Setting up an NB-IoT Measurement

This topic provides information on connecting and successfully demodulating a signal using the NB-IoT demodulator. 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 NB-IoT demodulator
    1. Select the NB-IoT demodulator
    2. Preset to a selected operation mode
  4. Setup NB-IoT signal parameters

    1. Downlink parameters

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

    3. Set Mirrored Spectrum when necessary

  5. Run the measurement

NB-IoT Measurement Setup Procedure

  1. Connect your Signal to the VSA

    • Single channel RF connection (default selection)

    • 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 NB-IoT 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

      By default, the center frequency of each measurement channel must be set to within approximately ±0.5x subcarrier spacing (7.5 KHz at the default subcarrier spacing) of the carrier frequency of the NB-IoT signal connected to that channel, otherwise the demodulator may not be able to lock onto your signal.

    2. Set the Frequency Span (optional)

      At this point, you can set the frequency span for the signal. The span should be larger than the bandwidth of the NB-IoT signal, and, for best results, set the span according to the NB-IoT standard.

      This step is optional because clicking Preset (this is part of Step 3 below) will set the span according to the selected NB-IoT operation mode.

    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. 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 NB-IoT demodulator

    1. Click MeasSetup > Measurement Type > Cellular > NB-IoT to enable the NB-IoT demodulator properties and measurement parameters.

    2. Set Direction to uplink or downlink

    3. Select Preset

      Demodulator measurement parameters will be set to typical values when Preset is used to select an NB-IoT operation mode.  In addition to setting the demodulator parameters, the measurement span will be set according to the standard.

      • Downlink: choose an operation mode. Select In-band (same PC), In-band (different PC), Guard Band or Standalone
      • Uplink: Preset configures parameters for the Standalone operation mode

  4. Set up NB-IoT signal parameters

    Configure the parameters that are not autodetected to match your signal as needed.

    1. Format tab

    2. Profile tab

    3. Time tab

      • Set the Result Length, Measurement Interval, and Measurement Offset. Result Length determines the available analysis data in terms of the number of slots + symbols. Set Result Length to capture the desired data. 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.

    4. Advanced tab

      • Set Mirror Freq. Spectrum when necessary. NB-IoT demodulation provides a feature that lets you configure the demodulator to conjugate the complex time-domain waveform. This has the effect of flipping the spectrum around the VSA's center frequency.

  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

About Option BHT: NB-IoT Modulation Analysis

NB-IoT Demod Properties Dialog

Troubleshooting