Evaluate Host Capture Performance

R2026b

Since R2023b

This example shows how to check your host performance capability for capturing data using the baseband receiver.

Introduction

When you capture data using a baseband application object, the capture function supports two operating modes. You can capture data using the onboard radio memory buffer, which guarantees contiguous samples. Alternatively, you can bypass the buffer and capture data directly to the host computer. Use the UseRadioBuffer name-value argument to control the buffering behavior.

Only direct-to-host capture is supported in these scenarios:

• The capture length exceeds the onboard radio memory buffer size.

• Your are using a USRP X310 radio with TwinRX daughterboards and capture data on more than two antennas. This requirement is a hardware limitation.

When you capture data directly to the host, the performance you can achieve depends on the capability of your host computer. Factors such as network configuration and data transfer rate can affect your ability to capture data without dropping samples. Use this example to evaluate whether your physical setup supports direct‑to‑host capture at high sample rates.

Set Up Radio

Call the radioConfigurations function. The function returns all available radio setup configurations that you saved using the Radio Setup wizard.

savedRadioConfigurations = radioConfigurations;

To refresh the list of saved configurations, click Update, then select the radio to use with this example.

savedRadioConfigurationNames = [string({savedRadioConfigurations.Name})];
radioConfig = savedRadioConfigurationNames(1) ;

Create a radio object by calling the radioConfigurations function with the selected radio configuration name.

radio = radioConfigurations(radioConfig);

Configure Baseband Receiver

Create a baseband receiver application object with the radio object.

The baseband receiver requires exclusive access to the radio hardware. Before running this example for the first time, clear any other objects associated with the specified radio. In subsequent runs, reuse the existing workspace object to reduce execution time.

if ~exist("bbrx","var")
    bbrx = basebandReceiver(radio);
end

Configure Behavior When Samples are Dropped

Set the DroppedSamplesAction property to 'none'. The default value is 'error', which stops the capture with an error message when samples are dropped.

bbrx.DroppedSamplesAction = 'none';

Evaluate Performance at Multiple Sample Rates

Set the capture length to 2 GB.

captureLength = 2*2^28;

Select a set of sample rates based on the network connection you have configured using the Radio Setup wizard. If you are using a 10 Gigabit network connection, set the highest sample rate to the highest supported rate of your radio. If you are using a 1 Gigabit network connection, set the highest sample rate to 25 MHz.

The example iterates from the selected highest rate downward at and interval rate of 5 MHz until a capture completes without dropping samples. Large captures at lower sample rates can take some time. For example, a single 2 GB capture at a sample rate of 10 MHz will take over 54 seconds.

highSpeedTest = true;
% Define the lowest sample rate once
lowRate = 1e6;

if ~highSpeedTest
    highRate = 25000000;
    intervalRate = 5e6;
    sampleRates = (highRate:-intervalRate:lowRate)';
else
    % Get maximum sample rate supported by the radio
    highRate = hMaxSampleRate(radioConfig);
    intervalRate = 10e6;
    % Construct sample rates: max, half-max, then intervals down to lowRate
    sampleRates = [highRate; highRate/2; (highRate/2-intervalRate:-intervalRate:lowRate)'];
    % Remove duplicates if highRate/2 falls on an interval
    sampleRates = unique(sampleRates, 'stable');
end

To automatically retry failed captures, set retryUnsuccessfulCaptures to true.

retryUnsuccessfulCaptures = true;

Iterate through the sample rates, starting with the highest sample rate, until you successfully capture data without dropping samples. Set the UseRadioBuffer name-value argument to false to capture directly to host.

% Preallocate
numRates = numel(sampleRates);
successfulCapture = false(numRates,1);

for idx = 1:numRates
    bbrx.SampleRate = sampleRates(idx);
    rateStr = num2str(bbrx.SampleRate/1e6, '%.2f'); % Format once

    disp(['Capturing at ' rateStr ' MHz']);

    % Attempt capture
    [~, ~, droppedSamples] = capture(bbrx, captureLength, UseRadioBuffer=false);

    % Retry if needed
    if retryUnsuccessfulCaptures && droppedSamples
        disp(['Retrying capture at ' rateStr ' MHz due to dropped samples']);
        [~, ~, droppedSamples] = capture(bbrx, captureLength, UseRadioBuffer=false);
    end

    successfulCapture(idx) = ~droppedSamples;

    % Exit loop after a successful capture
    if ~droppedSamples
        % Trim arrays to attempted rates only
        sampleRates = sampleRates(1:idx);
        successfulCapture = successfulCapture(1:idx);
        break;
    end
end

Capturing at 153.60 MHz

Retrying capture at 153.60 MHz due to dropped samples

Capturing at 76.80 MHz

Tabulate Capture Results

Display the result in a table. The results identify the highest sample rate at which the hardware setup captures contiguous IQ data without dropping samples. Results can vary between runs.

sampleRatesMHz = sampleRates/1e6;
captureResultsTable = table(sampleRatesMHz,successfulCapture);
disp(captureResultsTable)

    sampleRatesMHz    successfulCapture
    ______________    _________________

        153.6               false      
         76.8               true       

For more information about how to optimize the transfer speed between the host computer and the radio, see Resolve Issues with Data Transfer.