RF Unit VSWR Threshold Crossed

High VSWR on 3G ( Indoor System ) Phenomenon Description

Impact on the System Alarm Severity Major Minor

VSWR 2G Checking ( NMS)

VSWR 3G Checking (NMS)

VSWR Checking ( ONSITE)

ALARM HANDLING

ALM-26529 RF Unit VSWR Threshold Crossed Description If the forward transmit power of a transmit channel is greater than or equal to a certain value, the BTS monitors the VSWR at the antenna ports every two minutes. ALM-26529 RF Unit VSWR

Threshold Crossed is reported when the BTS detects that the antenna VSWR exceeds a specified range for three consecutive times. VSWR alarm thresholds have two levels: level 1 and level 2. You can run the MML command SET BTSRXUBP to change the thresholds to meet the requirements for antenna VSWR monitoring. 1. The default value of the level-1 VSWR threshold is 2.0. The minimum value of this threshold is 1.8. The BTS considers this threshold as 1.8 even if it is set to a value less than 1.8. 2. The default value of the level-2 VSWR threshold is 3.0. The value of this threshold must be greater than the value of the level-1 VSWR threshold. A minor alarm is reported when the BTS detects that the antenna VSWR is higher than the level1 VSWR threshold but lower than or equal to the level-2 VSWR threshold for three consecutive times. A major alarm is reported when the BTS detects that the antenna VSWR is higher than the level-2 VSWR threshold for three consecutive times. The alarm clearance conditions are as follows: 

A minor alarm is cleared when the BTS detects that the antenna VSWR is lower than the level-1 VSWR threshold for three consecutive times.



A major alarm is cleared when the TRX is reset while a normal antenna VSWR is ensured.

Parameters Name

Meaning

Cabinet No.

Cabinet number of the faulty board

Subrack No.

Subrack number of the faulty board

Slot No.

Slot number of the faulty board

TX Channel No.

TX channel number

Board Type

Type of the faulty RF unit

VSWR Alarm Threshold (0.1)

VSWR alarm threshold configured by the user

VSWR

Detected VSWR with the precision of 0.1

Output Power (0.1 dBm)

Output power of the RF unit

Impact on the System Alarm Severity Major

Alarm Severity Minor

System Actions The BTS does not process a minor alarm. A minor alarm is automatically cleared when the detected VSWR is smaller than the level-1 VSWR threshold. When the BTS detects a major alarm, it closes the transmit channel. A major alarm cannot be automatically cleared.

Possible Causes 

Inappropriate data configuration

A VSWR alarm threshold is set inappropriately. 

Hardware fault

The frequency band type of the TRX is inconsistent with that of the antenna components. The actual VSWR of the antenna components increases, leading to an abnormal antenna VSWR. The reason may be: 1. An antenna component is damaged. 2. A connector on an antenna component is not well prepared. 3. A connector on an antenna component is not tightened or is wet. 4. An antenna cable is bent or deformed. The two input ports on the 3 dB combiner or hybrider are not highly isolated. Therefore, the detected VSWR is higher than the actual VSWR, which leads to false VSWR alarms. This situation occurs when a combiner is used by multiple carriers working on the same frequency band. NOTE: The antenna system usually has the following components: antenna, feeder, jumper, combiner and splitter, 3 dB hybrider, directional coupler, filter, tower-mounted amplifier (TMA), and BIAS TEE. A transmit port on the RF unit is damaged. The VSWR detection circuit of the RF unit is faulty. Troubleshooting 

Verify that the VSWR alarm thresholds are set correctly.



Reset the TRX remotely.



Reset the TRX on site.



Verify that the connectors on the antenna components are tightened.



To check whether the antenna system is faulty, use a new antenna to replace the antenna connected to the TRX reporting this alarm.



Replace the faulty antenna components or TRX.

Workflow

Procedure 1. Check the VSWR alarm thresholds remotely. a. Run the MML command LST BTSRXUBP to query the VSWR thresholds for the RF unit and determine whether the thresholds are set correctly according to the configuration plan. Y => The thresholds are set correctly. Go to step 2. N => The thresholds are set incorrectly. Go to step b. b. Run the MML command SET BTSRXUBP to modify the VSWR thresholds for the RF unit.

If the alarm is a major alarm, reset the TRX. Ten minutes later, check whether the alarm is cleared. Y => The alarm is cleared. No further action is required. N => The alarm persists. Go to step 2. 2. Reset the TRX remotely. On the LMT, reset the TRX where the alarm is generated. Check whether the alarm is cleared. Y => The alarm is cleared. No further action is required. N => The alarm persists. Go to step 3. 3. Check the frequency band used by the RF unit and antenna components. a. Check whether the frequency band type of the RF unit is consistent with that used by the antenna components. Y => The frequency band types are consistent. Go to step 4. N => The frequency band types are inconsistent. Go to step b. b. Replace the antenna components with new ones that work on the same frequency band as the old components. If the alarm is a major alarm, reset the TRX. Ten minutes later, check whether the alarm is cleared. Y => The alarm is cleared. No further action is required. N => The alarm persists. Go to step 4. 4. CAUTION: 5. The check personnel must carry antenna components with the same frequency band type as that of the RF unit when checking VSWR faults at sites. 6. Check the antenna VSWR. a. Check the antenna VSWR as follows: If there is a VSWR tester, test the VSWR at the antenna ports in frequency mode. If there is no VSWR tester, replace the antenna to check whether the antenna system is faulty. Check whether the alarm is cleared. Y => The antenna VSWR is normal. Go to step 5. N => The antenna VSWR is abnormal. Go to step b.

b. Rectify the VSWR faults in the antenna system as follows: If there is a VSWR tester, check for antenna faults in distance to fault (DTF) mode and rectify the faults. If there is no VSWR tester, check for antenna faults by checking whether the connectors on the antenna components are tightened, whether the antenna components are damaged, or by replacing the antenna components, and then rectify the faults. If the alarm is a major alarm, reset the TRX. Ten minutes later, check whether the alarm is cleared. Y => The alarm is cleared. No further action is required. N => The alarm persists. Go to step 5. 7. Check whether a combiner is used. a. Check whether a combiner is used for multiple carriers. Y => A combiner is used. Go to step b. N => A combiner is not used. Go to step 6. b. Replace the existing combiner with a new combiner whose input ports are highly isolated. If the alarm is a major alarm, reset the TRX. Ten minutes later, check whether the alarm is cleared. Y => The alarm is cleared. No further action is required. N => The alarm persists. Go to step 6. 8. Reset the RF unit on site. a. Power off and then power on the RF unit. After the RF unit restarts, the RUN indicator blinks one second on and one second off if the RF unit works properly. Check whether the alarm is cleared. Y => The alarm is cleared. No further action is required. N => The alarm persists. Go to step 7. 9. Replace the RF unit on site. a. Replace the RF unit. Check whether the alarm is cleared. Y => The alarm is cleared. No further action is required.

N => The alarm persists. Reinstall the original board and contact Huawei customer service center.

Resolving Action Check VSWR at Jumper cable , Combiner and DAS with site master. It is found that the problem source is the multiband combiner. After replacing the faulty ony, VSWR back to normal.

Status After