EMPIRICAL PERFORMANCE EVALUATION OF ENHANCED THROUGHPUT SCHEMES OF IEEE802.11 TECHNOLOGY IN WIRELESS AREA NETWORKS

International Journal of Wireless & Mobile Networks (IJWMN) Vol. 5, No. 4, August 2013
DOI : 10.5121/ijwmn.2013.5413 171
EMPIRICAL PERFORMANCE EVALUATION OF
ENHANCED THROUGHPUT SCHEMES OF
IEEE802.11 TECHNOLOGY IN WIRELESS AREA
NETWORKS
Femi-Jemilohun Oladunni .Juliet, Walker Stuart
School Of Computer Science and Electronic Engineering University of Essex Colchester,
Essex, United Kingdom
{ojfemi and stuwal}@essex.ac.uk
ABSTRACT
The success in the growing wireless standards can be measured by the achievement of quality of service
(QoS) specifications by the designers. The IEEE802.11 wireless standards are widely accepted as wireless
technology for wireless LAN. Efforts have been made over the years by the task group to provide adequate
number of QoS enhancement schemes for the increasing numbers of multimedia applications. This paper
examines the empirical performances of ad hoc wireless networks deployed on IEEE802.11 standard
variants. A survey to some of the QoS schemes incorporated in IEEE802.11 wireless PHY layers were
carried out. Then the effects of this enhancement schemes in relation to data throughput and system
capacity and reliability in the newest technology deployed on IEEE802.11ac standards was investigated
using real time applications and simulation based approaches.
KEYWORDS
Beamforming, IEEE802.11ac, QoS
1. INTRODUCTION
The accessibility to simple, flexible, scalable, cheap and ubiquitous communication provided by
IEE802.11 standards had qualified it to be the major wireless technology all over the world. The
wave of spectrum licence in the microwaves bands has led to growth explosion in the multimedia
applications in the recent times hence; the demand for high throughput, streaming capability in
video audio, and web services on the go. The high quality of services required by these
applications, such as secured bandwidth, minimal data transfer delay spread, reduced jitter and
error rate, have been a huge challenge for IEEE802.11 standards group. The experience in the
wireless networks has been that of overcrowding poor quality of service, system degradation, as
well as co-channel interference among the co-existing access networks. [1].
In this work, the experiences of the networks deployed on the standards in the real world scenario
are being looked into. These standards are operated on the license free microwaves bands of the
frequency spectrum. Some works have been carried out to investigate the system performance in
IEEE802.11 wireless network systems, but the latest research works on the shielding
enhancement techniques for high throughput delivery was not included. Therefore, this work
intends to give a broad overview study of the enhancements schemes and their effects as
determined by the networks delivery performances based on the coverage areas, received signals,
interference between channels, and throughput capability in the IEEE802.11standards variants.

172
The rest of this work is organised as follows: Section two gives the overview of the related
published work on IEEE802.11 WLAN performances. The background study of IEEE802.11 and
the various shielding techniques for quality of service enhancement are addressed in section three.
The empirical investigations of co-located networks performances of IEEE802.11 standards
deployed on microwave bands and the newest technology: IEEE802.11ac, and development and
implementation of beamforming algorithm were reported in section four. The empirical models of
the measurement results of the signal strength distribution of the networks on microwave bands,
the upcoming technology: IEEE802.11ac and discussions were presented in section five. The
conclusion was given in section six.
.
2. RELATED WORKS.
In literature, there are some works on System performance evaluation and interference mitigation
techniques in WLAN deployed on IEEE802.11 standards. However, very few of these authors
have engaged physical devices in their works for real time applications assessment. Some of these
are highlighted below.
2.1. Related works of WLAN indoor coverage.
Different techniques have been adopted in the previous works to achieve the target. Some of these
techniques are: continuous wave transmitter with power meter receivers. [2] used a theoretical
hybrid model that combined a two-dimensional ray tracing model with a direct transmitted ray
(DTR) model to predict the radio coverage on single floors in multifloored buildings. Another
technique is Broadband Pulse channel sounding. [3], measured the pulse response of network at
2.4GHz inside a building, he modulated the carrier with a repetitive 5ns pulses and transmitted it
through a wideband biconical antenna. Also signal strength percentage reported by wireless LAN
card, [4] used measured data and empirical models to predict the propagation path loss in and
around residential area for the UNII band at 5.85GHz. While [5] developed throughput prediction
model using the available measurement software products called SiteSpy and LanFielder to
measure wireless LAN throughput and other network performances criteria and recorded the
results in a precise site-specific manner. His measurement was limited to IEEE802.11b/n wireless
system. [6] examined the impact of structural wall shielding on the system performance of an
interference limited CDMA system using ray-tracing propagation models based on Geometric
Optics and Uniform Theory of Diffraction to estimate the received signal. They observed a
logarithmic relationship between the average output probability and the extent of a shielding in a
typical single-floor office environment. They concluded that efficient deployment of shielding
will enhance both system capacity and signal strength of wireless system. [7], in their work
employed analytical approach using the Okumura’s model to determine the propagation range of
IEEE802.11 Radio LAN’s for outdoor applications. This work used a lot of assumptions and does
not reveal the performance range in the real application scenario. To evaluate the performance of
802.11b, [8] used two laptops equipped with Orinoco WLAN cards, and two PCs with D-Link
WLAN cards. The combination of equipment from different chipset manufacturer may not favour
adequate reading required. In [9] Discrete-event simulation of MAC portion of the IEEE802.11
protocol was used to evaluate the performance of the standard. [10-12] also used empirical
methods to show the coverage area and the signal strength inside the coverage area to reveal the
technology that gives better WLAN. [13] using computer simulation of a typical 802.11b/e access
to an IP core network through an access point in an infrastructure WLAN.in the same manner,
[14] conducted field performance comparison between IEEE802.11b and power line based
communication network. They concluded that power line network outperforms IEEE802 .11b.
[15-18] is similar in some aspects to what is done in this work. They used the experiment to
validate the analytical performance models for IEEE802.11b .It was noted in their results that

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analytical result estimate experimental data with a mean error of 3-5%. In [19] Primary-
Secondary transmission scheme was used to mitigate interference by beam forming and increase
system capacity in WLAN systems where matlab simulation was engaged. [20] Investigated the
efficiency of multi-cast beamforming optimization over IEEE802.11n WLAN. [21] Proposed the
combination of advanced distributed beamforming techniques at physical layer for the
improvement of the overall network capacity. Analytical modelling to evaluate the performance
of ad hoc networks with M-element array was conducted by [22]. The upper and lower bounds on
the transmission capacity in the multiple antenna ad hoc networks with multi-stream transmission
and interference cancellation at the receiver was derived by [23] to increase system capacity
through beamforming technique. Similar to our work, [24] gave the overview of the newest
technologies promised to deliver multi-gigabits throughput: Ieee802.11ac/ ad, they described the
channelization PHY design, and MAC modifications and beamforming in the standards.[25]
proposed a joint adaptive beamforming algorithm for interference suppression in GNSS( Global
Navigation Satellite System) receivers: first the orthogonal projection is used to suppress strong
interference by producing nulling in the array pattern, while the maximum post-correlated C/No
constrained is used to process the interference-free signal to further enhance the signal quality.
[26] designed an advance interference resilient scheme for asynchronous slow frequency hopping
wireless personal area networking and time division multiple access cellular system for
interference reduction in wireless system. Different approaches have been engaged by different
authors in their works to analyse the performances of wireless networks deployed on the
IEEE802.11 technology but none has employed real time application approach, especially in the
newest technology deployed in IEEE802.11ac for the empirical performances assessment. Hence
this work differs from all in this aspect.
3. IEEE802.11
This is a set of standards for implementing WLAN (wireless local area networking)
communications in the 2.4, 3.6, and 5 GHz frequency bands. The first in this group is IEEE80.11-
2007 which has been subsequently amended. Other members are 802.11b and 802.11g protocols.
These standards provide the basis for wireless network products using the Wi-Fi brand. IEEE
802.11b and g use the 2.4 GHz ISM band and are operated on WiFi channels. WiFi channel are
grouped into 14 overlapping channels. Each channel has a spectral bandwidth of 22MHz, (though
the nominal figures of the bandwidth of 20MHz are often given). This channel bandwidth exists
for all standards even though different speed is available for each standard: 802.11g standard has
1, 2, 5, or 11 Mbps while 802.11g standard has 54Mbps. The difference in speed depends on the
RF modulation scheme used. The adjacent channels are separated by 5MHz with the exception of
14 with the centre frequency separated from channel 13 by 12MHZ. From figure 1, it is obvious
that a transmitting station can only use the fourth or the fifth channel to avoid overlapping. Most
often, Wifi routers are set to channel 6 as the default, hence channels 1, 6, and11 have been
adopted generally and particularly in Europe being non-overlapping channels for wireless
transmission in the ISM band. This band can provide up to 11Mbps [8-10]
Figure 1. Structure of Wi-Fi Channels in the 2.4 GHz band [11, 12]

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The UNII (unlicensed national information infrastructure) band is allocated for two radio devices:
the unlicensed part is classified into A (5150-5350) MHz and B (5470-5725) MHz; the higher
band which is licensed is C (5725-5859) MHz used in the installation of Fixed wireless Access
(FWA) services, while A is for indoor mobile and B for indoor and outdoor WLANs. 5GHz U-
NII bands which offers 23 non-overlapping channels, can provide up to 54Mbps in the WLAN
and it is deployed in the IEEE802.11a/n standards.[11, 12]
Table 1. Wi-Fi channels in the 5GHz[27]
Channel Frequency
/GHz
Band(A,B) Maximum
EIRP
36 5.18 A 200mW
40 5.20 A 200mW
44 5.22 A 200mW
48 5.24 A 200mW
52 5.26 A 200mW
56 5.28 A 200mW
60 5.30 A 200mW
64 5.32 A 200mW
100 5.50 B 1W
104 5.52 B 1W
108 5.54 B 1W
112 5.56 B 1W
116 5.58 B 1W
120 5.60 B 1W
124 5.62 B 1W
128 5.64 B 1W
132 5.66 B 1W
136 5.68 B 1W
140 5.70 B 1W
149 5.745 C 4W
153 5.765 C 4W
157 5.785 C 4W
161 5.805 C 4W
.
Among these channels, there are eight widely used channels. These are divided into two called
lower band UNII-1(36, 40, 44, and 48) and upper band UNII-3(149, 153, 157, and161). The
remaining 15 channels are divided into lower UNII-2 having four channels, and upper UNII-2,
which has 11 channels. The reason for the four-unit gaps is that the channels are 20MHz wide,
while there is 5MHz spacing between one channel and the other. The upper bands uses 20 times
as much power as the lower bands and the more power used to send signal, the likelihood of
interference between networks [13].
3.2. IEEE808.11ac
In order to address the higher data rate throughput capacity require by the new technological
growth in wireless applications, the IEE task group in 2008,developed an amendment to the
IEEE802.11 PHY and MAC layer . IEEE802.11ac has an improving delivery capacity beyond its
counterpart, IEEE802.11n.It is the next evolution of the Wi-Fi standard with the capacity to

175
deliver multiple (High Definition) HD video streams simultaneously and provide improvements
over 802.11n.It can cover 33m propagation distance by using 80MHz on the 5GHz band[28-30]
This new technology proposed by IEEE802.11- VHT ,aims at higher throughput of 1Gbps and
with the frequency band of 6GHz or below excluding 2.4GHz frequency bandwidth of 80MHz
and 160MHz option building on the 40MHz available in 802.11n.For spectrum efficiency, MU-
MIMO technology is employed in this standard to achieve the aimed target throughput of
1Gbps.An obvious technical problem is envisaged in this technology. Due to its huge frequency
bandwidth which will only allow four frequency channels , will lead to severe inter cell
interference due to frequency channel shortage among multiple basic service sets.TGac and TGad
were established in Sep 2008 and Dec 2008 respectively, targeting completion of standardization
late in 2012[31-33] The final approval of the IEEE802.11ac standard amendment is expected in
December 2013, though as the moment, initial products with basic feature of 802.11ac has started
to emerge on the market[30].
Table 2. Feature Enhancement Schemes Comparison: 802.11n/802.11ac [34]
IEEE802.11n IEEE802.11ac
Frequency Band 2.4 and 5 GHz 5GHz only
Channel Widths 20, 40 MHz 20,40,80MHz, 106MHz
optional
Spatial Streams 1 to 4 1 to 8 total up to 4 per
client
Multi- User MIMO No Yes
Single Stream (1x1) Maximum
Client Data Rate
150Mbps 450Mbps
Three Stream (3x3) Maximum
Client Data Rate
450Mbps 1.3Gbps
3.3. Amendments to PHY and MAC layers for improved QoS
3.3.1. Higher Order Modulation Scheme
The maximum modulation in .11n is 64QAM constellation with six bits of coded information.
This has been increased to 256QAM constellation with eight coded bits.256QAM seems to be the
current practical limit of digital modulation scheme, though efforts are on to increase to 512 and
1024 QAM. There are 256 possible states in this scheme, with each symbol representing eight
bits. This makes this scheme very spectral efficient, the symbol rate is 1/8 of the bit rate. This is
revealed in the fig.3.1, 33% increase is realized when 256QaM is used instead of the 64QAM. On
the other hand, the constellation of this scheme are closely packed together, thus, more
susceptible to noise and distortion, leading to higher bit error rate in higher modulation scheme
[35, 36]

176
Figure 2. Performance enhancement in 802.11ac over 802.11n [37]
3.3.2. MIMO
MIMO (Multiple in Multiple out) techniques improves communication reliability as well as
increase data throughput through spatial division multiplexing (SDM), without necessarily
expanding the frequency band by using multiple antenna at the transmitter and receivers ends
This results in signal interference. SVD-MIMO (singular value decomposition –multiple in
multiple out) system can help in suppressing the signal interference as a result of lots of antenna
by beamforming. This is effective in large scale MIMO systems [38, 39] while orthogonal
division frequency multiplexing is a powerful tool to equalize received signals under multipath
fading environments. The combination of these techniques is currently undergoing a great deal of
attention in wireless communications[40, 41] Multiple-input multiple-output orthogonal
frequency multiplexing (MIMO-OFDM) is a powerful technology that enhances communication
capacity and reliance. This is being used in 802.11n WLAN system, defined as four spatial
streams in spatial division multiplexing (SDM), it is expected that the upcoming standardization
of 802.11ac will be defined in eight spatial streams in single-user MIMO (SU-MIMO[42]
3.3.3 Adaptive Beamforming Technology
This is one of the latest technologies in wireless communication system. It uses Smart Antenna
techniques to produce multiple beams concentration to enhance signal of interest, and at the same
time places nullity on the direction of interfering signal. The Beamformer varies a weight vector
for this adaptive process with the ultimate goal to improve communication channel. The figure1b
is the setup model for adaptive beamforming. The mathematical algorithms are shown in the
following equations [25]
, Where
is the power of the difference between the output and reference signals –step size
is power of incoming signal and is the deviation
The error signal is given by;
e = d (1)

177
(2)
y , (3)
e d y (4)
Estimated of weight vector at time n+1,
(5)
(6)
(a) (b)
Figure 3. (a) Antenna Array Beamforming, (b) Block Diagram of Adaptive Beamforming [28]

178
4. METHODOLOGY
4.1. Empirical Measurements of wireless transmission on 2.4GHz channels
Figure 4. Microwave bands transmission experimental setup
The field measurements of radio signals at different locations from the various access points were
taken with a net sniffer called Inssider, a 5GHz dual band dongle, GPS, and a laptop. Measurements
were repeated about 25 times in each location for the different networks. While conducting the
experiments, a huge amount of data was recorded in files and the data records include the time
information (t), MAC address of AP, Signal Strength (SS) information, transmitter channel of AP,
service set identifier (SSID).
The measured values were saved in kml file format from the personal computer and later extracted to
Excel .Xml. Figs. 5-7 are the empirical models from the acquired data .Out of 23 non-overlapping
channels in UNII band, only two were employed in the wireless network service of the University.
They are channels 36 and 48, which also engaged in frequency reuse pattern. This band has higher
data rate of 54Mbps hence higher throughput delivery compared to its unlicensed counterpart in the
ISM band. The transmission distribution measurement of this band was also conducted and the
simulations carried out. The following models are the outcomes.
4.2. Empirical Measurements of wireless transmission on IEEE802.11ac
To assess performance of 802.11ac, an ad-hoc system with the latest technology in wireless standards
was used. The AirStation 1750 (Buffalo) is amongst the first routers to implement the newest WiFi
standard: IEEE802.11ac. It promises throughput of 1300Mbps and also additional 450Mbps in the
802.11n radio.[30] The setup for the experiments are shown in figs 1&2 using WLI-4H-D1300 and
WZR-D 1800H for the transmission using 5GHz channels, For comparison, in fig two, the client was
changed to a WNDA 3100 N600 (Net gear) dual-band dongle using the 5GHz channels of 802.11n
The measurement of throughputs over a range of distances up to 30m was observed on the PC
connected to the wireless transmission link. The PCs were equipped with LANSpeedTest software for
the monitoring of the throughputs.

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(a) (b)
Figure 5. Buffalo AirStation AC1300/N900 Gigabit Dual Band Wireless Router and Client. (a) With
IEEE802.11ac Standard, (b) with Net gear WNDA3100N600 Wireless Dongle Receiver on IEEE802.11n
4.3. Matlab Simulation-Based Evaluation of Beamforming in IEEE802.11ac
Table 4. Parameters for Simulation
Carrier frequency 5GHz
Sampling frequency 2FC
Desires transmitted angle Pi/4
Interferer transmitted angle Pi/4
Step size 0.32
Number of element antenna
array
8
5. EMPIRICAL MODELS OF THE WIRELESS TRANSMISSION ON 2.4, 5GHZ,
IEEE802.11A, AND MATLAB SIMULATIONS
10 20 30 40 50 60 70 80
-100
-95
-90
-85
-80
-75
-70
-65
-60
-55
-50
D is tanc e betw een w ireles s trans m itter and rec eiver(m )
MeasuredSignalStrength(dBm)
Trans m is s ion of netw ork s on c hannel one at 2.4G H z
eduroam
es s ex 11 w ireles s
es s ex w ireles s s etup
Figure 6. Channel One Transmission at 2.4GHz Coverage Distribution

180
1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0
-1 0 0
-9 5
-9 0
-8 5
-8 0
-7 5
-7 0
-6 5
-6 0
-5 5
-5 0
D is t a n c e b e t w e e n w ire le s s t ra n s m it t e r a n d re c e ive r(m )
T ra n s m is s io n o f n e t w o rk s o n c h a n n e l s ix a t 2 . 4 G H z
e d u ro a m
e s s e x 1 1 w ire le s s
s m a rt c a m p u s
Figure 7. Channel Six Transmissions at 2.4GHz Coverage Distribution
0 10 20 30 40 50 60 70 80
-100
-95
-90
-85
-80
-75
-70
-65
-60
-55
-50
Distance between wireless transm itter and receiver(m )
Transm ission of networks on channel eleven at 5GHz
essex wireless setup
VoIp
sm art cam pus
Figure 8. Channel Eleven Transmissions at 2.4GHz Coverage Distribution
1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0
-1 0 0
-9 5
-9 0
-8 5
-8 0
-7 5
-7 0
-6 5
-6 0
-5 5
-5 0
D is ta n c e b e tw e e n w ire le s s tra n s m itte r a n d re c e ive r(m )
Tra n s m is s io n o f n e tw o rk s o n c h a n n e l th irty s ix a t 5 G H z
e s s e x w ire le s s s e tu p
V o Ip
Figure 9. Channel 36 Transmissions at 5GHz Coverage Distribution

181
1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0
-1 0 0
-9 5
-9 0
-8 5
-8 0
-7 5
-7 0
-6 5
-6 0
-5 5
-5 0
D is t a n c e b e t w e e n w ire le s s t ra n s m it t e r a n d re c e ive r(m )
T ra n s m is s io n o f n e t w o rk s o n c h a n n e l fo rt y e ig h t a t 5 G H z
e d u ro a m
s m a rt c a m p u s
Figure 10. Channel 48 Transmissions at 5GHz Coverage Distribution
0 5 10 15 20 25 30
0
50
100
150
200
250
Distance between wireless transmitter and receiver(m)
Throughput(Mbps)
Comparison of IEEE802.11ac and .11n
data rates in the uplink transmission
802.11ac
802.11n
trend 802.11ac
trend 802.11n
mean throughput
Figure 11. Uplink Transmission Throughputs with AirStation Receiver and Dongle Receiver
0 5 10 15 20 25 30
0
50
100
150
200
250
Distance between wireless transmitter and receiver(m)
Throughput(Mbps)
Comparison of IEEE802.11ac and .11n
data rates in the downlink transmission
802.11ac
802.11n
trend 802.11ac
trend 802.11n
mean throughput
Figure 12. Downlink Transmission Throughputs with AirStation Receiver and Dongle Receiver

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0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 5
x 1 0
9
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
x 1 0
- 1 5 D e s ire d a n d In t e rfe rin g s ig n a ls fre q u e n c y s p e c t ru m
fre q u e n c y H z
Fouriermagnitude
Figure 13. Frequency Spectrum of Interfering and Desired Signals
1 1.5 2 2.5 3 3.5 4 4.5 5
0
1
2
3
4
5
6
7
x 10
-16
Com paris on of s ignals frquenc y s pec trum
before and after beam form ing
F requenc y (G Hz )
Magnitude
Des ired and interfering s ignals without B eam form ing
Des ired and interfering with B eam form ing
Figure 14. Frequency Spectrum before and after Beamforming Technique
5.2. Discussion
Measurements of transmission on microwaves bands were taken at twelve different locations in
the University of Essex campus using the set up in figure 4.At each location, 25 signal strengths
sampling from the access points (Aps) were recorded. Simulations of the measured values were
carried out using the Excel.XML program, Haversine formula, and Frii’s propagation law. The
models are presented in figures 6-10. Some distance apart, show a measure of overlap. As shown
in the figures, none of the access points was protected against interference. Each of the access
points is degraded in throughput by certain percentage due to interference from other
neighbouring access points. It is noted that eduroam and essex wireless setup access points were
degraded by almost 100% in throughput.
The setup shown in figure 5 was used for wireless transmission on standard IEEE802.11ac
deployed on frequency of 5GHz. The router was fixed in a position while the client/mobile
terminal was moving at an equidistant points separated by 1m until a total coverage of 30m was
reached in a laboratory hall at the University of Essex, where the measurement was conducted.
The throughput levels received at each measure point is collected by a PC running with
application software called LANSpeed Test software, as we moved along various points of

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measurement to monitor the throughput from the client. Figures 11-12 show the level of uplink
and downlink throughputs of the Buffalo AirStation AC1300/N900 Gigabit Dual Band Wireless
router and client when it is configured to work only in 802.11ac, and WNDA3100 N600 wireless
dual-band dongle receiver when configured to work in 802.11n. As the figures show, the
propagation square law was minimal and more revealed in IEEE802.11n configuration than
IEEE802.11ac. There is appreciable measure of improved throughput in IEEE802.11ac over its
counterpart IEEE802.11n. This established the benefits of beamforming technology in preserving
the data to the targeted consumers. The matlab based simulation to investigate the effect of
beamforming as a QoS enhancement scheme is revealed in figures13 and 14. The magnitude of
the desired and interfering signals is shown in red before beamforming algorithms were
implemented, while the blue colour signifies the magnitude of the desired signal after
beamforming in figure 14. The drastic reduction in the magnitude is as a result of interference
suppression through the shielding technique: beamforming technique, applied while the reception
of desired signal is enhanced, hence improved quality of service.
6. CONCLUSION
The success in the growing wireless standards can be measured by the achievement of quality of
service specifications by the designers. It becomes imperative to ascertain the performances of
wireless devices. [31] Though. the theoretical peak data rates of 600Mbps and 1.3Gbps promised
in IEEE802.11ac and IEEE802.11n respectively.[32] may not be realizable due to propagation
impairment contending with wireless transmission in the real world scenario , nevertheless there
is a considerable data throughput improvement on the counterpart 802.11n. The experiments have
shown that IEEE802.11ac outperforms its lower counterpart IEEE802.11n in throughput delivery.
This is as a result of the beamforming technology incorporated into this standard as a shielding
technique for enhancement of system performance. The beamforming technology could be
conceivably be modified to have better performance. The simulation based evaluation depicted in
figures 13 and 14 revealed the effectiveness of beamforming technique.
ACKNOWLEDGEMENTS
This work is sponsored by the Federal Government of Nigeria through the Tertiary Education
Trust Fund (TETFUND) scheme.
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Femi-Jemilohun .O. Juliet is a Ph.D. candidate at the School of Computer Science and
Electronic Engineering the University of Essex, Colchester, United Kingdom .She became a
stude nt member of IEEE in 2013.She received her B.Eng. degree in Electrical and Electronics
engineering, Ondo State University,
Ado Ekiti, Nigeria in 1997 and her MEng degree from Federal University of Technology,
Akure, Ondo State, Nigeria in 2010.
Stuart D. Walker received the B.Sc. (Hons.) degree in physics from ManchesterUniversity,
Manchester, U.K., in 1973 and the M.Sc. and Ph.D. degrees in electronic systems
engineering from the University of Essex, Essex, U.K., in 1975and 1981, respectively. After
completing a period of contractual work for British Telecom Laboratories between 1979 and
1982, he joined the company as a Staff Member in 1982. He worked on various aspects of
optical system design and wa spromoted to Head of the Regenerator Design Group in 1987. In 1988, he
became Senior Lecturer and then Reader in Optical Communication at the University of Essex, U.K
Currently, He is the Director of Postgraduate School, University of Essex.

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