PRACH Preamble Analysis Troubleshooting

Possible Setup Issues

• Before performing a PRACH preamble analysis measurement, turn the UE on and wait for it to camp to the test set's signal. When the PRACH preamble analysis measurement is initiated, the test set pages the UE. The UE must be camped to the test set and in idle mode before performing the PRACH preamble analysis measurement.
• Recommended PRACH Preambles and PRACH Ramping Cycles (MMAX) settings

  The measurement requires a minimum of 3 PRACH preambles, so PRACH Preambles must be no less than 3. It is also recommended that you set PRACH Preambles to no greater than 3 and set PRACH Ramping Cycles (MMAX) to 1 to allow the UE's PRACH sequence to end as soon as possible. This helps avoid the following issue: Test set may lock up if operations are attempted before the UE completes its PRACH sequence .

• Importance of Setting Call Limit State to Off before Initiating a PRACH Measurement

  It is recommended that you set Call Limit State to Off before initiating this measurement. Then, when the measurement completes, if the UE is still sending PRACH preambles to the test set, the test set will acknowledge the UE. Note, when the test set acknowledges the UE, the call is not completed because the UE is attempting to establish a test set-originated call, whereas the test set acknowledges the UE expecting a UE-originated call. Acknowledging the UE helps prevent the UE from placing the test set into its cell barred list (see Test Set in Cell Barred List ). When the test set acknowledges the UE, you will see the call status move from Paging to Idle , to Setup , to Releasing and then back to Idle . Do not attempt to stop or re-initiate the measurement, or to start any new measurements until the test set has reached Idle state (see Test set may lock up if operations are attempted before the UE completes its PRACH sequence ).

  Setting call limit mode to off before initiating the measurement also avoids another issue: When the measurement completes, if you try to send signalling to the UE while it is still sending PRACH preambles to the test set, the UE will ignore the incoming messages and the signalling will fail. If call limit mode is set to off, the test set will acknowledge the UE and cause it to stop sending PRACH preambles, and then send the signalling you have requested to the UE.

• Available Subchannels (Bit Mask) must be set to only one available subchannel.
• During front panel operation of this measurement, you must press the START SINGLE key to initiate the measurement.
• No other measurements can be running when a PRACH preamble analysis measurement is performed. If any measurements are running when a PRACH preamble analysis measurement is initiated, they are closed and a message is displayed to indicate that they were closed.

Other Considerations

• Test set may lock up if operations are attempted before the UE completes its PRACH sequence

  When the measurement completes, you must wait until the UE has finished its PRACH sequence before turning off or re-initiating the measurement, or before starting any new measurements. Otherwise, the test set may lock up. If you are controlling the test set via remote program, you must include a wait period after the measurement completes.

  If you set Call Limit Mode to Off before initiating the measurement, you will know that the UE's PRACH sequence is complete when you see the call status move from Paging to Idle , to Setup , to Releasing and then back to Idle (see Importance of Setting Call Limit State to Off before Initiating a PRACH Measurement ). Do not attempt any of the above listed operations until the test set has reached Idle state.

  To allow the UE to complete its PRACH sequence as quickly as possible, it is recommended that you set PRACH Preambles to 4 and PRACH Ramping Cycles (MMAX) to 1 (see Recommended PRACH Preambles and PRACH Ramping Cycles (MMAX) settings ).

• The measurement will execute fastest if you only specify one available signature using the PRACH Signature setting.
• The PRACH preamble analysis measurement reports the PRACH signature used by the UE for the preamble burst being analyzed. This result may differ from the Detected PRACH Signature result if more than one signature is specified as available by the PRACH Signature setting.
• While on a faded channel (see Digital Bus Information ), the measurement will only return valid results if Trigger Source is set to RF Rise or External .
• Timing error is not reported when Trigger Source is set to RF Rise .
• FDD Test Operating Mode Considerations
  • When operating in FDD Test Operating Mode , you do not have access to the PRACH Signature setting, as the test set does not send this type of signalling to the UE in FDD test operating mode. However, when you initiate the measurement in FDD test operating mode, the measurement uses the value last set in the PRACH signature setting to determine which signatures to try to correlate to the PRACH preamble burst. Thus, you must switch to Active Cell Operating Mode and ensure that the PRACH Signature setting includes the signature that your UE will transmit before running this measurement in FDD test operating mode.
• If the PRACH preamble analysis measurement timeout is not on, the PRACH preamble analysis measurement will hang until it is triggered by a PRACH burst. You can reset the measurement by pressing the MEASUREMENT RESET key.

Interpreting Integrity Indicator Values

If Over Range (5) is returned, the measured signal exceeds the expected input level or exceeds the maximum allowed input power for the test set.

If Under Range (6) is returned, the measured signal is below the expected input level.

If Uncalibrated Due to Temperature (19) is returned, the temperature in the test set has changed by ± 10° C or more since the last calibration and should be calibrated again. Calibrating the Test Set

See Integrity Indicator .

Related Topics

• PRACH Preamble Analysis Measurement Description
• PRACH Preamble Analysis Measurement Input Signal Requirements
• PRACH Preamble Analysis Measurement Calibration
• Integrity Indicator