SDRu Transmitter

Send data to USRP device

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

  • SDRu Transmitter block

Libraries:
Wireless Testbench Support Package for NI USRP Radios

Description

The SDRu Transmitter block supports communication between Simulink® and a Universal Software Radio Peripheral (USRP™) device, enabling simulation and development for various software-defined radio applications. The SDRu Transmitter block and the USRP board must be on the same Ethernet subnetwork.

The SDRu Transmitter block accepts a column vector or matrix input signal from Simulink and transmits signal and control data to a USRP board using the Universal Hardware Driver (UHD™) from Ettus Research™. The SDRu Transmitter block is a Simulink sink that takes data from a model and sends it to a USRP board. The first call to this block can contain transient values, in this case the resulting packets contain undefined data.

This block diagram illustrates how Simulink, SDRu Transmitter and Receiver blocks, and USRP hardware interface.

For transmitting a radio signal over the air, pass the signal generated in Simulink to an SDRu transmitter block. The transmitter block forwards the signal to the radio hardware. For receiving a radio signal over the air, use an SDRu receiver block. The receiver block forwards the signal received from the radio hardware for post processing in Simulink.

If your computer is not connected to any USRP hardware, you can still use this block to develop a model that propagates sample time and data type information. To propagate this information, select Simulation >> Update diagram.

For information about the USRP hardware products that interface with this block, see Supported Radio Devices.

This icon shows all ports, including optional ones: SDRu transmitter block with all the ports

Note

Starting in R2024a, the MathWorks® products and support packages you require to use this Simulink block depend on your radio device.

Radio DeviceRequired MathWorks ProductsSupport Package Installation

USRP2™

USRP N200, N210

USRP B200, B210

  • Communications Toolbox™ Support Package for USRP Radio

Install Communications Toolbox Support Package for USRP Radio

USRP E320 (since R2025a)

USRP N300, N310, N320, N321

USRP X300, X310

USRP X410 (since R2025a)

  • Wireless Testbench™

  • Wireless Testbench Support Package for NI™ USRP Radios

Install Support Package for NI USRP Radios

For details on how to use this Simulink block with a radio device supported by Communications Toolbox Support Package for USRP Radio, see SDRu Transmitter.

Ports

Input

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Input data sent to the radio hardware, specified as a column vector or matrix. For a single channel radio, data is a column vector. For a multichannel radio, data is a matrix, where each column contains a channel of data. The range of values for data are [-1 1] for double or single precision data and [-32768, 32767] for int16 data.

Dependencies

To specify the output data type, use the Output data type parameter.

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

Center frequency setting in Hz, specified as a positive scalar.

Example: 88.9e6 tunes the transmitter to a center frequency of 88.9 MHz.

Dependencies

To enable this port, set Source of center frequency parameter to Input Port.

Data Types: double

Local oscillator (LO) offset in Hz, specified as a scalar.

Example: 10 sets the LO offset to 10 Hz.

Dependencies

To enable this port, set Source of LO offset parameter to Input Port.

Data Types: double

Transmitter gain setting in dB, specified as a scalar or vector. The valid range of this gain depends on the RF daughterboard of the USRP device.

Transmitter gain setting accounts combined analog and digital transmitter gains of the USRP hardware.

  • For a single channel, specify the value for the gain as a scalar in dB.

  • For multiple channels that use the same gain value, specify the gain as a scalar in dB. The gain is set by scalar expansion.

  • For multiple channels that use different gains, specify the values in a vector, for example, [5 12]. The Nth element of the vector is applied to the Nth channel specified by Channel mapping.

Example: 10 sets the transmitter gain level to 10 dB.

Dependencies

To enable this port, set Source of gain parameter to Input Port.

Data Types: double

Output

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Data discontinuity flag, returned as one of these values.

  • 0 — Data samples are not lost.

  • 1 — Data samples are lost.

Use this port as a diagnostic tool to determine real-time operation of the SDRu Transmitter block. If your model is not running in real time, you can adjust parameters that reduce the number of transported samples. To approach or achieve real-time performance, you can increase the interpolation factor.

Dependencies

To enable this port, select Enable overrun output port.

Lock status of the USRP radio to the 10 MHz clock signal, returned as one of these Boolean values.

  • 0 — The USRP radio is not locked to the 10 MHz clock signal of an external clock source or a global positioning system disciplined oscillator (GPSDO).

  • 1 — The USRP radio is locked to the 10 MHz clock signal of an external clock source or a GPSDO.

Dependencies

To enable this port, select the Enable ref_locked output port parameter.

Data Types: Boolean

Lock status of the GPSDO to the GPS constellation, returned as one of these Boolean values.

  • 0 — The GPSDO is not locked to the GPS constellation.

  • 1 — The GPSDO is locked to the GPS constellation.

Dependencies

To enable this port, select the Enable gps_locked output port parameter.

Data Types: Boolean

Parameters

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When you set block parameter values, the SDRu Transmitter block first checks that the values have the correct data types. Even if the values pass those checks, the values can still be out of range for the radio hardware. In that case, the radio hardware sets the actual value as close to the specified value as possible. When you next synchronize the block with the radio hardware by clicking Info, a dialog box open to display the actual values along with other radio information.

If a parameter is listed as tunable, then you can change its value during simulation.

Radio Connection

Radio to configure, specified as one of these options.

  • E320 — A connected USRP E320 radio. (since R2025a)

  • N300 — A connected USRP N300 radio.

  • N310 — A connected USRP N310 radio.

  • N320/N321 — A connected USRP N320 or USRP N321 radio.

  • X300 — A connected USRP X300 radio.

  • X310 — A connected USRP X310 radio.

  • X410 — A connected USRP X410 radio. (since R2025a)

IP address of the radio hardware, specified as a dotted quad expression.

This parameter must match the physical IP address of the radio hardware assigned when you set up your radio using the Radio Setup wizard. If you configure the radio hardware with an IP address other than the default, update IP address accordingly.

The IP address list displays IP addresses for USRP devices attached to the host computer. To specify another known dotted quad IP address, enter it directly into this field.

Refresh the list of all connected devices to update the IP address list. The updated list retains the value in focus before Refresh Device List is selected, even if the device with that setting was disconnected.

Provides information about the Platform of the radio associated with IP address. When you select the Info button, a new dialog box opens with information about the specified device.

Radio Properties

Channel output mapping for radio or bundled radios, specified as a positive integer scalar or vector. This table shows valid values for various radio platforms.

Platform ValueChannel mapping Value

E320 (since R2025a)

  • When IP address includes one IP address, specify this parameter as 1, 2, or [1 2].

  • When IP address includes N IP addresses, specify this parameter as 1-by-2N row vector.

N300

  • When IP address includes one IP address, specify this parameter as 1, 2, or [1 2].

  • When IP address includes N IP addresses, specify this parameter as 1-by-2N row vector.

N310

  • When IP address includes one IP address, specify this parameter as 1-, 2-, 3-, or 4-element row vector of channel numbers from the set {1, 2, 3, 4}

  • When IP address includes N IP addresses, specify this parameter as 1-by-4N row vector.

N320/N321

  • When IP address includes one IP address, specify this parameter as 1, 2, or [1 2].

  • When IP address includes N IP addresses, specify this parameter as 1-by-2N row vector.

X300 or X310

  • When IP address includes one IP address, specify this parameter as 1, 2, or [1 2].

  • When IP address includes N IP addresses, specify this parameter as 1-by-2N row vector.

X410 (since R2025a)

  • When IP address includes one IP address, specify this parameter as 1-, 2-, 3-, or 4-element row vector of channel numbers from the set {1, 2, 3, 4}

  • When IP address includes N IP addresses, specify this parameter as 1-by-4N row vector.

When Channel Mapping is a scalar, 1, or 2, the radio operates in single input single output (SISO) mode. When Channel Mapping is a vector, the radio operates in multiple input multiple output (MIMO) mode.

When IP Address contains multiple IP addresses, the channels defined by Channel Mapping are ordered first by the order in which the IP addresses appear in the list and then by the channel order within the same radio.

For example, if Platform is "X300" and IP Address is "192.168.20.2, 192.168.10.3", then the Channel Mapping must be [1 2 3 4]. Channels 1 and 2 of the bundled radio refer to channels 1 and 2 of the radio with IP address 192.168.20.2, respectively. Channels 3 and 4 of the bundled radio refer to channels 1 and 2 of the radio with IP address 192.168.10.3, respectively.

Data Types: double

Select source of center frequency, specified as:

  • Dialog — Set the center frequency using the Center frequency (Hz) parameter.

  • Input port — Set the center frequency using the fc input port.

RF center frequency in Hz, specified as a nonnegative finite scalar or vector of nonnegative finite scalars. The valid range of this parameter depends on the RF daughterboard of the USRP device.

  • For a single channel (SISO), specify the value for the center frequency as a scalar.

  • For multiple channels (MIMO) that use the same center frequency, specify the center frequency value as a scalar. The center frequency is set by scalar expansion.

  • For multiple channels (MIMO) that use different center frequencies, specify the values in a vector. The ith element of the vector is applied to the ith channel specified by Channel mapping.

Note

  • The channels corresponding to the same RF daughterboard of a USRP N300 or N310 radio must have the same center frequency.

  • For a MIMO scenario, the center frequency for a USRP N300 radio must be a scalar. You cannot specify the frequencies as a vector.

Dependencies

To enable this parameter, set the Source of center frequency to Dialog.

Data Types: double

Select source of LO offset, specified as:

  • Dialog — Set the LO offset using the LO offset (Hz) parameter.

  • Input port — Set the LO offset using the LO offset input port.

Offset frequency for the local oscillator, specified as a scalar or vector. The valid range of this parameter depends on the RF daughterboard of the USRP device.

This figure shows that the local oscillator offset affects the intermediate center frequency in the USRP hardware. It does not affect the transmitted center frequency.

Impact of LO frequency on the intermediate center frequency of the USRP radio

  • fLO offset is the local oscillator offset frequency.

  • fcenter represents the center frequency specified by the block.

To move the center frequency away from interference or harmonics generated by the USRP hardware, use the LO offset.

  • For a single channel (SISO), specify the value for the LO offset as a scalar.

  • For multiple channels (MIMO), the LO offset must be zero. This restriction is due to a UHD limitation. You can specify the LO offset as a scalar or as a vector.

Dependencies

To enable this parameter, set Source of LO offset to Dialog.

Select source of gain, specified as:

  • Dialog — Specify the gain using the Gain (dB) parameter.

  • Input port — Specify the gain using the gain input port.

Transmitter gain in dB, specified as a scalar or vector. The valid range of this gain depends on the RF daughterboard of the USRP device.

Set the value of gain based on the Channel Mapping configuration:

  • For a single channel (SISO), specify the gain as a scalar.

  • For multiple channels (MIMO) that use the same gain value, specify the gain as a scalar. The gain is set by scalar expansion.

  • For multiple channels (MIMO) that use different gains, specify the values in a row vector. The ith element of the vector is applied to the ith channel specified by Channel Mapping.

Dependencies

To enable this parameter, set Source of gain to Dialog.

Data Types: double

Pulse per second (PPS) signal source, specified as one of these values.

  • Internal — Use the internal PPS signal of the USRP radio.

  • External — Use the PPS signal from an external signal generator.

  • GPSDO — Use the PPS signal from a GPSDO.

To synchronize the time for all channels of the bundled radios, you can:

  • Provide a common external PPS signal to all of the bundled radios and set this parameter to External.

  • Use the PPS signal from the GPSDO that is available on the USRP radio by setting this parameter to GPSDO.

To synchronize the USRP time to the valid GPS time, set this parameter to GPSDO. You must also enable the Ensure sync GPS time parameter if the GPSDO is not locked to the GPS constellation at the start of the simulation.

Select this parameter to enable the gpsLocked output port, which indicates the lock status of the GPSDO to the GPS constellation.

Dependencies

To enable this parameter, set the PPS source parameter to GPDSO.

Select this parameter to ensure that the USRP radio time is synchronized to the valid GPS time.

When you select this parameter, the block checks the lock status of the GPSDO. When the GPSDO is locked to the GPS constellation, the block sets the USRP radio time to the valid GPS time.

Dependencies

To enable this parameter, set the PPS source parameter to GPSDO.

Clock source, specified as one of these values.

  • Internal — Use the internal clock signal of the USRP radio.

  • External — Use the 10 MHz clock signal from an external clock generator.

  • GPSDO — Use the 10 MHz clock signal from a GPSDO.

The external clock port is labeled REF IN.

To synchronize the frequency for all channels of the bundled radios, you can:

  • Provide a common external 10 MHz clock signal to all of the bundled radios and set this parameter to External.

  • Provide a 10 MHz clock signal from each GPSDO to the corresponding radio and set this parameter to GPSDO.

Select this parameter to enable the refLocked output port, which indicates the lock status of the USPR radio to the 10 MHz clock signal.

Dependencies

To enable this parameter, set the Clock source parameter to External or GPDSO.

Master clock rate, specified as a scalar in Hz. The master clock rate is the A/D and D/A clock rate. The valid range of values for this property depends on the radio platform that is connected.

Platform ValueSupported Master clock rate (Hz) Values

E320 (since R2025a)

Scalar in the range from 200e3 to 61.44e6.

When you use a USRP E320 radio with two transmit channels or two receive channels, the clock rate must be less than or equal to 30.72e6. This restriction is a hardware limitation for two-channel operations on USRP E320 radios.

The default value is 30.72e6.

N300 or N310

122.88e6, 125e6 (default), or 153.6e6

N320/N321

200e6 (default), 245.76e6, or 250e6.

X300 or X310

184.32e6 or 200e6 (default).

200e6 — When TwinRX daughterboard is selected.

X410 (since R2025a)

245.76e6 or 250e6 (default).

Data Types: double

Interpolation factor for the SDRu transmitter, specified as an integer in the range [1,1024] with restrictions that depend on the radio you use.

Radio DeviceSupported Interpolation Factors

USRP E320 (since R2025a)

USRP N300

USRP N310

USRP N320

USRP N321

USRP X410 (since R2025a)

1

2

3

Even integer in the range from 4 to 256

Multiple of 4 in the range from 256 to 512

Multiple of 8 in the range from 512 to 1016

USRP X300

USRP X310

Integer in the range from 1 to 128

Even integer in the range from 128 to 256

Multiple of 4 in the range from 256 to 512

Multiple of 8 in the range from 512 to 1016

The radio uses the interpolation factor when it upconverts the complex baseband signal to an intermediate frequency (IF) signal.

Option to enable timed transmission and reception. To enable the radio to transmit or receive data after a specified time, select Enable time trigger.

When you select Enable time trigger parameter, you can:

  • Transmit or receive after the time specified in the Trigger time parameter.

  • Transmit or receive at the specified GPS time in the Trigger time parameter if you set the PPSSource parameter to GPSDO.

  • Simultaneously transmit and receive after the time specified in the Trigger time parameter.

Trigger time in seconds, specified as a nonnegative scalar. Specify the trigger time after which you want the radio to transmit or receive data. The Trigger time value must be greater than the current USRP radio time.

When you set the PPS Source parameter to GPSDO, specify the Trigger time parameter as the exact GPS time in seconds at which the radio transmits and receives data.

Note

For AD936x-based N3xx USRP radios, you can expect a consistent delay between the specified trigger time and the start of transmission or reception.

Dependencies

To enable this parameter, select the Enable trigger time parameter.

Data

This parameter is read-only.

Baseband sample rate of output signal, in Hz, specified as a scalar.

This parameter displays the computed baseband sample rate derived from the Master clock rate (Hz) and Interpolation factor parameter values. This computation uses the formula, Baseband sample rate = Master clock rate/Interpolation factor. If you change the Interpolation factor during simulation, then the block changes hardware data rate, but does not change the Simulink sample time.

To get more information on sample time, see What Is Sample Time? (Simulink).

Data Types: double

Transport data type, specified as:

  • int16 — Uses 16-bit transport. Achieves higher precision than 8-bit transport.

  • int8 — Uses 8-bit transport. Uses a quantization step 256 times larger and achieves approximately two times faster transport data rate than 16-bit transport.

Specifying transport data rate data type as int16, assigns 16 bits for the in-phase component and 16 bits for the quadrature component, resulting in 32 bits for each complex sample of transport data.

To measure the number of samples lost during transmission, select this parameter.

If your model is not running in real time, you can adjust parameters that reduce the number of transported samples. To approach or achieve real-time performance, you can increase the interpolation factor.

Option to enable burst mode. To produce a set of contiguous frames without an overrun or underrun to the radio, select Enable burst mode. Enabling burst mode helps you simulate models that cannot run in real time.

When burst mode is enabled, specify the desired amount of contiguous data using the Number of frames in burst parameter.

Number of frames in a contiguous burst, specified as a nonnegative integer.

Dependencies

To enable this parameter, select Enable burst mode.

Data Types: double

More About

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Extended Capabilities

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C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2011b

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See Also

Blocks

Objects

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