Setting up a cdma2000 measurement (cdma2000/1xEV-DV)

When setting up a cdma2000 demodulation measurement, there are several things you need to consider. This topic provides information to connect your signal to the 89600 VSA Software and successfully demodulate cdma2000 signals. Additional information for setting up a 1xEV DV measurement is in Setting up an 1xEV-DV measurement. A typical measurement includes the following measurement setup procedure (each step is discussed in the following text):

  1. Connecting Your Signal to the VSA

  2. Configure the Center Frequency and Span

  3. Configure the Input Range

  4. Configure Triggering (if required)

  5. Verify input signal capture and initial parameter settings

  6. Configure the Demodulator

    1. Select the cdma2000(3GPP) demodulator. (For 1xEV-DV signals see Setting up an 1xEV-DV measurement topic.)

    2. Set the channel link Direction

    3. Set the Long Code Mask (Reverse link only)

    4. Set the Chip Rate, Symbol Rate, and Walsh Code Length

    5. Set the Base Walsh Code Length and Walsh Code QOF (Forward link only)

    6. Set the Result Length

    7. Set the Mirror Frequency Spectrum

    8. Select the measurement filter (not required)

    9. Selecting Predefined F-PDCH Active Channels (not required)

  7. Run the measurement

 

Additional Measurement topics

cdma2000 Measurement Setup Information

  1. Connecting Your Signal to the VSA

    The VSA lets you connect your carrier signal or, if your measurement hardware has two input channels, the raw I (In-phase) and Q (Quadrature-phase) signals.

    For all receiver configurations except I + jQ, connect your signal to Channel 1. In this case, the VSA assumes that your signal contains both the I and Q components (the carrier signal). If your VSA has two input channels, the VSA ignores the second input channel.

    If your VSA has a second input channel, you can also connect the raw I (In-phase) and Q (Quadrature- phase) signals. To do this, select Input >Channels >I + jQ. With this configuration, the VSA removes the quadrature mixer from the demodulator's signal flow, which lets you connect the I component of your signal to Channel 1; the Q component to Channel 2.

    Notes for I+jQ input:

    • Selecting an I+jQ configuration enables DC coupling.
    • Use User Correction to correct for any offset or gain imbalance between the I and Q signals.
    • Range is set independently for the I and Q inputs, but can be coupled by selecting the Couple Paired Channels parameter.

  2. Configuring the Center Frequency and Span

    1. Setting the Center Frequency

      The VSA's center frequency must be set within approximately ± 500 Hz of the carrier frequency of the cdma2000 signal, otherwise the VSA may not be able to lock onto your signal.

    2. Setting the Frequency Span

      When selecting a frequency span, select the narrowest span that includes all of your signal components (select a span that is slightly larger than the bandwidth of your signal). If you select a span that is too narrow, your measurement may have excessive errors or the VSA may lose carrier lock. If the span is less than the (Chip Rate x 1.204), the VSA displays "DATA?" to indicate that the results may not be accurate.

      For best results, the frequency span should be set according to the following formula (filter alpha is the filter characteristic of the Nyquist filter used to demodulate the cdma2000 signal):

       Frequency Span ³ (1.204 x Chip Rate)

      If you select a span that is too wide, your measurement may be affected by excessive noise and slower speed.

      Using the Preset to Standard configuration settings will select a default span that should work well.

  3. Configuring the Input Range

    The input range must be set correctly to obtain accurate measurements. Input ranges that are too low overload the VSA's ADC Analog-to-Digital Converter. Input ranges that are too high increase noise, which increases errors reported in error data results, such as EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format..

    cdma2000 signals can have a relatively large Peak-to-RMS voltage ratio potentially requiring a higher range setting than for other digitally modulated signals.

  4. Setting up triggering (if required)

    The default triggering mode is set to FreeRun. However, if you want to use a different trigger mode, now is the time to configure the triggering.

  5. Verify input signal capture and initial parameter settings

    View your signal in the frequency domain to verify the initial parameter settings.

  6. Configuring the demodulator for cdma2000 measurements

    You can manually configure the demodulator parameters or you can use the Preset to Standard parameter. Preset to Standard will automatically set up the demodulator parameters to one of the provided standard defaults (see Using a Standard Setup topic).

    1. Set the demodulator to cdma2000/1xEV-DV.

      This will enable the cdma2000 demodulator properties and measurement parameters. For 1xEV-DV measurements, you must also select Enable 1xEV-DV analysis (see Setting up a 1xEV-DV measurement).

    2. Selecting the Reverse/Forward channel direction

      The VSA can demodulate both reverse link and forward link cdma2000 signals using spread rate one (SR1). Therefore you must select the desired reverse or forward direction. Forward link refers to the Base Station Transceiver transmitted signal and reverse link refers to the mobile station (or User Equipment) transmitted signal.

    3. Setting Long Code Mask (Reverse link only)

      For reverse link channel measurements, you must specify the Long Code Mask to match the measured cdma2000 signal.

      Due to very long scrambling sequence, the VSA can generally only lock when the Long Code Mask is set to zero.

    4. Setting the Chip Rate, Symbol Rate and Walsh Code Length

      To successfully demodulate cdma2000 signals, the VSA chip rate must match the chip rate of your cdma2000 signal. The Walsh Code Length determines the Symbol Rate per the following equation.

      Symbol Rate = Chip Rate/Walsh Code Length

       

       

      Chip Rate: 1.2288 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second.

       

      Walsh Code Length (Symbol Rate)

       

      (Forward Link)

      (Reverse Link)

       

      --

      2 (614.4 ksym/s)

       

      4 (307.2 ksym/s)

      4 (307.2 ksym/s)

       

      8 (153.6 ksym/s)

      8 (153.6 ksym/s)

       

      16 (76.8 ksym/s)

      16 (76.8 ksym/s)

       

      32 (38.4 ksym/s)

      32 (38.4 ksym/s)

       

      64 (19.2 ksym/s)

      --

       

      128 (9.6 ksym/s)

      --

       

    5. Set the Base Code Length and Walsh code QOF (Forward link only).

      Some cdma2000 forward link signals are based on a fundamental Walsh Code Length of 64 while others use 128. The Base Code Length parameter lets you decide which code length the VSA will use as the fundamental Walsh code length.

      Similarly, some cdma2000 use a QOF value other than zero, set the Walsh code QOF parameter to match the input signal.

    6. Setting the Result Length

      Result Length determines the signal capture length in terms of Power Control Groups (PCGs) or equivalent PCG time. This is the data used by the VSA for demodulation and signal analysis. Make sure that the result length is long enough to capture all the desired data.

      Result Length may be entered as an integer number of PCGs, frames or time. If you choose to enter seconds, the VSA will automatically increment your entry as necessary to obtain an integer number of PCGs.

    7. Mirror Frequency Spectrum

      The cdma2000 demodulation provides a feature that lets you configure the VSA's demodulator to conjugate the complex time-domain waveform. This has the effect of flipping the spectrum around the VSA's center frequency. This feature is useful when the cdma2000 signal is inverted, or flipped due to an IF down conversion.

    8. Select the measurement filter (not required)

      For most measurements, the default measurement filter is best. But for measurements in the presence of adjacent carriers, the multi-carrier tolerant measurement filter can be enabled, select Use Multicarrier Filter on the Advanced tab (MeasSetup > cdma2000/1xEV-DV Demod Properties > Advanced tab).

    9. Predefined F-PDCH Active Channels (not required)

      See Setting up a 1xEV-DV measurement.

  7. Run the measurement

See Also

Measurement Speed and Resolution Considerations (cdma2000/1xEV-DV)

Selecting cdma2000 Demodulation

Troubleshooting