Change of TFC (Transport Format Combination) Measurement Description

Last updated: January 16, 2009

This section is only applicable to the lab application.

How is a Change of TFC Measurement Made?

When a UE changes its TFC, it must change its output power in accordance with any resulting change in data rate. The 3GPP TS 34.121 5.6 Change of TFC test addresses the case of an uplink 12.2k RMC operating in DTX (Discontinuous Transmission) mode, wherein the DPDCH is periodically turned off. The test confirms that the UE's output power level changes properly when its DPDCH is turned off.

The change of TFC measurement requires an RB Test Mode connection between the test set and UE, in either loopback mode 1 or 2. When the measurement is initiated, the test set stops sending a constant stream of data (to be looped back by the UE), and instead sends a block of data, then a block of no data, repeatedly. This causes the UE to turn its DPDCH on and off on a block-by-block basis. The test set monitors the uplink TFCI and the change of TFC measurement is triggered when the TFCI indicates no data is present on the DPDCH (the DPDCH is thus off for that block). The test set then measures the mean power in the timeslot before and after the transition from DPDCH on to DPDCH off, and before and after the transition from DPDCH off to DPDCH on. The power measurements do not include the transient periods of 25 us on either side of the timeslot boundaries. Thus, the measurement interval is 2368 chips, or 617 us. The measurement then reports the step change in power ( P as described in 3GPP TS 34.121 5.6) for both transitions (see Step Down Relative Power (in dB) and Step Up Relative Power (in dB) ).

3GPP TS 34.121 5.6.2 Transmit template during DTX

Required Initial Conditions

Before performing the change of TFC measurement, you must:

Set Operating Mode to Active Cell Operating Mode .
Establish a Radio Bearer Test Mode connection. Note, this measurement is not supported on HSDPA or HSPA connections.
Set Uplink Dummy DCCH Data toOff .
Ensure that the initial output level of your UE is such that its output power level with DPDCH on and off falls within the measurement's required input level (see Change of TFC Measurement Input Signal Requirements ).

Recommended Initial Conditions

The following settings are recommended based on the 3GPP TS 34.121 5.6 requirements:

UE Target Power =0 dBm .
UL CL Power Control Mode =Alternating bits .
UL CL Power Ctrl Algorithm = Two .
Uplink DPCH Bc/Bd Control =Auto . This ensures that and are (automatically) set to the values specified by the standards (for example, 0.5333 and 1.0 for 12.2k RMC).

No other measurements can be running when a change of TFC measurement is performed. If any measurements are running when a change of TFC measurement is initiated, they are closed and a message is displayed to indicate that they were closed. Likewise, if any other measurements are initiated while a change of TFC measurement is running, the change of TFC measurement is closed and a message is displayed.

Change of TFC Measurement Parameters

Multi-Measurement Count
See Statistical Measurement Results . When multi-measurement count is on, the test set measures the mean power in the timeslot before and after the transition from DPDCH on to DPDCH off, and before and after the transition from DPDCH off to DPDCH on, and then repeats for the next available DPDCH on/off/on transition until the requested number of samples has been taken.
Measurement Timeout
See Measurement Timeouts .

The following four parameters can be independently set for the 12.2k RMC, 33k No Coding RMC, 64k RMC, 144k RMC and 384k RMCs:

Step Down Size
You can specify the expected step down change in power for each RMC. Step Down Pass/Fail is determined using thisStep Down Size setting and the Step Error Limit: Upper and Step Error Limit: Lower settings.
Step Up Size
You can specify the expected step up change in power for each RMC. Step Up Pass/Fail is determined using thisStep Up Size setting and the Step Error Limit: Upper and Step Error Limit: Lower settings.
Step Error Limit: Upper
You can specify the upper limit for the difference between the expected Step Down Size or Step Up Size and the measured step change in power for each RMC. Step Down Pass/Fail and Step Up Pass/Fail are determined using thisStep Error Limit: Upper setting and the Step Error Limit: Lower setting.
Step Error Limit: Lower
You can specify the lower limit for the difference between the expected Step Down Size or Step Up Size and the measured step change in power for each RMC. Step Down Pass/Fail and Step Up Pass/Fail are determined using the Step Error Limit: Upper setting andthis Step Error Limit: Lower setting.

Change of TFC Measurement Results

Step Down Relative Power (in dB)
TheStep Down Relative Power is the mean power while the DPDCH is off minus the mean power while the DPDCH is on, for an on-to-off transition.
Step Down Error (in dB)
TheStep Down Error is the difference between the measured Step Down Relative Power (in dB) and the Step Down Size setting. If Multi-Measurement Count is on, the error of the greatest magnitude is reported.
Step Down Pass/Fail
Fail is returned if Step Down Error (in dB) is greater than Step Error Limit: Upper or less than Step Error Limit: Lower .

Pass is returned if Step Down Error (in dB) is less than or equal to Step Error Limit: Upper and greater than or equal to Step Error Limit: Lower .
Step Up Relative Power (in dB)
TheStep Up Relative Power is the mean power while the DPDCH is on minus the mean power while the DPDCH is off, for an off-to-on transition.
Step Up Error (in dB)
TheStep Up Error is the difference between the measured Step Up Relative Power (in dB) and the Step Up Size setting. If Multi-Measurement Count is on, the error of the greatest magnitude is reported.
Step Up Pass/Fail
Fail is returned if Step Up Error (in dB) is greater than Step Error Limit: Upper or less than Step Error Limit: Lower .

Pass is returned if Step Up Error (in dB) is less than or equal to Step Error Limit: Upper and greater than or equal to Step Error Limit: Lower .

Change of TFC Measurement Input Signal Requirements

Frequency: 800 to 1000 MHz, 1700 to 1990 MHz, or 2480 MHz to 2580 MHz.
Input level: -61 dBm to +28 dBm.
Step change in power when transitioning between DPDCH off and on states must not exceed 15 dB.

Change of TFC Measurement Calibration

You must calibrate this measurement using the measurement calibration procedure (see Calibrating the Test Set ).