Information Technology Reference
In-Depth Information
where
K
is the total number of macroblocks in the frame. The summation in (9)
represents the error propagation through the MBs.
tp
m
b
F
p
=
1
−
(
−
ρ
)
quantifies
the fraction of distortion of the
m
th
reference video frame, which should be consid-
ered in the propagation loss calculation and
F
m
is the size of the frame area
contained in the observed packet.
Packets are then distributed on the basis of the estimated distortion to the re-
spective bit-streams. Packets with higher expected distortion are put on the sub-
channel with higher protection.
4 Experimental Results
This section explains the experimenting environment used to verify the model pre-
sented in the earlier sections and their results.
4.1 Experimental Setup
The performance of the proposed scheme has been tested using a simulated
WLAN environment, implemented with the Network Simulator 2 (NS-2) plat-
form. NS-2 is a widely used open source network simulation tool developed at the
UC Berkley [33]. The specific version used for these experiments has been built
upon version 2.28 with an 802.11e EDCA extension model implemented [34].
A wireless scenario with six nodes is considered. Four different Access Classes
(AC), namely AC_VO, AC_VI, AC_BE, and AC_BK are employed for voice,
video, best-effort and background traffic respectively. The AC_VO has the highest
access priority whereas AC_BK class traffic has the least access priority. The 3D
video streaming from Access Point (AP) to Node 2 is carried over three traffic
flows, one each for the higher priority stream, the lower priority stream and the
depth information. After considering the perceptual importance of each 3D video
stream, they are allocated to the AC_VO, AC_BE, and AC_BK access classes.
Due to the allocation of different access priorities for 3D video streams, they are
subjected to different Average Packet Loss Rates (Av PLRs). The services used by
each node and their access classes are listed in Table 1.
