Digital Signal Processing Reference
In-Depth Information
8
7.5
7
6.5
WF
6
5.5
No-WF
5
4.5
4
3.5
3
4
5
6
7
8
9
10
M
R
(a)
8
7.5
7
WF
6.5
6
5.5
5
No-WF
4.5
4
3.5
3
4
5
6
7
8
9
10
M
T
(b)
FIgure 4.5
WF and no-WF capacities of a MIMO system with
M
R
>
M
T
= 4 (left) and
M
T
>
M
R
= 4 (right), Rayleigh flat fading, SNR = 3 dB,
P
out
= 0.01.
of ST schemes have been proposed for MIMO systems. The key criteria in the design
of ST codes are the coding gain and the diversity gain. The first one aims at achieving
high rate by capitalizing on the MIMO capacity, whereas the latter aims at profiting
from the space diversity to reduce fading at the Rx. The two extreme schemes corre-
sponding to these criteria are respectively spatial multiplexing and transmit diversity.
For instance, orthogonal space-time block codes (OSTBCs) [50, 51] aim at diversity gain
and some coding rate; space-time trellis codes (STTCs) [52] and linear constellation
precoding (LCP) [53] aim at both coding and diversity gain; spatial multiplexing or the
V-BLAST architecture maximizes the coding rate [28]; and the more general family of
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