Debugging Performance Issues

Q: What are the commonly reported issues?

After provisioning LTE AP and enabling transmission, there may be rare scenarios that can cause performance issues.

The following table is a list of typical performance issues and suggested corrective actions.

Table 1. Performance Issues and Corrective Actions
ID Issue Details Corrective Action
1 Poor data rate Poor data rate measured in DL/UL or both directions compared to expected throughput.
  1. Check the backhaul capacity/throughput rating.
  2. Obtain the RF logs and check sources of interference (RSRP/RSRQ values).
  3. Check for UE handing off multiple times (also known as ping-pong effect) between more than one LTE AP.
2 UE disconnects frequently from network. UE connection is dropped frequently and reconnects after unplugging. If using a USB dongle/Wi-Fi Device over USB, check the dongle USB connection.
3 EPC connection down. S1 connection disconnected after successful connection during initial setup.
  1. Check the S1 status via get S1APConfigParam command to match EPC parameters.
  2. Check the IP reachability (try pinging the MME IP address from the AP).
  3. Capture the Wireshark trace (or tcpdump) on the switch via port mirroring.
  4. Open the "S1AP" messages and follow the sequence to learn the reason for rejection or setup failure.
4 AP not transmitting although all connection are successful. All LEDs are solid Green but LTE is dark - transmission stopped.
  1. Check whether the AP service button is ON.
  2. Check alarms to detect if there are any issues reported with SAS availability/ response.
  3. Check the statistics to obtain the CurrentGrant status.
  4. Check the logs for SAS-CBSD communication and check for any error codes that have been reported.
5 Timing sync lost/ SYNC LED starts to blink. In general, when a timing sync is lost, the SYNC LED is dark/blinking indicating it is trying to regain connection with timing master/GPS.
  1. When in PTP-slave mode: Check connection with the Timing Master AP using the IP address.
  2. When in PTP-Master mode: Check visibility to satellites/ line of sight to open sky, and relocate to a new position closer to the window or door.

Case 1: LTE AP is in sync but has disconnected from the ACS and/or Mgmt SecGW

Review the following information.

  1. An AP reboots 24 hours after disconnection with the AP management platform when it is unable to reach LTE AP Management.
  2. After reboot, an AP connects to the SC-R.
  3. The SC-R sets relevant IP address of the SecGW and LTE AP management (ACS) on an LTE AP.
  4. The LTE AP attempts to connect to the LTE AP Management
  5. If an LTE AP is unable to connect, it keeps on retrying for 24 hours. On completion of 24 hours, steps 1, 2, and 3 mentioned above are repeated.
  6. An AP repeats the above steps for a total of 3 times, one each reboot after 24 hours.
  7. After a total of 96 hours from the first disconnection, AP reverts to the factory reset. In this case, any configuration that was set from ACS or using the CLI, get reset and in this case the earlier AP configuration is erased.
    Note: The above-mentioned behavior is for the disconnection/not reachable case only. SC-R: sc-registrar - A database/ service in the management platform that provides each AP important connectivity information upon power up.

Case 2: LTE AP is in not in sync and has disconnected from the ACS and/or Mgmt SecGW:

Review the following information.

  1. If after startup, the PTP hard sync does not occur, the behavior for network disconnection mentioned in case I above should be used.
  2. If an external PTP device is configured (not using a Ruckus AP as the Timing Master) to provide timing information to the network, ensure that the following settings are set on the PTP source:

    1. Ensure that the PTP source and rest of the APs are on the same Layer 2 network and the PTP traffic is allowed on any firewalls in between.
    2. Select the 8275.2 profile on your timing source administration/ configuration page.
    3. Set Domain to 44.
  3. If GPS synchronization is does not occur from startup or the PTP phase sync is not achieved (but the PTP hard sync has been achieved), RSC reboots every hour till the synchronization is achieved. The timers mentioned in case I above does not apply in this case that is the LTE AP does not go to SC-R or perform a factory reset.
  4. If AP was already synchronized when the network disconnected, and if it loses synchronization that is goes into holdover.

    a. LTE AP reboots after 1 hour in the case of the PTP master assuming that 24 hours of the network disconnection have not occurred

    b. LTE AP reboots after 2 hours in the case of the PTP slave assuming that 24 hours of the network disconnection have not occurred

  5. If after reboot, AP achieves synchronization, but is still disconnected from the network, in that case behavior for network disconnection mentioned in case I above shall be used. Note that the disconnect reboot timer is applicable from the reboot in such a case.
  6. If after a reboot, AP does not achieve synchronization, the behavior mentioned in this case II is applicable.