SATNAC 2009 Conference Papers
Access Networks
Title: Testbed Validation for
the Evaluation of a Delay Aware Routing Metric for Ad Hoc Networks
Authors: Melvin Ferreira (
Abstract: There
is a growing need for real-time multimedia applications to be supported in ad
hoc networking environments. Most
current ad hoc routing protocols only support best-effort routing. By adopting
Quality of Service (QoS) aware routing metrics, one can extend the set of
multimedia services that run in an ad hoc network. Firstly, in this paper we
present a 4 node wireless prototype testbed that was constructed to analyse ad
hoc routing protocol behaviour. The testbed architecture is described and its
ability to allow for repeatable and reproducible experimentation is
verified. Secondly, we practically
implement enhancements to the AODV (Ad Hoc On-demand Distance Vector) routing
protocol. The routing metric is changed from
hop count to measured end-to-end delay. This allows AODV to take the requirements
of delay-sensitive applications such as voice and video services into account
when selecting a route. Evaluation in the prototype testbed shows that the
delay metric exhibits beneficial QoS properties.
Title: Effect of RLC Transmission Modes for Differentiated
Traffic Types in HSDPA via GEO Satellite
Authors: Aiyetoro Gbolahan (
Abstract: This paper investigates the effect of the Radio Link Control (RLC)
operation modes for different types of UMTS traffic over a Satellite High Speed
Downlink Packet Access (S-HSDPA) air interface. Satellite Systems are expected
to complement the terrestrial access network and work with the same core
network. The geostationary bent-pipe satellite has been considered for this
work. The transmission of different traffic types was observed for both
Acknowledge Mode (AM) and Unacknowledged Mode (UM) by investigating the effect
of the cross-layer interactions between the application layer and RLC sub-layer
of the data link layer. Our aim is to recommend which transmission mode is best
for each traffic types and to compare the results with the Terrestrial HSDPA
air interface scenario.
Title: Predicting Low Earth
Orbit Satellite Communications Quality and Visibility over Time
Authors: John Gilmore (
Abstract: Low-Earth-orbit
satellite communication link margins vary greatly as the satellite moves in its
orbit around the Earth. A major design consideration that needs to be addressed
for any satellite system is the choice of
forward-error correction code (FEC). The type of FEC and the optimal
packet length are chosen so as to optimise the system for all expected link
margins. This optimisation takes into account the fact that the link margin varies
over time. FECs are used to minimise the amount of power used in the
transmitter. This paper presents a link quality prediction scheme, that would
enable both the satellite and ground station to adjust the coding rates used in
real-time. The error performance of the code as a function of predicted link
quality will be optimised by this scheme.
An adaptive coding and modulation scheme would make the satellite
communication system more efficient by increasing the volumetric data
throughput.
Title: Performance
Evaluation of Low-Complexity Decision-Feedback Detector for SM-MIMOOFDM Systems
Authors: Eugene Golovins (
Abstract: Spatially multiplexed
multiple–input multipleoutput orthogonal frequency division multiplexing
(SM-MIMOOFDM) technology is envisaged to raise transmission capacity over the wireless
channels up to 10bps/Hz, allowing for ubiquitous access to multimedia services
in the 4G cellular networks. Future transceivers will incorporate MIMO antenna
arrays of larger dimensions than those specified in the presently existing
standards (with maximum 4 antennas). Thus, a crucial part of the cost-effective
system design will deal with the lowcomplexity detector architecture, providing
for optimal or suboptimal performance. In this paper, we propose such a
detection technique and examine its error rate performance in the conditions of
the dynamic channel model.
Title: Channel Capacity Performance of Transmit Antenna
Selective MIMO System in Weibull Fading
Authors: Mzabalazo Lupupa (
Abstract: Multiple-input
multiple-output (MIMO) systems play a great role in improving communication in wireless
systems. But an increase in the number of antennas used in a communication
system results in increased system complexity. To address this drawback
associated with MIMO systems we propose the use of a transmit antenna selective
MIMO system. In this the best performing transmit antenna is selected from all
the available antennas for communication. The signalto- noise ratio (SNR)
performance of the proposed system is studied as the number of antennas used in
the system is increased. In studying the SNR performance,
maximal-ratio-combining (MRC) is used as the optimal combining technique at the
receiver end. Average channel performance is also investigated as we vary the
number of antennas used. The Weibull fading channel is considered in studying
the performance of the transmit antenna selective MIMO system. We further
illustrate the effect of the Weibull fading parameter on the average channel
capacity performance.
Title: Performance
Evaluation of IMS Multimedia over WiMAX
Authors: Francis Masuabi (
Abstract: Telecommunication has evolved
steadily to meet the ever increasing demand of users. Hence, the Internet
Protocol Multimedia Subsystem (IMS) will make it possible to provide ubiquitous
computing to the end-user. WiMAX is based on the IEEE 802.16 standard
engineered to provide wireless broadband access, but the main focus of this
study, is the use of fixed WiMAX as a backhaul for VoIP and IPTV. A performance
aluation of VoIP and IPTV quality of service was done over the WiMAX network.
We examine the performance of these services over various codecs, analyzing the
key performance metrics such as delay, latency, jitter and packet loss. With
respect to VoIP sessions, the quality of the service was measured using the
ITU-T E Model. Our results concluded that the G.711 (PCMA and PCMU) is the
better VoIP codec as it used no compression scheme in addition to its bit rate
being relatively higher than that of GSM.
Title: DRMACSN: New MAC protocol for Wireless Sensor
Networks
Authors: Thippeswamy Muddenahalli (
Abstract: In
this paper, we propose a new distributed, load balanced, and route aware medium
access control protocol for Code Division Multiple Access (CDMA) based Wireless
sensor networks (DRMACS). Wireless
Sensor networks (WSN), a new class of devices, have the potential to
revolutionize the capturing, processing, and communication of critical data for
use by first responders. Sensor networks consist of small, low-power, and
low-cost devices with limited computational and wireless communication
capabilities. They represent the next step in wireless communication’s
miniaturization, and their power and size make it feasible to embed them into
wearable vital sign monitors, location-tracking tags in buildings, and first
responder uniform gear. The sensor nodes can only transmit a finite number of
bits before they run out of energy. Thus, reducing the energy consumption per bit
for end-to-end data transmission is an important design consideration for such
networks. We show how our design would improve the MAC protocol with sleep and
wakeup schemes that could achieve greater energy savings, reliability and
increased system capacity. In this paper, we present findings for the delay,
and the throughput of a new improved proposed MAC protocol.
Title: Evaluation of LDPC
Forward Error Correction Schemes for Telemetry Satellite Systems
Authors: Francois Olivier (
Abstract: This
paper evaluates the proposed implementation of short length low density parity check
(LDPC) codes within the telemetry space protocol. Due to the varying orbital
patterns of low earth orbit (LEO) satellites, limited communication time
windows need to be optimised to maximise data throughput. Most popular
connection oriented protocols focus on correcting congestion related link
errors, but with a unique set of link related bit errors introduced on the
satellite channel, conventional protocols degrades the performance of LEO
satellite communication. The telemetry (TM) protocol specified by the European
Cooperation for Space Standardisation will be evaluated with a mission specific
implementation for error control coding. Using iterative decoding schemes,
short length LDPC show large coding gains with low complexity hardware
requirements. A coding scheme implementing an approximation algorithm is shown
as a low complexity solution with good error performance.
Title: Range Based Power
Control for Multi-Radio Multi-Channel Wireless Mesh Networks
Authors: Thomas Olwal (Tshwane University of
Technology), Barend van Wyk (Tshwane University of
Technology), Karim
Djouani (F’SATIE), Yskandar Hamam (F’SATIE), Patrick
Siarry
(F’SATIE), Ntsibane Ntlatlapa (Council for Industrial and
Scientific Research)
Abstract: Multi-Radio Multi-Channel (MRMC) systems are key to power control
problems in WMNs. In this paper, we present a range based dynamic power control
for MRMC WMNs. First, WMN is represented
as a set of disjoint Unified Channel Graphs (UCGs). Second, each radio assigned
to a unique UCG adjusts the transmission power locally using predicted connectivity ranges
with other nodes. A new power selection MRMC unification protocol (PMMUP) is
proposed that coordinates local power optimizations at the radios of a node.
The efficacy of the proposed method is investigated through simulations.
Title: Design and
Implementation of Wireless Sensor Network for Wildlife Monitoring
Authors: Nolan Pillay (Eskom), Thippeswamy Muddenahalli (
Abstract: Wireless Sensor Networks (WSN) is a popular and
interesting field of research in the study of wildlife. In this paper, the
design of a WSN that will be used to remotely monitor wildlife is proposed. The
sensor nodes designed were small, low powered units to allow them to be mounted
onto animals. Each sensor node was designed to monitor the body temperature of
the animal it was mounted to and the light intensity of the animal’s
external environment. This sensed data was then relayed to a base station node
for further processing. A user application program running on the base station
computer was developed to receive the data from the base station node and store
it in a structured text file format for further analysis. Both the hardware and
software designs of the WSN and the data sample collected from the sensor nodes
relating to temperature and light are presented.
Title: Linear Detector Performance in Ill-Conditioned
MIMO OFDM Channels
Authors: Rehoboam Radzokota (
Abstract: This work investigates the
performance of linear detector based receivers in MIMO OFDM systems. Two linear
detectors are compared that is: Zero Forcing (ZF) and the Minimum Mean Square
Error (MMSE). The introduction of interference cancellation will be shown to
greatly improve linear detector Bit Error Rates (BER). The performance of one
successive interference detector, called the V-Blast, is further evaluated in
ill-conditioned channel conditions. This work investigates performance of MIMO
OFDM detectors in a spatially correlated channel so as to enhance Quality of
Service (QoS). The Weichselberger channel model with ill-conditioned
characteristics will be used in the performance evaluation of the MIMO OFDM
detectors. Tikhonov regularization is
used to improve the performance of successive interference based
detectors.
Title: Per Cell Propagation Model Calibration Approach for
Mobile Positioning
Authors: Dominic Samoita (
Abstract: This paper presents results of research on per cell propagation
calibration-based mobile positioning for GSM. A novel mobile positioning system
for GSM networks is proposed and assessed by field measurements and
simulations. It utilizes timing advance, Received Signal Strength (RSS) and a
per celltuned propagation prediction model. Clutter features are modelled to
closely represent the real environment to enhance the accuracy of the signal
strength prediction. The obtained results indicate that estimation of the mobile position at a sufficient accuracy
for most of the location-based services does not have to involve significant
changes in the terminals and in the network infrastructure. The performed field
measurements and simulation of the designed mobile positioning system reveal
that mobile users can be located with an accuracy of 40 meters. Furthermore,
the method is computationally light-weight and can be integrated onto any
RSS-based algorithm.
Title: A Comparison of Scheduling Algorithms in HSDPA
Authors: Stefan Scriba (Telkom SA), Fambirai Takawira (University of
KwaZulu-Natal)
Abstract: This
paper compares the behaviour of EDF and Opportunistic-EDF (O-EDF) with that of
Round Robin, PFT, and MaxC/I. Video, voice and web traffic are transmitted
through an HSDPA air interface. The resultant queueing delay and fairness are
measured and compared for each scheduler.
Authors: Nyah
Temaneh (
Abstract A Monte-Carlo technique based methodology for
the estimation of a probability of interference in a cellular communication
network is presented. This probability is considered for the case of mobile
to base (Up Link or Reverse channel) and base to mobile (Down Link or Forward
channel) interferences. The effect of random user location in their respective
cells is taken into account, and the impact of lognormal shadowing is also
studied. The simulation results obtained, when compared with known results are
found to be in agreement.
Title: Baseband Carrier Recovery and Phase Tracking as a
Doppler Compensation Technique for A Zero-IF SDR
Authors: Ewald van der Westhuizen (
Abstract: Compensating for
the Doppler effect is a significant problem in low earth orbit (LEO) satellite
communications. The effect of Doppler shift is that the baseband carrier signal
is shifted in the frequency spectrum. This paper presents the design and
analysis of a two-stage baseband carrier recovery algorithm for
software-defined radio (SDR). The first-stage frequency-locked loop calculates
a coarse estimate of the baseband carrier frequency. After a predetermined settling time, the
coarse estimation stage switches to the second stage, in which fine tracking is
performed by digital phase-locked loop. Two methods for the first-stage coarse
carrier frequency estimation are compared. The first uses a feed-forward
method, while the second method uses a feedback mechanism. The algorithms are
implemented as part of an SDR modem running on a Freescale DSP56311 digital
signal processor. Care is also taken in ensuring efficient implementation, e.g.
by avoiding operations such as division, and by avoiding computationally
intensive calculations.