Troubleshooting Dual Transfer Mode

Last updated: December 3, 2008

According to 3GPP TS 03.55 Version 8.4.0, any TCH Assignment message received on the FACCH by a mobile station during a DTM session will result in the mobile station aborting the current packet data connection. The default setting is for the test set to send TCH Tx Level assignments to the mobile station on a TCH assignment message sent on the FACCH.

However, when the DTM is triggered, the TCH MS Tx Level parameter has no effect on the DUT. DTM CS MS Tx Level parameter is used in the circumstance. When FACCH level signaling is enabled (default), changing the TCH MS Tx Level parameter will cause a DTM Assignment to be sent to the DUT. When FACCH level signaling is disabled, the change to the TCH MS Tx Level parameter via SACCH signaling will be stored but not applied until the DTM session ends. The DTM CS MS Tx Level parameter has no effect when DTM is not triggered.

The GPIB command to set FACCH level signaling is CALL:TCHannel:(FACCH|FACChannel):MS:TXLevel .