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Master Thesis
Implementation and Evaluation of IEEE
802.11e Wireless LAN in GloMoSim
My master thesis is titled Implementation and Evaluation of IEEE 802.11e Wireless LAN in GloMoSim
and it was done under the supervision of Ph.Lic Thomas Nilsson.
He also taught us Mobile and Wireless Networks course. His personal web page can be reached
here. The work on thesis was started in mid of August 2005 and the thesis
was presented on February 10th, 2006. Bilal Rauf was my partner in the thesis
work.
A brief overview of GloMoSim comes next following by links to thesis report and other relevant documents
as well as some general information about thesis.
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GloMoSim
GloMoSim (Global Mobile Information System Simulator) is a scalable simulation
environment for mobile and wireless networks, developed at UCLA Parallel Computing Laboratory.
GloMoSim is a discrete event simulator built using PARSEC, a C based environment designed for parallel simulations,
also developed at UCLA Parallel Computing Laboratory. GloMoSim is built using a layered approach similar to
the OSI seven layers network architecture, with standard APIs between layers. This
makes it easy to implement and integrate new protocols and models at different layers.
A wide range of models and protocols are supported at different layers. GloMoSim is a scalable
simulator and has capabilities to simulate thousands of mobile nodes.
The layered design benefits from the features of modular development,
such that the layers as well as the protocols and models at different layers are
treated as independent modules and can be modified or replaced without affecting other layers.
The modular design allows people to develop and implement new protocols at
different layers such that the design conforms with the standard API used between the
layers. The plug and play feature enables people to work without the concern for the
inner working of the simulator.
GloMoSim is written in C and utilizes PARSEC (Parallel Simulation Environment
for Complex Systems), which is a simulation environment developed for parallel
and sequential execution of discrete event simulations. By discrete event it means that
the execution is mainly based on event handling, i.e., the execution consists of set of
events and as an event occurs, the appropriate action is taken in its response. An event
is defined as an incident which results in the change of state of the system. A certain
event or combination of events may invoke other events and so on, and this is how the
execution proceeds. Some examples are arrival of packet at a particular layer, expiry of
a timer, etc. Events only occur at discrete units of time are not permitted to occur in
between these units of time.
GloMoSim is freely available for educational purposes. However this free version only supports sequential execution of simulations.
GloMoSim can be downloaded
here (note that you must be on .edu domain to download it).
Here are a couple of good tutorials on GloMoSom: A Tutorial on GloMoSim by Thomas Nilsson and
A Comprehensible GloMoSim Tutorial by Jorge Nuevo.
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| Thesis Report |
| Summary of Thesis Report: A short summary of thesis report. |
| Conclusions:
Conclucions of the thesis work. More specifically, important key points extracted from the evaluation phase. |
| Bibliography: List of referecned books and conference and journal papers. |
| An Overview of IEEE WLAN Standards 802.11 and 802.11e Selected chapters from
thesis report, used as course material later on. |
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Title: Implementation and Evaluation of IEEE 802.11e Wireless LAN in GloMoSim
(Preliminary title: Implementation and Evaluation of IEEE 802.11e EDCA in GloMoSim) |
| Researchers: Jahanzeb Farooq (int04jfq), Bilal Rauf
(int04brf) |
| Credits: 20 x 2 (30 x 2 ECTS) |
| Supervisor: Ph.Lic Thomas Nilsson
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| Examiner: Dr. Per Lindström |
Preliminary Timeline:
| Time Period
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Description |
| Requirement Analysis and Background Reading |
| 07/08/05 - 30/08/05 |
Studying and understanding 802.11e, literature review
The first and most crucial task is to study and understand 802.11e, how it
works, specially the functions that provide enhancements to legacy 802.11 by
providing Quality of Service.
A complete and thorough understanding of the
standard is required in order to implement it. As the standard is not approved
and released yet, it is available in form of drafts. The latest version is 13th.
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| 01/09/05 - 30/09/05 |
Learning GloMoSim
To learn GloMoSim. It includes understanding its system
architecture and the APIs that operate on each layer, more specifically the MAC
sub-layer where the new protocol will be implemented. A detailed study of
GloMoSim will facilitate to develop the new protocol more easily and
efficiently.
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| Software Development Life Cycle |
| 01/10/05 - 30/10/05 |
Analysis and Design |
| 01/11/05 - 30/11/05 |
Implementation and Testing
Next step is to analyze, design and implement 802.11e for MAC layer in
GloMoSim.
The main part is to implement the major function of 802.11e i.e.,
the distributed channel access function EDCA.
802.11e introduces a so-called Hybrid
Coordination Function (HCF) containing two medium access mechanisms:
contention-based channel access (EDCA) and controlled channel access
(HCCA).
EDCAF (Enhanced Distributed Channel Access Function) is the enhanced
version of DCF (Distributed Coordination Function) in legacy 802.11, and enables
prioritized channel access to the traffic of different priorities as labeled by
the higher layer. HCCA (HCF Controlled Channel Access) is the enhanced version
of PCF (Point Coordination Function), and provides centralized channel access
with polling. Development will be done using C programming language, the
language GloMoSim is developed in.
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| Evaluation of IEEE 802.11e |
| 01/12/05 - 30/12/05 |
Design and Simulations |
| 01/01/06 - 30/01/06 |
Analysis and Evaluation
After implementation, final step is to perform simulations of 802.11e under
different traffic scenarios and then to analyze and visualize the simulation
data. Based on simulation results, final step is to evaluate performance and
improvements of 802.11e over the legacy 802.11.
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| February 2006 |
Presentation |
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Introduction:
Background:
The IEEE 802.11 Wireless Local Area Network (WLAN) is one of the most widely
deployed wireless network technologies in the world today. With the enhanced versions
802.11b and 802.11a, it supports data transmission rates of up to 11 and 54 Mbps,
respectively.
The basic MAC (Medium Access Control) mechanism of 802.11 is called Distributed
Coordination Function (DCF). DCF is based on distributed channel access and employs
CSMA (Carrier Sense Multiple Access) protocol for the medium access. IEEE 802.11
also defines an optional access mechanism, called Point Coordination Function (PCF),
based on centrally controlled access. Most of the 802.11 installations today use DCF,
whereas the PCF is hardly implemented mainly due to its complex design and inefficient
access mechanism.
Although IEEE 802.11 has become more and more popular due to its low cost and
easy deployment, it does not provide quality of service (QoS) support. QoS refers to the
ability of network to provide some consistent services for data transmission, and measured
in terms of qualitative characteristics, such as throughput, delay, jitter and packet
loss, which describes quality of data traffic over a network. Basically all types of data
traffic are treated equally in both DCF and PCF, regardless of the QoS requirements of
the traffic, which vary from application to application. Specifically, multimedia applications
such as audio/video streaming, teleconferencing, Internet telephony and interactive
games require certain level of QoS guarantees. Lost packets or delays can seriously destroy
the performance of these applications. Some kind of service differentiation must
be employed to let higher priority multimedia traffic get better served. This inability of
802.11 MAC mechanism in providing QoS support is a big hurdle in the adaptation of
modern multimedia applications in 802.11 networks.
Thus, a lot of research works have been carried out to enhance the QoS support in
IEEE 802.11 networks. IEEE 802.11 Working Group is currently focusing on an enhanced
version of IEEE 802.11, known as 802.11e, in order to support Quality of
Service. IEEE 802.11e is in its standardization process and the final draft has been
released. IEEE 802.11e defines two new mechanisms for distributed and centrally controlled
access, which are basically the improved versions of DCF and PCF in the original
standard. The distributed access mechanism of 802.11e is called EDCA (Enhanced
Distributed Channel Access), and supports Quality of Service by introducing service
differentiation. Different types of traffic are assigned with different priorities based on
their QoS requirements, and service differentiation is introduced by using a different set
of medium access parameters for each priority.
Task:
The task was divided into two parts. The first part wa to implement the IEEE 802.11e EDCA in GloMoSim (Global Mobile Information System Simulator), which is a
simulation software for mobile and wireless networks, developed by Parallel Computing
Laboratory at UCLA. GloMoSim is built using a layered approach similar to the OSI
seven layers network architecture, with standard APIs between the layers. A wide range
of protocols are supported at each layer. IEEE 802.11 DCF is currently one of the
several protocols available at the MAC layer.
The second part of the task was to evaluate the performance of IEEE 802.11e EDCA in
comparison to IEEE 802.11 DCF using the implemented 802.11 EDCA. More specifically,
the goal was to study the effectiveness of EDCA’s service differentiation mechanism in
providing QoS support to different types of data traffic and to evaluate its performance
with the help of a wide range of traffic scenarios and performance metrics.
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