>On Tue, 15 May :48:, "lanbaba" <lanbaba@gmx.ch> wrote:
>
>>>On Mon, 14 May :38:, "lanbaba" <lanbaba@gmx.ch> wrote:
>>>
>>>>>On 12 May :13:, Mark <makolber@yahoo.com> wrote:
>>>>>
>>>>>>On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>>>>>>> On 11 May :01:, Mark <makol...@yahoo.com> wrote:
>>>>>>>
>>>>>>> >> Noise is different, since the noise instances in the samples
>>will
>>>>not
>>>>>>> >> be correlated if the noise is white.
>>>>>>>
>>>>>>> >> So, really, it depends on the channel model.   Noise?   Sure,
>>>>>>> >> oversampling improves "diversity".   Fading?   Not gonna help
at
>>>>all.
>>>>>>>
>>>>>>> >If the signal has passed through a bandpass filter near the
>>Nyquist
>>>>>>> >BW, which is the usual case in a receiver, will not the noise
>>during
>>>>>>> >samples taken of any particular symbol, be highly correlated
thus
>>>>>>> >reducing any gain of oversampling?
>>>>>>>
>>>>>>> >Mark
>>>>>>>
>>>>>>> Remember that this case is just the usual SNR improvement due to
>>the
>>>>>>> processing gain from oversampling and filtering.   Nothing magic
>>>>going
>>>>>>> on there, it's just that the 'diversity' point of view is another
>>way
>>>>>>> to look at it.
>>>>>>>
>>>>>>>
>>>>>>This usual SNR improvement processing gain applies only to wideband
>>>>>>noise generated after the channel filter and does not apply to
narrow
>>>>>>band noise generated before the channel filter..
>>>>>>
>>>>>>Mark
>>>>>
>>>>>Certainly the relative bandwidth of the noise matters.   The OP
didn't
>>>>>specify the architecture, so we can only speculate or generalize.
>>>>>
>>>>>That's why I tried to clarify that diversity really only works if
the
>>>>>impairments in the diversity sources are decorrelated.  As long as
>>>>>that's true there'll be gain due to diversity.   That applies to
noise
>>>>>as well, so you're right, if the noise is correlated there won't be
an
>>>>>opportunity for gain via diversity combining.
>>>>>Eric Jacobsen
>>>>>Minister of Algorithms
>>>>>Abineau Communications
>>>>>http://www.ericjacobsen.org
>>>>>
>>>>
>>>>The last sentence confused me. Let's consider double spatial
diversity.
>>>>Assume the additive noise at both signal branches are fully
correlated.
>>I
>>>>can still achieve a diversity gain by any combining schemes if both
>>branch
>>>>signals are not fully correlated, cannot I?
>>>
>>>Well, I can clarify what I meant:   If noise is the only impairment,
>>>then diversity combining of two signals will provide gain as long as
>>>the noise is not correlated between the diversity sources.    With two
>>>separate input streams I think it would be pretty tough get the noise
>>>correlated, but with one input stream and the "diversity" obtained by
>>>taking additional samples, the noise could become correlated if a lot
>>>of filtering had been applied.
>>>
>>>So, in your example, as I understand it, if there are additional
>>>fading impairments that are uncorrelated across the two channels, then
>>>even if the noise *were* correlated (which would be a pretty cool
>>>trick), then there could still be substantial gain due to overcoming
>>>the uncorrelated fading.
>>>
>>>Eric Jacobsen
>>>Minister of Algorithms
>>>Abineau Communications
>>>http://www.ericjacobsen.org
>>>
>>
>>What even more confuses me is why you are talking about noise
correlation 
>>all the time in conjunction with diversity gain. If the RX does not get
>>uncorrelated replica of transmitted signals you can combine as you like
>>and get no diversity gain, and this has nothing to do with the
correlation
>>of the additive noise. In the case of "oversampling", I would even not
call
>>it a "diversity combining" since there is no diversity conceptually. I
>>would rather call it denoising by averaging if I have to give it a
name.
>
>Perhaps you missed my first post in the thread where I said:
>
>"I think if you really want to stretch the usual use of the term
>"diversity" you could make that argument, although some people might
>raise an eyebrow at the idea."
>
>I don't disagree with you, but as I mentioned earlier if noise is the
>only impairment then oversampling a signal, with a noise BW wide
>enough that the noise is decorrelated between samples, is essentially
>the same thing as using time diversity to transmit the signal twice
>and combine them.   So from that perspective oversampling to overcome
>noise is essentially the same thing as time diversity reception.
>
>I thought it was important to clarify that because if the impairment
>is fading then oversampling will be unlikely to provide any diversity
>gain (since the fading will be correlated), but time diversity *would*
>still be likely to provide gain as long as the transmissions were
>separated by more than the channel coherence time.
>
>So there's a difference between whether the primary impairment is
>noise or fading, and to the OPs point noise is the only case that
>would really work to fit his description.
>
>Eric Jacobsen
>Minister of Algorithms
>Abineau Communications
>http://www.ericjacobsen.org
>

That was a neat summary.
LBB

_____________________________________
Do you know a company who employs DSP engineers?  
Is it already listed at http://dsprelated.com/employers.php ?

On Tue, 15 May 2007 06:48:27 -0500, "lanbaba" <lanbaba@gmx.ch> wrote:

>>On Mon, 14 May 2007 14:38:05 -0500, "lanbaba" <lanbaba@gmx.ch> wrote:
>>
>>>>On 12 May :13:, Mark <makolber@yahoo.com> wrote:
>>>>
>>>>>On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>>>>>> On 11 May :01:, Mark <makol...@yahoo.com> wrote:
>>>>>>
>>>>>> >> Noise is different, since the noise instances in the samples
>will
>>>not
>>>>>> >> be correlated if the noise is white.
>>>>>>
>>>>>> >> So, really, it depends on the channel model.   Noise?   Sure,
>>>>>> >> oversampling improves "diversity".   Fading?   Not gonna help at
>>>all.
>>>>>>
>>>>>> >If the signal has passed through a bandpass filter near the
>Nyquist
>>>>>> >BW, which is the usual case in a receiver, will not the noise
>during
>>>>>> >samples taken of any particular symbol, be highly correlated thus
>>>>>> >reducing any gain of oversampling?
>>>>>>
>>>>>> >Mark
>>>>>>
>>>>>> Remember that this case is just the usual SNR improvement due to
>the
>>>>>> processing gain from oversampling and filtering.   Nothing magic
>>>going
>>>>>> on there, it's just that the 'diversity' point of view is another
>way
>>>>>> to look at it.
>>>>>>
>>>>>>
>>>>>This usual SNR improvement processing gain applies only to wideband
>>>>>noise generated after the channel filter and does not apply to narrow
>>>>>band noise generated before the channel filter..
>>>>>
>>>>>Mark
>>>>
>>>>Certainly the relative bandwidth of the noise matters.   The OP didn't
>>>>specify the architecture, so we can only speculate or generalize.
>>>>
>>>>That's why I tried to clarify that diversity really only works if the
>>>>impairments in the diversity sources are decorrelated.  As long as
>>>>that's true there'll be gain due to diversity.   That applies to noise
>>>>as well, so you're right, if the noise is correlated there won't be an
>>>>opportunity for gain via diversity combining.
>>>>Eric Jacobsen
>>>>Minister of Algorithms
>>>>Abineau Communications
>>>>http://www.ericjacobsen.org
>>>>
>>>
>>>The last sentence confused me. Let's consider double spatial diversity.
>>>Assume the additive noise at both signal branches are fully correlated.
>I
>>>can still achieve a diversity gain by any combining schemes if both
>branch
>>>signals are not fully correlated, cannot I?
>>
>>Well, I can clarify what I meant:   If noise is the only impairment,
>>then diversity combining of two signals will provide gain as long as
>>the noise is not correlated between the diversity sources.    With two
>>separate input streams I think it would be pretty tough get the noise
>>correlated, but with one input stream and the "diversity" obtained by
>>taking additional samples, the noise could become correlated if a lot
>>of filtering had been applied.
>>
>>So, in your example, as I understand it, if there are additional
>>fading impairments that are uncorrelated across the two channels, then
>>even if the noise *were* correlated (which would be a pretty cool
>>trick), then there could still be substantial gain due to overcoming
>>the uncorrelated fading.
>>
>>Eric Jacobsen
>>Minister of Algorithms
>>Abineau Communications
>>http://www.ericjacobsen.org
>>
>
>What even more confuses me is why you are talking about noise correlation 
>all the time in conjunction with diversity gain. If the RX does not get
>uncorrelated replica of transmitted signals you can combine as you like
>and get no diversity gain, and this has nothing to do with the correlation
>of the additive noise. In the case of "oversampling", I would even not call
>it a "diversity combining" since there is no diversity conceptually. I
>would rather call it denoising by averaging if I have to give it a name.

Perhaps you missed my first post in the thread where I said:

"I think if you really want to stretch the usual use of the term
"diversity" you could make that argument, although some people might
raise an eyebrow at the idea."

I don't disagree with you, but as I mentioned earlier if noise is the
only impairment then oversampling a signal, with a noise BW wide
enough that the noise is decorrelated between samples, is essentially
the same thing as using time diversity to transmit the signal twice
and combine them.   So from that perspective oversampling to overcome
noise is essentially the same thing as time diversity reception.

I thought it was important to clarify that because if the impairment
is fading then oversampling will be unlikely to provide any diversity
gain (since the fading will be correlated), but time diversity *would*
still be likely to provide gain as long as the transmissions were
separated by more than the channel coherence time.

So there's a difference between whether the primary impairment is
noise or fading, and to the OPs point noise is the only case that
would really work to fit his description.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

>On Mon, 14 May 2007 14:38:05 -0500, "lanbaba" <lanbaba@gmx.ch> wrote:
>
>>>On 12 May :13:, Mark <makolber@yahoo.com> wrote:
>>>
>>>>On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>>>>> On 11 May :01:, Mark <makol...@yahoo.com> wrote:
>>>>>
>>>>> >> Noise is different, since the noise instances in the samples
will
>>not
>>>>> >> be correlated if the noise is white.
>>>>>
>>>>> >> So, really, it depends on the channel model.   Noise?   Sure,
>>>>> >> oversampling improves "diversity".   Fading?   Not gonna help at
>>all.
>>>>>
>>>>> >If the signal has passed through a bandpass filter near the
Nyquist
>>>>> >BW, which is the usual case in a receiver, will not the noise
during
>>>>> >samples taken of any particular symbol, be highly correlated thus
>>>>> >reducing any gain of oversampling?
>>>>>
>>>>> >Mark
>>>>>
>>>>> Remember that this case is just the usual SNR improvement due to
the
>>>>> processing gain from oversampling and filtering.   Nothing magic
>>going
>>>>> on there, it's just that the 'diversity' point of view is another
way
>>>>> to look at it.
>>>>>
>>>>>
>>>>This usual SNR improvement processing gain applies only to wideband
>>>>noise generated after the channel filter and does not apply to narrow
>>>>band noise generated before the channel filter..
>>>>
>>>>Mark
>>>
>>>Certainly the relative bandwidth of the noise matters.   The OP didn't
>>>specify the architecture, so we can only speculate or generalize.
>>>
>>>That's why I tried to clarify that diversity really only works if the
>>>impairments in the diversity sources are decorrelated.  As long as
>>>that's true there'll be gain due to diversity.   That applies to noise
>>>as well, so you're right, if the noise is correlated there won't be an
>>>opportunity for gain via diversity combining.
>>>Eric Jacobsen
>>>Minister of Algorithms
>>>Abineau Communications
>>>http://www.ericjacobsen.org
>>>
>>
>>The last sentence confused me. Let's consider double spatial diversity.
>>Assume the additive noise at both signal branches are fully correlated.
I
>>can still achieve a diversity gain by any combining schemes if both
branch
>>signals are not fully correlated, cannot I?
>
>Well, I can clarify what I meant:   If noise is the only impairment,
>then diversity combining of two signals will provide gain as long as
>the noise is not correlated between the diversity sources.    With two
>separate input streams I think it would be pretty tough get the noise
>correlated, but with one input stream and the "diversity" obtained by
>taking additional samples, the noise could become correlated if a lot
>of filtering had been applied.
>
>So, in your example, as I understand it, if there are additional
>fading impairments that are uncorrelated across the two channels, then
>even if the noise *were* correlated (which would be a pretty cool
>trick), then there could still be substantial gain due to overcoming
>the uncorrelated fading.
>
>Eric Jacobsen
>Minister of Algorithms
>Abineau Communications
>http://www.ericjacobsen.org
>

What even more confuses me is why you are talking about noise correlation 
all the time in conjunction with diversity gain. If the RX does not get
uncorrelated replica of transmitted signals you can combine as you like
and get no diversity gain, and this has nothing to do with the correlation
of the additive noise. In the case of "oversampling", I would even not call
it a "diversity combining" since there is no diversity conceptually. I
would rather call it denoising by averaging if I have to give it a name.

LBB






_____________________________________
Do you know a company who employs DSP engineers?  
Is it already listed at http://dsprelated.com/employers.php ?

On Mon, 14 May 2007 14:38:05 -0500, "lanbaba" <lanbaba@gmx.ch> wrote:

>>On 12 May :13:, Mark <makolber@yahoo.com> wrote:
>>
>>>On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>>>> On 11 May :01:, Mark <makol...@yahoo.com> wrote:
>>>>
>>>> >> Noise is different, since the noise instances in the samples will
>not
>>>> >> be correlated if the noise is white.
>>>>
>>>> >> So, really, it depends on the channel model.   Noise?   Sure,
>>>> >> oversampling improves "diversity".   Fading?   Not gonna help at
>all.
>>>>
>>>> >If the signal has passed through a bandpass filter near the Nyquist
>>>> >BW, which is the usual case in a receiver, will not the noise during
>>>> >samples taken of any particular symbol, be highly correlated thus
>>>> >reducing any gain of oversampling?
>>>>
>>>> >Mark
>>>>
>>>> Remember that this case is just the usual SNR improvement due to the
>>>> processing gain from oversampling and filtering.   Nothing magic
>going
>>>> on there, it's just that the 'diversity' point of view is another way
>>>> to look at it.
>>>>
>>>>
>>>This usual SNR improvement processing gain applies only to wideband
>>>noise generated after the channel filter and does not apply to narrow
>>>band noise generated before the channel filter..
>>>
>>>Mark
>>
>>Certainly the relative bandwidth of the noise matters.   The OP didn't
>>specify the architecture, so we can only speculate or generalize.
>>
>>That's why I tried to clarify that diversity really only works if the
>>impairments in the diversity sources are decorrelated.  As long as
>>that's true there'll be gain due to diversity.   That applies to noise
>>as well, so you're right, if the noise is correlated there won't be an
>>opportunity for gain via diversity combining.
>>Eric Jacobsen
>>Minister of Algorithms
>>Abineau Communications
>>http://www.ericjacobsen.org
>>
>
>The last sentence confused me. Let's consider double spatial diversity.
>Assume the additive noise at both signal branches are fully correlated. I
>can still achieve a diversity gain by any combining schemes if both branch
>signals are not fully correlated, cannot I?

Well, I can clarify what I meant:   If noise is the only impairment,
then diversity combining of two signals will provide gain as long as
the noise is not correlated between the diversity sources.    With two
separate input streams I think it would be pretty tough get the noise
correlated, but with one input stream and the "diversity" obtained by
taking additional samples, the noise could become correlated if a lot
of filtering had been applied.

So, in your example, as I understand it, if there are additional
fading impairments that are uncorrelated across the two channels, then
even if the noise *were* correlated (which would be a pretty cool
trick), then there could still be substantial gain due to overcoming
the uncorrelated fading.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

>On 12 May :13:, Mark <makolber@yahoo.com> wrote:
>
>>On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>>> On 11 May :01:, Mark <makol...@yahoo.com> wrote:
>>>
>>> >> Noise is different, since the noise instances in the samples will
not
>>> >> be correlated if the noise is white.
>>>
>>> >> So, really, it depends on the channel model.   Noise?   Sure,
>>> >> oversampling improves "diversity".   Fading?   Not gonna help at
all.
>>>
>>> >If the signal has passed through a bandpass filter near the Nyquist
>>> >BW, which is the usual case in a receiver, will not the noise during
>>> >samples taken of any particular symbol, be highly correlated thus
>>> >reducing any gain of oversampling?
>>>
>>> >Mark
>>>
>>> Remember that this case is just the usual SNR improvement due to the
>>> processing gain from oversampling and filtering.   Nothing magic
going
>>> on there, it's just that the 'diversity' point of view is another way
>>> to look at it.
>>>
>>>
>>This usual SNR improvement processing gain applies only to wideband
>>noise generated after the channel filter and does not apply to narrow
>>band noise generated before the channel filter..
>>
>>Mark
>
>Certainly the relative bandwidth of the noise matters.   The OP didn't
>specify the architecture, so we can only speculate or generalize.
>
>That's why I tried to clarify that diversity really only works if the
>impairments in the diversity sources are decorrelated.  As long as
>that's true there'll be gain due to diversity.   That applies to noise
>as well, so you're right, if the noise is correlated there won't be an
>opportunity for gain via diversity combining.
>Eric Jacobsen
>Minister of Algorithms
>Abineau Communications
>http://www.ericjacobsen.org
>

The last sentence confused me. Let's consider double spatial diversity.
Assume the additive noise at both signal branches are fully correlated. I
can still achieve a diversity gain by any combining schemes if both branch
signals are not fully correlated, cannot I?

LBB
 


_____________________________________
Do you know a company who employs DSP engineers?  
Is it already listed at http://dsprelated.com/employers.php ?

On 12 May 2007 18:13:12 -0700, Mark <makolber@yahoo.com> wrote:

>On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>> On 11 May 2007 13:01:57 -0700, Mark <makol...@yahoo.com> wrote:
>>
>> >> Noise is different, since the noise instances in the samples will not
>> >> be correlated if the noise is white.
>>
>> >> So, really, it depends on the channel model.   Noise?   Sure,
>> >> oversampling improves "diversity".   Fading?   Not gonna help at all.
>>
>> >If the signal has passed through a bandpass filter near the Nyquist
>> >BW, which is the usual case in a receiver, will not the noise during
>> >samples taken of any particular symbol, be highly correlated thus
>> >reducing any gain of oversampling?
>>
>> >Mark
>>
>> Remember that this case is just the usual SNR improvement due to the
>> processing gain from oversampling and filtering.   Nothing magic going
>> on there, it's just that the 'diversity' point of view is another way
>> to look at it.
>>
>>
>This usual SNR improvement processing gain applies only to wideband
>noise generated after the channel filter and does not apply to narrow
>band noise generated before the channel filter..
>
>Mark

Certainly the relative bandwidth of the noise matters.   The OP didn't
specify the architecture, so we can only speculate or generalize.

That's why I tried to clarify that diversity really only works if the
impairments in the diversity sources are decorrelated.  As long as
that's true there'll be gain due to diversity.   That applies to noise
as well, so you're right, if the noise is correlated there won't be an
opportunity for gain via diversity combining.
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

On May 11, 7:52 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> On 11 May 2007 13:01:57 -0700, Mark <makol...@yahoo.com> wrote:
>
>
>
>
>
>
>
> >> Noise is different, since the noise instances in the samples will not
> >> be correlated if the noise is white.
>
> >> So, really, it depends on the channel model.   Noise?   Sure,
> >> oversampling improves "diversity".   Fading?   Not gonna help at all.
>
> >If the signal has passed through a bandpass filter near the Nyquist
> >BW, which is the usual case in a receiver, will not the noise during
> >samples taken of any particular symbol, be highly correlated thus
> >reducing any gain of oversampling?
>
> >Mark
>
> Remember that this case is just the usual SNR improvement due to the
> processing gain from oversampling and filtering.   Nothing magic going
> on there, it's just that the 'diversity' point of view is another way
> to look at it.
>
>
This usual SNR improvement processing gain applies only to wideband
noise generated after the channel filter and does not apply to narrow
band noise generated before the channel filter..

Mark


Mark

On May 11, 4:44 pm, julius <juli...@gmail.com> wrote:
> On May 11, 3:01 pm, Mark <makol...@yahoo.com> wrote:
>
> > > Noise is different, since the noise instances in the samples will not
> > > be correlated if the noise is white.
>
> > > So, really, it depends on the channel model.   Noise?   Sure,
> > > oversampling improves "diversity".   Fading?   Not gonna help at all.
>
> > If the signal has passed through a bandpass filter near the Nyquist
> > BW, which is the usual case in a receiver, will not the noise during
> > samples taken of any particular symbol, be highly correlated thus
> > reducing any gain of oversampling?
>
> > Mark
>
> For your noise model, that is correct, assuming idealized filters etc.
> But often the noise is generated by the amplifiers, and within the
> ADC itself.  What about in that case?
>
> Julius

OK, oversampleing can be used to reduce the effect of quantizing noise
in the A/D and other components after the channel filter but not to
reduce the noise generated in the front end.  In any well designed
receiver, the front end noise dominates.    Based on the context of
the OPs question I think the architecture we are talking about is A/D
conversion after the (analog) chanel filter (where the noise during
any one symbol period will correlate) ....perhaps this is an incorrect
assumption on my part.
Mark

Mark

>As oversampling produces several baud rate signal sequences (for example,
>oversampling by a factor of 2 produces two baud rate sequences with an
>offset of half baud duration), could these sequences be viewed as a kind
>of diversity? and what's its gain?
>
>
>
>
>_____________________________________
>Do you know a company who employs DSP engineers?  
>Is it already listed at http://dsprelated.com/employers.php ?
>

Do some matlab simulations with and without oversampling. There is no
diversity gain unless you see the BER-SNR curve gets steeper with
oversampling. 

I guess there is no diversity gain since there is no diversity signal
path, and you could probably only see a shift of the BER-SNR curve with
oversampling. This is merely a power gain, which is equivalent to doubling
the transmitter power instead of oversampling by two.

LBB


_____________________________________
Do you know a company who employs DSP engineers?  
Is it already listed at http://dsprelated.com/employers.php ?