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ham & Badawy, 2009; Belghit & Nuaymi, 2008).
To opt for a defined design the factors of fairness
and resources wastage are always prioritised.
Traditionally, scheduling techniques were initiated
from wired mechanisms and include Weighted
Round Robin (WRR), Deficit Round Robin
(DRR), First Input First Output (FIFO) and its
modifications like modified Early Deadline First
(EDF) and others (Cocinetti, Lenzini & Mingozzi,
2006). These are also referred to as homogeneous
algorithms with simple implementation and low
processing complexity. A number of scheduling
strategies fall into vast multitude of the existing,
specifically elaborated, witnessed effective algo-
rithms widely reviewed and reported in research
literature (Rashwan, Hesham & Badawy, 2009;
Belghit & Nuyami, 2008). To opt for a defined
design the factors of fairness and resources
wastage are always prioritised. Traditionally,
scheduling techniques were initiated from wired
mechanisms and include Weighted Round Robin
(WRR), Deficit Round Robin (DRR), First Input
First Output (FIFO) and its modifications like
modified Early Deadline First (EDF) and others
(Cocinetti, Lenzini & Mingozzi, 2006). These
are also referred to as homogeneous algorithms
with simple implementation and low processing
complexity.
However, these algorithms underperform when
compared with newly-developed architectures
aiming at supporting specific application-based or
broadcasting /multicasting delivery over WiMAX
networks. More complicated and improved tech-
niques when combined with legacy scheduling
algorithms resulted in hybrid schemes such as EDF
+ Weighted Fair Queuing (WFQ) and WRR+RR
(Nijah, Dhrona & Hassanein, 2009). A common
feature of hybrid scheduling is related to assigning
each scheduling strategy to a certain scheduling
service of service category. This approach can
optimise transmission schemes and resource
allocation between priority-based connections.
However, such hybrid schemes could sometimes
lead to non work-conserving behaviour, e.g. when
the bandwidth is not completely utilised.
Cross-layer optimisation is widely used when
designing WiMAX scheduling to achieve better
utilisation of varying channel state conditions to
allocate available slots on the basis of best channel
indication information and exploiting multiuser
diversity gain (Liu, Jan & Ko, 2006). The cross-
layer approach takes an advantage of upper layer
QoS information and lower PHY layer OFDMA
values to adapt scheduling policies and change
priority indicators in line with timely essential data
about physical conditions of SS channel before
configuring each burst profile. Cross-layer design
often demonstrates better simulation results than
those of traditional scheduling, but still complexity
of the implementation model coupled with com-
plicated inter-layered communication algorithm
obviously respond to non-optimal costly solution.
For our study we have chosen conventional WRR
algorithm for UL scheduling and developed soft-
ware model on the basis of the proposed program
module (Chen, Wang & Tsai, 2006). We tested
our segmented approach for edged scheduling
scenario: the selected WRR refers to the easy -
implemented and simple for modelling WRR. The
strategy is to ensure optimistic results for further
investigations with more specified and elaborated
scheduler design to apply for a relevant real-time
data distribution support.
SIMULATION SCENARIOS AND
EXPERIMENTAL RESULTS
Tests of a New Segmented
Distribution Scheme
In the developed simulation model we imple-
mented the direct functional correlation between
the ES and QoS scheduling categories offered in
WiMAX. We assume that ES with its QoS set can
refer to a certain IEEE 802.16 MAC connection
identified for the related service class UGS, rtPS
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