Burst Mode

In the Communications Toolbox™ Support Package for USRP®[1] Embedded Series Radio, if a receiver block or System object™ cannot keep up with the radio hardware, the model or code is not processing data in real time. Burst mode enables you to buffer a set of contiguous samples without losing samples by setting the number of frames in a burst. The number you can set is hardware-dependent. The block or object grabs a fresh set of samples for each burst. Therefore lost samples can happen between bursts, especially with large burst sizes. If your model can keep up in real time, do not use burst mode.

Determine If You Need Burst Mode

It is recommended that you enable burst mode when your application requires fresh samples from the hardware or guaranteed contiguous samples. To see if the received data is contiguous, enable the overflow indicator on the receiver block or object. For more information, see Detect Underruns and Overruns.

Enable Burst Mode

Enable Burst Mode in Receiver Block

The E3xx Receiver block has an Enable burst mode parameter. When you select this parameter, the block produces a set of contiguous frames without an overrun to the radio hardware. Enable burst mode to simulate models that cannot run in real time. Specify the amount of contiguous data using the Frames in burst parameter. The default number of frames in a burst is 1.

Enable Burst Mode in Receiver System Object

The comm.SDRRxE3xx System object has an EnableBurstMode property. When you set this property to true, the object produces a set of contiguous frames without an overrun to the radio hardware. For example:

rx = sdrrx('E3xx');
rx.EnableBurstMode = true;

This setting can help simulate models that cannot run in real time. You can specify the amount of contiguous data using the NumFramesInBurst property. The default number of frames in a burst is 1.

Limitations

Burst mode requires a fresh set of samples from the hardware. Therefore, when you call a receiver System object for the first time with burst mode enabled, the overflow output argument is 1. Likewise, the first time-step of a block with burst mode enabled asserts the overflow port.

See Also

Blocks

Objects

Related Topics


[1] USRP, USRP2, UHD, and Ettus Research are trademarks of National Instruments Corp.