1 research outputs found
CROSS-LAYER DISTORTION CONTROL FOR DELAY SENSITIVE SOURCES
The existence of layers in the traditional network architecture facilitates the network design by modularizing it and thus enabling
isolated design of the different layers. However, due to the inherent coupling and interactions between these layers, their
isolated design often leads to suboptimal performance. On the other
hand, the recent popularity of realtime multimedia applications has
pushed the boundaries of layered designs. Cross-layer network design
provides opportunities for significant performance improvement by
selectively exploiting the interactions between layers, and
therefore has attracted a lot of attention in recent years.
Realtime multimedia applications are characterized by their
delay-sensitivity and distortion-tolerance. The focus of this thesis
is on Source Coding for Delay-Sensitive Distortion-Tolerant data. In
particular, we notice that even though using longer descriptions for
source symbols results in smaller distortion for each particular
symbol, it also increases the delay experienced in the network,
which in turn causes information loss for a delay-sensitive source,
and therefore, increases the overall distortion of the received
message. In this thesis we investigate this trade-off across the
layers by considering two different problems.
In the first problem, we focus on a single source-destination pair
to exploit the interconnection between Source Coding, traditionally
a presentation layer component, and Parallel Routing, a network
layer issue. We use a Distortion Measure that combines signal
reconstruction fidelity with network delay. We minimize this measure
by jointly choosing the Encoder Parameters and the Routing
Parameters. We look at both single-description and
multiple-description codings and perform numerical optimizations
that provide insight into design tradeoffs which can be exploited in
more complex settings.
We then investigate the problem of finding minimum-distortion
policies for streaming delay-sensitive distortion-tolerant data. We
use a cross-layer design which exploits the coupling between the
presentation layer and the transport and link layers. We find an
optimum transmission policy for error-free channels, which is
independent of the particular form of the distortion function when
it is convex and decreasing. For a packet-erasure channel, we find
computationally efficient heuristic policies which have near optimal
performance