Hi everbody,
I am doing my M.SC thesis on the topic "ICI cancellation in OFDM". I
have very limited time, if you can help me I will be grateful to
you....
I can implement the OFDM structure in AWGN channel, it works very
well..
But when i try to implement the system in a "rayleighchan", I obtain
very bad BER results.
--------------------------
N=3D256 ; % carriers
GI=3DN/4; % Guard =C4=B1nterval=3DCyclic prefix
DataBit =3D randint(N,1,2); % obtain 0 and 1's
DataMod =3D qammod(DataBit,2); % obtain modulated symbols (BPSK)
Ifft=3DIfft (DataMod, N); %Take ifft of the symbols
x_t =3D [Ifft(N- GI + 1 : N);Ifft];
%Here x_t enters the channel
%CHANNEL
pathgains=3D[1,0.63,0.1,0.01];
gain=3D 10*log10(pathgains); % convert to dB
pathdelays=3D[0,0.2,0.4,0.6]*1E-6;
samplingtime=3D0.2E-6;
fdoppler=3D50 ; % 50 Hz
chan=3Drayleighchan(samplingtime,fdoppler,pathdelays,gain);
chan.ResetBeforeFiltering=3D0;
y_t=3Dfilter(chan,x_t);
.=2E...
.=2E..
------------------------------------
I have some questions:
1) Which parameters determine the sampling time of x_t and sampling
time of the channel parameters? (It is a basic question sorry but I am
confused...)
(I think sampling time=3D0.2E-6 and x_t's sampling rate are not
correlated in my code, may be it is the problem)
2) I do not determine any parameters like ; carrier frequency =3D2
MHz , OFDM symbol duration =3D 200us etc...
May I determine them, then how i can I put them in the code...(Again
it is a basic question sorry but I am confused...)
2)If i use only "chan=3Drayleighchan(samplingtime, fdoppler)" then
there is no problem, BER results are good...So am I choosing wrong
pathdelays and samplingtime or am I doing wrong channel
estimation&equalization?
3) How can I get channel impulse response? (Because chan.PathGains
gives the path gains , not channel impulse response complex values)
4)I am taking chan.ResetBeforeFiltering=3D0 but not sure about it, am I
doing this wrong?
Burkay Etiler