Re: [Discuss-gnuradio] questions about bpsk rx with different noise voltage

[Alick Zhao]

On Thu, 12 Apr 2012 13:33:01 -0400, Tom Rondeau wrote:
> 
> Alick,
> 
> Why are you using 1's and 0's? Is this just for some academic exercise
> or are you trying to do something with this kind of a constellation?
> I'm only asking out of curiosity.
> 
> It also looks like you're heavily biasing the output to be all 1's and
> very few 0's. That's going to be problematic for the recovery loops.
> In particular, the FLL uses bandedge filters that rely on the excess
> bandwidth. If you are never, or rarely, transitioning between symbols,
> the excess bandwidth of the signal is going to be pretty much absent.
> So I'd add the randomizer back in and see how that works.
> 
> For simulation purposes, you can probably go in and remove the FLL
> from the receiver chain in generic_mod_demod.py.
> 
> Tom

Hi Tom, thank you for pointing out the issue of my set up. I want to
embed channel estimation function into the receiver with training
sequences (here all 1's). In a practical configuration, I think frame
structure with preamble containing training sequences and (randomized)
payload should work. (Is it so?) But now I haven't looked deep into the
packet/frame related code, and I am not sure how to find frame header
right on constellation. (Could you give some advice?) So I just begin
with the set up above, which is problematic for the recovery loops.

Besides, yes I will add the scrambler back in and do some tests.

alick