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From: Matteo Mascarino on 31 May 2010 04:30
"Lance " <whiteninja(a)gmail.com> wrote in message <gr5ug5$5k7$1(a)fred.mathworks.com>...
> Idin Motedayen-Aval <run.signature(a)MATLAB.for.email> wrote in message <gr5s1q$nod$1(a)fred.mathworks.com>...
> > Lance wrote:
> > > I'm trying to simulate a concatenated code communication system with BPSK modulation over a Rayleigh Multipath channel for a digital communications course.
> > >
> > > I'm trying to display the BER errors of the Convolutional Encoder -> BPSK Modulator-> Rayleigh Channel -> BPSK Demodulator -> Viterbi Decoder with a tracback of 34.
> > >
> > > When I use an AWGN channel I get the correct BER, but when I use a Rayleigh Channel I get a BER of about 0.5.
> > >
> > > Im guessing it has to do with the delay in the Error Rate Calculator, which I have set to 34.
> > >
> > > In the Raleigh Channel I have delay vector set to [0 2e-6] and the gain vector set to [0 -30] (which should mean only the the 0s delayed signal goes through, with only a negligible delayed signal correct ?).
> > >
> > > My question is, is it the delay that is the problem with the BER calculation? if so, what should it be set to?
> > >
> > > Thanks
> > > Lance
> >
> > Lance,
> > It's not just the time delay. A Rayleigh fading channel (even a flat
> > fading channel) will introduce a phase rotation, which you must correct
> > before (or during) demodulation/decoding. If you put a constellation
> > plot on the output of your channel you will see your constellation
> > points rotating. Search under my name on the File Exchange; I have a
> > couple of simple models that show a fading channel simulation in
> > Simulink. The cases I've shown are uncoded, but you can easily add
> > coding to those models.
> >
> > HTH,
> > Idin
> >
> > --
> > Idin Motedayen-Aval
> > The MathWorks, Inc.
> > zq=[4 2 5 -15 -1 -3 24 -57 45 -12 19 -12 15 -8 3 -7 8 -69 53 12 -2];
> > char(filter(1,[1,-1],[105 zq])), clear zq
>
> I'm slowly starting to understand this stuff better. I'll have a look at your models, I'm sure they will help me a lot.
> Thanks a lot
>
> Lance


Hi all,
I need more info on phase rotation correction in Rician Fading Channel block in Simulink with two path model.
Is possible to obtain a constant phase delay on the secondary path?

Thank you very much!

Matteo
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