling Flow............................................................................. 3-3

3.1.3 BTS Operation Failure Handling Flow .................................................................... 3-7

3.2 Troubleshooting Procedure ............................................................................................... 3-7

3.2.1 Checking BTS Power Distribution........................................................................... 3-7

3.2.2 Checking Part Status on Site .................................................................................. 3-9

3.2.3 Checking Part Status through LMT....................................................................... 3-10

3.2.4 Checking Optical Fiber Connection....................................................................... 3-10

3.2.5 Blocking/Unblocking Resource ............................................................................. 3-12

3.2.6 Checking Communication Status of EAC ............................................................. 3-14

3.2.7 Checking RF Connection ...................................................................................... 3-14

3.3 Troubleshooting of Clock Faults ...................................................................................... 3-16

3.3.1 Jump of Phases or Frequencies of the Clock System.......................................... 3-16

3.3.2 Failure to Trace GPS Satellites............................................................................. 3-17

3.3.3 Failure to Trace Enough GPS Satellites ............................................................... 3-20

3.3.4 A Long Time Required to Trace Enough Satellites............................................... 3-21

3.3.5 Case Library of Clock Faults................................................................................. 3-23


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Maintenance ManualAirbridge BTS36 Series CDMA Base Station Chapter 3 Troubleshooting


3-1

Chapter 3 Troubleshooting

This chapter introduces the troubleshooting of BTS36 series base station through

flowcharts and procedure description.

The following provides some indexes for easy reading.

To locate a specific fault, see section 3.1 , Troubleshooting Flow

To handle a specific fault, see section 3.2 , Troubleshooting Procedure.

To handle the clock fault, see section 3.3 , Troubleshooting of Clock Faults.

To replace parts such as boards and modules during troubleshooting procedure,

see Chapter 4, Part Replacement. To learn something about common operations, see Chapter 5, Common

Operations.

Note:

For the difference among MML commands of cBTS3612, BTS3612A, and BTS3606, see Chapter 1,

"Routine Maintenance".

3.1 Troubleshooting Flow

The following describes troubleshooting flow and flowchart. For the description of

symbols in flowcharts, see section 2.1.5, Description of Symbols in Emergency

Maintenance Flowchart.

3.1.1 Power Failure Handling Flow

The power failure handling flow consists of:

Handling power input and conversion failure

Handling 24 V power distribution failure

Figure 3-1and Figure 3-2show the flowcharts.


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3-3

Is any board indicator

on?

Is the cable from the

PSUDC/DC to switch

box connected correctly?

Y

N

Is the cable from the

switch box to board

connected correctly?

N

N

Y

3

Is the switch box

damaged?

Y

Y

Contact Huawei

technical support

engineer

Connect the

cable properly

Replace the

switch box

NReplace the

switch box

Is any board indicator

on?

N

Y

Go to 4

Figure 3-2Flowchart of handling 24 V power distribution failure

3.1.2 BTS Start Failure Handling Flow

The BTS start failure handling flow consists of:

Handling start failure (near-end)

Handling start failure (far-end)

Handling Abis interface link failure


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3-4

Figure 3-3, Figure 3-4, and Figure 3-5show the flowcharts.

Is the communication

connection normal?

Is the connecting cable

connected to the BCKM

Ethernet interface?

Y

N

Is the cable a crossover

network cable?

N

N

Y

4

Are the two connectors

of the cable connected?

Y

Y

Contact Huawei

technical support

engineer

Connect thecable properly

Use crossover

network cable

NFasten the cable

connector

Is the Telnet client

started?

Y

Set up communication

connection with the BTS

at near end

NStart the Telnet

client

Does the BCKM

operate normally?

N

Is the IP address

for login correct?

Y

N

Query BTS alarm

information. Is there any

current alarm?

Y

Reset or replace

the BCKM

Obtain the correct

IP address

Y

Handle the

current alarm

Go to

5

N

Figure 3-3Flowchart of handling start failure (near-end)


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3-5

5

Start the LMT at far end

Does the panel diagramdisplay all boards/modules

installed?

Y

N

N

Are calls made successfully inthe BTS coverage area?

YEnd

Is the clock cableconnected properly?

N

N

Remove and insert theboards and modulesdisplayed abnormally

The spanner or captive screwof the board or module is

installed in position

Does the panel diagramdisplay all boards/modules

installed?

Replace the boards ormodules displayed

abnormally.

Contact Huaweitechnical support

engineer

Connect thecable properly

7

Is there any BTS equipmentpanel diagram?

Y

N Go to8

6

Y

Y

Figure 3-4Flowchart of handling start failure (far-end)


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3-6

Is the physical link at BTS side

connected normally?

Y

Re-connect the link

until it is normal.

N

Is the physical link at BSC side

connected normally?

Y

Re-connect the link

until it is normal.

N

N

Perform loopback test on

the physical link of Abis

interface

Y

Reconfigure

the physical

link

Is the physical link of Abis

interface in the loopback state?

Re-connect the link

until it is normal.

Y

NIs the link loopback

normal?

Check the BER of Abis

interface physical link

Y

NIs the BER

normal?

Solve the

transmission BER

problem

Check Abis interface

data

Y

Is the Abis interface

data consistent?

Y

NIs the link configuration consistent

with that of physical connection?

Solve the

transmission problem

8

Go to

6

N Modify the Abis

interface data

Contact Huawei

technical support

engineer

Figure 3-5Flowchart of handling Abis interface link failure


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3-7

3.1.3 BTS Operation Failure Handling Flow

Figure 3-6shows the flowchart of handling BTS operation failure.

1

Start

Does BTS have

current alarms?

Is Abis interface

transmission interrupted?

N

N

YHandling them

Y

Handle it

Does BTS have any

more current alarms?

Y

NEnd

Is BTS power supply

disconnected?

N

YHandle it

Go to 1

Figure 3-6Flowchart of handling BTS operation failure

3.2 Troubleshooting Procedure

After locating a fault according to the troubleshooting flow, perform the following

operations as appropriate to handle the fault.

3.2.1 Checking BTS Power Distribution

You can judge whether the BTS power distribution is normal by checking the

indicators on the panel of the board. If the indicator is on, the BTS power distribution

is normal.

BTS power distribution varies with the models of BTS.

Table 3-1 provides the power distribution paths of cBTS3612, BTS3606, and

BTS3612A. For details about power distribution, see the technical manual of each

BTS, for example,Airbridge cBTS3612 CDMA Base Station Technical Manual.


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3-8

Table 3-1Power distribution path

BTS model Power input Power distribution path Remark

48 V DC

EMI filterDC/DC Power Supply Module

(PSUDC/DC) Switch boxEach board ormodule

The 48 V DC input power is

converted into +27 V DC on thePSUDC/DC.

cBTS3612 orBTS3606

+24 V DC Switch boxEach board or module

BTS3612AAC powerinput

Power supply air breakerAC power

distribution air breakerAC/DC PowerSupply Module

(PSUAC/DC)PSUDC/DCSwitch boxEachboard and module

When the AC power is led in tothe AC/DC power subrack, it isalso sent to the air conditioner.

The AC power is converted into48 V DC on the PSUAC/DC.

The 48 V DC power is sent to theDC/DC power subrack, and also

to the power consumption unitssuch as the batteries,transmission equipment, fans, andilluminating devices.

The 48 V DC power is convertedinto +27 V DC on the PSUDC/DC.

To check the BTS power distribution path, ensure that:

I. There is power supply input

If no power is led in, solve the power input problem with the relevant manager.

II. The standby power system operates normally (applies to BTS3612A only)

When there is power input, the standby power system is in charging state. When

there is no power input, the standby power system is in discharging state.

III. The power input cable is correctly connected to the lightning protection

and filter unit of AC power supply

There are N, L1, L2, and L3 wire post and three-phase short-circuiting clamp. Ensure

that the phase connection is correct.

The three-phase short-circuiting clamp is used only when the monophase AC power

is input.

IV. The PSUAC/DCand PSUDC/DCare properly installed

The PSUAC/DCapplies to the BTS3612A only.


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3-9

For the configuration of the PSUAC/DC and PSUDC/DC, see the related technical

manuals.

3.2.2 Checking Part Status on Site

You can check the status of parts through the LMT or indicators on the parts.

To check the status of parts on site, proceed as follows:

I. Check indicators on the panels of baseband boards.

The standard indicators on the panel of baseband boards include:

RUN: Board status indicator.

ALM: Alarm indicator.

ACT: Working indicator.

For detailed description of indicators, see Airbridge BTS36 Series CDMA Base

Station Hardware Description.

You can check the following baseband boards on site:

BCKM

BCIM

BCPM or CCPM

BRDM HPCM

II. Check indicators on the panels of other parts

For detailed description of indicators, see Airbridge BTS36 Series CDMA Base

Station Hardware Description.

You need to check the following parts:

BTRM or CTRM

BRFM

RLDU

PSUAC/DC

PSUDC/DC

PMU

BPLI

III. Ensure that all parts are installed in position

For the parts installed, if there are ejector levers on the front panel, turn them towards

the middle of the panel and tighten the screws clockwise.


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3-10

3.2.3 Checking Part Status through LMT

You can check the status of parts through the LMT or by checking indicators on the

parts.

To check the status of parts through the LMT, proceed as follows

I. Enter equipment panel node

To enter equipment panel node:

1) On the navigation tree of Service Maintenance System, select the tab

[Maintenance].

2) Select the site to be viewed.

3) Open Equipment Panel node.

II. View equipment panel diagram

Double-click on the selected rack in the Equipment Panel node. The equipment

panel diagram of the rack is displayed in the output window.

The baseband boards, Radio Frequency (RF) modules, and power modules are also

displayed in the equipment panel diagram.

III. Check the part status

First check whether the parts displayed are consistent with those configured, and

then check whether the status is normal.

There is an icon like an indicator on each part. It is used to indicate the status of the

part (for example, normal, standby normal, faulty, blocked, offline, or unknown).

3.2.4 Checking Optical Fiber Connection

The BRDM of the cBTS3612 or BTS3612A connects with the BTRM or ODU3601C

through optical fibers.

The BTS3606 cabinet needs no optical fiber. But if the BTS3606 needs to connect

with the ODU3601C, the CCPM with optical interface must be configured to connect

to the ODU3601C using optical fibers

The following introduces the fiber connection between the BRDM and BTRM or

ODU3601C.


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3-11

Caution:

Never directly look at the fiber connector of the board with naked eyes.

The optical fiber is fragile. Never pull the optical fiber by force, or bend it with the radius of less than

25 mm.

The removal and insertion of fiber connectors may affect the corresponding carrier service.

To check the optical fiber connection:

I. Check the terminal connection

Check the fiber connection. Ensure that the Tx terminal of the BRDM is connected to

the Rx terminal of the BTRM or ODU3601C and the Rx terminal of the BRDM to the

Tx terminal of the BTRM or ODU3601C.

If the optical fibers are connected inversely, you cannot insert the connectors.

II. Clean the connectors

Remove the fiber connector, clean it with dedicated sanitary materials, and then insert

it again.

For details about the removal and insertion of fiber connectors, see Chapter 4, Part

Replacement.

III. Replace optical fiber to locate fault

Caution:

The optical fiber connecting with the ODU3601C cannot be replaced with that connecting with the

BTRM. That is because the former is a single-mode fiber, while the latter is a multi-mode fiber.

Replacement of the optical fiber may affect the normal fiber connection and eventually the BTS

service.

If some fiber connections are normal, but some are abnormal, you can locate the fault

through replacement check. Proceed as follows:

Exchange the abnormal optical fiber for the normal one on the BRDM.

Exchange the abnormal optical fiber for the normal one on the

BTRM/ODU3601C.


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Compare the connection before and after the exchange to determine whether the

BRDM, optical fiber (including fiber connectors), or the BTRM/ODU3601C is faulty.

Then, replace the faulty parts following the instructions described in Chapter 4, Part

Replacement.

IV. Test optical fiber

You can judge whether the optical fiber is faulty through an optical power meter. For

details, see the operation manual of the optical power meter.

3.2.5 Blocking/Unblocking Resource

To avoid affecting the BTS service, block the logical resource and physical resource

before operating on the specific board or module. After that, unblock the resources.

In addition, to avoid the exposure to the RF radiation, block the relevant logical

resource before approaching the RF antenna or other parts with RF signal leakage.

After that, unblock the resource.

The following lists blocking levels from high to low:

Immediate blocking: After the selection of immediate blocking, all resources are

blocked. As a result, all calls handled by the BTRM/CTRM or BCPM/CCPM are

dropped.

Delay blocking: After a preset period of delay, all resources are blocked. As a

result, all calls handled by the BTRM/CTRM or BCPM/CCPM are dropped. If the

cell is idle, the resources will be blocked immediately.

Idle blocking: Resource is blocked only when the resource is idle. Idle blocking

does not cause call drop.

Caution:

The blocking of BTS physical resource may cause the block of relevant cells or sectors and

interruption of on-going services.

If the power of the dedicated BTRM/CTRM or BCPM/CCPM must be cut off, it is necessary to select

a proper blocking level to avoid the impact on the BTS service.

To block the physical resource is to block the BCPM. If it is necessary to remove

BCPM on site, block this BCPM first.

To block and then unblock the logical resource:


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3-13

I. Block logical resource

To block logical resource, proceed the following:

--Obtain the authority of the network administrator.

--Select a proper blocking level.

--Execute the command BLK BTSLOGRES.

II. Cut off the relevant power supply

Find the relevant power switch of the BTRM/CTRM in the switch box and turn it off.

III. Perform other operations

Perform other scheduled operation. For example, replace modules, or repair the

antenna system.

IV. Connect the relevant power supply

V. Unblock logical resource

Execute the command UBL BTSLOGRESto unblock the logical resource previously

blocked.

To block and then unblock the physical resource:

VI. Block physical resource

To block physical resource, proceed the following:

--Obtain the permission of the network administrator.

--Select a proper blocking level.

--Execute the command BLK BTSPHYRES.

VII. Perform other operations

Perform other scheduled operation. For example, replace the BCPM/CCPM.

VIII. Unblock physical resource

Execute the command UBL BTSPHYRES to unblock the physical resource

previously blocked.


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3.2.6 Checking Communication Status of EAC

The indoor BTS is generally configured with an Environment Alarm Chest (EAC) to

monitor the room environment.

Check whether the communication between the EAC and BTS is normal according to

the following steps.

If you are in the BTS equipment room, directly go to step 3.

To check the communication status of the EAC:

I. Query alarm information

Check through Telnet or LMT whether there is an alarm indicating the EAC

communication failure.

If yes, the communication between the EAC and BTS is abnormal.

If no, the communication may be normal, or it is believed that no EAC is

configured because the BTS does not receive the information of EAC when

starting.

To confirm the above case further, go to the next step.

II. Query ambient temperature and humidity

Execute the command DSP BTSENVPARA to query the ambient temperature and

humidity of the BTS equipment room.

If the message returned is Environment Alarm Chest absent or link

disconnected, the communication of EAC is abnormal.

If the ambient temperature and humidity are returned, the communication is

normal.

III. Check the indicator

If you are in the BTS equipment room, check the indicator of the EAC, and judge

whether the indicator status is normal based on the relevant manual of EAC.

3.2.7 Checking RF Connection

If the forward and reverse coverage area of the BTS is affected, a fault may occur to

the RF connection, including:

Connection between the RF antenna and RF front-end module

Connection between the RF front-end module and power amplifier module

Connection between the power amplifier module and transceiver module


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Caution:

RF signals may do harm to human beings. Therefore, it is necessary to turn off the relevant power

amplifier module before cutting off the RF connection.

To check the RF connection:

I. Test return loss of antenna

Test the return loss of RF transmit-receive path by following the instructions in section

5.7, Instructions for Return Loss Test. If the measured standing wave ratio is great

(values less than 1.3 are preferable), it is necessary to check the RF connection

segment by segment.

II. Perform short circuit test on feeder (including jumper) shielding layer and

core wire

See section 3.3 , Troubleshooting of Clock Faults.

III. Perform continuity check on feeder (including jumper) core

See section 3.3 , Troubleshooting of Clock Faults.

IV. Perform visual check

Check the RF connection from the antenna to the BTRM/CTRM segment by

segment.

Check the following items:

Whether the antenna and jumper connector are connected securely.

Whether the jumper and feeder (including jumpers at the antenna side and

equipment side) connector are connected securely and in good contact. Whether the jumper and the feeder connector on the cabinet are connected

securely and in good contact.

Whether the jumper inside the cabinet and the connector on the RF front-end

module are connected securely and in good contact.

Whether the fins of the connector on the RF subrack backplane are damaged

and whether jumpers are connected securely and in good contact.

Whether the ultra flexible jumpers between the RF module panels are connected

securely and in good contact.

Whether the RF blind mate connector is well connected.

Whether water comes into the feeder.


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3.3 Troubleshooting of Clock Faults

In regard to the importance of the clock to the CDMA system, this section details the

clock fault troubleshooting procedures. Typical cases are also provided to explainhow to handle the clock fault.

Faults of the BTS36 series base station feature the following symptoms:

The quality of speech is poor.

Handoff between BTSs fails.

Calls are often dropped.

The ACT indicator of BCKM flashes at 0.25 Hz.

The ACT indicator of BTRM flashes at 0.5 Hz.

The causes for clock faults are as follows:

The phases or frequencies of the clock system jump.

The satellites traced are insufficient.

It takes a long time to trace enough satellites.

It is impossible to trace satellites.

For the above causes, the fault location and troubleshooting procedure are presented

below.

3.3.1 Jump of Phases or Frequencies of the Clock System

I. Fault symptom

The following alarms are found through the LMT.

ALARM 31469 Fault Important BSS 10580 Hardware System

Alarm Name = Master Clock Out of Lock

Alarm Generation Time = 2003-04-01 12:55:03

Location Information = BTS Name=###, BTS ID=19, Board Type=BCKM_CLK, Board

ID=0, Details=Freq/Phase Jump in PHASE_ADJUST State

Restore Status = Normal restore

Restore Time = 2003-04-01 12:55:05

Acknowledging Status = Unacknowledged;

You may also query BTS alarms through Telnet. If you find the following alarms, it

also indicates that jump of phases happens in the BTS clock.

HW CBTS>lst curalm:brdtp=bckm clk,brdid=0

Query result:

HW CBTS>

OccurTime = [2003-04-01 12:55:03] EndTime = [2003-04-01 12:55:05]

AlarmType = Alarm, AlarmLevel = Notice


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AlarmItem = [ 65] star link failure

Type = BCKM_CLK, Id = 0

SubUnitType = [255] default subunit type, SubUnitId = 255

Details = Phase/Freq Jump in PHASE_ADJUST State

II. Fault location

If the BTS generates alarms of jump of clock frequency or phase occasionally, it

indicates that unknown electromagnetic interference affects the measurement result

of the Phase-Frequency Detector (PFD) on the BCKM. However this exception only

affects the system briefly and can be ignored.

If the BTS generates these alarms frequently, it is very likely that the hardware of the

BCKM is faulty. In this case, trace the phase of the clock phase-locked loop to judge

whether the hardware is faulty.

Enter the following command through Telnet:

str infotrace:brdtp=bckm clk,brdid=0,item="spll"

If the BCKM can trace enough satellites, and the voltage of the phase-locked loop is

unstable, it can be concluded that the hardware of BCKM is faulty. In this case,

replace the BCKM.

3.3.2 Failure to Trace GPS Satellites

I. Fault symptom

The BTS cannot trace any satellite.

II. Fault location

In this case, you must first verify that the current reference source is not the internal

reference source (inclk) and check whether the clock parameters are correctly

configured. Then follow the following order to locate faults.

1) Verify whether the Global Positioning System (GPS) antenna is installed in the

right place.

To ensure that BTS receives the optimal GPS signals, the installation position of

the GPS antenna must satisfy the following conditions.

Install the GPS antenna in an open area without any shelter within the range

that is ten or more degrees from the horizon.

Install the antenna in the center of building roof rather than at the corners or

on the parapets around the building roof to avoid lightning strikes.


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Avoid short-distance radiation of the main beam of mobile communication

antennae. Do not install the antenna under microwave antennae, high-voltage

cables, and TV transmission towers.

2) Check the connection of GPS antenna.Check the following items:

Insulation

Disconnect jumpers with the GPS antenna and the cabinet. Measure the

insulation resistance between shielding layers of jumpers with core layers.

The resistance must be several mega-ohm or above.

If the resistance is small or cables are short-circuited, measure the resistance

section by section to locate the short-circuited cable.

The conductor of the feederDisconnect jumpers with the GPS antenna and the cabinet. Short-circuit the

shielding layer of one end of the jumper and the core layer. Measure the

resistance between the shielding layer and the core layer at the other end of

the jumper. The resistance must be very small.

If the resistance is infinite, it indicates that the conductor is disconnected.

Measure section by section to locate the short-circuited position.

The short cable (white) between the GPS receiver and BCKM panel.

The cable might be unable to receive GPS signals because it has been

twisted too long.

You can replace the cable with a 10 MHz output cable or a 2S output cable to

verify whether it is the cable failure that causes the incapability of BTS to

receive GPS signals.

3) Check the GPS antenna lightning arrester.

The installation of the GPS antenna lightning arrester varies with the types of the

lightning arrester.

For the iS-MR50LNZ+6 type, its PROTECTED end must face the BTS.

For DGXZ+6NF NM-A type, its EQUIPMENT end must face the BTS.

If a lightning arrester is inversely installed, the insertion loss of the GPS receive

channel will increase, which affects the reception of GPS signals.

If the lightning arrester fails, the BTS cannot receive GPS signals normally. In

this case, remove the lightning arrester and check how the BTS traces GPS

satellites to verify whether the lightning arrester fails.

4) Check the GPS receiver (you may also apply to replace the BCKM or the GPS

receiver if you are in the equipment room.).


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The following lists major faults of the GPS receiver and explains how to locate

these faults.

The feed voltage drops abnormally.

To locate the fault, disconnect the feeder from ANT port on the front panel of

the BCKM and measure the voltage the GPS receiver outputs to the GPS

antenna. In normal case, the output voltage of the SMA socket is more than

4.8 V.

If the feed voltage is less than 4.5 V, it is likely that the hardware of the GPS

receiver is faulty. In this case, replace the GPS receiver.

The GPS receiver card does not export 1PPS signals.

To locate the fault, check the current alarms of the BCKM clock module

through Telnet and see whether the following alarms exist.HW CBTS>lst curalm:brdtp=bckm clk,brdid=0

Query result:

HW CBTS>

OccurTime = [2000-01-01 00:00:00]

AlarmType = Alarm, AlarmLevel = Minor

AlarmItem = [ 66] ref clk resource failure

CardType = BCKM_CLK, CardId = 0

SubUnitType = [255] default subunit type ,SubUnitId = 255

Details = No Ref Clk Source

HW CBTS>

OccurTime = [2000-01-01 00:00:00]





Details = 1PPS No Output

If the alarms exist and do not disappear, it indicates that the 1PPS output part

of the GPS receiver is faulty. In this case, replace the GPS receiver. The communication serial port of the GPS receiver card is faulty.

To locate the fault, check the current alarms of the BCKM clock module

through Telnet and see whether the following alarms exist.


Query result:

HW CBTS>

OccurTime = [2000-01-01 00:00:00]




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Details = Clk Src Communication Stop

If the alarms exist and do not disappear, it indicates that the communicationserial port of the GPS receiver card is faulty. In this case, replace the GPS

receiver.

The GPS antenna is faulty.

You can use the exclusive method to locate the fault.

First perform the above three steps to exclude the above three faults. If the

above three faults are excluded and the GPS signals still cannot be received,

the GPS antenna may be faulty.

Check the current alarms of the BCKM clock module through Telnet and seewhether the following alarm exists.

HW CBTS>lst_curalm:brdtp=bckm clk,brdid=0

Query result:

HW CBTS>

OccurTime = [2000-01-01 00:00:00]





Details = Antenna Connection Open or signal weak

This alarm is generated the working current of the antenna is lower than the

detection threshold of the GPS receiver.

You can replace the GPS antenna to make further judgment. If the alarm

disappears, the GPS antenna is faulty. If the alarm does not disappear, check

the connection between GPS antenna and the GSP receiver.

3.3.3 Failure to Trace Enough GPS Satellites

I. Fault symptom

The BTS reports the alarm Failure to trace enough GPS satellites.

The meaning of the alarm varies with versions.

Versions earlier than cBTS3612V100R002B02D003

This alarm means that the number of satellites traced by the GPS receiver is

less than four.

Version cBTS3612V100R002B02D003 or later


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When the alarm occurs before the BTS clock synchronizes the GPS for the first

time, it means that the number of satellites traced by the GPS receiver is less

than four.

When the alarm occurs while the GPS receiver is in position holdover mode, it

means that the number of satellites traced by the GPS receiver is less than two.

II. Fault location

Check the special statuses of the clock module through Telnet. If the RM Position

Hold status is enabled, the GPS receiver is in position holdover mode. If the RM

Position Hold status is disabled, it indicates that the GPS receiver card is not in the

position hold mode.

If the BTS can trace more than one GPS satellite, it can be concluded that thehardware failure does not occur to the GPS antenna, the connection cable, the

lightning arrester, or the GPS receiver card. (You can obtain the number of GPS

satellites by checking the special statuses of the BTS clock module.)

It is possible that the installation position of the GPS antenna is inappropriate. Check

the installation position of the GPS antenna. For details, see section 3.3.2 , Failure

to Trace GPS Satellites.

3.3.4 A Long Time Required to Trace Enough Satellites

I. Fault symptom

The BTS fails to trace enough GPS satellites in a long time (more than 30 minutes)

after it is powered on for the first time.

Before enough satellites are traced, the following two alarms of the BTS clock module

can be found: Can not Traced Enough Satellites and PP2S Phase does not

synchronize with GPS.


Query result:

HW CBTS>

OccurTime = [2003-04-09 15:52:55]





Details = Can not Traced Enough Satellites

HW CBTS>

OccurTime = [2003-04-09 15:52:43]


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AlarmType = Alarm, AlarmLevel = Major

AlarmItem = [ 67] main clk unlock



Details = PP2S Phase does not synchronize with GPS

alarm recorder inquiring has been finished!

II. Fault location

The above symptom does not necessarily mean that the BTS module is faulty. It is

possible that the 3D information (longitude, latitude and altitude) stored in the GPS

receiver is quite different from the actual position of the BTS.

For example, the site is in east longitude and north latitude. But the 3D information

stored in the GPS receiver card is west longitude and south latitude.

In this case, the BTS will spend a long time calculating the 3D information when it is

first powered on. Therefore, it takes a long time to for the BTS to trace enough

satellites.

To locate the fault,

1) Obtain the 3D information stored in the GPS receiver card.

You may use the command that is used for checking the special information of

the BTS clock module.

2) Enter the BTS 3D information.

The cBTS3612V100R002B02D003 or later versions provides an interface for

entering the 3D information to shorten the time spent on GPS satellites tracing

and 3D location.

In general, it takes the BTS less than 30 minutes (ten minutes typically) to trace

enough GPS satellites after the 3D information is entered. You can log in to the

BTS through Telnet and execute the following command to enter the 3D

information:

set btsinitpos: BRDID=, lat=< >, long=< >, alt=< >

brdid : bckm id from 0 (slot 7) to 1 (slot 8)

lat : latitude value from -90 to 90 (latitude of GPS)

long : longitude value from -180 to 180 (longitude of GPS)

alt : altitude value from -500 to 10000 (altitude of GPS)

You can obtain the longitude, latitude and altitude information from other BTSs

that can trace satellites, or from the parameter list of the network planning. You

may also obtain the approximate 3D information from the maps of the local area.


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Note:

In general, it is not necessary to enter the 3D information when the BTS is powered on for the first

time.

If the longitude, latitude and altitude information obtained through checking special statuses of the

BCKM_CLK module differs greatly from the actual ones, the setting of the BTS 3D information speed

up the satellites location and locking of the GPS receiver.

Do not use commands to change the BTS 3D information when the BTS is running normally to avoid

the phase jump of the PP2S signals.

3.3.5 Case Library of Clock Faults

The following are typical cases for clock faults.

I. Failure to trace GPS satellites due to the failure of GPS lightning arrester

Fault symptom

The BTS fails to trace GPS Satellites.

Fault location

Log in to the BTS through Telnet. Check the alarms of BCKM. The antenna

connection open alarm can be found. Locate the fault step by step. After the

GPS lightning arrester is removed, the alarm disappears. The BTS can trace

enough satellites.

It can be concluded that the failure of the GPS lightning arrester causes the

problem.

II. Failure of the BTS to trace GPS satellites due to microwave interference

Fault symptom

The alarm that satellites are lost occurs from 8:00 A.M to 9:30 A.M. every day.

The number of satellites traced is less than three.

Fault location

The above symptom indicates that the hardware of the BTS equipment is not

faulty. The BTS is installed on the highest building without shelters around. But

there is a microwave antenna facing the GPS antenna obliquely.

It is possible that the microwave interference causes the fault.

Test the performance of the GPS receiver by holding it at the place where the

BTS antenna is installed. Test result shows that the receiver can trace the same


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number of satellites as the BTS does. That is, at most five satellites can be

traced.

This indicates that nothing is wrong with the equipment of the BTS. The

installation position of the GPS antenna is appropriate. The microwave radiation

affects the receiving performance of the GPS antenna.

Lower the installation position of the GPS antenna to avoid the interference of

the microwave antenna, and the BTS can trace seven satellites. In most cases,

the BTS can trace six satellites. The performance of the GPS antenna is greatly

improved.

III. System clock failure due to failure of the constant-temperature crystal

oscillator of the phase-locked loop

Fault symptom

Clock alarms are detected frequently in a site after kickoff.

These alarms include:

--Exception of the channel processing chip clock

--Exception of the system clock

--The primary clock is unlocked

The performance measurement result shows that the call drop rate of the BTSreaches up to 6.9%, much higher than the average rate (1.6%).

Fault location

The above symptom indicates that the BTS can trace GPS satellites normally

and that the frequent occurrence of alarms is caused by the hardware fault of the

BCKM phase-locked loop.

As it is impossible to find out which part of the BCKM is faulty, the whole BCKM

is replaced to solve the problem. Later the faulty BCKM is tested in the lab and it

is found out that the 10 MHz crystal oscillator is faulty.

IV. The BTS takes a long time to trace GPS satellites

Fault symptom

A BTS cannot trace enough GPS satellites (four) for a long time after it is

powered on, and the number of the traced satellites changes from three to zero.

Fault location

This problem occurs before the GPS receiver completes the location task. If the

position information of the GPS receiver is correct, this problem will not occur

again.


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Check the special status of the clock during the power-on of the BTS, and the

result is as follows:

HW CBTS>dsp btsbrdspecstat:brdtp=bckm_clk,brdid=0

clk ref source : gps

satellites traced : 4

latitude : N30o2'7"

longitude : E125o5'42"

altitude : -439m

pll status : search (freq adjust)

GMT offset : eastern 8:0

(Note: When the BTS traces four satellites, the number of the traced satellites

soon changes to zero.)




latitude : N30o2'7"


altitude : -439m

pll status : search (freq adjust)


The information after location is as follows:




latitude : N27o35'4"


altitude : +108m


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pll status : lock


The result of the special status shows that the 3D information differs greatly

before and after the location of the GPS receiver.

The GPS receiver calculates the 3D information by iteration to verify whether it

has traced GPS satellites. The history 3D information is needed for the

calculation process. But the history 3D information differs greatly from the actual

one, which prolongs the iteration process. Therefore, it takes a long time before

the BTS can trace enough GPS satellites after it is powered on.

Documents

BTS3606 Troubleshooting