An Enhanced EDD QoS Scheduler for IEEE 802.11e WLAN - Advances in Computational Science and Engineering - page 55

4.1 Simulation Scenarios
IEEE 802.11e scenario was constructed using a star type topology to analyze
the performance of the proposed algorithm. QAP and QSTA were used as the
components of the network and each QSTA have an up-link trac stream to
transmit data to QAP. We compared performance during 1000s by increasing
the number of QSTAs from 1 to 12. Physical layer used in this simulation is IEEE
802.11b. For MAC level, IEEE 802.11e HCCA module which was developed by
Pisa University in Italy [13] was used. Parameters used in the simulation are
summarized in Table 1.

Table 1. Simulation Parameters

Parameters Value
Slot Time 20s
SIFS 10s
PIFS 30s
Preamble Length 144 bits
PLCP Header Length 48 bits
PLCP TX Rate 1 Mbps
MAC Header Length 60 Bytes
Basic Tx Rate

1 Mbps

Data Rate 11 Mbps

The two simulation scenario were used. Scenario 1 used VoIP for CBR trac
and measured throughput and mean delay. Scenario 2 used MPEG4 video(Jurassic
Park) for VBR trac [14] and measured the burst trac characteristics in VBR
such as throughput rate, mean delay, jitter and packet loss ratio. Characteristic of
the tra c used in the simulation are shown in Table 2.

Table 2. Parameters of TSPEC

TSPEC CBR trac VBR trac

Mean Data Rate 83Kbps 128Kbps

Peak Data Rate 83Kbps 1.7Mbps

Nominal MSDU SIze 208Bytes 1,300Bytes

Maximum MSDU Size 208Bytes 5,211Bytes

Maximum Burst Size 576Bytes 5,211Bytes

Minimum PHY Rate 11Mbps 11Mbps

Maximum Service Interval 30ms 40ms

Delay Bound 60ms 80ms

4.2 Analysis of the Simulation Results
Figure 6 shows throughput in scenario 1. For CBR trac, the reference scheduler,
SETT-EDD and our scheduler peform very well. There is no dropped packets
for all three schedulers.