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Re: [oc] DPLL

Hi,
           I have a problem about  bit synchronization when use QPSK in satellite communication. When design the demodulator , how can i get the
bit clock?  Some one said because of the fading and unknown delay , you can not synchroniza to the transmitter . so must  use the equalizer to estimate the channel. Is it right?








"Sam Gladstone" <samg@t-and-t.com>@opencores.org on 11/15/2001 06:29:28 AM

Please respond to cores@opencores.org

Sent by:  owner-cores@opencores.org


To:     <cores@opencores.org>
cc:      (bcc: Haoguang Guo/SHA/SC/PHILIPS)
Subject:  Re: [oc] DPLL
Classification:



I take it you are demodulating back to a certain softbit size?
There is several books out there that are pretty good. I will find the
one I used when we were writing an 802.11a phy for a company.

The main idea is to demodulate each dimension of the QPSKconstellation data
seperately by
breaking the real and imaginary up into two seperate demodulations.  Linear
extrapolations can be used to generate softbits for a first order method.
There are more cost effective, but
harder to understand methods available as well.
(Assuming that you have already done the proper power and phase
corrections.)
I think the number of softbits generated looks like this table.
BPSK - 1 softbit per constellation
QPSK - 2 softbits per constellation
QAM-16 - 4 softbits per constellation
QAM-64 - 6 softbits per constellation
(QAMs get nasty because they are like combinations of different codings that
have
to have multiple softbits generated per demension because of grey coding
with the
modulution module. Yuck! )

I will try to find the book name and send it out.

Regards,
  Sam

----- Original Message -----
From: <aolmo@grupoeyp.com>
To: <cores@opencores.org>
Sent: Wednesday, November 14, 2001 9:24 AM
Subject: [oc] DPLL


> Hi,
>
> I take the liberty disturbing you.
> I am a friend from Taiwan.
> After reading your posts on Web, I know you are a professional
> communication designer.
> Now I am designing QPSK demodulator for wireless Lan with verilog.
> Where can I find more helpful material, such as verilog code for DPLL.
> Please kindly to give me some advice.
> Thank you a lot!
> --
> To unsubscribe from cores mailing list please visit
http://www.opencores.org/mailinglists.shtml
>
>


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