Re: [Discuss-gnuradio] (no subject)

[Tom Rondeau]

On Mon, Apr 1, 2013 at 2:46 PM, vamshi krishna dodla
<address@hidden> wrote:
> I have some questions regarding the coastas loop implemented, does it also
> consider the snr estimate too? like a Maximum Likelihood loop(tanh* snr).

Hi Vamshi,

No, the Costas loop does not account for SNR. This is among a series
of improvements that I'd like to see happen. We have an SNR estimator
block that sends tags and one that we can easily outfit to send
messages. We would then use this to send a message to blocks like this
so they can adjust their behavior based on current SNR estimates. I
wouldn't want to recalculate the SNR every time its needed.

> Also can you suggest me any interpolator for timing recovery and also
> polyphase bandedge filters implementation. This would be really helpful to
> me.As there is very little material available online, also as you are
> experts in these fields your guidance will be very useful

Take a look at gr-digital/lib/fll_band_edge_cc for a frequency locked loop.

There's a lot of debate over the merits of using just the band edge
information to do timing recovery, since you'd be throwing away
information by not taking the information in the entire symbol (also
effects of multipath and adjacent channel interference).
Implementations are very welcome, though. One thing we can do well in
GNU Radio is pit algorithms against each other under real signal
conditions to see how they work.

For timing recovery, look at gr-digital/lib/pfb_clock_sync_ccf.

Tom