TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

lost packet at the receiver. Consequently, a particular Access Unit can be restored. Failures in the
decoding process are rather distributed toward the less important objects, and then UEP reduces
the effects of spatial and temporal errors propagation. This observation is shown in Figure 4-21
where the decoded object ratio of configuration A is always better than configuration B.
In this scenario, we setup two networks configurations to demonstrate the effect of the crosslayer
system. For this reason, we mark each packet according to its priority score and we study the
effect of this marking. We transmit the protected MPEG-4 scene over IP Best Effort network
(Configuration C) and over IP Diffserv network (Configuration D). Figure 4-22 shows results of
the comparison between the loss rate for configuration C and D. The X-axis represents the
throughput of the background traffic. At each point of load, a set of four bars in Figure 4-22 shows
the loss rate for O1, O2, O3, and the background traffic. In configuration D (Figure 4-22 (a)), loss
rate approximately follows a uniform distribution. This is due to the IP Best Effort routers which
uses a simple drop policy (i.e. Drop Tail). When the queue is full, all the incoming packets are
dropped with the same probability. In contrast, Diffserv network provides a differentiated level of
QoS for each stream depending to its priority class. It is visible for configuration D(Figure 4-22
(b)), that the losses happen mainly on the lower priority streams (i.e., O1 and some of background
traffics which are marked with high drop precedence).
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Loss rate
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Loss rate
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2,5 3,0 3,5 4,0 4,5
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Background Traffic (Mbps)
Background Traffic (Mbps)
(a) Best Effort
(b) Diffserv-based protection
O3 O2 O1 Others
Figure 4-22: Loss rate vs. background traffic load
Figure 4-23 shows in more details the performance of our cross-layer system. The X-axis
represents the loss ratio related to the MPEG-4 traffic (i.e., the sum of O1, O2, and O3 traffics).
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