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infrastructure. We utilise a coded representation of
media objects (Mpeg4 standard overview, 2002)
where each object is part of a complex audiovisual
scene and can be perceived and processed sepa-
rately. However, their combination of the objects
in a strict order will result in the initial video. Most
video distribution techniques aim at delivering
MPEG streams with defined recommendation for
protocol stack exploited within communication
procedure. The QoS-supported network transmis-
sion technologies provide mechanisms for MPEG
video distribution over its infrastructure inherently
dictated by dynamic nature of video traffic. In
WiMAX networks service categories rtPS, ertPS
and nrtPS are used for video-application data de-
livery depending on QoS needs for a certain video
flow. Each elementary stream (ES) belonging to
MPEG audiovisual flow can be characterised by
stringent QoS requirements which are generally
referred to one out of five service categories
exploited in WiMAX.
Therefore, MPEG video could be transmitted
through a defined MAC service connection of
WiMAX system or, alternatively, many service
connections of different service classes can be
assigned to incoming MAC SDUs of elementary
streams segmented from the basic MPEG audio-
visual scene.
The structural framework of traffic distribu-
tion in a WiMAX simple topology is illustrated
in Figure 2. As shown, the BS is fully responsible
for UL and DL traffic scheduling and virtual UL
scheduling is integrated into BS MAC architecture.
The diagram schematically demonstrates data and
signalling flows for UL communication between
SS and BS. UL traffic from upper layer of MAC
SDU units will be classified on the basis of QoS
demands inherently allocated between already
existed service connections or put in buffer for
further connection established in line with grant/
rejection generated by BS. Successfully approved
packets go to mapping for new connections and
will be stored in queues correlated to specific QoS
categories. Each service connection with stored in
queue packets has a Unique Connection Identifier
(CID) and Service Flow Identifier (SFID) mapping
to deliver packets with certain QoS guarantees to
destination address. Scheduling algorithm plays a
major role in assigning burst profiles to awaited
packets and will be re-allocating the available
resources following the distribution function and
mechanism presented in its design. We extended
the functionality of the conventional classify/ana-
lyzer module integrated in WiMAX MAC layer
to a number of specific tasks required to support
the proposed algorithm. The upper SDU units will
be analyzed with the purpose of determining IP
packets belonging to segmented ESs or generic
packets with MPEG payload. Furthermore, those
from ESs are to be classified on the basis of QoS
needs and then sent to mapping block to correlate
packets with QoS categories offered by WiMAX.
Classified ES packets will be finally marked as
application-based traffic in the category with
similar QoS application needs. After that, the
mapping module distributes traffic between unique
service connections for supported QoS queues.
The significant value of the integrated
Extended
Classificator
is to simultaneously treat packets
from both conventional MPEG-structured and
segmented ES video streams to provide freedom
for end-users for optional use of either one or
another, or both, video transmission schemes.
This separation could face premium/lower quality
difference and be beneficially applied by service
operators in commercial implementation. How-
ever, we assume that ES segmentation process is
to be performed at upper layers that is IP packets
incoming to WiMAX system elements contain
signalling information about its segmented param-
eters and initial audiovisual source. Synchronisa-
tion data should be integrated into the single ES
with premium QoS to provide sufficient resources
for delivery.
A number of scheduling strategies fall into vast
multitude of the existing, specifically elaborated,
witnessed effective algorithms widely reviewed
and reported in research literature (Rashwan, Hes-
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