Re: [Discuss-gnuradio] USRP2 and Data Rate

[Garrett Wenger]

I am not quite sure what data rate I am getting.  I've been using a signal analyzer to receive and demod what I'm transmitting and it can generally pick up the bit sequence that I am now sending out, but I get an error rate the fluctuates from about 5% all the way up to 70% or higher. 
My cpfsk mod index is set to 1 and the distance between the peaks is about 10kHz, so it really seems like my data rate is somewhere around what I want it to be, but the error rate is just way to high.

Also, I went ahead and added in the interpolating filter like you suggested, but just for future reference, what is bad about having a high samples per symbol value?

-Garrett

On Wed, Jul 7, 2010 at 12:41 PM, Matt Ettus <address@hidden> wrote:

On 07/07/2010 08:32 AM, Garrett Wenger wrote:

Hi all,
A few days ago I made a simple program using grc to fsk modulate and
transmit a pn sequence at 10kbps. Since I was using a USRP1, I set my
samples per symbol to 25 and the interpolation to 512 to get this data
rate.

The place I work at just received a couple USRP2's, so I am trying to
get this same program working with the new devices.  I realize that the
DAC rate for the USRP2 is 100 MS/s instead of 128 MS/s, so I changed the
samples per symbol and interpolation rate to  25 and 400, respectively,
but this does not give me the 10kbps rate like I expected it would.

Is there something major that I am missing here?

Your calculations appear correct, so I'm not sure why you aren't seeing 10kbs.  What rate does it give you?

Also, 25 samples per symbol is a lot.  You would probably be better off doing an additional software decimate/interpolate by 5 operation (using an interpolating/decimating FIR filter) and using 5 samples per symbol.


Matt