Cryptography Reference
In-Depth Information
leads to the
Parallel Interference Cancellation
(PIC) method. The Gauss-Siedel
method leads to the
Successive Interference Cancellation
(SIC) method. Fig-
ure 11.23 gives the diagram for implementing the
SIC
(with
K
=4
users and
M
=3
iterations) where
ICU
m,k
is the
interference cancellation unit
(or ICU)
for the
k
-th user at iteration
m
(see Figure 11.24). The binary elements are
initialized to zero: at iteration
m
=0
b
0
,k
=0
for
k
=1
,
···
,K
.
Figure 11.23 - Iterative SIC (
Successive Interference Cancellation
) detector, with
K
=
4
users and
M
=3
iterations.
Figure 11.24 - Interference cancellation unit
ICU
m,k
for user
k
, at iteration
m
.
Function
FA
k
(respectively
FA
−
k
) is the despreading (respectively spread-
ing) of the
k
-th user. Function
φ
(
.
)
can be chosen as a non-linear function or
quite simply as being equal to the identity function (see also the choice of
φ
(
.
)
in the case of turbo CDMA). If we choose the identity function, the ICU unit of
Figure 11.24 can of course be simplified and is easy to define. In this case, we
can verify that, for user
k
and at iteration
m
, the output of the receiver can be
written as the result of linear filtering:
k
−
1
m
−
1
I
s
j
s
j
b
m,k
=
s
k
Φ
p
K
r
=
g
m,k
r
−
(11.68)
j
=1
p
=0
