Repeated Downlink FACCH

Repeated Downlink FACCH

Last updated: December 3, 2008

This section is only applicable to the lab applications.

The Repeated FACCH functionality allows the downlink FACCH Blocks to be repeated to improve the robustness of FACCH signaling during handovers. You can enable the Repeated FACCH parameter in the test set to repeat all downlink FACCH blocks once.

The mobile station attempts to decode any downlink FACCH blocks independently of other received FACCH blocks. If the mobile station is unsuccessful, it uses a different decoding scheme that uses information from each identical downlink FACCH block. The repeated FACCH is sent nine frames after the first burst of the downlink FACCH containing the first instance of a LAPDm frame if a SACCH or and idle burst is transmitted between the two FACCH blocks. Otherwise, the repeated FACCH is sent eight frames after the first burst of the downlink FACCH containing the first instance of a LAPDm frame.

3GPP TS 44.006 Version 6.1.0 Release 6 Section 10.2 states, "On a channel using Repeated Downlink FACCH the value of T200 should be increased to cope with the case where an MS fails to decode the downlink FACCH block used to send the first instance of a repeated LAPDm frame."

Therefore, timer T200 is extended 42 ms to account for the maximum additional time (9 TDMA frames) that may be needed when the Repeated FACCH parameter is enabled.

The GPIB command to enable/disable the Repeated FACCH parameter is CALL:TCHannel:(FACCH|FACChannel):REPeat[:STATe] .

The following precedure details how to set the Repeated Downlink FACCH feature.

  1. Press the CALL SETUP screen key.
  2. Press TCH Parameters ( F8 ).
  3. Press the More key untill screen 3 of 3 of the TCH Parameters menu is displayed.
  4. Press Call Signaling Parameters ( F7 ) and the Call Signaling Parameters menu appears in the center of the screen.
  5. Use the knob to highlight and set Repeated FACCH.

For more information about Repeated FACCH, please refer to 3GPP TS 44.006 Section 10.

Related Topics

Fixed Timer Messages

Repeated SACCH