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From: Muhammad on 15 Jul 2010 12:10
"nanren888 " <nanren888.remove.this(a)hotmail.com> wrote in message <hho86v$c32$1(a)fred.mathworks.com>...
> "Hosso Hosso" <gamavor_535(a)hotmail.com> wrote in message <hhnb8n$m34$1(a)fred.mathworks.com>...
> > Dear Friends,
> > I am trying to simulate a fading channel using Matlab's rayleighchan() function, my question is how one can assure the generated fading is slow or fast. What i know is that the condition for slow fading is Tc >> Ts otherwise it is fast fading , where Tc is the coherence time and Ts is the symbol duartion.
> > I am using the function rayleighchan(Ts,Fd) so that the above equation is achieved it seems to work with slow fading but what about fast fading??
> > I think the function is always assuming slow fading. Is this right?
> > Thanks,
> > Hoseb
>
> I have not used this function, but maybe I can offer some small insight.
> Not sure what you mean by "slow or fast".
> Commonly, "fast" is used to refer to the Rayleigh, multipath scattering & "slow" is used to refer to the slower, shadowing, often modelled as log-normal.
>
> The quick answer is that if "slow fading" means to you "shadowing", then I doubt that a function named after Rayleigh will cover that, being more commonly considered lognormal.
>
> Your question suggests, though that with "fast & slow" you might be interested in the fade rate.
> The help on this says,
> With the above two syntaxes, a smaller fd (a few hertz to a fraction of a hertz) leads to slower variations, and a larger fd (a couple hundred hertz) to faster variations.
>
> (Not sure that I buy the "syntaxes" word)
> I do have issues with characterisation of the fading with fd, but it should be as they simply say. The fd as a measure of the maximum Doppler should allow control of the fade rate.
> If you have a spatial model in mind, you can picture a uniform Jakes scenario with consequent well defined max abs Doppler & that the fade rate seen will relate to this.
> If you are simply driven from statistical signal processing, then I guess you imagine that the correlation & psd are transform pairs. The fading rate & hence correlation (in the absense of that nasty shadowing) are therefore related to what can be considered the Doppler frequency spectrum.
> If you have simple assumptions on the distribution, eg uniform angle, or such, you can parameterise.
> If that didn't help, perhaps vary fd & look for the effect.
From: Muhammad on 15 Jul 2010 12:15
"nanren888 " <nanren888.remove.this(a)hotmail.com> wrote in message <hho86v$c32$1(a)fred.mathworks.com>...
> "Hosso Hosso" <gamavor_535(a)hotmail.com> wrote in message <hhnb8n$m34$1(a)fred.mathworks.com>...
> > Dear Friends,
> > I am trying to simulate a fading channel using Matlab's rayleighchan() function, my question is how one can assure the generated fading is slow or fast. What i know is that the condition for slow fading is Tc >> Ts otherwise it is fast fading , where Tc is the coherence time and Ts is the symbol duartion.
> > I am using the function rayleighchan(Ts,Fd) so that the above equation is achieved it seems to work with slow fading but what about fast fading??
> > I think the function is always assuming slow fading. Is this right?
> > Thanks,
> > Hoseb
>
> I have not used this function, but maybe I can offer some small insight.
> Not sure what you mean by "slow or fast".
> Commonly, "fast" is used to refer to the Rayleigh, multipath scattering & "slow" is used to refer to the slower, shadowing, often modelled as log-normal.
>
> The quick answer is that if "slow fading" means to you "shadowing", then I doubt that a function named after Rayleigh will cover that, being more commonly considered lognormal.
>
> Your question suggests, though that with "fast & slow" you might be interested in the fade rate.
> The help on this says,
> With the above two syntaxes, a smaller fd (a few hertz to a fraction of a hertz) leads to slower variations, and a larger fd (a couple hundred hertz) to faster variations.
>
> (Not sure that I buy the "syntaxes" word)
> I do have issues with characterisation of the fading with fd, but it should be as they simply say. The fd as a measure of the maximum Doppler should allow control of the fade rate.
> If you have a spatial model in mind, you can picture a uniform Jakes scenario with consequent well defined max abs Doppler & that the fade rate seen will relate to this.
> If you are simply driven from statistical signal processing, then I guess you imagine that the correlation & psd are transform pairs. The fading rate & hence correlation (in the absense of that nasty shadowing) are therefore related to what can be considered the Doppler frequency spectrum.
> If you have simple assumptions on the distribution, eg uniform angle, or such, you can parameterise.
> If that didn't help, perhaps vary fd & look for the effect.
Hi there,
I am doing a project in cognitive radio and i want to simulate spatially correlated log normal shadowoing in collaborative spectrum sensing but i dont know how to do it can any one give me idea i have done simlulation for log normal shadowing but when the cognitive radio are collaborating i dont know where do i have to put the formula for urban and suburban area R(d)= e^-ad as i am using chi squre distrubution method can any one please give me some idea.
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