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I want to send signal with data rate (3.84 M) using USRP1, but when I transmit the signal it tells me some thing like this in the terminal :

WARNING

Target data rate: 3840000 bps

Actual data rate: 4000000 bps

but I'm trying to implement TX working with the UMTS air interface and I don't want this error in the data rate, anyone can help?????

Zangetsu
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1 Answers1

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Your sample rate is dependent on the master clock rate you are using with your USRP. Your USRP1 has a master clock rate of 64 MHz, and you can only sample at integer decimations of that value, by default, which is why you cannot sample at 3.84 MSps.

UHD is auto-correcting your requested sample rate to a rate that is supported by your USRP, for you. This is actually desirable behavior.

You have two options:

  1. Replace the clock on the USRP1 that will divide down to the rate you want.
  2. Use a rational re-sampler. GNURadio provides this block for you, if you want to use it.

I would suggest using a rational resampler before attempting a hardware mod, which may permanently destroy your USRP if you do it incorrectly.

bhilburn
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  • how can I use the "rational re-sampler" and what values shoult I put it in this block to support this data rate, can you describe more plz ?? thanx for you reply – Zangetsu Jul 17 '12 at 09:27
  • I don't have experience with it, so I can't tutor you on how to use it. If you Google for it though, it looks like there are a number of mailing list discussions. – bhilburn Jul 18 '12 at 19:37
  • Is there a reason you unaccepted this answer? Is your problem unsolved? – bhilburn Aug 18 '13 at 20:20