MC CDMA & rayleighchan

[ammaralwazzan]

hi,,

i am doing a code for MC CDMA system using rayleighchan
First of all i write a matlab code for OFDM-CDMA system. the following picture shows the structure of the system :

but i have some problem with the result :

CP = 0 , CP = 4 (1/16 from OFDM_Symbol_Size), CP = 8 (1/8 from OFDM_Symbol_Size), CP = 16 (1/4from OFDM_Symbol_Size)

change in size of cyclic prefix:


why i got no change in the BER ? also when i change the size of FFT from 64 to 128 to 256 there is no change !!

any help will be appreciated

 

[ammaralwazzan]

sorry i forget to explain that i used 802.11a as a standard for OFDM part , so the rayleighchan specification is :
bitrate = 20000000; % Bit Rate
ts = 1/bitrate; % ts is the sample time of the input signal, in seconds (bit rate is 10Mbps)
fd = 0.0001 ; % fd is the maximum Doppler shift, in Hertz
H = stdchan(ts, fd, 'itur3GPAx'); % Creat Channel

is this specifications is correct?

with :

delay = [0 110 190 410] * 1e-9;
path gains = [0 -10 -20 -23]; % in dB

thank you to every one

 

[ammaralwazzan]

Any Help ?

 

[moessh]

i need to get channel impulse response for rayleighchan fn? how?