Synchronization questions

GNU Radio
1

Hi
My appologies if the question is too vague or sounds naive-
I have read a number of papers(specially IEEE communication society
journals) on synchronization issues in communication- frequency, time
and
phase sync. All these papers address the issue of synchronization in
baseband and no reference is made to the AFC present in transciever
chips
(which in all probablity is controlled by baseband processor according
to
some algorithm) . On the other hand literature from receiver circuit
perspective present approaches for synchronization in hardware by using
AFC/PLL etc and this is performed on RF signal. Considering this, I
have
the following questions-

  1. Is the baseband approach of frequency synchronization only of
    theroretical interest or are they actually used in products
  2. Is the synchronization task perfomed in two stages? eg- first at
    RF/IF
    level and then remaining offset in baseband software
  3. How is synchronization achieved in USRP- at daughterboard hardware or
    gnuradio software

Thanks
SQ

2

2007/1/15, science quest [email protected]:

AFC/PLL etc and this is performed on RF signal. Considering this, I have
the following questions-

  1. Is the baseband approach of frequency synchronization only of
    theroretical interest or are they actually used in products

With the development of full-digital receiver, now the baseband
frequency
synchronization is already used in products.

  1. Is the synchronization task perfomed in two stages? eg- first at
    RF/IF

level and then remaining offset in baseband software

I’m not familiar with RF/IF. In my opinion, two stages are better. But
only
one stage is also acceptable. It depends on the signal characters.

  1. How is synchronization achieved in USRP- at daughterboard hardware or

gnuradio software

On the daughterboards, there is no synchonization processing. Everything
is
made in gnuradio software. You may use ‘soft PLL’ or ‘soft baseband
SYNC’.

Thanks

3

Lin,
Thanks for the reply
I am a newbie in the practical implementation world

On the daughterboards, there is no synchonization processing. Everything
is
made in gnuradio software. You may use ‘soft PLL’ or ‘soft baseband
SYNC’.

The daughterboard(FLEX 2400) has a PLL with frequency synthesizer. I
think
this is used for frequency synchronization and although I am not
sure,but,
there should be some way to change its frequency/phase on the fly. May
be
Marc or Eric can tell us more about this.

With the development of full-digital receiver, now the baseband
frequency
synchronization is already used in products.

Can you please give one example of such a commercial product.

I’m not familiar with RF/IF. In my opinion, two stages are better. But
only
one stage is also acceptable. It depends on the signal characters.

can you please explain why two stages are better and where are they
implemented- in RF front end or both in Baseband only. More over, if
only
one stage is acceptable, where is it implemented- in RF front end or
baseband.

My questions are targetted towards typical receiver architectures as
used in
commercial products so that I can qualify the benefits involved in
purely
software implementations.

Thanks once again
SQ

On 1/14/07, Lin HUANG On the daughterboards, there is no synchonization
processing. Everything is made in gnuradio software. You may use ‘soft
PLL’