Re: [Discuss-gnuradio] RFX 2400 transmit-receive turnaround

[Bob Vincent]

At 11:37 AM 5/11/2006, Eric Blossom wrote:
> On Thu, May 11, 2006 at
> 10:03:05AM -0400, Bob Vincent wrote:
> > We've been doing some testing on the RFX, and have found that
> delaying 
> > between packets sometimes causes receive errors. I suspect it may
> have to 
> > do with the transmit/receive turnaround. Do you have any information
> on the 
> > design of the RFX that might help me diagnose the source of the
> problem?
>
> Bob,
>
> If you're not kludging up the padding to ensure that the output of
> the
> sample stream for a given frame is a multiple of 128 complex samples
> (512 byte USB packet), the tail of the frame may not be getting
> across the USB.
>
> Do you see this with the gmsk2 code and/or psk?  The gmsk code has
> the
> proper alignment kludge.  [ We *really* do need that m-block stuff
> ;) ]

gmsk2 under the tunnel_ip_null_mac.py.

I haven't made much headway on psk yet, because the receive
gets an error about 2 times in 3.
python: gri_mmse_fir_interpolator_cc.cc:66: gr_complex
gri_mmse_fir_interpolator_cc::interpolate(const gr_complex*, float):
Assertion `imu >= 0' failed.

If it runs for a while, it eventually gets :
python: gr_dd_mpsk_sync_cc.cc:191: virtual int
gr_dd_mpsk_sync_cc::general_work(int, gr_vector_int&,
gr_vector_const_void_star&, gr_vector_void_star&): Assertion `ii
<= ninput_items[0]' failed.

I think I may be parameterizing the interpolator (costas_gain, gain_mu)
incorrectly. I'm a little stumped by the effects of changing these right
now. If you could point me at a reference it might help.


> Can you reproduce the problem
> with benchmark_gmsk_{tx,rx}?
> If you haven't already, please try the --discontinuous option to
> tx.
>
> Eric 
Yes. I'm running with around 40 dB of headroom, and I
see some dropped bits on the first packet of the burst around 1 time in
5.