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From: mahmud_dbm on 21 Feb 2010 09:02
Dear Idin Sir..

I'm repeating my question, I'm using reyleighchan, say for 1000 bits of 100 parallel streams. now i set my channel with chan=rayleighchan and some required parameters, then coeff=chan.PathGain; wud give me the channel status and at the receiver i simply divide received streams by coeff; and i'm getting exact performance.

Now my question is
What kind of Equalization is this, i think it is somewhat more than adaptive equalization, because i'm getting 100 different Coeffs for 100 different streams and i'm simply dividing by the status very easily, now in practice "which kind of Equalization" wud give me this Performance..????

Practically how would i get this status directly like this. ? or is it possible at all.?
Note: My System doesn't have pilot or anything to get CSI from the channel.

Thank You

Mahmud
From: mahmud_dbm on 22 Feb 2010 22:12

> Do you use multipath propagation ? Like let say 11 taps :
> pdb=[0.6286 0.4895 0.3813 0.2969 0.2312 0.1201 0.1403 0.1092 0.085 0.0662 0.0515];
> chan = rayleighchan(4e-6, 200, tau, pdb);
> y = filter(chan,trans);
> coeff=chan.PathGains;
>
> Then your coeff will be a matrix with size : length(trans) per 11 (no of paths/taps).
> How do you compute the CSI now ?
>
> One more question : what happens if there is ofdm transmission -> then you need to perform fft...
>
> Thanks,
> Robert


Thanks Robert..

I was trying to help you with this problem, i'm sorry i couldn't find what will happen if there are multiple number of coeffs.

anyway i think, we need some theoretical funda here, i mean what theoretically happens after traveling through different channels, as far i can remember, "different delay taps are there for different paths" to extract the exact signal from the delayed one... or something like that.

If i find the solution, i will let you know. All the best.
From: Robert Orzechowski on 23 Feb 2010 16:08
"mahmud_dbm " <mahmud_dbm(a)yahoo.com> wrote in message <hlrecs$dob$1(a)fred.mathworks.com>...
> Dear Idin Sir..
>
> I'm repeating my question, I'm using reyleighchan, say for 1000 bits of 100 parallel streams. now i set my channel with chan=rayleighchan and some required parameters, then coeff=chan.PathGain; wud give me the channel status and at the receiver i simply divide received streams by coeff; and i'm getting exact performance.
>
> Now my question is
> What kind of Equalization is this, i think it is somewhat more than adaptive equalization, because i'm getting 100 different Coeffs for 100 different streams and i'm simply dividing by the status very easily, now in practice "which kind of Equalization" wud give me this Performance..????
>
> Practically how would i get this status directly like this. ? or is it possible at all.?
> Note: My System doesn't have pilot or anything to get CSI from the channel.
>
> Thank You
>
> Mahmud

Mahmud,
Dividing singal by the channel coeff is something like ZeroForcing, however, no receiver knows exact channel coefficient, so this is any kind of Equalization - this is just assuming perfect channel information state. Normally channel coeff, or channel are estimated from pilots or something else.
regards,
Robert

Could you write here down any simple MATLAB example ?
From: mahmud_dbm on 5 Mar 2010 04:02
> Mahmud,
> Dividing singal by the channel coeff is something like ZeroForcing, however, no receiver knows exact channel coefficient, so this is any kind of Equalization - this is just assuming perfect channel information state. Normally channel coeff, or channel are estimated from pilots or something else.
> regards,
> Robert
>
> Could you write here down any simple MATLAB example ?

Dear Robert,

I doubt whether i really can get CSI directly like this practically...! till i don't get any exact equalization like this, i cant use this. because target is to practically get CSI and implement It.

anyway about your programming part.

Form OFDM symbol "Frame", then

chan = rayleighchan(Ts, fd);
chan.resetBeforeFiltering=1;

for k=1:nS
chanbit(k,:)=filter(chan,Frame(k,:));
chanCoeff(k,:)=chan.PathGains;
end

nbit=awgn(chanbit,EbN0(i));

% nS is the number of the symbol
% because symbols are individually filtered.

% then at the receiver divide affected streams, will get equalized streams

eqbit=nbit./(repmat(chanCoeff,1,80));
% You Are Done.

Hope it Helps.

Regards

Mahmud
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