transmit

Transmit waveform using baseband transmitter or transceiver

Since R2022a

Add-On Required: This feature requires the Wireless Testbench™ Support Package for NI™ USRP™ Radios add-on.

Syntax

transmit(bba,waveform,mode)

transmit(___,StartTime=tStart)

Description

transmit(bba,waveform,mode) transmits the IQ waveform waveform to the air using the specified baseband transmitter or baseband transceiver bba. The input mode specifies continuous or single-shot transmission. To stop a continuous transmission, call stopTransmission(bba).

transmit(___,StartTime=tStart) schedules the transmission to start at the specified start time tStart. (since R2025a)

Examples

Configure Baseband Transmitter and Transmit Waveform

Create a baseband transmitter object, specifying a radio setup configuration previously saved in the Radio Setup wizard.

bbtx = basebandTransmitter("MyRadio")

bbtx = 
  basebandTransmitter with properties:

          RadioGain: 10
    CenterFrequency: 2.4000e+09
         SampleRate: 250000000
           Antennas: "RF0:TX/RX"

Set the baseband sample rate and center frequency.

bbtx.SampleRate = 122.88e6;
bbtx.CenterFrequency = 2.2e9;

Generate random transmit waveform.

txWaveform = complex(randn(1000,1),randn(1000,1));

Transmit the generated waveform continuously with the radio associated with the baseband transmitter object using the default antenna.

transmit(bbtx,txWaveform,"continuous");

Stop the continuous transmission after 5 seconds.

pause(5);
stopTransmission(bbtx);

Configure Baseband Transceiver to Transmit and Capture Data

Create a baseband transceiver object, specifying a radio setup configuration previously saved in the Radio Setup wizard.

bbtrx = basebandTransceiver("MyRadio")

bbtrx = 
  basebandTransceiver with properties:

          TransmitRadioGain: 10
    TransmitCenterFrequency: 2.4000e+09
           TransmitAntennas: "RF0:TX/RX"
           CaptureRadioGain: 10
     CaptureCenterFrequency: 2.4000e+09
            CaptureAntennas: "RF0:RX2"
            CaptureDataType: "int16"
       DroppedSamplesAction: "error"
                 SampleRate: 250000000

Set the baseband sample rate.

bbtrx.SampleRate = 122.88e6;

Set the transmit and capture center frequencies.

bbtrx.TransmitCenterFrequency = 2.2e9;
bbtrx.CaptureCenterFrequency = 2.2e9;

Generate a random transmit waveform.

txWaveform = complex(randn(1000,1),randn(1000,1));

Transmit the generated waveform continuously with the radio associated with the baseband transceiver object using the default transmit antenna.

transmit(bbtrx,txWaveform,"continuous");

Capture IQ data with the radio associated with the baseband transceiver object using the default capture antenna.

[data,~] = capture(bbtrx,milliseconds(3));

Stop the continuous transmission after data capture is complete.

stopTransmission(bbtrx);

Transmit Data on Multiple Antennas with Baseband Transmitter

Create a baseband transmitter object, specifying a radio setup configuration previously saved in the Radio Setup wizard. Specify two antennas, each with a different center frequency.

bbtx = basebandTransmitter("MyRadio", ...
    Antennas=["RF0:TX/RX" "RF1:TX/RX"], ...
    CenterFrequency=[2.2e9 2.4e9])

bbtx = 
  basebandTransmitter with properties:

          RadioGain: 10
    CenterFrequency: [2.2000e+09 2.4000e+09]
         SampleRate: 153600000
           Antennas: ["RF0:TX/RX"    "RF1:TX/RX"]

Generate two random complex transmit waveforms.

txWaveform = [complex(randn(1000,1),randn(1000,1)), ...
    complex(randn(1000,1),randn(1000,1))];

Transmit the generated waveform once with the radio associated with the baseband transmitter object.

transmit(bbtx,txWaveform,"once");

Transmit and Capture Data on Multiple Antennas with Baseband Transceiver

Create a baseband transceiver object, specifying a radio setup configuration previously saved in the Radio Setup wizard. Specify two transmit antennas and two capture antennas, each with a different center frequency.

bbtrx = basebandTransceiver("MyRadio", ...
    TransmitAntennas=["RF0:TX/RX","RF1:TX/RX"], ...
    TransmitCenterFrequency=[2.2e9,2.4e9], ...
    CaptureAntennas=["RF0:RX2","RF1:RX2"], ...
    CaptureCenterFrequency=[2.2e9,2.4e9])

bbtrx = 
  basebandTransceiver with properties:

          TransmitRadioGain: 10
    TransmitCenterFrequency: [2.2000e+09 2.4000e+09]
           TransmitAntennas: ["RF0:TX/RX"    "RF1:TX/RX"]
           CaptureRadioGain: 10
     CaptureCenterFrequency: [2.2000e+09 2.4000e+09]
            CaptureAntennas: ["RF0:RX2"    "RF1:RX2"]
            CaptureDataType: "int16"
       DroppedSamplesAction: "error"
                 SampleRate: 153600000

Generate two random complex transmit waveforms with a length of 1000 samples.

length = 1000;
txWaveform = [complex(randn(length,1),randn(length,1)), ...
    complex(randn(length,1),randn(length,1))];

Transmit the generated waveform continuously with the radio associated with the baseband transceiver object.

transmit(bbtrx,txWaveform,"continuous");

Capture IQ data with the radio associated with the baseband transceiver object.

[data,~] = capture(bbtrx,length);

The output data is a 1000-by-2 array. Each column contains the data captured on one antenna, in the order that they are specified.

Stop the continuous transmission when the capture is complete.

stopTransmission(bbtrx);

Transmit Data at Scheduled Time with Baseband Transmitter

Create a radio object, specifying a radio setup configuration previously saved using the Radio Setup wizard.

radio = radioConfigurations("MyRadio")

radio = 
  X310 with properties:

           Name: "MyRadio"
       Hardware: "USRP X310"

      IPAddress: "192.168.10.2"

    ClockSource: "internal"
     TimeSource: "internal"

       LOSource: "internal"
     LOExported: 0

Create a baseband transmitter object, specifying your radio object. Specify the Preload name-value argument as true to load the application onto the radio during object creation. Specify the RF properties during object creation.

bbtx = basebandTransmitter(radio,Preload=true, ...
    SampleRate=50e6,CenterFrequency=2.4e9, ...
    TransmitDataType="double")

bbtx = 
  basebandTransmitter with properties:

           RadioGain: 10
     CenterFrequency: 2.4000e+09
          SampleRate: 50000000
            Antennas: "RFA:TX/RX"
    TransmitDataType: "double"

Schedule the start time for the transmit operation to be 5 seconds in the future.

startTime = getRadioTime(radio) + 5

startTime = 
5.5661

Generate a random transmit waveform.

txWaveform = complex(randn(1000,1),randn(1000,1));

Transmit the generated waveform in a single shot with the radio associated with the baseband transmitter object.

transmit(bbtx,txWaveform,"once");

Input Arguments

bba — Baseband application

basebandTransmitter object | basebandTransceiver object

Baseband application, specified as a basebandTransmitter object or basebandTransceiver object.

Note

If you do not preload the application onto the radio during object creation, the first object function call in which you specify this object as an input requires a few extra seconds to load the application onto the radio. To load the application onto the radio during object creation, specify the Preload name-value argument:

bbtrx = basebandTransceiver("MyRadio",Preload=true);

waveform — IQ waveform to transmit

complex-valued column vector | complex-valued matrix

IQ waveform to transmit, specified as one of these options:

• Complex-valued column vector with even number of rows — Use this option to send an IQ waveform on a single transmit antenna.

• Complex-valued matrix with even number of rows — Use this option to send IQ waveforms on multiple transmit antennas. The number of antennas specified must match the number of matrix columns.

  • If the bba input is a basebandTransmitter object, the number of antennas is specified by the Antennas property.

  • If the bba input is a basebandTransciever object, the number of antennas is specified by the TransmitAntennas property. (since R2024b)

If you specify a waveform with a single or double data type, you must scale the transmit data sample values to the range [–1, 1].

The waveform length across all applicable antennas must be relative to the onboard radio memory buffer size.

Radio Device	Memory Buffer Size	Maximum Data Samples
USRP™ N300	2 GB	229
USRP N310	2 GB	229
USRP N320	2 GB	229
USRP N321	2 GB	229
USRP X300	1 GB	228
USRP X310	1 GB	228
USRP X410	4 GB	230

Note

• Transmit and capture data samples on the baseband transceiver are buffered in the onboard radio memory. Therefore, if the bba input is a baseband transceiver, you must also take into account the data capture length that you specify when calling the capture function.

• To avoid underflow during the transmission of a waveform of length less than 513 samples, the function reserves up to 1024 samples on the onboard radio memory.

• If the bba object uses a Farrow rate converter to achieve the sample rate that you specify with the SampleRate object property, the object resamples the transmit waveform. The resulting waveform has an increased number of data samples. For more information, see Baseband Sample Rate in NI USRP Radios.

Data Types: int16 | single | double
Complex Number Support: Yes

mode — Transmission mode

"continuous" | "once"

Transmission mode, specified as one of these options:

• "continuous" — The function transmits the waveform waveform continuously to the air by repeating the data samples until you call stopTransmission(bba).

• "once" — The function transmits the waveform waveform once in a single-shot transmission.

Data Types: string

tStart — Start time for transmission

positive numeric scalar

Since R2025a

Start time for transmission, specified as a positive numeric scalar. To schedule a transmission to start at a future time, first use the getRadioTime function to get the current radio time in seconds. Then, specify the radio time at which you want to start transmitting data.

Note

• A delay occurs when initializing the transmit function, which depends on the specific application and your host capability. The start time you specify must allow enough time for the function to be initialized. These factors increase the initialization time:

  • Specifying a long waveform. The waveform is loaded into the onboard radio memory buffer during initialization.

  • Specifying the SampleRate property of the bba object as a value that uses a Farrow rate converter. In this case, the object resamples the transmit waveform and the resulting waveform has an increased number of data samples. For more information, see Baseband Sample Rate in NI USRP Radios.

• To use this name-value argument to schedule a transmission, you must create your baseband application object bba in a specific way:

  • Load the application onto the radio during object creation by specifying the Preload name-value argument as true. Because updating object properties can cause the radio time to reset, be sure to specify properties during object creation.

  • Specify RF properties during object creation using the PropertyName=Value syntax.

  • Specify the data type of the transmit waveform using the TransmitDataType property with the data type that corresponds to the transmit waveform waveform.

For more information about how to schedule transmit and capture operations, see Time Synchronize Operations on NI USRP Radios.

Example: getRadioTime(radio)+0.5 schedules the capture operation to start 500 milliseconds in the future.

Data Types: double

Limitations

If you have a USRP X410 radio and you change the SampleRate property of the bba input object between a sample rate greater than 250 MHz and a sample rate less than or equal to 250 MHz, a new FPGA image is loaded to the radio when you call the transmit. This can take up to a minute.

Version History

Introduced in R2022a

R2025a: Schedule start time of transmission

You can now schedule the start time of a transmit operation by specifying the StartTime name-value argument equal to tStart.

R2025a: Transmit data at up to 500 MS/s with USRP X410

The basebandTransmitter and basebandTransceiver objects now support the following master clock rates (MCRs) on USRP X410 radios:

• 491.52 MHz

• 500 MHz

To transmit data at sample rates equal to these MCRs, set the SampleRate property on the bba input object.

R2024b: Transmit data on multiple antennas with baseband transceiver

You can now transmit data on multiple antennas with the basebandTransceiver object. Specify multiple antennas using the CaptureAntennas property of the bba input when it is a baseband transceiver.