Questions about the Channel Model block from gr::channels::channel_model Noiose Voltage and Frequency Offset work as expected. I've been using a Seed of 0 and no multipath so Taps of 1+0i. Have not seen any issue there although one does have to be careful to not use Taps of just 1 for whatever reason - you have to fully specify the complex number or weird stuff will happen. The default is 1+1j and I guess you use that and just shift stuff 45 degrees which will likely be un-noticed, I have not tried that.
Anyhow, my questions relate to the Epsilon that lets you simulate sample rate error at baseband, which you can use for a controlled symbol timing error. I read the code and figured out that 1 is perfect timing. Values less than 1 will add samples (input rate over output rate equals Epsilon), which will make my sync late and I see this. Also I see the opposite for values greater than 1. That seems as expected. What I have encountered, did not expect and have some trouble with, is the way non-unity Epsilon affects the frequency response of the band edges in a time-varying fashion. With Epsilon just slightly offset from unity I can see this causing the edges of my signal to droop and then come back at a rate proportional to the offset I am using. This gets to be problematic when I have a pilot tone near the band edge which is having not only its amplitude but its phase shifted. Anyone try to use this before? Really all I need is just something to stick extra samples in (or remove them) at some rate. I suppose I could loop thru the USRP at slightly different Tx and Rx sample rates. Thanks, John _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
