ABSTRACT
This study is concerned with the analysis of signal strength and loss pattern of IEEE 802.11
wireless LANs. The efforts of which involved Electromagnetic Compatibility (EMC) assessment
of the various access points (APs) operating in both 2.4GHz and 5GHz Frequencies from the
Ahmadu Bello University Zaria, Wireless Network, at varied locations and times, using
Middleton Class A model and MATLAB/SIMULINK model. The result indicate
Electromagnetic Interference (EMI) based error of 0.612 and 0.743 at the 2.4GHz and 5GHz
Radio Frequency respectively, indicating a better throughput at the side of 2.4GHz Frequency.
TABLE OF CONTENTS
TITTLE PAGE………………………………………………………………………………………………………………… i
DECLARATION…………………………………………………………………………………………………………….. i
CERTIFICATION ………………………………………………………………………………………………………….. ii
DEDICATION………………………………………………………………………………………………………………. iii
ACKNOWLEDGEMENTS…………………………………………………………………………………………….. iv
TABLE OF CONTENT…………………………………………………………………………………………………… v
LIST OF FIGURES ……………………………………………………………………………………………………… viii
LIST OF TABLES…………………………………………………………………………………………………………. ix
LIST OF SYMBOLS AND ABBREVIATIONS ………………………………………………………………… x
ABSTRACT…………………………………………………………………………………………………………………. xii
1.1 INTRODUCTION TO EMC ………………………………………………………………………………………. 1
1.1.1 Concept of Electromagnetic Compatibility……………………………………………………………… 1
1.2 TYPES OF INTERFERENCE…………………………………………………………………………………….. 2
1.2.1 Continuous Interference ……………………………………………………………………………………….. 2
1.2.2 Transient (Pulse) Interference ……………………………………………………………………………….. 3
1.3 ELEMENTS OF AN EMC PROBLEM ……………………………………………………………………….. 4
1.4 WIRELESS NETWORKING STANDARDS……………………………………………………………….. 5
1.5 RESEARCH OBJECTIVE …………………………………………………………………………………………. 7
1.6 PROBLEM STATEMENT……………………………………………………………………………………….. 7
1.7 THESIS OUTLINE……………………………………………………………………………………………………. 8
CHAPTER TWO ……………………………………………………………………………………………………………. 9
LITERATURE REVIEW AND THEORETICAL BACKGROUND…………………………………….. 9
2.1 LITERATURE REVIEW ………………………………………………………………………………………… 9
2.2 RADIO PROPAGATION THEORY …………………………………………………………………………. 13
2.3 NOISE FLOW ………………………………………………………………………………………………………… 15
2.4 IMPULSIVE NOISE MODELLING………………………………………………………………………….. 15
2.4.1 Middleton Class A Model: ………………………………………………………………………………….. 16
2.5 AN EMPIRICAL STUDY OF ABU WIRELESS NETWORK……………………………………… 19
2.5.1 DEFINITION OF TERMS………………………………………………………………………………… 19
2.5.2 Base Station …………………………………………………………………………………………………. 19
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2.5.3 Client Stations………………………………………………………………………………………………. 19
2.5.4 Satellite (VSAT) …………………………………………………………………………………………… 19
2.5.5 Modem………………………………………………………………………………………………………… 19
2.6 IEEE802.11 STANDARDS USED ON THE ABU WLAN …………………………………………. 19
2.6.1 IEEE 802.11 a………………………………………………………………………………………………. 19
2.6.2 IEEE 802.11 b | g………………………………………………………………………………………….. 20
2.6.3 IEEE 802.11 b |g versus IEEE 802.11a……………………………………………………………….. 20
2.7 ABU-ZARIA WIRELESS NETWORK LAYOUT………………………………………………………. 20
2.7.1 Senate West Base Station……………………………………………………………………………………. 22
2.7.2 Senate East Base Station …………………………………………………………………………………….. 23
CHAPTER THREE: ……………………………………………………………………………………………………… 26
3.1 INTRODUCTION …………………………………………………………………………………………………… 26
3.2.1 Data Acquisition………………………………………………………………………………………………… 26
3.2.2 Procedure of Data Analyses ………………………………………………………………………………… 26
3.3 SIMULINK-BASED MODELLING………………………………………………………………………….. 29
3.3.1 DEVELOPMENT OF SIMULINK MODEL……………………………………………………………. 29
3.3.2 Simulink …………………………………………………………………………………………………………… 31
3.3.3 Blocks Used in the Model …………………………………………………………………………………… 32
CHAPTER FOUR…………………………………………………………………………………………………………. 34
RESULT AND ANALYSIS…………………………………………………………………………………………… 34
4.1 INTRODUCTION ………………………………………………………………………………………………. 34
4.1.1 Data Calculations ………………………………………………………………………………………………. 34
4.2 RESULTS OBTAINED……………………………………………………………………………………………. 36
4.3 RESULT ANALYSIS BASED ON SIMULINK MODEL DISPLAY……………………………. 45
4.4 DISCUSSION OF RESULTS OBTAINED ………………………………………………………………… 47
CHAPTER FIVE ………………………………………………………………………………………………………….. 49
CONCLUSION AND RECOMMENDATION…………………………………………………………………. 49
5.1 INTRODUCTON…………………………………………………………………………………………………….. 49
5.2 LIMITATIONS……………………………………………………………………………………………………….. 49
5.3 SIGNIFICANCE OF WORK DONE …………………………………………………………………………. 49
5.4 CONCLUSION……………………………………………………………………………………………………….. 50
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5.5 RECOMMENDATIONS FOR FURTHER WORK……………………………………………………… 50
REFERENCES …………………………………………………………………………………………………………….. 52
APPENDIX I: MATLAB PROGRAM…………………………………………………………………………….. 57
2.4GHz SENATE WEST MATLAB PROGRAM …………………………………………………………. 57
5GHz matlab programme……………………………………………………………………………………………. 63
APPENDIX II: 90 Days Signal Strength Data for ABU Network ……………………………………….. 66
CHAPTER ONE
INTRODUCTION
1.1 INTRODUCTION TO EMC
One major trend in the implementation of networking is the increased adoption of wireless
networks, primarily due to the advantages it offers over its wired counterpart. Current generation
of wireless networking is considerably slower than conventional wired networks, limited by
Shannon’s information capacity theorem. More importantly is by the use of wireless signals
susceptibility to the electromagnetic propagation in an omnidirectional manner. This gives rise to
the characteristics of wireless propagation (e.g. interference and attenuation) and the resulting
objects (e.g. metallic objects and other unlicensed 2.4Ghz products) that can hinder or impair
wireless network transmissions. This ultimately results in higher loss rates, which reduces the
bandwidth available to the end user. Thus understanding wireless characteristics in
electromagnetic environment is fundamental for improving transport protocols leading to a
reduction in errors and resulting in increased network throughput and determining an optimum
position to achieve maximum wireless performance. (Wilson, 1988)
1.1.1 Concept of Electromagnetic Compatibility
Electromagnetic compatibility (EMC) is the branch of electrical sciences which studies
propagation and reception of electromagnetic energy with reference to the unwanted effects
(Electromagnetic interference, or EMI) that such energy may induce( Loyka, 2002). The goal of
EMC is the correct operation, in the same electromagnetic environment, of different equipment
which use electromagnetic phenomena, and the avoidance of any interference effects.(Loyka,
1999)
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In order to achieve this, EMC pursues two different kinds of issues. Emission issues are related
to the unwanted generation of electromagnetic energy by some source, and to the
countermeasures which should be taken in order to reduce such generation and to avoid the
escape of any remaining energies into the external environment. Susceptibility or immunity
issues, in contrast, refer to the correct operation of electrical equipment, referred to as the victim,
in the presence of unplanned electromagnetic disturbance and hence electromagnetic
compatibility is achieved primarily by addressing both emission and susceptibility issues, i.e.,
quieting the sources of interference and hardening the potential victims. The coupling path
between source and victim may also be separately addressed to increase its attenuation. ( Loyka,
2002)
1.2 TYPES OF INTERFERENCE
Electromagnetic interference divides into several categories according to the source and signal
characteristics. The origin of noise can be man-made or natural. (Mordachev and Loyka 1998)
1.2.1 Continuous Interference
Continuous, or Continuous Wave (CW), interference arises where the source regularly emits a
given range of frequencies. This type is naturally divided into sub-categories according to
frequency range, and as a whole is sometimes referred to as “DC to daylight”.
a. Audio Frequency, from very low frequencies up to around 20 kHz. Frequencies up to 100 kHz
may sometimes be classified as Audio. Sources include:
i. Mains hum from power supply units, nearby power supply wiring, transmission lines and
substations.
ii. Audio processing equipment, such as audio power amplifiers and loudspeakers.
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iii. Demodulation of a high-frequency carrier wave such as an FM radio transmission.
b. Radio Frequency Interference, RFI, from 20 kHz to a limit which constantly increases as
technology pushes it higher. Sources include:
i. Wireless and Radio Frequency Transmissions
ii. Television and Radio Receivers
iii. Industrial, scientific and medical equipment
iv. High Frequency Circuit Signals (For example microcontroller activity)
c. Broadband noise may be spread across parts of either or both frequency ranges, with no
particular frequency accentuated. Sources include:
i. Solar Activity
ii. Continuously operating spark gaps such as arc welders
iii. CDMA mobile telephony
1.2.2 Transient (Pulse) Interference
Electromagnetic Pulse, EMP, also sometimes called Transient disturbance, arises where the
source emits a short-duration pulse of energy. The energy is usually broadband by nature,
although it often excites a relatively narrow-band damped sine wave response in the victim.
Sources divide broadly into isolated and repetitive events.
a. Sources of isolated EMP events include:
i. Switching action of electrical circuitry, including inductive loads such as relays, solenoids,
or electric motors.
ii. Electrostatic Discharge (ESD), as a result of two charged objects coming into close
proximity or even contact.
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iii.Lightning Electromagnetic Pulse (LEMP)
iv. Nuclear Electromagnetic Pulse (NEMP), as a result of a nuclear explosion.
v. Non-Nuclear Electromagnetic Pulse (NNEMP) weapons.
vi. Power Line Surges/Pulses
b. Sources of repetitive EMP events, sometimes as regular pulse trains, include:
i. Electric Motors
ii. Gasoline engine ignition systems
iii. Continual switching actions of digital electronic circuitry.
1.3 ELEMENTS OF AN EMC PROBLEM
There are three essential elements to an EMC problem as illustrated in Figure 1.1. There must be
a source of electromagnetic energy, a receptor (or victim) that cannot function properly due to
the electromagnetic energy, and a path between them that couples the energy from the source to
the receptor. Each of these three elements must be present although they may not be readily
identified in every situation. Electromagnetic compatibility problems are generally solved by
identifying at least two of these elements and eliminating (or attenuating) one of them.
(Rajendra,2009).
Figure 1.1 The Three Essential Elements of an EMC P
1.4 WIRELESS NETWORKING STANDARDS
Institute of Electrical and Electronics Engineers (IEEE) (WLAN Association, 2002) has specified
various WLAN standards. Some
in Table 1.1.
Table 1.1 IEEE WLAN Standards
Standard Description
IEEE 802.11 Data rates up to 2Mbps in 2.4
IEEE 802.11a Data rates up to 54Mbps in 5
IEEE 802.11b Data rates up to 11Mbps in 2.4
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Problem.
important standards in the context of this thesis are summarized
Approved
2.4-GHz ISM band July 1997
5-GHz UNII band
Sept 1999. End user products
began shipping in early 2002
2.4-GHz ISM band
Sept 1999. End user products
began shipping in early 2000
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Other standards are the following:
IEEE 802.11g
In 2002 and 2003, WLAN products supporting a newer standard called 802.11g emerged in the
market. 802.11g attempts to combine the best of both 802.11a and 802.11b. 802.11g supports
bandwidth up to 54 Mbps, and it uses the 2.4 GHZ frequency for greater range. 802.11g is
backwards compatible with 802.11b, meaning that 802.11g access points will work with 802.11b
wireless network adapters and vice versa. (WLAN Association, 2002)
IEEE 802.11n
The newest IEEE standard in the WiFi category is 802.11n. It was designed to improve on
802.11g in the amount of bandwidth supported by utilizing multiple wireless signals and
antennas (called MIMO technology) instead of one. When this standard is finalized, 802.11n
connections should support data rates of over 100 Mbps. 802.11n also offers somewhat better
range over earlier WiFi standards due to its increased signal intensity. 802.11n equipment
will be backward compatible with 802.11g gear. IEEE 802.11n (2009)
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1.5 RESEARCH OBJECTIVE
Wireless LAN communication suffers distortions as a result of continuous interference of signal
arising from the following: radio transmitters, power lines, electronic circuits, lightning, lamp
dimmers, electric motors, arc welders, solar flares and just about anything that utilizes or creates
electromagnetic energy. The main objective of this work is to identify EMC issues if any and
provide a means by which the Susceptibility or immunity of the wireless network can be
enhanced.
1.6 PROBLEM STATEMENT
The primary concern of a wireless local area network (WLAN), like any other communication
network, is to ensure that the technology is deployed in a way that preserves the integrity of the
information technology infrastructure and delivers an acceptable level of service for the users of
that technology. It is a known fact that there are problems associated with most if not all wireless
networks. These includes electromagnetic interference, insecure data due to signal spill, ad-hoc
unauthorized access points and suppression and degradation of signal due to physical barriers
along the line of sight, attenuations, scattering, reflections e t c.
This study will thus seek to assess the electromagnetic compatibility issues that are found within
the A B U Zaria 2.4GHz and 5GHz wireless network community, with the intent of exploring
and determining a possible remedy.
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