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8960 GSM/GPRS/EGPRS Online User's Guide
E1968A, E6701F, E6704A
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GSM Bad Frame Indication (BFI) Measurement Description

Last updated: December 2, 2008

This section is only applicable to the lab applications and is not applicable to GPRS or EGPRS.

You can use the GSM Bad Frame Indication (BFI) measurement to verify the mobile station's ability to detect bad frames under DTX conditions.

How is the BFI Measurement Made?

The test set must be set to operate as a base station transmitting in DTX mode. In this mode, there are periods where no transmission occurs. The BFI measurement is made by transmitting GMSK modulated pseudo-random bit sequence (PRBS) data in the periods where no transmission should occur. The mobile station should indicate these frames as bad by setting all the bits to zero before looping them back to the test set. From the number of frames with bits not set to zero, the test set returns results indicating the rate of undetected bad frames.

Operating Considerations

The BFI measurement can only be performed in Active Cell Operating Mode.

The connection type must be Auto.

The BFI measurement in the test set supports full-rate (FR), half-rate (HR), adaptive full-rate (AFS) and adaptive half-rate (AHS) speech channel modes. See Channel Mode Setup for more information about channel modes.

For expected results, the test set must be properly configured. See How do I make a GSM Bad Frame Indication (BFI) Measurement? or Programming a GSM Bad Frame Indication (BFI) Measurement for the proper procedure.

BFI Measurement Parameters

  • Samples to Test - The number of frames to be looped back from the mobile station and received by the test set for the measurement to complete.
  • Speech Frame Delay

    The mobile station's loopback delay expressed in frames. The default setting for this parameter is 5. However, this value is mobile station specific. You may not get expected results if this is not configured correctly. You can determine the speech frame delay using the test set. To do this, perform the Bit Error Measurement and use the value it automatically displays for the Loopback Delay.

    The GPIB command to set this parameter is SETup:<BFINdication|BFI>:SFDelay .

  • Trigger Arm - (See Trigger Arm (Single or Continuous) Description .)
  • Measurement Timeout - (See Measurement Timeouts .)

BFI Measurement Results

  • Integrity Indicator - (see Integrity Indicator )
  • Frames Sampled - The number of frames looped back from the mobile station and received by the test set.
  • SIDs Sent - The number of SIDs sent to the mobile station by the test set.
  • Undetected Bad Frames - The number of bad frames that are echoed back to the test set by the mobile station without the BFI bit being set.
  • SIDs Marked as BFI - The number of SID frames with the BFI bit set.
  • Undetected Bad Frame Rate - The ratio of Undetected Bad Frames to Frames Sampled.
  • SIDs Marked as BFI Rate - The ratio of SIDs Marked as BFI to SIDs Sent.

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