07-11-2012 12:01 PM
I would like to transmit my PN code as fast as I can. However, I found the maximum transmitting IQ rate I can reach is 2M. If it is larger, the error will come to be "niUSRP Write Tx Data (CDB).vi<ERR>Underflow: the Tx buffer was emptied before new data was provided. Consider reducing the IQ rate, increasing the Write rate, or increasing the number of samples per Write."
I have tried to increase the number of samples per write to be a very high value. However, it doesn't work.
Could anyone tell me how to increase the Tx IQ Rate efficiently?
07-11-2012 12:28 PM
Streaming data at IQ rates of 5 or 10 MS/s should be achievable on most systems. I have a few questions and a few suggestions for you.
Suggestions that have worked for myself and my coworkers
There are a lot of different factors that can cause poor performance with a USRP. Please let me know a bit more about your system and the code you are running so I can better help troubleshoot this problem.
07-11-2012 03:40 PM
I use a 64-bit SONY laptop with AMD Athlon(tm) II P340 Dual-Core Processor and 4GB RAM. The Ethernet port is gigabit type. I connect the board to the laptop through Ethernet cables via a gigabit switch. An Tx example in the driver (in the attachment) is used for test.
After I take your suggestions that change the computer's power setting to "high performance", turn off the virus scanner, the rate still can't reach higher.
09-27-2012 11:27 AM
If you have tried everything mentioned above, you should also try changing your registry key. How to do this is described in detail in this post:
10-10-2012 05:51 PM
Hi Sarah and others,
I need to send data at 16 Ms/sec in my application. But I am having problem doing so.
Is this possible ? I checked the various threads on this forum and can now write at 4 Msamp/sec, but I am not able to go beyond it.
I am using:
- Intel Core2 Quad CPU with 8 GB RAM
- Windows 7
- RealTek RTL8168D/8111D family PCI-E Gigabit Ethernet NIC
- I am using the "NI USRP Write Tx Data (poly)" vi
I changed the registry key to HEX2400, amde sure that the firewall is turned off, and changed the power options to high performance mode.
When I try a Tx sampling rate of 8 Ms/s, the subCallConfigTX.vi return a Tx sampling rate of 7.69 Ms/s and I get the following error.
"niUSRP Write Tx Data (CDB Cluster).vi<ERR>Underflow: the Tx buffer was emptied before new data was provided. Consider reducing the IQ rate, increasing the Write rate, or increasing the number of samples per Write."
I would appreciate any help.
10-10-2012 06:20 PM
If you can manage with 8 bits samples ,this would half the data sendt to the USRP,
try change the network-adapter Transmit buffer size , it may help
i manage receiving at 25 MSPS i 8 bit mode, but i have a dedicated network adapter directly to the USRP,
it is only stable if you don't do any other network access to another network-adapter.