Setting up a MB-OFDM Measurement

This topic provides information for connecting your signal to an 89600 VSA for successful demodulation of MB-OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. signals. A typical measurement includes the following measurement setup process (each step is discussed in the following text):

  1. Connect your signal
  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. Configuring the demodulator for MB-OFDM measurements
    1. Select the MB-OFDM demodulator
    2. Select the Time Frequency Code
    3. Select the Data Rate
    4. Set Preamble Type
    5. Set the Result Length
  7. Run the measurement

MB-OFDM Measurement Setup Information

  1. Connecting Your Signal: If your input hardware has a second input channel, the raw I (In-phase) and Q (Quadrature-phase) signals can be connected (Input > Channels > I+jQ). With this configuration, the VSA removes the quadrature mixer from the demodulator's signal flow, which connects the I-component of your signal to Channel 1, and 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 ±300 kHz kiloHertz: A radio frequency measurement (one kilohertz = one thousand cycles per second). of the carrier frequency of the MB-OFDM Band Group signal, otherwise the VSA may not be able to lock onto your signal. To review the Band Group carrier frequencies, see Band Group and Band Frequencies.
    2. Setting the Frequency Span: When selecting a frequency span, select the narrowest span that includes all of your signal components, a nominal 528 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second. for non-hopping and 1584 MHz for hopping.

    Using Preset to Standard or setting the Band Group measurement parameter will automatically set Center Frequency and Span according to the standard.

    Set Band Group before setting Center Frequency and Frequency Span when using a non-standard center frequency or span for a certain Band Group.

  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 Analog-to-Digital Converter (ADC Analog-to-Digital Converter). Input ranges that are too high increase noise, which increases errors reported in error summary data, such as Error Vector Magnitude (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 (if required): The default triggering mode is set to "FreeRun". However, if a different trigger mode is preferred, now is the time to configure the triggering (Input > Triggering).
  5. Verify the input signal and initial parameter settings: View your signal in the frequency domain to verify the parameter settings set in the previous steps.
  6. Configuring the demodulator for MB-OFDM measurements: Configure the demodulator parameters manually or use the Preset to Standard parameter. Preset to Standard is preset by the Band Group first and then by the Time-Frequency Code (TFC Transport Format Combination).
    1. Set the demodulator to MB-OFDM (MeasSetup > Measurement Type > Other standard formats > Ultra Wideband MB-OFDM). This enables the MB-OFDM demodulator properties and measurement parameters.
    2. Set the Time-Frequency Code (MeasSetup > MB-OFDM Demod Properties > Format Tab > Time Frequency Code).
    3. Select Data Rate (MeasSetup > MB-OFDM Demod Properties > Format Tab > Data Rate).
    4. Set Preamble Type to Auto (MeasSetup > MB-OFDM Demod Properties > Format Tab > Preamble Type).
    5. Set the Result Length (MeasSetup > MB-OFDM Demod Properties > Time Tab > Result Length) where Result Length determines the signal capture length in terms of the number of OFDM symbol-times, making sure that the result length is long enough to capture at least one MB-OFDM packet. For more information, see Lengths, Intervals, and Offsets.
  7. Run the Measurement

See Also

Selecting the MB-OFDM Demodulator

Using Standard Setups/Presets (MB-OFDM)

MB-OFDM Demod Properties Dialog Box