Re: [bluetooth] Re: Clock Recovery in BT

["Ling Su" <lingsu1@home.com>]

The threshold should be 6 if we set it statically, since the encoding method
of Access Code give 6 coding distance. Of course, I didn't see some paper
talking about dynamic change the threshold.

We can not simply ignore the preample, since it gives the most accurate
sender clock information. As you may all know, the receiver side will
working in a recovered clock instead of a system clock, the recovered clock
will be retrieved from preample. Usually a wireless system has a preample
like 10 or more bits, which gives more time to do clock recovery, but in
bluetooth, there is only 4 bits, so it will be more chanllenging.

Regards,
-Ling


----- Original Message -----
From: "Jamil Khatib" <khatib@ieee.org>
To: <bluetooth@opencores.org>
Sent: Thursday, July 26, 2001 2:34 PM
Subject: Re: [bluetooth] Re: Clock Recovery in BT


> Hi,
> Try to look at the access code correlator I designed (you can find it in
the bluetooth project pages).
> the correlator keeps comparing hte inputs till both the input and the
expected value are matched within
> certain threshold. Till now I do not know how to select this threshold.
> regarding the preamble  ( and since the correlator does not look for the
exact pattern) I think we can
> ignore them
>
> Note: the correlator is too slow and it needs lot of modifications to get
faster
>
> Any comments
> Jamil Khatib
>
> > Hello Mr. Khatib
> >
> > Yes that symbol recovery is what I am talking about.
> > There is a preamble of 1010 or 0101 before 68-bit
> > access code which helps in determining the symbol
> > rate. In inquiry and other packets which have no
> > header or payload, access code is only 68 bits,
> > without any preamble. also due to settling time of
> > radio, it is less likely that we can receive all the 4
> > bits of preamble at receiver. In all these cases (that
> > is no preamble and unknown number of preamble bits)
> > how symbol recovery can be done? I will be thankful to
> > you if you can guide me on this.
> >
> > regards
> > Faisal
> > --- Ling Su <lingsu@palmmicro.com> wrote:
> > > I guess it would't be access code correlator, it
> > > means the symbol recovery
> > > before you feed the data into your logic. Bluetooth
> > > need pretty fast
> > > recovery, since it only has 4 sync symbol.
> > >
> > > -Ling
> > >
> > > ----- Original Message -----
> > > From: "Jamil Khatib" <jamilkhatib75@yahoo.com>
> > > To: <bluetooth@opencores.org>
> > > Cc: <faisalmaalik@yahoo.com>
> > > Sent: Wednesday, July 25, 2001 1:39 PM
> > > Subject: Re: [bluetooth] Clock Recovery in BT
> > >
> > >
> > > > Hi,
> > > > sorry for the delay.
> > > > do you mean the access code correlator?
> > > >
> > > > if not can you explain it to me because it seems
> > > the I
> > > > am missing something.
> > > >
> > > > regards,
> > > > Jamil
> > > >
> > > > --- Faisal <faisalmaalik@yahoo.com> wrote:
> > > > >
> > > > > Hello
> > > > >
> > > > > can any one help me in designing of the clock
> > > and
> > > > > data recovery sub-block of bluetooth baseband
> > > > > receiver. Any suggestions, ideas or relevant
> > > > > information would be welcome.
> > > > >
> > > > > Faisal
> > > > >
> > > > >
> > > > >
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> --
>    Jamil Khatib
> OpenCores Organization
> http://www.opencores.org
>
>
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