How is RACH access delay calculated?

The following definition is not clear:

The access delay is calculated based upon the value of IE numberOfPreamblesSent and
IE contentionDetected reported by UE inside UEInformationResponse message.

The measurement is incremented each time a UEInformationResponse message containing rach-Report-r9 IE is received.

Any easy explanation for this?

  • eNB perform RACH optimization based on: UE feedback and neighboring eNB’s RACH configuration.
    Network request the UE to report rach information, based on UE information response message, which contains numberOfPreamblesSent and contentionDetected, RACH optimization can automatic adjust Power Control parameter(P0) and Preamble format to reduce access delay.