Setting up an LTE-Advanced Measurement

This topic provides information on connecting and successfully demodulating a signal using the LTE Long Term Evolution-Advanced demodulator.

The LTE-Advanced demodulator performs simultaneous but separate demodulation of each component carrier and measurement results are provided in separate traces for each component carrier.

The frame settings Direction and Duplex Mode and the time settings Analysis Start Boundary and Result Length are common to all component carriers. The other parameters can be set independently for each component carrier.

Settings in tabs other than the Common tab which apply to all component carriers are disabled unless the All component carrier button is selected at the top of a tab.

A typical measurement includes the following measurement setup process (each step is discussed in the following text).

  1. Connect your signal to the VSA
  2. Configure measurement setup and input parameters
    1. Set the Center Frequency
    2. Set the Frequency Span
    3. Configure the Input Range
    4. Configure Triggering (when required)
    5. Verify input signal and initial parameter settings
  3. Configure the LTE-Advanced demodulator
    1. Select the LTE-Advanced demodulator
    2. Set up Component Carriers
    3. Set Duplex Mode
    4. Set Direction
    5. Preset to Standard for a selected bandwidth
  4. Setup LTE signal parameters

    1. Downlink parameters

    2. Uplink parameters

    3. Set the Result Length, Measurement Interval, and Measurement Offset

    4. Set Mirrored Spectrum when necessary

  5. Run the measurement

LTE-Advanced Measurement Setup Procedure

  1. Connect your Signal to the VSA

    • Single or multiple channel connection

      Connect the antenna signals to the hardware input channels.

      Click Input > Channels and select the number of channels.

    • I+jQ connections

      Connect the I and Q signals to the measurement hardware. To configure the VSA, choose one of the I+jQ selections: Input > Channels > I + jQ

      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.

    • Recorded signal

      Recall the recorded signal by selecting File > Recall > Recall Recording

      The center frequency and input range will be set by the recording.

      Information about sample LTE-Advanced signals included with the 89600 VSA software can be found in the Demo and Recorded Signals topic.

    For more information about your specific measurement hardware, see the Measurement Hardware book.

  2. Configure Measurement Setup and Input Parameters

    1. Set the Center Frequency

      For ease of setting component carrier frequency offsets, set the VSA center frequency to the center frequency of one of the component carriers.

    2. Set the Frequency Span

      Set the frequency span to be wider than the bandwidth of all the LTE-Advanced component carriers.

    3. Configure the Input Range

      The input range must be set correctly to obtain accurate measurements. Input ranges that are too low overload the measurement hardware's ADC Analog-to-Digital Converter. Input ranges that are too high increase noise, which increases errors reported in error summary data, 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..

    4. Set up triggering (optional) 

      The default triggering mode is set to "FreeRun." However, you can configure a different type of configuring if you wish (such as an external frame trigger).

    5. Verify the input signal and initial parameter settings 

      View your signal in the frequency domain (Spectrum trace) to verify the parameters you set.

  3. Configure the LTE-Advanced demodulator

    To configure the demodulator to use a E-UTRA Evolved Universal Terrestrial Radio Access Test Model, see Selecting LTE-A Test Models.

    1. Click MeasSetup > Demodulator > 3G/4G Cellular > LTE-Advanced to enable the LTE-Advanced demodulator properties and measurement parameters.

    2. Set up Component Carriers
      1. Set the Number of Component Carriers

      2. Set frequency offset for each component carrier

        By default, the frequency offset must be set to within approximately ±0.5x subcarrier spacing (7.5 KHz at the default subcarrier spacing) of the component carrier's center frequency, otherwise the demodulator may not be able to lock onto the component carrier.

        Frequency lock range can be extended to 2.5x subcarrier spacing by selecting Extended Freq Lock.

    3. Click the Format tab and select the All button at the top of the tab to set global Component Carrier settings.

    4. Set Duplex Mode to FDD Frequency Division Duplex: A duplex scheme in which uplink and downlink transmissions use different frequencies but are typically simultaneous. or TDD Time Division Duplex: A duplexing technique dividing a radio channel in time to allow downlink operation during part of the frame period and uplink operation in the remainder of the frame period.

      For TDD:

      1. Set uplink-downlink configuration (UL/DL Config)

      2. Set special subframe configuration (Dw/GP/Up Len)

    5. Set Direction to uplink or downlink

    6. Set Result Length

      Result Length determines the available analysis data in terms of the number of slots + symbols. Set Result Length to capture the desired data. 

  4. Setup LTE component carrier signal parameters

    These parameters are not autodetected and will need to be set when the default values are not correct for your signal.

    1. Select component carrier to configure

      Click the CCx button at the top of a tab to configure settings for component carrier x.

    2. Demodulator measurement parameters for the component carrier will be set to typical values (see Using a Standard Setup topic) when Preset to Standard is used to select a bandwidth.  

    3. Downlink: see the Downlink user allocations topic for instructions on configuring user allocations.

      Uplink: see the Uplink user allocations topic for instructions on configuring user allocations.

    4. Set the Measurement Interval and Measurement Offset

      Measurement Interval specifies the data that will be demodulated, and Measurement Offset specifies an offset from the beginning of the Analysis Start Boundary to the Measurement Interval.

    5. Set Mirrored Spectrum when necessary

      LTE-Advanced demodulation provides a feature that lets you configure the demodulator to conjugate the complex time-domain waveform of a component carrier. This has the effect of flipping the spectrum around the component carrier's center frequency.

    6. Repeat steps a-e for the remaining component carriers

      When the component carriers have similar settings, you can configure one component carrier and use the Copy CCx To... button to copy the settings to the other component carriers and then configure the remaining settings that are different.

      You can also import the configuration for a component carrier from an existing LTE setup file using the Import LTE Settings to CCx... button.

  5. Run the Measurement

    Press the Restart () button to restart the measurement.

    For help when your signal is not demodulating correctly, see the Troubleshooting topic.

See Also

Measurement Speed Considerations

Troubleshooting

Using a Standard Setup

About Opts BHG and BHH: LTE-Advanced Modulation Analysis