Channel Power Measurement Description

Last updated: June 12, 2007

How is a Channel Power measurement made?

Channel power measurements are used to determine the power contained in a 1.2288 MHz bandwidth of a CDMA channel. The input signal is downconverted and sampled using the test set's DSP (see Block Diagram ). The DSP then searches the sampled data to find those portions of the data record in which the input signal was non-gated. Using the portion of the samples representing the non-gated signal the DSP calculates the power within a 1.23 MHz measurement bandwidth. The result is cross correlated with the digital average power to derive an absolute power which is represented in the measurement's result (dBm/1.23 MHz).

Channel Power Measurement Parameters

Multi-Measurement Count

When ON, this enables averaging of multiple channel power results. For example, when multi-measurement count is set to 3, three channel power measurements are made sequentially and the results of all measurements are averaged to determine the final result. (See Statistical Measurement Results ).
Trigger Arm - (see Trigger Arm (Single or Continuous) Description ).
Measurement Speed - (see Measurement Speed ).
Timeout Time/State - (see Timeouts ).

Measurement Speed

The test set provides three channel power measurement speed selections: Normal, Fast and Very Fast (see also SETup:CPOWer:MSPeed ). These selections provide additional information for the test set to select a trigger source, sample record length, power search algorithm, and processing time, all of which will influence the time required to perform the measurement.

Normal speed channel power measurements are made by sampling 10 ms of the input signal triggered by the 20 ms frame clock. The DSP then locates within the sample record the power control groups in which the input signal appears to be non-gated. In a CDMA system there will be at least one non-gated power control group within each half frame (10 ms).

A Fast speed channel power measurement assumes that an non-gated input signal is being measured. The trigger for the measurement is the 20 ms frame clock but the sample record is only 1.25 ms or a single power control group in length. There is no search since it is assumed that the input signal is always non-gated.

The Very Fast speed channel power measurement also assumes the measurement of an non-gated signal. It is triggered immediately upon receipt of the measurement request. There is no synchronization with the frame clock. The input signal is then sampled for 0.3125 ms or one quarter of a power control group.

The actual measurement speed used by the test set may be different than the current measurement speed selection. This is primarily because the triggering and search algorithms needed for measuring channel power on gated input signals is only available when using the Normal measurement speed. If Fast or Very Fast measurement speeds are selected when the channel configuration is such that a gated signal could reasonably be expected from the mobile station the Normal measurement speed algorithm will be applied even though a different measurement speed is selected. This provides the highest confidence that the measurement result will be accurate even though it might take longer than expected to obtain the result.

Impact of the Test Set Configurations on R-FCH Gating Transmission shows the actual measurement speed applied for the different test set configurations.

Impact of the Test Set Configurations on R-FCH Gating Transmission
System Type	Operating Mode	Radio Config ¹	Service Option ²	Traffic Data Rate ³	R-FCH Gating Mode ⁴	Expected R-FCH Gating	Actual Measurement Speed
IS-95	Active Cell	Not applicable	SO1, SO3, SO17, SO68, or SO32768	Not applicable	Not applicable	Sometimes gated ⁵	Always Normal
			SO2, SO9 (loopback)	Half, Quarter, Eighth, or Random		Always gated (Half, Quarter, Eighth) or sometimes gated (Random)	Always Normal
			SO2, SO9 (loopback)	Full		Non-gated	Same as the specified speed.
IS-2000	Active Cell	(Fwd1, Rvs1), (Fwd2, Rvs2)	SO1, SO3, SO17, SO68, or SO32768	Not applicable	Not applicable	Sometimes gated ⁵	Always Normal
			SO2, SO9, or SO55 (loopback)	Half, Quarter, Eighth, or Random		Always gated (Half, Quarter, Eighth) or sometimes gated (Random)	Always Normal
			SO2, SO9, or SO55 (loopback)	Full		Non-gated	Same as the specified speed.
		(Fwd3, Rvs3) (Fwd4, Rvs3) (Fwd5, Rvs4)	SO2, SO9, or SO55 (loopback)	Eighth or Random	On	Always gated (Eighth) or sometimes gated (Random)	Always Normal
				Eighth or Random	Off	Non-gated	Same as the specified speed
				Full, Half, Quarter,	Not applicable	Non-gated	Same as the specified speed.
			SOs other than loopback	Not applicable	On	Sometimes gated ⁵	Always Normal
			SOs other than loopback	Not applicable	Off	Non-gated	Same as the specified speed
	Test Mode	(Fwd1, Rvs1), (Fwd2, Rvs2)	Not applicable	Half, Quarter, or Eighth	Not applicable	Always gated	Always Normal
		(Fwd1, Rvs1), (Fwd2, Rvs2)	Not applicable	Full		Non-gated	Same as the specified speed.
		(Fwd3, Rvs3) (Fwd4, Rvs3) (Fwd5, Rvs4)	Not applicable			Non-gated	Same as the specified speed.
See Radio Configuration for details. See Service Option for details. It is only applied to loopback service option. See Traffic Data Rate for details. It is only available in the lab application and in IS-2000 system, (Fwd3, Rvs3) and above. See R-FCH Gating for details. Sometimes gated indicates that the test set does not control the rate on the reverse link and therefore can not guarantee if the R-FCH/R-PICH will be gated.

NOTE

It is recommended to turn off other measurements if you expects to make the fast/very fast channel power measurements take as little time as possible. Turning on other measurements at the same time causes your measurements to run slower than expected. See Concurrent Measurements .

Channel Power Measurement Results

Integrity Indicator - (see Integrity Indicator ).
Channel Power (in dBm/1.23 MHz) - If Multi-Measurement Count is on, average, maximum and minimum channel power results are displayed on the measurement screen and available by remote program query ( FETCh:CPOWer ).
Measurement Speed - (see Measurement Speed )
Expected Mobile Power - the Expected Mobile Power (see Expected Power ) is also displayed on the measurement screen when the test set is configured as:
- receiver power control is set to auto (see Automatic Receiver Control ).
- the test set does not make the R-FCH data rate assumption (see Reverse Traffic Channel Data Rate Determination ) when calculating the expected mobile power. That is, the test set is in a loopback call (SO2, SO9, or SO55, see Service Option ) with the Traffic Data Rate set to other than Random .

A typical measurement result is shown below:

Input Signal Requirements

The channel power measurement meets or exceeds specifications when the following input signal requirements are met:

The frequency of the signal being measured must be within the range of 412 MHz to 483 MHz, 800 MHz to 960 MHz, or 1.7 GHz to 2.0 GHz, and be within 100 kHz of the expected frequency.
The signal level into the test set's RF IN/OUT connector must be between -61 dBm to +37 dBm. The test set can autorange to a signal that is within +/- 9 dB of the expected input level (see RFANalyzer:AUTO:POWer[:SELected]? ).

Key TIA/EIA-98-E Tests Performed Using the Channel Power Measurement

Testing 4.4.6 Minimum Controlled Output Power

Calibrating the Channel Power Measurement

Refer to Calibrating the Test Set for a description of channel power calibration.