24-04-2012, 11:17 AM
Utility-Based Rate-Controlled Parallel Wireless Transmission of Multimedia Streams with Multiple Importance Levels
Utility-Based Rate-Controlled Parallel Wireless Transmission of Multimedia Streams with Multiple .pdf (Size: 2.2 MB / Downloads: 33)
INTRODUCTION
AS the major wireless communication services shift from
voice to multimedia, it has become one of the hot
issues to design and develop advanced networks with
efficient transmission methods that support the quality of
service (QoS) demanded by multimedia connections. Much
recent research on existing and future wireless networks
has focused on how to achieve high utilization of radio
resources without introducing excessive computation complexity.
To transport multimedia traffic over wireless links
with limited power and bandwidth in a cost-effective
manner, various error-resilience coding methods have been
proposed [1], [2], [3], [4], [5]. In general, these schemes take
advantage of the fact that the data bits in a compressed
video stream have different levels of importance and,
hence, different error tolerance. Some bits carry vital
information such as picture types and quantization values.
MODEL DESCRIPTION
Model Description
In practice, the data of a multimedia stream may have
multiple levels of importance. However, for the sake of
simplicity, we first present a simple example with two
levels of data importance and then consider the generalized
problem. Fig. 2 illustrates four transmission scenarios
between a sender and receiver communicating over a
wireless channel, and compare these scenarios with respect
to the BER, transmission rate, and utility. Suppose that the
sender has a two-bit packet to transmit to the receiver,
where one bit has a higher importance than the other bit.
Different coding and modulation schemes can be applied
over the wireless channel according to the respective BER
targets.
Mapping Data Layers to Channel Sets with
Different Reliability Levels
In a multicarrier transmission system, a source node can use
multiple carriers to transmit its data to the other node.
Multicarrier code-division multiple access (MC-CDMA) and
OFDMA are examples for multicarrier transmissions. In this
paper, we consider a scheduling method under UEP. In other
words, we consider how to schedule the channel resources to
support UEP. A simple example to realize this kind of
scheduling in multicarrier systems is to make the multiple
subcarriers have different reliability levels so that the most
important part is loaded on the most reliable data channel
and so on. Even in a multicarrier system, it is likely that the
source node may be assigned merely a single carrier if there
is no better available option.
CONCLUSIONS
Because not all the bits in a multimedia traffic stream have
the same importance, the vital part of it needs to be sent
through a more reliable link, whereas the supplementary
parts may be sent through links with lower levels of
reliability. Furthermore, it is attractive to separately control
the transmission rates for vital and supplementary layers so
that, if necessary, the sender may not send some of the
supplementary layers at all under some channel conditions.
In this paper, we have presented an efficient rate control
method for multimedia delivery over a wireless channel
supporting multiple links with heterogeneous QoS.