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34
Another algorithm that uses the MA approach is presented in [33]. In this paper, the authors
propose a blockwise subcarrier allocation algorithm that is shown in Figure 16.
N
subcarriers
are divided into
M
blocks and each block has
n
adjacent subcarriers. The bandwidth of each
block of subcarriers is smaller than the coherence bandwidth of the channel and hence the
channel is flatfading for each block. Also, the subcarriers in a block are assumed to be highly
correlated to each other. Each user is assigned a certain number of blocks based on his or her
minimum data rate constraint. The authors define the problem as:
P
=
min
P
m
m
=
1
M
∑
with the constraints P
≤
P
o
and r
k
≥
R
k
…(E26)
P
o
is the total power constraint and R
k
is the minimum required rate for user
k
. r
k
is the allocated
rate of user
k
and is given by:
r
k
=
f
km
F
P
m
h
k
2
(
k
)
σ
n
2
⎛
⎝
⎜
⎞
⎠
⎟
m
=
1
M
∑
…(E27)
To solve the problem, the authors first calculate and assign
C
k
(
∀
k
∈
[1,
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 Spring '09
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