Analysis of Quality of Service in Wimax networks

 
 
 
 
CHAPTER 3 
CASE STUDIES AND SIMULATION ENVIRONMENT 
In the first part of the chapter, the simulation setup used for experimentation is 
described. Various approaches that were taken before arriving at the final setup are 
explained. The QoS parameters that are considered to analyze network performance 
and the equations to calculate each of them are presented. It is followed by the 
descriptions of various experiments performed. The results obtained are presented in 
the next chapter, along with comments on each of the results. 
3.1 Analysis Strategy 
To analyze QoS in a network it is necessary to study real life scenarios. The 
simulation set up would reflect the actual deployment of the WiMAX network.
Based on the network reference model described earlier in Chapter 2, Figure 3 shows 
the setup that will be used. There are multiple SS’s in the range of a base station.
The base station is connected to the core network. The focus of analysis will be the 

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connection between the subscriber and the base station. Various types of traffic can 
be set up from the subscriber station to mimic real life scenarios. For example, the 
subscriber can place a VOIP call. 
Figure 3 Simulation Setup 
3.2 Simulation Details 
Different approaches were considered in the beginning of the work.
An attempt was made to write an event driven simulation in C++. However, by that 
time, couple of WiMAX simulators became available in the pubic domain. These 
included the work by Chen et al [23] at Chang Gung University, Taiwan, available 
through their website [24]. The other available simulator was the WiMAX module 
written in a collaborative effort of Application Architecture Task Group (AATG), 
Core Network
Base Station
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2
3
4
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WiMAX Forum and National Institute of Standards and Technology (NIST) [7].
Both simulators were modules available to be used in conjunction with ns-2. 
The network simulator 2 (ns-2) [6] is a popular tool for the simulation of 
packet-switched networks. It provides substantial support for simulation of TCP, 
routing, and MAC protocols over wired and wireless networks. The simulator core is 
written in C++. It has an OTcl (Object Tool Command Language) interpreter shell as 
the user interface and allows input models written as Tcl (Tool Command Language) 
scripts to be executed. Most network elements in ns-2 simulator are developed as 
classes, in object-oriented fashion. It is freely distributed and all the source code is 
available.