Digital Signal Processing Reference
In-Depth Information
2
ψ
δχ βρρκ
λ ξ
=
()
+
( )
d
D
Var
δ
1
,
ICIkn
,,
is
k
L
(10.4 0)
2
ψ
δςβρρκ
λ ξ
=
()
+
( )
d
Var
δδ
D
1
,
ISIkn
,,
is
L
where δ
is
= (
P
- 1)/
P
is a measure of the relative impact of the interference generated by
the other paths on a given path of the desired user (for a Rayleigh fading channel with
P
equal paths). The SINR on the
k
t h
carrier can be estimated as
2
ψ
D
SINR
=
.
(10.41)
ISRk
,
+
+
+
d
d
d
2
Var
δ
Var
δ
Var
δ
κσ
MAI
,,
kn
ICI
,,
kn
ISI
,,
kn
N
Note that the SINR expression above applies to MRC as well by setting κ = 1 and ρ
λ
=
ρ
ξ
= 0 in equations (10.35) and (10.40). Note also that in [46], we provide the variance of
the interference for an MC-CDMA system with a rectangular pulse. In this chapter, we
improve the analytical performance evaluation by deriving the variance of the interfer-
ence with a more practical band-limited square-root raised cosine waveform. The BER
performance on the
k
t h
carrier is then given as follows:
=
( )
P
e
k
Ω SINR
,
(10.4 2)
ISRk
,
where Ω represents the single-user bound (SUB), which is classically defined as a con-
ditional Gaussian Q-function over ψ
D
and ψ
I
. When using this classical representation,
the average BER is derived by first finding the probability density functions (pdfs) of ψ
D
and ψ
I
and then averaging over those pdfs. Since it is difficult to find a simple expression
for the pdfs of ψ
D
and ψ
I
that takes into consideration antenna diversity, imperfect power
control, and imperfect channel identification, we may consider an approximative pdf.
In this analysis, we choose to simulate Ω without imposing any pdf approximation. For
each multicarrier configuration, we run single-user and single-carrier link-level simula-
tions. We reproduced as much as possible most of the real-world operating conditions:
time and frequency synchronization, imperfect power control, channel identification
errors, antenna diversity, etc. These link-level simulations gave a realistic Ω :
BER
=
Ω(
SNR
). The simulations will later consider a multiuser and multicarrier environment.
The average BER performance of the MC-ISR receiver is given by
K
1
21
∑
k
P
=
P
.
(10.43)
e
e
K
+
=−
kK
10.3.3.2 System-Level Performance
In order to compare the different MC-ISR configurations, the link-level curves pro-
vide a good picture of the performance of each system. But limiting comparisons to the
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