symbol timing recovery using interpolation filter method:suggestion

Hi,
  i am Sreenivas, i want to clarify from you, "Can the the symbol
timing recovery be acheived by using interpolation filter method or not
?". Actuall i am working at 32MHz sampling rate, can i apply this
method at this rate for symbol timing recovery or not.
It is mentioned in "Interpolation in Digital Modems-Part-1 :
Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
"interpolation is not and appropriate technique to be applied to
wideband signals".
if it is not suitable,  why it is not suitable? and suggest what are
other methods will give better results.
if it is suitable, kindly suggest me some book or links where i can get
good description of how to implement it in fpgas.

Thankyou for your time and valuable suggestions in advance.

Regards,
Sreenivas

<asnivas223@gmail.com> wrote in message
news:1128432149.209707.305820@f14g2000cwb.googlegroups.com...
> Hi,
>   i am Sreenivas, i want to clarify from you, "Can the the symbol
> timing recovery be acheived by using interpolation filter method or not
> ?". Actuall i am working at 32MHz sampling rate, can i apply this
> method at this rate for symbol timing recovery or not.
> It is mentioned in "Interpolation in Digital Modems-Part-1 :
> Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
> "interpolation is not and appropriate technique to be applied to
> wideband signals".
> if it is not suitable,  why it is not suitable? and suggest what are
> other methods will give better results.
> if it is suitable, kindly suggest me some book or links where i can get
> good description of how to implement it in fpgas.
>
> Thankyou for your time and valuable suggestions in advance.
>
> Regards,
> Sreenivas

What kind of modulation are you trying to recover the symbol timing for?
Your sample rate isn't as relevant as the bandwidth of the signal you are
receiving.

Cheers
Bhaskar

asnivas223@gmail.com wrote:
> It is mentioned in "Interpolation in Digital Modems-Part-1 :
> Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
> "interpolation is not and appropriate technique to be applied to
> wideband signals".
> if it is not suitable,  why it is not suitable?

What do you mean by "wideband" in relation to your sampling
rate?

Sinc reconstruction methods of interpolation are usually only
useful with signals that are band-limited before sampling.


IMHO. YMMV.
-- 
rhn A.T nicholson d.O.t C-o-M

rhnlogic@yahoo.com wrote:
> asnivas223@gmail.com wrote:
> 
>>It is mentioned in "Interpolation in Digital Modems-Part-1 :
>>Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
>>"interpolation is not and appropriate technique to be applied to
>>wideband signals".
>>if it is not suitable,  why it is not suitable?
> 
> 
> What do you mean by "wideband" in relation to your sampling
> rate?
> 
> Sinc reconstruction methods of interpolation are usually only
> useful with signals that are band-limited before sampling.

Sampled signals are usually useful only if they were band limited before 
the sampling

-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

Jerry Avins wrote:
> rhnlogic@yahoo.com wrote:
> > Sinc reconstruction methods of interpolation are usually only
> > useful with signals that are band-limited before sampling.
>
> Sampled signals are usually useful only if they were band limited before
> the sampling

This is a stronger statement than I'd be willing to make with respect
to artificial modulation schemes.  Consider cases with very redundant
data encodings and using statistical data recovery.  One might be able
to get useful information out of a severely undersampled signal.
But you wouldn't be able to reconstruct that signal.


IMHO. YMMV.
-- 
rhn A.T nicholson d.O.t C-o-M

rhnlogic@yahoo.com wrote:
> Jerry Avins wrote:
> 
>>rhnlogic@yahoo.com wrote:
>>
>>>Sinc reconstruction methods of interpolation are usually only
>>>useful with signals that are band-limited before sampling.
>>
>>Sampled signals are usually useful only if they were band limited before
>>the sampling
> 
> 
> This is a stronger statement than I'd be willing to make with respect
> to artificial modulation schemes.  Consider cases with very redundant
> data encodings and using statistical data recovery.  One might be able
> to get useful information out of a severely undersampled signal.
> But you wouldn't be able to reconstruct that signal.
> 
> 
> IMHO. YMMV.

To save face, I'd classify that as "unusual".

jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

asnivas223@gmail.com wrote:
> Hi,
>   i am Sreenivas, i want to clarify from you, "Can the the symbol
> timing recovery be acheived by using interpolation filter method or not
> ?". Actuall i am working at 32MHz sampling rate, can i apply this
> method at this rate for symbol timing recovery or not.
> It is mentioned in "Interpolation in Digital Modems-Part-1 :
> Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
> "interpolation is not and appropriate technique to be applied to
> wideband signals".
> if it is not suitable,  why it is not suitable? and suggest what are
> other methods will give better results.
> if it is suitable, kindly suggest me some book or links where i can get
> good description of how to implement it in fpgas.
>
> Thankyou for your time and valuable suggestions in advance.
>
> Regards,
> Sreenivas

Wideband is a relative term. What matters is how many samples per baud
are available to estimate the value of a signal between sampling
instants using a weighted average or curve fit based on the surrounding
samples. Intuitively, the signal should not change much between
sampling instants in order for the estimate to be good. As a practical
matter, that will be the case if at least two samples per baud are
available.

John

john wrote:
> asnivas223@gmail.com wrote:
> > Hi,
> >   i am Sreenivas, i want to clarify from you, "Can the the symbol
> > timing recovery be acheived by using interpolation filter method or not
> > ?". Actuall i am working at 32MHz sampling rate, can i apply this
> > method at this rate for symbol timing recovery or not.
> > It is mentioned in "Interpolation in Digital Modems-Part-1 :
> > Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
> > "interpolation is not and appropriate technique to be applied to
> > wideband signals".
> > if it is not suitable,  why it is not suitable? and suggest what are
> > other methods will give better results.
> > if it is suitable, kindly suggest me some book or links where i can get
> > good description of how to implement it in fpgas.
> >
> > Thankyou for your time and valuable suggestions in advance.
> >
> > Regards,
> > Sreenivas
>
> Wideband is a relative term. What matters is how many samples per baud
> are available to estimate the value of a signal between sampling
> instants using a weighted average or curve fit based on the surrounding
> samples. Intuitively, the signal should not change much between
> sampling instants in order for the estimate to be good. As a practical
> matter, that will be the case if at least two samples per baud are
> available.
>
> John

Hi thank you for the reply. Actually i'm looking at Non-Data-Aided(NDA)
method of timing recovery in which i'm having only the incoming data
and only. My data rate is fixed at 2Mbps. I'm basically looking at the
method which is not using NCO or DPLL or PLL. I'd like to do it using
interpolators.
---srinivas

As you will see from the Gardner paper, the interpolation phase is
determined by the NCO value after a wrap occurs. Typically the NCO
frequency and phase are adjusted by filtering the output of a timing
error detector (TED) through a lead-lag loop filter, creating a second
order PLL. The TED is normally chosen to give an error value
proportional to the timing offset when a transition occurs and zero
when no transition occurs (Gardner has a paper on this too). The only
thing required to lock onto the timing is a reasonable density of
transitions, not a particular bit pattern. So I would say this
qualifies as NDA.

John

On 4 Oct 2005 21:50:39 -0700, asnivas223@gmail.com wrote:

>
>john wrote:
>> asnivas223@gmail.com wrote:
>> > Hi,
>> >   i am Sreenivas, i want to clarify from you, "Can the the symbol
>> > timing recovery be acheived by using interpolation filter method or not
>> > ?". Actuall i am working at 32MHz sampling rate, can i apply this
>> > method at this rate for symbol timing recovery or not.
>> > It is mentioned in "Interpolation in Digital Modems-Part-1 :
>> > Fundamentals" by Floyd M.Gardner, Fellow, IEEE.-1993. that it
>> > "interpolation is not and appropriate technique to be applied to
>> > wideband signals".
>> > if it is not suitable,  why it is not suitable? and suggest what are
>> > other methods will give better results.
>> > if it is suitable, kindly suggest me some book or links where i can get
>> > good description of how to implement it in fpgas.
>> >
>> > Thankyou for your time and valuable suggestions in advance.
>> >
>> > Regards,
>> > Sreenivas
>>
>> Wideband is a relative term. What matters is how many samples per baud
>> are available to estimate the value of a signal between sampling
>> instants using a weighted average or curve fit based on the surrounding
>> samples. Intuitively, the signal should not change much between
>> sampling instants in order for the estimate to be good. As a practical
>> matter, that will be the case if at least two samples per baud are
>> available.
>>
>> John
>
>Hi thank you for the reply. Actually i'm looking at Non-Data-Aided(NDA)
>method of timing recovery in which i'm having only the incoming data
>and only. My data rate is fixed at 2Mbps. I'm basically looking at the
>method which is not using NCO or DPLL or PLL. I'd like to do it using
>interpolators.
>---srinivas

How do you plan to steer the interpolators?


Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org