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Ak
51.5
SNR−TEMP
TEMP−SNR
51
50.5
50
49.5
49
48.5
48
8
9
10
11
12
13
14
15
16
SNR
Fig. 3.
Performance of the cross-layer optimization using the Temporal-SNR and the
SNR-Temporal mappings of scalable layers (“Akiyo” sequence)
consider the video encoding QP values in the range of 16 to 50 and RCPC coding
rates of
R
c
=8
/K
:
K
, which are obtained by punctur-
ing a mother code of rate 8
/
32 with constraint length of 3 and a code generator
[23;35;27;33]
o
. Quadrature amplitude modulation (QAM) is used with the pos-
sible constellations size
M
=
∈{
32
,
28
,
24
,
20
,
16
,
12
}
. The total number of subcarriers
N
for
the OFDM system is fixed at 64. This includes a cyclic prefix (CP) of 1
/
8and
guard interval (GI) of 1
/
8 of the total number of subcarriers. The packet size is
chosen as
γ
= 100 bytes. Both the Temporal-SNR and SNR-Temporal priority
mappings are considered.
Average PSNR results obtained for transmission of the “Foreman” sequence
over the MIMO-OFDM system after the optimal selection of the application
layer and physical layer parameters (on a GOP-by-GOP basis) for a channel
SNR of 8dB, 10dB, 12 dB and 18dB are shown in Figure 2. Overall, we can see
that the SNR-Temporal mapping performs better (in the PSNR sense) than the
Temporal-SNR mapping.
Similarly, in Figure 3, we show the average PSNR value comparison of the SNR-
Temporal and Temporal-SNR mappings for the “Akiyo” sequence. The PSNR re-
sults are obtained after the optimal parameter selection for a channel SNR of 8dB,
10db, 12dB and 16dB. However, we can clearly see that the behavior (in the PSNR
sense) for a low motion sequence is opposite compared to the previous case, i.e.,
the Temporal-SNR mapping performs better than the SNR-Temporal mapping.
{
4, 8, 16
}
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