# power delay profile

Started by December 5, 2005
```Dear All,
I'm given a power delay profile figure, I have to calculate the
corresponding impulse response
values.
How can I do this? Please tell me the steps as I'm doing this problem for
days now..
Thank you
Frank

```
```On Mon, 5 Dec 2005 18:47:20 +0100, "Frank Benett" <frank_b@gmail.com>
wrote:

>Dear All,
>I'm given a power delay profile figure, I have to calculate the
>corresponding impulse response
>values.
>How can I do this? Please tell me the steps as I'm doing this problem for
>days now..
>Thank you
>Frank

Hi Frank,
describe your problem a little more clearly.
I'm not sure what you mean by "power delay profile".
(It sounds like something related to gasoline engines.)

I'm gonna guess that a "power delay profile" is some
sort of graph.  If that's true, what are the dimensions
along the horizontal and vertical axes?

guys here have in providing some useful guidance for you.

[-Rick-]

```
```"Rick Lyons" <R.Lyons@_BOGUS_ieee.org> wrote in message
news:4394c203.339547062@news.sf.sbcglobal.net...
> On Mon, 5 Dec 2005 18:47:20 +0100, "Frank Benett" <frank_b@gmail.com>
> wrote:
>
>>Dear All,
>>I'm given a power delay profile figure, I have to calculate the
>>corresponding impulse response
>>values.
>>How can I do this? Please tell me the steps as I'm doing this problem for
>>days now..
>>Thank you
>>Frank
>
> Hi Frank,
>  I'll bet someone here can help you if you can just
> describe your problem a little more clearly.
> I'm not sure what you mean by "power delay profile".
> (It sounds like something related to gasoline engines.)
>
> I'm gonna guess that a "power delay profile" is some
> sort of graph.  If that's true, what are the dimensions
> along the horizontal and vertical axes?
>
> guys here have in providing some useful guidance for you.
>
http://people.deas.harvard.edu/~vahid/VT-2004-00306.R1.pdf

Has descriptions of several things that might be called power delay profiles
, does yours correspond to one of these?

If so, it seems that you will need to provide some side information before
you can try to get a statistical description of impulse responses that might
create a similar power delay profile and also fit with your local radio
environment in some sense.

Best of Luck - Mike

```
```Thanks for your answer In power deleay profile I mean the plot of the tap
delay (us) on the x axis,
and the corresponding amplitude (dB) on the y axis..
All of the channel models (rural,hilly..etc) are given in this form, and I
need to calculate the impulse response value (h).
thank you,
regard,
Frank

"Mike Yarwood" <mpyarwood@btopenworld.com> az al&#2013265921;bbiakat
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dn2jat\$rr2\$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com...
>
> "Rick Lyons" <R.Lyons@_BOGUS_ieee.org> wrote in message
> news:4394c203.339547062@news.sf.sbcglobal.net...
>> On Mon, 5 Dec 2005 18:47:20 +0100, "Frank Benett" <frank_b@gmail.com>
>> wrote:
>>
>>>Dear All,
>>>I'm given a power delay profile figure, I have to calculate the
>>>corresponding impulse response
>>>values.
>>>How can I do this? Please tell me the steps as I'm doing this problem for
>>>days now..
>>>Thank you
>>>Frank
>>
>> Hi Frank,
>>  I'll bet someone here can help you if you can just
>> describe your problem a little more clearly.
>> I'm not sure what you mean by "power delay profile".
>> (It sounds like something related to gasoline engines.)
>>
>> I'm gonna guess that a "power delay profile" is some
>> sort of graph.  If that's true, what are the dimensions
>> along the horizontal and vertical axes?
>>
>> guys here have in providing some useful guidance for you.
>>
> http://people.deas.harvard.edu/~vahid/VT-2004-00306.R1.pdf
>
> Has descriptions of several things that might be called power delay
> profiles , does yours correspond to one of these?
>
> If so, it seems that you will need to provide some side information before
> you can try to get a statistical description of impulse responses that
> might create a similar power delay profile and also fit with your local
> radio environment in some sense.
>
> Best of Luck - Mike
>
>
>

```
```in article dn3092\$mcm\$1@namru.matavnet.hu, Frank Benett at frank_b@gmail.com
wrote on 12/05/2005 22:24:

> Thanks for your answer In power deleay profile I mean the plot of the tap
> delay (us) on the x axis,
> and the corresponding amplitude (dB) on the y axis..

this is the magnitude of the tap coefficient expressed in dB?  why would
anyone do that?  to show exponential trend as linear?

> All of the channel models (rural,hilly..etc) are given in this form, and I
> need to calculate the impulse response value (h).

so, after throwing away the sign information of h[n], you want to recover
h[n] including the signs of the negative taps?  can we assume that the first
h[n] is > 0?  if so, we might be able to infer zero crossings and toggle the
sign every zero crossing.

--

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

```
```"robert bristow-johnson" <rbj@audioimagination.com> wrote in message
news:BFBA750F.CA9D%rbj@audioimagination.com...
> in article dn3092\$mcm\$1@namru.matavnet.hu, Frank Benett at
> frank_b@gmail.com
> wrote on 12/05/2005 22:24:
>
>> Thanks for your answer In power deleay profile I mean the plot of the tap
>> delay (us) on the x axis,
>> and the corresponding amplitude (dB) on the y axis..
>
> this is the magnitude of the tap coefficient expressed in dB?  why would
> anyone do that?  to show exponential trend as linear?
>
>> All of the channel models (rural,hilly..etc) are given in this form, and
>> I
>> need to calculate the impulse response value (h).
>
> so, after throwing away the sign information of h[n], you want to recover
> h[n] including the signs of the negative taps?  can we assume that the
> first
> h[n] is > 0?  if so, we might be able to infer zero crossings and toggle
> the
> sign every zero crossing.
>
Hi Frank - have you looked through the models and tutorials at
http://itpp.sourceforge.net/3.8.0/index.html   ?

Best of Luck - Mike

```
```"Mike Yarwood" <mpyarwood@btopenworld.com> wrote in message
news:dn4dbv\$64o\$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com...
>
>>
> Hi Frank - have you looked through the models and tutorials at
> http://itpp.sourceforge.net/3.8.0/index.html   ?
>

Mike,

How should we interpret the claim that IT++ is "wildly used"?

Fred

```
```Frank Benett wrote:
> Thanks for your answer In power deleay profile I mean the plot of the tap
>  delay (us) on the x axis,
>  and the corresponding amplitude (dB) on the y axis..
>  All of the channel models (rural,hilly..etc) are given in this form, and I
>  need to calculate the impulse response value (h).
>  thank you,
>  regard,
>  Frank
>
>

If the tap values you are  talking about are in the DFE equalizer, then
I think (I'm not sure) the tap values are simply equal to the channel
impulse response  (in dB of course)

In other words, if the DFE  tap at 5 us is activated at -10 dB, then
the channel has an echo delayed by 5 us that is -10 dB and this (along
with the main path) is the impulse response.

(It's a little more compoicated for an FFE)

No???

Mark

```
```this is the magnitude of the tap coefficient expressed in dB?  why
would
anyone do that?  to show exponential trend as linear?

for the same reasons we typically use dB for SNR etc....

to show a wide dynamic range on a single graph and because the value
relative to the main tap is important..i.e the relative level of the
reflection is important.....

they are typically shown  as dB relative to the main tap...

M

```
```"Fred Marshall" <fmarshallx@remove_the_x.acm.org> wrote in message
news:FMednWw5yuHuRgjeRVn-sA@centurytel.net...
>
> "Mike Yarwood" <mpyarwood@btopenworld.com> wrote in message
> news:dn4dbv\$64o\$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com...
>>
>>>
>> Hi Frank - have you looked through the models and tutorials at
>> http://itpp.sourceforge.net/3.8.0/index.html   ?
>>
>
> Mike,
>
> How should we interpret the claim that IT++ is "wildly used"?
>
Hah yes! - english ain't their first language so it's a bit of a hoot in
places but interesting for the different ITU and COST models they've
released.

Best of luck - Mike

```