error - occured niUSRP WRITE Tx Data (underflow)

[chandra.ha]

Hello

i am trying to make 2x2 MIMO OFDM system using two USRP 2922 as transmitter and one USRP 2943.

when i run my program for transmitter for IQ Rate 500k, its running smoothly but when i change the IQ rate for 20M, occured error like this picture.

what should i do to fix this error because i need my program to rum with bandwidth up to 20MHz so i need IQ rate 20M?

thank you

[WillyWad]

Hey chandra.ha,

Your rate equals bandwidth*1.25, so you should specify an IQ rate of 25MS/s  to achieve your 20MHz bandwidth.

Underflow means the USRP hardware is attempting to transmit samples that haven;t been written to its buffer from software yet. There could be a couple reasons for this. Another forum post discusses a few approaches you can take to address the underflow.

-Will

[chandra.ha]

thank you for your reply

But i still don't know waht should i do to fix underflow error

i have tried changing

1.this  ** HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\AFD\Parameters\, I don't see any "FastSendDatagramThreshold".  but its still error underflow

2. change write rate by increase my data but i got this error

3. i don't know how to set samples write

if you have solution please share