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From: commengr on 9 Dec 2009 11:02
Hello,

I am simulating the performance of an OFDM based communication system,
where I convolve OFDM symbols with the Channel Impulse Response (7-Tap
Rayleigh distributed)

The problem is that Matlab function conv( ) takes a lot of processing
time. I tried to declare the output variable as a vector of zeros. This did
help, but only slightly.

Under Monte Carlo's method, it gets really annoying. Another alternate is
the filter( ) command, where I can assume the channel is an FIR filter,
however, this approach makes the use of cyclic prefix redundant (changing
CP does not have any affect on BER)

Any suggestions?


---
Oh, by the way, since the data is not cyclic, I can't do Fast Convolution
via DFT


On an unrelated matter, after modeling the channel as an FIR filter and
checking its frequency response using the freqz( ) function, the phase
apparently shows as 'non-linear', so many books say that phase of an FIR
filter is always linear like Ifeachor's book etc


From: Rune Allnor on 9 Dec 2009 11:25
On 9 Des, 17:02, "commengr" <communications_engin...(a)yahoo.com> wrote:
> Hello,
>
> I am simulating the performance of an OFDM based communication system,
> where I convolve OFDM symbols with the Channel Impulse Response (7-Tap
> Rayleigh distributed)
>
> The problem is that Matlab function conv( ) takes a lot of processing
> time.

> Oh, by the way, since the data is not cyclic, I can't do Fast Convolution
> via DFT

IDIOT!!

You, for listening to the delusions of almost all the
regulars here; Almost all the regulars for messing around
with the cyclic proerties of the DFT causing this
kind of confusion among the incopmpetent and mentally
challenged!

Of course you can use the DFT. Just zero-pad the data
sufficiently to avoid the wrap-around effects. This is
so basic that it is covered in *all* textbooks on DSP.

Rune
From: Greg Berchin on 9 Dec 2009 11:44
On Wed, 09 Dec 2009 10:02:20 -0600, "commengr"
<communications_engineer(a)yahoo.com> wrote:

>On an unrelated matter, after modeling the channel as an FIR filter and
>checking its frequency response using the freqz( ) function, the phase
>apparently shows as 'non-linear', so many books say that phase of an FIR
>filter is always linear like Ifeachor's book etc

The phase of a FIR filter CAN BE linear, but does not have to be.

This is really fundamental stuff. If your text is teaching that all FIR filters
exhibit linear phase, then it is a very bad book.

Greg
From: commengr on 9 Dec 2009 11:54
>On 9 Des, 17:02, "commengr" <communications_engin...(a)yahoo.com> wrote:
>> Hello,
>>
>> I am simulating the performance of an OFDM based communication system,
>> where I convolve OFDM symbols with the Channel Impulse Response (7-Tap
>> Rayleigh distributed)
>>
>> The problem is that Matlab function conv( ) takes a lot of processing
>> time.
>
>> Oh, by the way, since the data is not cyclic, I can't do Fast
Convolution
>> via DFT
>
>IDIOT!!
>
>You, for listening to the delusions of almost all the
>regulars here; Almost all the regulars for messing around
>with the cyclic proerties of the DFT causing this
>kind of confusion among the incopmpetent and mentally
>challenged!
>
>Of course you can use the DFT. Just zero-pad the data
>sufficiently to avoid the wrap-around effects. This is
>so basic that it is covered in *all* textbooks on DSP.
>
>Rune
>

===========================================================

RUNE, THERE ARE BETTER WAYS TO START AN ANSWER!

I think your answer is offensive!

If you thought it was a poor question you should have not
answer it!
===========================================================

I do not want to increase the number of bits to what I already have due to

monte carlo.



From: commengr on 9 Dec 2009 11:58
>On Wed, 09 Dec 2009 10:02:20 -0600, "commengr"
><communications_engineer(a)yahoo.com> wrote:
>
>>On an unrelated matter, after modeling the channel as an FIR filter and
>>checking its frequency response using the freqz( ) function, the phase
>>apparently shows as 'non-linear', so many books say that phase of an
FIR
>>filter is always linear like Ifeachor's book etc
>
>The phase of a FIR filter CAN BE linear, but does not have to be.
>
>This is really fundamental stuff. If your text is teaching that all FIR
filters
>exhibit linear phase, then it is a very bad book.
>
>Greg
>

Thanks Greg. Any idea on a faster method for convolution?



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