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8960 Wireless Communications Test Set
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Block Error Measurement Description

Last updated: May 8, 2002

This measurement is not applicable to GSM.

How is a Block Error (BLER) Measurement Made?

Block Error (BLER) measurements can be used in the production process to test the performance of a GPRS mobile station's receiver.

The BLER measurement which the test set provides is based on GPRS receiver tests defined in 3GPP 51.010 (formerly ETSI GSM 11.10), section 14.16.

The BLER measurement is made using one of the following two methods, depending on the test set's configuration:

  • If the test set's data connection type is set to ETSI Type B in Active Cell operating mode, or the operating mode is set to GPRS BCH+PDTCH test mode:

    • The test set generates one or more downlink PDTCHs at a known level with data of the payload pattern that you specify. The mobile station receives the data, loops it back to its transmitter, and returns the data to the test set. The test set compares data sent to data received. A block that is received which has one or more bit errors within it is marked as having a block error.

      The BLER measurement result is calculated irrespective of the Layer 1 reported demodulation status. If a corrupted burst error or missing burst error is received, the burst is still included in the BLER measurement result and contributes to the Block Error count.

  • If the test set's data connection type is set to BLER in Active Cell operating mode.

    • The test set periodically polls the mobile station, deriving the BLER measurement result from the Radio Link Control (RLC) layer's Packet ACK/NACK (Acknowledged/Not Acknowledged) message. Polling the mobile station for this message provides an indication of which blocks have been successfully received, and which blocks have been received with an error.
The number of blocks indicated to be in error and the total number of blocks received are counted. The polling interval can be set using CALL:FUNCtion:DATA:BLER:POLLing:INTerval .

BLER measurements cannot be made when the data connection type is set to ETSI Type A in Active Cell operating mode, nor in BCH test mode.

The test set's operating mode can be set using CALL:OPERating:MODE . The data connection type can be set using CALL:FUNCtion:DATA:TYPE .

You can send SETup subsystem commands to the test set which specify the number of blocks to test, block delay, trigger arm, and measurement timeout values.

Note

In case the test set is not able to correlate the data it transmits on the downlink with the data it receives on the uplink, a Measurement Timeout value should be set. If a timeout is not set and the test set is unable to correlate, the measurement will appear to "hang".

Note

Types of Signal BLER can Measure

BLER measurements can be made on these types of input signals:

  • One or more GPRS uplink and downlink PDTCH pairs with the mobile station in active cell mode and the data connection type set to ETSI Type B or BLER. If you want to optimize measurement speed, it is important that the mobile station is set up for the same number of uplink and downlink PDTCHs.
  • One or more GPRS uplink and downlink PDTCH pairs with the mobile station in GPRS BCH+PDTCH test mode (see CALL:OPERating:MODE for details on setting the cell operating mode). Note that you have to manually set your mobile station to synchronize its internal frequency and timing reference with the test set. You also have to command the mobile station to loop back the PDTCH data.

BLER Measurement Results

The results of a BLER measurement can be displayed in two ways; the number of block errors counted or the ratio of bad blocks (errors) to total blocks counted. If you are using the test set manually, both Count and Block Error Ratio are displayed on the Block Error measurement screen. If you are using the test set remotely, these results are available using the FETCh command, see FETCh:BLERror:COUNt? or FETCh:BLERror:RATio? . Alternatively the command FETCh:BLERror[:ALL]? can be used to return all of the following results:

  • Integrity Indicator
  • Block Error Ratio
  • Blocks Tested
  • Block Error Count

In addition, the Intermediate Count of Blocks Tested result can be queried using FETCh:BLERror:ICOunt? and the Block Delay can be queried using FETCh:BLERror:DELay? .


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