‫بسم هللا الرحمن الرحيم‬
Classification of CDMA
CDMA
Hybrid CDMA
Pure CDMA
DS
Narrow
band
FH
Wide
band
Fast
Frequency
Hopping
TH
Slow
Frequency
Hopping
DS/FH
DS/TH
TDMA/CDMA
FH/TH
DS/FH/TH
MC-CDMA
MT-CDMA
Orthogonal Frequency Division
Multiplexing (OFDM)

OFDM is split the
data stream to be
transmitted into N
parallel streams of
reduced data rate
and to transmit each
of them on separate
sub-carrier. These
are made orthogonal
by making the peak
of each sub-carrier
signal coincide with
the nulls of other
signal, this is saving
the bandwidth.
the spectrum of OFDM signal
Concept of OFDM signal (a) FDM (b) OFDM
Analysis of MC-CDMA in frequency
selective rayleigh fading channel

The MC-CDMA Schemes are mainly categorized into
two groups


the spreading is done in the frequency domain.
the spreading is done in the time domain.
Spreading in frequency
Downlink MC-CDMA Transmitter
M 1 N 1
S (t ) 
 d
m 0
n0
c
m n ,m
e
 n 
t
j 2  

NT
 c
0  t  NT c
Channel Model for downlink MC-CDMA
Through the multipath fading channel, the received
signal is written as:

L 1
r (t ) 
/

l0

 x (l )  
a ( l ) s  t  
 
 c 

^
 
x (l ) 
x (l ) 

s t 
  Re  s  t 
. exp
c 
c 

 
^
L 1
r (t ) 

l 0
L 1
h (t ) 

l0

x (l )   

 j 2  f c  t 
  
c  


x (l )  
x (l ) 

a ( l ) exp   j 2
  t 
 s (t )
  
c 

x (l ) 

a ( l ) exp(  j  )   t 

c 

N 1
h ( t )  g ( t ) exp(  j  ( t )) 

n0
gn e
j n
Receiver Model for downlink MC-CDMA
M 1
r (t ) 
N 1
 
m 0
n0
d m c n ,m g n e
j n
e
 n 
t
j 2 
 NT 
c 

  (t )