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8960 W-CDMA/HSPA Online User's Guide
E1963A, E6703E
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Channel Power Measurement Description

Last updated: January 16, 2009

How is a Channel Power Measurement Made?

The channel power measurement is made on the RF input signal after frequency downconversion and an analog to digital conversion (see Block Diagram ). The actual power measurement is performed by the test set's digital signal processor (DSP).

Differences between the Channel Power and Thermal Power Measurements

When the RRC Filter for the channel power measurement is turned on, the results are typically about 0.25 dB lower than the thermal power measurement results.

Thermal power performance is only specified for signals down to -10 dBm, while the channel power measurement is able to accurately measure signals down to -61 dBm.

Triggering the Channel Power Measurement

You must specify how you want to trigger the channel power measurement using the Trigger Source setting. You must also specify the Measurement Interval and may then choose to move the Measurement Interval relative to the trigger using the Trigger Delay setting.

For example ( for lab applications or feature-licensed test applications only ), given the following example power profile, to align the measurement trigger to measure the power level of the ACK portion of the HS-DPCCH signal (excluding the 25 us transient periods on either side of the slot boundaries), set Trigger Source to HS-DPCCH , set HS-DPCCH Trigger Subframe Alignment to 0 , set Measurement Interval to 616.7 us and set Trigger Delay to 25 us . To measure the power level of the statDTX, simply change HS-DPCCH Trigger Subframe Alignment to 3.

Channel Power Measurement Parameters

  • Multi-Measurement Count: (see Statistical Measurement Results ).

  • RRC Filter

    The signal can be filtered in the DSP with a root-raised cosine (RRC) filter with a rolloff of 0.22 and a bandwidth equal to the chip rate (3.84 MHz) to comply with 3GPP 34.121 conformance specifications that require RRC filtered power. The filter can also be turned off for conformance specifications requiring a mean power measurement. When the RRC filter is Off , the bandwidth of the channel power measurement is greater than (1+alpha) times the chiprate, where alpha=0.22.

  • Trigger Arm: (see Trigger Arm (Single or Continuous) Description ).

  • Trigger Source

    You may set Trigger Source to the following: (for more information on these trigger types, see Trigger Source Description ).

    • Auto: if the UE is synchronized to the test set, it uses protocol triggering; otherwise, it uses immediate triggering.

    • External

    • HS-DPCCH:

      This setting is only applicable to the lab application or a feature-licensed test application.

      When Trigger Source is set to HS-DPCCH , you can specify on which uplink subframe the measurement triggers using the HS-DPCCH Trigger Subframe Alignment setting.

      Trigger Source can only be set to HS-DPCCH when Channel Type = 12.2k RMC + HSDPA or 12.2k RMC + HSPA .

    • Immediate

    • Protocol: Derived from the 10 ms downlink DPCH frame clock.

    • RF Rise: RF Rise triggering can be used to measure power during PRACH bursts. The burst's on state level must be >-40 dBm and the off state level must be <-60 dBm for this trigger to work correctly.
  • Trigger Delay

    You can move the Measurement Interval relative to the measurement trigger using the Trigger Delay setting. See Triggering the Channel Power Measurement .

  • Measurement Interval

    This measurement can be made over a period of 10 us to 12 ms (the default is 1 timeslot or 666.7 us) by altering the Measurement Interval .

  • Auto Range

    When Auto Range is set to on, the test set automatically determines the expected power level from the UE before performing a channel power measurement. However, note that the measurement takes longer to execute when Auto Range is set to on. Also, the UE's output power must be stable in order for the autoranging algorithm to operate properly.

    When Auto Range is set to off, you must specify the expected power level from the UE as described in Manual Power Range Offset .

  • Manual Power Range Offset

    This setting is only applicable when Auto Range is off.

    When Auto Range is off, the test set uses the UE Target Power setting (for automatic receiver power control) or the Manual Power setting (for manual receiver power control; see Receiver Control ) to determine the expected power level from the UE. However, the UE Target Power setting (or Manual Power setting) only drives the DPCCH+DPDCH power level of the UE. When HS-DPCCH, E-DPCCH and/or E-DPDCH channels are present, the actual output power of the UE is greater than the UE Target Power setting. Thus when Auto Range is off, you must specify how much additional power is in the UE's signal due to the HSDPA and HSUPA channels (using the Manual Power Range Offset setting) to avoid an over range error.

    Power Change Due to HS-DPCCH, E-DPCCH and E-DPDCH = 10log 10 (Beta c ^2 + Beta d ^2 + Beta hs ^2 + Beta ec ^2 + Beta ed ^2) - 10log 10 (Beta d ^2 + Beta c ^2). For example, for 34.121 v7.5.0 Table C.11.1.3 sub-test 1, Power Change Due to HS-DPCCH, E-DPCCH and E-DPDCH = 14 dB. Thus, Manual Power Range Offset should be set to 14 dB for sub-test 1 when Auto Range is off. Manual Power Range Offset should be set as follows for the other sub-tests - sub-test 2: 5 dB, sub-test 3: 13 dB, sub-test 4: 2 dB, sub-test 5: 16 dB.

  • Measurement Timeout: (see Measurement Timeouts ).

  • HS-DPCCH Trigger Subframe Alignment

    This setting is only applicable to the lab application or a feature-licensed test application.

    When Trigger Source is set to HS-DPCCH , you can specify on which uplink subframe the measurement triggers. You can then use the Trigger Delay setting to move the Measurement Interval relative to that subframe boundary. See Triggering the Channel Power Measurement .

  • RMSCubed State

    This setting is only available via GPIB command ( SETup:WCPower:RMSCubed:STATe ). This setting determines whether the RMSCubed measurement result is available.

Channel Power Measurement Results

  • Integrity Indicator
  • Channel Power (in dBm)
  • RMSCubed

    This result is only available when RMSCubed State is set to on, and is only available via GPIB command. This result returns the root mean square of the cubic normalized voltage waveform (20log 10 ((v_norm 3 ) rms )), to aid in the calculation of CM (Cubic Metric) and MPR (Maximum Power Reduction) as defined in 3GPP TS 25.101 s6.2.2.

Channel Power Input Signal Requirements

  • If Auto Range is set to off, you must set the expected power level from the UE as described in Manual Power Range Offset .
  • The frequency of the signal being measured must be in the range of 800 MHz to 1000 MHz, 1700 MHz to 1990 MHz, or 2480 MHz to 2580 MHz.
  • The level into the test set's RF IN/OUT connector must be in the range of -61 dBm to +28 dBm, measured in a 3.84 MHz bandwidth.

Channel Power Measurement Calibration

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

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