SATNAC 2007 Conference Papers
Access Networks
Title: Performance
Evaluation of An Integrated Vertical Handover Model for
Next Generation Mobile Networks Using Virtual MAC Addresses
Authors:
Hossen Altwelib
(The Higher Institute of Industry, Libya),
Majdi Ashibani (The Higher Institute of Industry), Fathi Ben Shatwan
(The Higher Institute of Industry)
Abstract:
The integration of existing cellular systems with wireless access
technologies, such as wireless LANs, have attracted considerable
attention during the past few years. There are a number of challenges
need to be addressed including authentication, security, QoS support,
and mobility management. Efficient mobility management, and especially
handover management, is considered one of the major factors toward a
seamless connectivity across networks of different technologies. This
paper proposes a link layer (layer 2) handover ,the proposed link layer
handover presents a possible UMTS-WLAN interworking architecture and
proposes a new method facilitates seamless vertical handover (VHO)
between UMTS and WLAN networks. Our proposal is based on provisioning a
virtual media access control (VMAC) addressing the mobile user on the
UMTS network at the time of vertical handover to the WLAN. In this
paper, we also describe the design and implementation of the Gateway
Hotspot Support node (GHSN) in detail and present experimental
performance results that have been obtained from the simulation model
to validate our proposal architectural. In this paper, we have come up
with novel integrated model that has augmented the UMTS and WLAN
individual models.
Title: Wireless
Broadband: Comparartive Analysis of HSDPA vs. WiMAX
Authors:
Otieno Amimo-Rayolla
(French South African Technical Institute in
Electronics),
Anish Kurien (Tshwane University of Technology), Damien Chatelain
(French South African Technical Institute in Electronics), Marcel
Odhiambo (University of South Africa)
Abstract:
The ever growing demand for data and multimedia content has seen a
surge in evolutionary wireless networking. This growth, largely driven
by the success of data and media streaming over the all-encompassing
communication medium, the internet, and ubiquitous availability of
digital multimedia technology, has seen a sudden influx of partly
complementary, partly substitutive network technologies such as HSPA,
WLAN, WI-FI, Flash-OFDM, DVB-H and Bluetooth, bringing with them an
upsurge in throughput (in Mbs). This paper gives an overview of the
comparative analysis of two major technologies HSDPA and WiMAX, as a
precursor to the complete experimental and simulation study of
real-time streaming services (video) and optimization of existing
networks. This paper will focus on technical comparisons with
simulation examples, giving suggestions as to why the disparities in
performance exist.
Title: The
Factors Influencing Signal Propagations in the Underground Cable
for Broadband Power-Line Communications (PLC) Systems
Authors:
Justinia Anatory (University of Dar es
Salam),
Nelson Theethayi (Uppsala University)
Abstract:
Recently power-line network has been proposed for broadband power-line
communications. The network construction in most of the countries is
the mixture of overhead and underground networks. The underground cable
power transmission system is widely used in urban low voltage power
distribution systems. In order to access the performance of such
distribution systems as a low voltage broadband power line
communication (BPLC) channel, this paper investigates the effects of
load impedance, line length and branches on such systems, with special
emphasis to the power line networks found in Tanzania. From the
frequency response of the transfer function (ratio of the received and
transmitted signals), it is seen that position of notches and peaks in
the magnitude are largely affected (observed in the time domain
responses too) by the above said network configuration and parameters.
The observations presented in the paper could be helpful in suitable
design of the PLC systems for a better data transfer and system
performance.
Title: Service-Class-Based
Joint Call Admission Control and Adaptive Bandwidth
Management Scheme for Heterogeneous Wireless Networks
Authors:
Olabisi Falowo
(University of Cape Town),
H. Anthony Chan (University of Cape Town)
Abstract:
Joint call admission control (JCAC) can significantly improve
connection-level quality of service (QoS) in heterogeneous wireless
networks. This paper proposes serviceclass based JCAC and adaptive
bandwidth management scheme to enhance connection-level QoS in
heterogeneous cellular networks, where each cellular network is
optimized to support specific classes of service. We develop an
analytical model for the JCAC scheme using a multi-dimensional Markov
chain. Two connection-level QoS metrics, new call blocking probability
and handoff call dropping probability, are derived and evaluated for
the heterogeneous cellular network. Numerical results show that the
proposed JCAC scheme reduces handoff call dropping probability and new
call blocking probability in heterogeneous cellular networks.
Title: Optimisation
of the Pilot-to-Data Power Ratio in the MQAM-Modulated
OFDM Systems with MMSE Channel Estimation
Authors:
Eugene Golovins (University of Cape Town),
Neco Ventura (University of Cape Town)
Abstract:
Modern high-rate wireless OFDM systems use dedicated pilot subcarriers
to obtain regular estimates of the channel frequency response and
perform equalisation followed by coherent detection on other (data)
subcarriers. Boosting power of the pilot subcarriers relative to the
data subcarriers can increase channel estimation accuracy. However due
to the overall transmit signal power constraint, dictated by energy
conservation and restricted service zone radius, it will inevitably
lead to degradation of performance of the equaliser detector couple
being a result of the receiver noise level growth on the data
subcarriers. In this article we derive an analytical expression for the
optimal pilot-to-data power ratio (PDR) providing maximum
signal-to-noise power ratio (SNR) at the output of the equaliser and
hence improving BER performance. We also examine effects of the optimal
and suboptimal minimum mean squared error (MMSE) channel estimator
design and their impact on PDR selection.
Title: Fountain
Codes and their possible application in standards like GSM
Authors:
Trienko Grobler (University of Pretoria),
Corne Olivier (University of Pretoria), Jacobus Vlok Olivier
(University of Pretoria)
Abstract:
In this paper we review the concept of a fountain code and explore its
possible application in standards like GSM. Our main focus is on the
decoding of Tornado codes (predecessor of fountain codes) in typical
mobile wireless channels encountered in GSM and WiMax standards.
Channel conditions considered include AWGN and flat fading. The
application of fountain codes in GSM is appealing due to the graph
structure of these codes and the coding configuration in current GSM
standards.
Title: Low
Complexity Adaptive Frequency-Domain Equalizer for Quasi-Orthogonal
Space-Time Block Code over Frequency-Selective Channels
Authors:
Lethukuthula Gumede (University of
Kwazulu-Natal),
Hong-Jun Xu (University of Kwazulu-Natal), Fambirai Takawira
(University of Kwazulu-Natal)
Abstract:
This paper investigate the performance of an adaptive frequency-domain
equalizer for quasi-orthogonal space-time block coded (QSTBC) over
frequency selective fading channels. The QSTBC takes the
advantage of the intrinsic orthogonal space-time block code (OSTBC)
within it to reduce the complexity of the recursive least square (RLS)
to that of least mean square (LMS) without compromising
performance. The receiver with perfect channel state
information
is compare to the adaptive receiver under investigation. Also
the
effects of some of the parameters of the receiver are presented in the
simulations. The simulation results for the OSTBC adaptive
receiver are used as benchmark to compare with receiver under
investigation.
Title: Overview
of the Meraka wireless grid test bed for evaluation of ad-hoc
routing protocols
Authors:
David Johnson
(Meraka Institute, CSIR),
Albert Lysko (Meraka Institute, CSIR)
Abstract:
Predicting the performance of ad-hoc networking protocols has typically
been performed by making use of software
based simulation tools. Experimental study and validation of such
predictions is vital to obtaining more realistic results, but may not
be possible under the constrained environment of network simulators.
This paper presents experimental comparisons of routing protocols using
a 7 by 7 grid of closely spaced WiFi nodes. It firstly demonstrates the
usefulness of the grid in its ability to emulate a real world multi-hop
ad-hoc network. It specifically compares hop count, routing traffic
overhead, throughput, delay and packet loss for three protocols which
are listed by the IETF MANET working group. These are AODV, OLSR and
DYMO
Title: **
Cellular Network Fault Prediction Using Mobile Intelligent Agent
Technology
Authors:
Paul Kogeda (University of the Western
Cape),
Johnson Agbinya (University of Technology Sydney)
Abstract:
Proactive cellular network fault automation models using mobile
intelligent agent are presented in this paper. Cellular networks are
uncertain and dynamic in their behaviours and therefore we use
different artifi-cial intelligent techniques to develop platform
independ-ent, autonomous, reasoning, scalable and robust agent that can
report on any unforeseen anomaly within the cellular network service
provider. The specific design and implementation is done using Java
Agent DEvelop-ment Framework (JADE). We set up a simple wire-less
network consisting of four devices for our experi-ments, which lasted
seven days. The partial results ob-tained from the experiments
conducted are presented and discussed in this paper.
Title: Turbo
Space-Time Multiuser Detection for DS-CDMA Systems in Rayleigh
Fading Channels
Authors:
Derrick B. Mashwama (University of Cape Town),
Emmanuel O. Bejide (University of Cape Town)
Abstract:
In this paper, we investigate the performance of the partitioned and
the iterative approach to concatenation of the Parallel Interference
Cancellation (PIC) technique with turbo detection in the Space-Time
Block Coded (STBC) system. The paper studies the comparative
performance of both concatenation approaches. It was observed that at
low Signal to Noise Ratio (SNR) the Iterative Approach (IA) performs
better than the Partitioned Approach (PA). However, as the fidelity of
the received signal increases the PA starts to have a better
performance than the IA. Both PA and IA system performances are shown
to be dependent on the diversity level, system loading, channel
conditions and detector parameters. A case is made for the design of a
switching algorithm that monitors the ‘crossover’
point and
switches to the better performing concatenation approach for a given
system setup.
Title: Low-Density
Parity-Check Code Design for GSM
Authors:
Andre Martin Mc Donald (University of Pretoria),
Jan Corne Olivier (University of Pretoria)
Abstract:
We present a technique for designing low-density parity-check (LDPC)
code matrices for the MCS-1 to MCS-4 coding schemes of GSM. We
demonstrate that these codes have significant performance gains over
randomly constructed LDPC codes in the GSM setup. The new codes also
show significant gains in performance over the conventional MCS-1 to
MCS-4 GSM coding schemes when compared in terms of the bit-error rate.
Title: A
Performance Comparison of Wireless Multi-Hop Network Topologies Based
on Average Node Degree
Authors:
Pragasen Mudali
(University of Zululand),
Thulani Nyandeni (University of Zululand), Matthew Adigun (University
of Zululand)
Abstract:
The average node degree of a wireless multihop network is an important
factor in the overall network performance. This paper evaluates five
practical network topologies that leverage the regular layout of
buildings. The performance comparisons are based on the
network’s
average node degrees with the purpose of discovering the optimum
average node degree. Simulation results show that the optimal node
degree amongst the network topologies surveyed is four. This
information is useful for the planning of an ever-increasing number of
wireless multi-hop network deployments throughout the world.
Title: Rainfall
Rate Distribution For LOS Radio Systems in Botswana
Authors:
Chrispin Mulangu
(University of Kwazulu-Natal),
Pius Owolawi (University of Kwazulu-Natal), Thomas Afullo (University
of Kwazulu-Natal)
Abstract:
The estimated cumulative distributions (CDFs) of rainfall rate for 4
locations in Botswana are reported in this paper based on 10-year
rainfall data. The daily rainfall sampled over 24 hours is converted to
the ITU-R recommended integration time of one minute. The method used
is based on cumulative distribution identity of known one-minute
rain-rate sites with their corresponding daily integration time
compared with sites having unknown one-minute integration time.
Consequently, values of coefficients a and b so determined are used to
convert daily rain rates into oneminute rain rates for corresponding
similar CDF sites of the target regions of Botswana. The resulting
cumulative rainfall rate and relations between them are compared with
the relevant ITU-R Recommendation P.837-1 and P.837-4. Based on this,
an additional two rain zones are proposed alongside the seven ITU-R
rain zones for Southern Africa.
Title: Extending
WiFi Access For Rural Reach
Authors:
Kribashnee Naidoo
(University of Kwa-Zulu Natal),
Rathilall Sewsunker (University of Kwa-Zulu Natal)
Abstract:
WiFi can be used for last-mile IP connectivity to rural users. In
initial roll-out, hotspots can be positioned at community centres such
as schools, clinics, hospitals or call-centres. The study will consider
a typical South African rural region, with telecommunications services
traffic estimates. The study focuses on IEEE 802.11G deployment option
based on the requirements of the South African case. The research
investigates the maximum number of VoIP calls with reasonable QoS that
can be sustained on a WiFi network.
Title: Dynamic
Power Control On-demand Routing Protocol
Authors:
Elisha Oketch Ochola
(Tshwane University of Technology / F'SATIE),
Damien Chatelain (F'SATIE), Anish Kurien (Tshwane University of
Technology), James Oyedapo (Tshwane University of Technology)
Abstract:
Power control for mobile Ad hoc networks has received an increasing
research interest in recent years. Routing is one of the major sources
of power consumption in mobile nodes. In particular, consumption is
significantly high when Ad hoc routing is employed as nodes are
assigned additional operations to support the routing of packets from
other nodes. In this paper, we optimise transmission power in slow
mobile Ad hoc networks to reduce power consumption. This is adaptively
and deterministically achieved by arriving at the optimum transmission
power between every two nodes within the transmission range of each
other (neighbors), without use of heuristic safety factors. We simulate
an Ad hoc On-demand Distance Vector routing (AODV); and provide an
optimum transmission power aware routing algorithm for mobile Ad hoc
network. The on-demand algorithm sends out request for routes to the
destination only if the source has data packet(s) to transmit and does
not maintain routes that are not in active communication. Simulation
results show that our scheme improves energy efficiency for AODV
routing protocol leading to a considerable reduction in total power
consumption to route a packet from source to destination node.
Title: Repeat-Puncture
Superorthogonal Convolutional Turbo Codes in AWGN and
Flat Rayleigh Fading Channels
Authors:
Narushan Pillay
(University of Kwazulu-Natal),
Hongjun Xu (University of Kwazulu-Natal), Fambirai Takawira (University
of Kwazulu-Natal)
Abstract:
Repeat-Puncture Turbo Codes (RPTC), an extension of the conventional
turbo coding algorithm, has shown a significant increase in performance
at moderate to high signal-to-noise (SNR) ratios.
Superorthogonal
Convolutional Turbo Codes (SCTC) makes use of superorthogonal signals
to improve the performance of conventional Turbo Codes (TC). By
combining Superorthogonal Convolutional Turbo Codes and Repeat-Puncture
Turbo Codes a coding scheme that exhibits a more superior performance
results. In this paper, we study a new low-rate coding scheme
Repeat-Puncture Superorthogonal Convolutional Turbo Codes (RPSCTC) that
makes use of superorthogonal signaling, together with repetition and
puncturing to improve the performance of Turbo Codes for reliable and
effective communications. Simulation results in additive white Gaussian
noise (AWGN) and flat Rayleigh fading (FRF) channels are presented
together with analytical bounds of bit-error probabilities derived from
transfer function bounding techniques.
Title: Field
testing of the Alvarion BreezeMAX as a last mile access technology
Authors:
Ingrid Siebörger (Rhodes
University),
Alfredo Terzoli (Rhodes University)
Abstract:
With an alarmingly low teledensity of approximately 12 % in South
Africa, and not much hope of further wired infrastructure at the local
loop level – as the costs incurred are high compared to
potential
revenue – wireless connectivity could be a great asset and
service in South Africa. This paper looks at how WiMAX technologies,
and specifically the Alvarion BreezeMAX, could be used in providing
much needed telecommunications infrastructure to both rural and urban
areas in South Africa, providing broadband data throughput rates
together with excellent network reliability and low latency.
Title: Performance
Evaluation of WiMAX for Rural Backhaul
Authors:
Verosha Singh
(University of KwaZulu-Natal)
Rathilall Sewsunker (University of KwaZulu-Natal)
Abstract:
Technologies such as WiFi and WiMAX, can be powerful driving forces for
increasing rural connectivity. This paper proposes the use of WiMAX as
backhaul to WiFi hotspots in order to provide sustainable and easy to
deploy rural telecommunication services. The hotspots will take the
form of telecentres. The IP-based network will provide voice, data and
Internet services. This work evaluates the performance of WiMAX as a
backhaul technology based on a typical South African rural region as a
case study. Telecommunication traffic estimates for the region are
determined. The future demands on the proposed network are also
considered. Quality of service measurements based on these user
requirements include IP packet loss and delay, as well as perceived
voice quality during peak traffic periods.
Title: A
Measurement-Aided Model-Based Admission Control Scheme for IEEE
802.11e EDCA Wireless LANs
Authors:
Conroy Andre Smith
(University of Cape Town),
Neco Ventura (University of Cape Town)
Abstract:
The IEEE 802.11e standard was introduced to overcome the lack of
Quality of Service (QoS) support for the legacy IEEE 802.11 Wireless
LANs. However, channel overloading still remains a major problem, as
the QoS of traffic flows are degraded with a heavy load on the wireless
channels. This paper proposes a measurement-aided model-based admission
control scheme for IEEE 802.11e Enhanced Distributed Channel Access
(EDCA) Wireless Local Area Networks (WLANs). It presents an overview of
an Admission Control Unit (ACU) that is capable of providing
quantitative QoS guarantees to all existing flows. The ACU in the
Access Point (AP) makes use of measured collision statistics to
estimate the achievable throughput that stations can achieve at
saturated network conditions. The achievable throughput estimations are
based on a 2-state markov chain model of the IEEE 802.11 contention
based channel access scheme. Simulation results indicate that the
analytical model is fairly accurate.
Title: **
PowerLine Communications an Integrative Solution to the Digital
Divide and Broadband Delivery in the Rural Community of South Africa
Authors:
Loyd Tinarwo (University of Fort Hare),
Martin Mandioma (University of Fort Hare), Hippolyte Muyingi
(University of Fort Hare)
Abstract:
Ensuring Broadband delivery and addressing Digital Divide needs
integration of solutions that positively influence and affect the
“Broadband for All” theme in South Africa. The
authors
argue that though relatively new, Broadband PowerLine Communications
(PLC) is capable of solving the Digital Divide problem, characterizing
the non-broadband communities of South Africa. Besides defining what
is, Digital Divide and citing the advantages of the broadband PLC
technology, the study present a comparative analysis of the PLC Network
and the Ethernet Network under FTP load experiments in an Open Source
Software Environment. The research investigates the competitiveness and
comparability of PLC Network as technology that can bring substantial
effect to the South African non-broadband communities if implemented at
an extensive scale.
Title: A
Performance Comparison of Candidate 4G Air-Interfaces in a Simulated
Cellular Environment
Authors:
Ryan van den Bergh (University of the
Witwatersrand),
Hu Hanrahan (University of the Witwatersrand)
Abstract:
Development of the Fourth Generation of mobile communication systems,
or 4G, has already begun in various organizations and research
institutions worldwide. There is currently no single conclusive
definition for 4G systems, and the process of 4G standardization will
only begin after the World Radiocommunication Conference in 2007. The
purpose of this paper is to evaluate the performance of two candidate
4G air-interface architectures, namely OFDMA and MC-CDMA, so that a
recommendation can be made as to which architecture should form the
core component of a new 4G access network system. To determine the
appropriate choice of air-interface for 4G systems, a series of
simulations was run using a realistic model of a cellular wireless
environment. The results from those simulations were analysed and it
was determined that, due to the absence of multiple access interference
as found in MC-CDMA, OFDMA systems better met the defined requirements
for a 4G air-interface.
Title: Towards
Gigabit DSL (GDSL): Design of a CC/MC-CDMA modem
Authors:
Jacques van Wyk (University of Pretoria),
Louis Linde (University of Pretoria)
Abstract:
With the introduction of VDSL2 and the implementation of
Fibre-to-the-Curb (FTTC), the theoretical limit of DSL technology is
pushed even further than currently known ADSL technology. Current
research is investigating the possibility of symmetric DSL at 1 Gbps
(GDSL). This paper addresses the design and implementation of a
complete complementary multi-carrier code-division multiple access
(CC/MC-CDMA) transmitter / receiver pair.This fully functional modem
combines the virtues of both orthogonal frequency division multiplexing
(OFDM) and conventional code division multiple access (CDMA) to support
many users simultaneously with higher spectral efficiencies than
conventional CDMA systems and better noise tolerance than existing DSL
solutions. By expanding the proposed system further, symmetric Gigabit
DSL (GDSL) can be supported.