Quick guide to common troubleshooting during commissioning

Key inspection items in project review

• Topology check

  Check the actual connections of the equipment to ensure that the connection relationship is the same as that specified in the design drawing and is the same as the topological connection relationship configured at the back end. If not, it may cause the MAU, PB, and Pico RRU links to fail.

• Optical fiber check

  1. An optical fiber is connected only when the two indicators at the two ends are lit respectively. If only one indicator is lit, the optical fiber is disconnected.

  2. On the PB and MAU, the receive status indicator and transmit status indicator are separated. The baseband board has the receive status indicator only. The receive status indicator needs to be especially noticed. The single-core link (remote-end transmitting and local-end receiving) is connected only when the receive status indicator is lit. If the indicator is lit, it indicates that the optical fiber is connected. If the indicator flashes, it indicates that data is being transmitted.

• Ethernet cable check

  Use the Ethernet cable tester to check whether the Ethernet cable of the Pico RRU is disconnected. Ensure that the Ethernet cable is connected in the correct core sequence and all the eight cores are connected. QCell2.0 uses the PoE power supply mode, with a rate of 2.5 Gbps. Thus all the eight cores are used, different from the traditional rate of 1 Gbps by using only four cores.

Quick Fault Query of Common Faults

• Quick Fault Query: The PB Link Is Disconnected
• Quick Fault Query: PoE Failure Is Reported by the Ethernet Interface of the PB Corresponding to the pRRU
• Quick Fault Query: Ethernet Link Disconnection Is Reported by the Ethernet Interface of the PB Corresponding to the pRRU
• Quick Fault Query: The QCell-GSM Cell Has No Signals
• Quick Fault Query: Signals in a QCell-GSM Cell Fluctuate Greatly & Signal Strength Decreases Sharply & Service Quality Is Unstable

Quick Fault Query: The PB Link Is Disconnected

In accordance with the actual condition, the PB link is disconnected due to the following causes:

1. Topology problem. The actual connection relationship of the PB is different from the plan, meaning that it is different from the back-end configuration. The topology relationship of the PB is configured at the back end, but the PB connection does not actually exist. Thus, the PB link is disconnected. For the disconnected PB, check whether the optical module of the upper-end optical interface is in position at the back end. If not, the PB is not connected properly. Check the actual physical connections at the front end.

2. Optical fiber fault. Check the indicators at the two ends of the optical fiber to see whether they are operating properly. If not, the physical optical fiber link is faulty. In this case, you need to troubleshoot problems related to optical fibers and optical modules.

3. Optical module rate problem. The QCell can use 10G optical modules only and does not support other types of optical modules. Therefore, when the PB is disconnected, check whether the optical modules at the two ends are 10G optical modules.

4. If the above causes are excluded but the fault persists, deal with the problem in accordance with the fault reporting flow.

Quick Fault Query: PoE Failure Is Reported by the Ethernet Interface of the PB Corresponding to the pRRU

In accordance with the actual condition, the PoE failure is due to the following causes:

1. Topology problem. The actual connection relationship of the PB is different from the plan, meaning that it is different from the back-end configuration. The topology relationship of the pRRU is configured at the back end, but the pRRU connection does not actually exist. Thus, the alarm is reported. In this case, check whether the Ethernet interface of the PB is connected to an Ethernet cable at the front end.

2. Check whether the pRRU is in position and check whether the two ends of the Ethernet cable is installed properly.

3. Ethernet cable fault. Use the Ethernet cable tester to verify that the Ethernet cable is connected in the correct core sequence and all the eight cores are connected.

4. Cross-validation and replacement-validation. Perform cross-validation for the Ethernet interface at the PB side and perform replacement-validation for the pRRU to check whether the PB and pRRU are operating properly.

Quick Fault Query: Ethernet Link Disconnection Is Reported by the Ethernet Interface of the PB Corresponding to the pRRU

This alarm is reported if the pRRU can be powered on but the data link is disconnected. The fault is mainly due to Ethernet cable problems. Use the Ethernet cable tester to verify that the Ethernet cable is connected in the correct core sequence and all the eight cores are connected. You can also remove the pRRU and connect a short Ethernet cable to the Ethernet interface of the PB to check whether the fault is due to Ethernet cable problems.

Quick Fault Query: The QCell-GSM Cell Has No Signals

Frequency locking is required in the QCell-GSM test; otherwise, other macro GSM cells or indoor GSM cells may be accessed first. If no QCell-GSM cell can be detected in the case of frequency locking, perform the following troubleshooting steps:

1. Check the pRRU first to see whether the GSM channel of the pRRU has output power. In most cases, the output power of the pRRU ranges from 8 dbm to 17 dbm. (It is recommended that not more than eight GSM carriers be fed to the QCell.)

2. If the GSM channel of the pRRU has output power, the signals are faulty, causing UEs unable to access the cell. In this case, you need to troubleshoot the problem that UEs cannot access the cell.

   1. Check the signal source fed to the QCell to verify that the GSM signal source is correct. For example, in a project of China Mobile, GSM site signals of China Unicom are fed in.

   2. Check whether the source GSM cell has users and whether it can be accessed properly.

   3. Verify the number of TX channels of the source cell and compare it with the number of actually fed-in physical connections. Check whether all TX channels are fed in, combined, and connected to the MAU. If only the service carrier is fed in but the BCCH carrier is not fed in, signals may exist but UEs cannot access the cell. In this case, check the feed-in power in idle hours and busy hours respectively. If the feed-in power fluctuates greatly, it is diagnosed that only the service carrier is fed in and the BCCH carrier is not fed in.

3. If the GSM channel of the pRRU has no output power, check whether the feed-in power is normal. The feed-in power must range from −20 dbm to +10 dbm. Feed GSM signals to the physical connections, ensure that the physical connections are normal, and check whether the signal source is operating properly.

Quick Fault Query: Signals in a QCell-GSM Cell Fluctuate Greatly & Signal Strength Decreases Sharply & Service Quality Is Unstable

The possible fault causes include:

1. The signals initially received by a UE are BCCH pilot signals. The service carrier is allocated to the UE to conduct services, but the allocated service carrier has no power. Thus, it is observed on the UE that signal strength decreases sharply.

2. The internal over-power protection mechanism of the QCell causes no signal output.

Troubleshooting procedure:

1. Verify the number of TX channels of the source cell, and check whether the feed-in connection solution is correct. The number of TX channels configured for the source cell must be the same as the number of feed-in links.

2. Check the configuration data to ensure that the GSM configuration is the same as that at the signal source side.

3. Check whether the fault is due to the over-power protection mechanism. Decrease the insertion loss to 3 dB, 7 dB, and 10 dB respectively to see whether the problem is resolved. If the problem is resolved, the GSM feed-in configuration is incorrect. In this case, verify that the GSM source information and actual insertion loss are correct.