|
|
|
Issue 1, Volume 7,
January 2008
Title
of the Paper: A Simple Adaptive p-persistent MAC Scheme for Service
Differentiation and Maximum Channel Utilization
DOWNLOAD FULL PDF
Authors:
Bai Xiang, Mao Yu-Ming
Abstract: In this paper, we propose an adaptive p-persistent MAC scheme,
named QDA-MAC (QoS differentiation based adaptive MAC scheme), for WLAN to
maximize the channel utilization and provide the service differentiation
among different traffic stations. Specifically, different from the previous
works, the proposed scheme does not need to estimate the number of active
stations for each priority class and still achieves the channel utilization
close to its optimal value by exploiting a new parameter, persistent factor,
whose optimal value can dynamically follow the change of the load based on a
simple estimation of the network status. At the same time, the transmission
probability of each priority class can be updated by optimal persistent
factor. Simulation and numerical results show that QDA-MAC can achieve much
higher channel utilization and shorter delay than standard IEEE 802.11 DCF
and IEEE 802.11e EDCA in all different WLAN environments.
Keywords: QoS differentiation; p-persistent; persistent factor;
adaptive scheme; transmission attempt
Title
of the Paper: New Algorithm for Power Control in Cellular Communication
with ANFIS
DOWNLOAD FULL PDF
Authors:
Shahab Asoodeh
Abstract: Transmitter power is an important resource in cellular mobile radio
systems. Effective power control can increase system capacity and quality of
service. A commonly used measure of the quality of service is the Carrier to
Interference Ratio (CIR) at the receiver. The main idea on power control
schemes is to maximize the minimum CIR in each channel of system. In this
paper a new adaptive neuro fuzzy distributed power control algorithm which
can be used to maximize the minimum CIR among all of co-channel users, has
been introduced. Simulations and results have been compared with classical
method and show that intelligent control system has better performance than
other existing methods.
Keywords: Cellular mobile communication, Power control, ANFIS, MF
Title
of the Paper: Design of Optimal Space-Time Codes in TDD/TDMA 4G
Systems
DOWNLOAD FULL PDF
Authors:
Zhaogan Lu, Jincang Han, Paul Fahamuel, Taiyi Zhang
Abstract: Under the scenarios of fast mobile frequency selective channels, it
is a very intractable issue to design the optimal space time codes (ST) that
can achieve the optimal diversity and multiplexing gains tradeoff with
full-diversity full-rate (FDFR) constrains. Therefore, an optimal space time
design scheme is given in this paper for one novel 4G cellular communication
systems with time division duplex (TDD) and time divisions multiple access
(TDMA). The system is designed to overcome the great channel estimation
overhead and the complexity of multiple user detectors in the cases of
multiple antennas at transceivers. Here, one FDFR code given in recent
literatures is adopted for the proposed TDD/TDMA 4G systems, which was proved
in this paper to achieve the optimal diversity-multiplexing gain tradeoff. In
typical cellular channel profiles, several space time schemes with optimal or
sub-optimal tradeoff are tested with TDD/TDMA 4G systems with 8x2 antenna
configurations at base and mobile stations respectively. Numerical results
show that the FDFR design could achieve the maximal system throughout with
better adaptive capacity to wireless link states than that of space time
block codes (STBC) and Diagonal Bell Laboratories Layered Spare-Time Codes
(D-BLAST). Furthermore, the performance of the proposed FDFR design for
TDD/TDMA 4G systems could achieve better tradeoff for throughput and system
symbol error rates than that of the cyclic-division-algebra (CDA) space time
codes.
Keywords: MIMO, diversity and multiplexing tradeoff, 4G, space time
codes, full-diversity and full-rate
Issue 2, Volume 7,
February 2008
Title
of the Paper: Energy Balancing by Combinatorial Optimization for
Wireless Sensor Networks
DOWNLOAD FULL PDF
Authors:
J. Levendovszky, A. Bojarszky, B. Karlocai, A. Olah
Abstract: In this paper novel protocols are developed for wireless sensor networks
(WSNs) in order to ensure reliable packet transmission and maximize lifespan
at the same time. The optimal transmission energies are derived which
guarantee that the packets are received by the Base Station (BS) with a given
reliability subject to achieving the longest possible lifespan. These
protocols can be applied in biomedical applications where energy consumption
and longevity is of crucial importance. The optimization has been carried out
for the chain protocol (when nodes are forwarding the packets toward the BS
via the neighbouring nodes) and for the shortcut type of protocols (when a
packet may get to the BS by being first transferred in the chain up to a
certain node which then sends it directly to the BS). The new results have
been tested by extensive simulations which also demonstrated that the
lifespan of WSN can significantly be increased by the new protocols.
Keywords: Communication systems, Communication system routing, Network
reliability, Protocols.
Title
of the Paper: Push-Pull Incentive-based P2P Live Media Streaming System
DOWNLOAD FULL PDF
Authors:
Poo Kuan Hoong, Hiroshi Matsuo
Abstract: Peer-to-peer (P2P) file sharing has become increasingly popular,
accounting for as much as 70% of Internet traffic by some estimates. Recently,
we have been witnessing the emergence of a new class of popular P2P
applications, namely, P2P audio and video streaming. While traditional P2P
file distribution applications target elastic data transfers, P2P streaming
focuses on the efficient delivery of audio and video content under tight
timing requirements. In these applications, each node independently selects
some other nodes as its neighbors and exchanges streaming data with
neighbors. In this paper, we propose and investigate a full distributed,
scalable, and cooperative protocol for live video streaming in an overlay
peer-to-peer network. Our protocol, termed P2P Unstructured Live Media
Streaming (PALMS), makes use of combination of push-pull score-based
incentive method to achieve high performance (in term of delay, stream
continuity, cooperation, etc.). The main contribution of PALMS is that it
reduces the end-to-end streaming delay and in turn results better delivered
quality. Furthermore, with the implementation of score-based incentive
mechanism, PALMS is resilient to existence of free-riders and encourage
cooperation among participating nodes. We have extensively evaluated the
performance of PALMS. Our experiments demonstrate that PALMS achieves good
streaming quality even under the existence of free-riders.
Keywords: peer-to-peer, streaming, free-riders, overlay, push-pull
Title
of the Paper: Diversity Techniques to
Combat
Fading in WiMAX
DOWNLOAD FULL PDF
Authors:
Anou Abderrahmane, Mehdi Merouane, Bensebti Messaoud
Abstract: The IEEE 802.16 standard is often referred to as WiMAX today. It
represents a distillation of the most advanced technology and an industry
consensus permitting equipment interoperability. It holds the promise of
delivering high speed internet access to business and residential customers
and to remote locations where traditional broadband services are unavailable.
In the present work, the PHY specified for the Wireless MAN-OFDM case is
studied and implemented. Various modulation techniques involved are explored
and each of the performances enhancing techniques is evaluated with regard to
its functionality in the system. The simulation results show that the
Space-Frequency Coded system coupled with Reed-Solomon codes and
Convolutional codes efficiently exploits diversity techniques.
Keywords: WiMAX, BWA, OFDM, MIMO, STBC, Convolutional Codes,
Reed-Solomon codes
Title
of the Paper: Information-Theoretic Comparison of Channel Capacity for
FDMA and DS-CDMA in a Rayleigh Fading Environment
DOWNLOAD FULL PDF
Authors:
Panagiotis Varzakas
Abstract: In this paper, a comparative estimate of the channel capacity
assigned to each user for frequency-division multiple-access (FDMA) and
direct-sequence code-division multiple-access (DS-CDMA) schemes operating in
a Rayleigh fading channel is presented. Then, the achievable channel capacity
per user (in the Shannon sense) is estimated in an average sense considering
the inherent diversity potential that both schemes provide in a Rayleigh
fading channel. The non-equal user rate for the DS-CDMA case is studied,
considering the ratio of two neighboring user channel capacities. Hence, it
is shown that, in contrast to the equal user rate, for non-equal user rate
case in DS-CDMA and under normalized conditions, the average channel capacity
per user, in FDMA, is higher than that of DS-CDMA and this result is
quantitatively evaluated in terms of a defined average capacity gain factor.
Keywords: Channel capacity, code-division multiple-access,
frequency-division multiple-access, Rayleigh fading.
Title
of the Paper: A New Group Mobility Model for Mobile Adhoc Network based on
Unified Relationship Matrix
DOWNLOAD FULL PDF
Authors:
S.
Gunasekaran, N.
Nagarajan
Abstract: is meaningful when they use realistic movement mobility models,
which directly impacts the performance of the protocols. Once the nodes have
been initially distributed, the mobility model dictates the movement of the
nodes within the network. If this movement is unrealistic, the simulation
results obtained may not correctly reflect the true performance of the
protocols. The majority of existing mobility models for adhoc networks do not
provide realistic movement. Mobility model based on social network theory
predicts the node movements more realistic. Our paper reinforces the model by
using Unified Relationship Matrix, which improves the movements of groups. Unified
Relationship Matrix helps to represent the relationships of inter and intra
type of nodes. Movements of nodes and groups are evaluated by keeping a small
distance between each node and maintaining each group velocity, direction and
movements. Group velocity is calculated by inter relationship matrix and
cumulative nodes velocity. Group movements are calculated and directed by
Unified Relationship Matrix.
Keywords: Adhoc networks, Mobility, Social Networks, Unified
Relationship Matrix, Mobile Nodes, Mobile Groups
Title
of the Paper: Performance Improvement of Clustered Mobile Ad hoc Networks
using a CDMA Single Channel and Based on Admission Control Approach
DOWNLOAD FULL PDF
Authors:
Zouhair El-Bazzal, Michel Kadoch, Basile Agba, Francois Gagnon
Abstract: Clustering has been proven to be a promising approach for mimicking
the operation of the fixed infrastructure and managing the resources in
multi-hop networks. In this paper, we propose an Efficient Clustering
Algorithm (ECA) in Mobile Ad hoc Networks based on the quality of service’s
(QoS) parameters (cluster throughput/delay, packet loss rate). The goals are
yielding low number of clusters, maintaining stable clusters, and minimizing
the number of invocations for the algorithm. The performance changes greatly
for small and large clusters and depends strongly on the formation and
maintenance procedures of clusters which should operate with minimum
overhead, allowing mobile nodes to join and leave without perturbing the
membership of the cluster and preserving current cluster structure as much as
possible. In this manner, while QoS does not perform well under high traffic
load conditions, admission control becomes necessary in order to provide and
support the QoS of existing members. Based on the results from the proposed
analytical model, we implement a new admission control algorithm that
provides the desired throughput and access delay performance in order to
determine the number of members inside an ECA cluster that can be
accommodated while satisfying the constraints imposed by the current
applications. Through numerical analysis and simulations, we have studied the
performance of our model and compared it with that of WCA. The results demonstrate
the superior performance of the proposed model.
Keywords: Clustering, Weight, Election, Throughput, Delay
Title
of the Paper: Channel Coding as a Cryptography Enhancer
DOWNLOAD FULL PDF
Authors:
Natasa Zivic, Christoph Ruland
Abstract: In this work, channel decoding is considered as a promising way for
improvement of cryptographic functions. Use of MAC/H-MAC values and digital
signatures is analyzed in a context of code concatenation, together with
convolutional codes using MAP decoding algorithm. Soft Input Decryption
method, which uses L-values from channel decoder, presents an efficient
method for integrating cryptography into decoding. The results of computer
simulations that implement this method have been also presented. Additionally,
the number of L-values verifications has been tested and compared with the
theoretical results.
Keywords: Soft Input Decryption, Code Concatenation, L-values,
MAC/H-MAC, MAP, Channel Decoding, Turbo Decoding, CCER
Title
of the Paper: Challenge of Channel Estimations and Its Way Out in MIMO
OFDM Systems for Mobile Wireless Channels
DOWNLOAD FULL PDF
Authors:
Zhaogan Lu, Taiyi Zhang, Zhengwei Gong, Liejun Wang
Abstract: In current common channel estimation schemes for MIMO OFDM systems,
channel state information is usually achieved by estimating channels
according to frequency domain pilot sequences. However, when the length of
MIMO OFDM symbols is larger than that of wireless channel delay, there are
two intractable issues in the case of cellular fast fading channel scenarios
with large numbers of users, i.e., the bandwidth overhead of channel
estimation and the difficulty to construct large numbers of orthogonal
training sequences. Inspired from the Steiner channel estimation method in
multi-user CDMA uplink wireless channels, we proposed a new design scheme of
training sequence in time domain to conduct channel estimation in MIMO OFDM
systems. According to the proposed schemes, training sequences of different
transmit antennas can be simply obtained by truncating the circular extension
of one basic training sequence, and the pilot matrix assembled by these
training sequences is one circular matrix with good reversibility. Furthermore,
when the length of channel profiles is less than that of MIMO OFDM symbols,
more bandwidth resources can be saved, as the training sequence only occupies
a part of MIMO OFDM symbols. At last, we analyze the classical common time
and frequency domain schemes in terms of channel overheads and computation
complexity, and the results disclose the proposed scheme can be one way out
for current common frequency domain channel estimation issues. For typical
ITU indoor, pedestrian and vehicular channel profiles, the corresponding
numerical results indicate the proposed method can save abundant bandwidth
and achieve good channel estimation accuracy when compared with classical
frequency and time domain approaches, respectively.
Keywords: channel estimation, wireless communications, MIMO, OFDM,
pilot sequences
Title
of the Paper: Yaw Phase Mode Attitude Control Using Z Wheel for LEO
Microsatellite
DOWNLOAD FULL PDF
Authors:
A.
M. SI Mohammed, M. Benyettou, A. Boudjemai Y. Hashida, M.
N. Sweeting
Abstract: A control system is proposed for a low Earth orbit gravity gradient
stabilised microsatellite using Z wheel. The microsatellite is 3-axis
stabilized using a yaw reaction wheel, with dual redundant 3-axis
magnetorquers. Two vector magnetometers and four dual sun sensors are carried
in order to determine the full attitude. The attitude was estimated using an
Euler angles (small libration version) on based extended Kalman filter (EKF).
After the satellite has been detumbled and deploy the gravity gradient boom,
in order to have the accurate Nadir pointing we will use the Z zero-bias mode
controller. The Z momentum wheel will be damped by the magnetorquers. This
paper describes the attitude determination and control system design of LEO
microsatellite using Z reaction wheel for yaw phase mode control.
Keywords: Modelling, Simulation, Microsatellite, LEO, Attitude, Yaw,
Control, Z Wheel, Magnetorquer.
Title
of the Paper: Two-Valued Integrand Coding Transmission of Multi-Rate
Quasi-Synchronous CDMA Signals Convolved by Real-Valued Self-Orthogonal
Finite-Length Sequences
DOWNLOAD FULL PDF
Authors:
Jiong Le, Yoshihiro Tanada
Abstract: The next generation mobile communication system is desired to
transmit multimedia information at multi-rate. Two-valued integrand codes are
applied to the realization of the multi-rate quasi-synchronous CDMA system
using real-valued self-orthogonal finite-length sequences with zero correlation
zone. Each user data of multi-level and multi-interval and a common
synchronizing sequence are convolved with the user sequence and converted to
two-valued integrand coding signal. The signal passes through low pass
filters in a transmitter and a receiver and is changed to a real-valued
signal. In the receiver, the desired data are detected by the correlation
processing with the respective code. This transmission system suppresses
distortion on amplitude limitation and quantization, and interchannel and
intersymbol interferences. Two-valued integrand coding contributes to easy
amplification and modulation.
Keywords: multi-rate transmission, two-valued integrand code,
self-orthogonal finite-length sequence, zero correlation zone, convolution,
amplitude distortion, quasi-synchronous CDMA.
Title
of the Paper: Identification of Communication Solution designated for
Transport Telematic Applications
DOWNLOAD FULL PDF
Authors:
Tomas Zelinka, Miroslav Svitek
Abstract: Communications solution represents one of the key parts of the
Intelligent Transport system (ITS). Goal of our research is to improve
over-ground traffic efficiency and security, specifically on the airport
territory, where pilot installation was set-up and tested with aim to confirm
its ability to improve conditions for efficient management of the over-ground
traffic of all moving object in area including moving aircrafts and all types
of service vehicles. ITS system requirements on the communications
environment are usually quantified indirectly by telematic sub-system
performance indicators. Correct selection and configuration of the
appropriate communication solution are achievable, if "transformation
matrix" between vectors of communications and telematic performance
indicators is correctly identified. Principles of developed method based on
such transformation matrix identification are introduced. Application of the
proposed methodology is demonstrated on the CaMNA communications system
identification and its parameters settings. Airport territory has got quite
complex arrangement and there are very different requirements on telematic
system performance in different parts of the airport area. This fact leads to
application core wireless access service securely combined with set of the
alternative technologies applied in areas, where the core service is not
available for technical or economical reason. Management of such system is
based on implementation of the CALM family of standards or its mutations with
implemented effective and safe decision processes. Correctly designed
decision processes supporting selection of the “best possible” alternative
represent one of key issues of the whole solution. Results of the
communication solution parameters tests processed within limited pilot
installation and relevant recommendations are presented as the last part of
this paper.
Keywords: Intelligent Transport Systems, Telecommunications
Performance Indicators, Telematic Performance Indicators, Global Navigation
Satellite System, handover, Quality of Service
Title
of the Paper: Middleware Design of Bandwidth Constrained QoS Model for
Multi Hop Ad Hoc Networks
DOWNLOAD FULL PDF
Authors:
M.
Sulleman Memon, Niaz A.
Memon,
Manzoor Hashmani
Abstract: Middleware is actually a resource manager that guarantees the implementation
of all policies, contracts to be satisfied, and it ensures that contracts do
not go beyond the limits of network capacity. It also authentication, so that
only the legitimate users could avail the network resources according to the
agreed format. The middleware is supposed to be the backbone for QoS
assurance and the system behavior depends on it. This paper proposes design
of a middleware based on a bandwidth constrained QoS model for multi hop ad
hoc networks. Our model is designed not only on the basis of
conceptualization but we have considered the basic functionalities available
in networking equipments like routers etc. The elements of QoS aware
middleware are admission control, resource reservation, policy control and a
feedback module. Finally we discuss our future work to find the primary and
alternative route to the destinations by keeping the bandwidth constraints in
mind.
Keywords: Multi hop, Ad hoc Networks, Packet Classifier, Resource
Reservation, Quality of Service, Real Time Applications
Issue 3, Volume 7,
March 2008
Title
of the Paper: Performance Evaluation of IEEE 802.1x Authentication Methods
and Recommended Usage
DOWNLOAD FULL PDF
Authors:
Monis Akhlaq, Baber Aslam, Muzammil A Khan, John Mellor, M Noman Jafri,
Irfan Awan
Abstract: The wide spread acceptance of IEEE WLANs is a result of industrial
standardization to ensure product compatibility and reliability among various
manufacturers. Several WLANs solutions are available with varying
characteristics and interoperability. The IEEE Standard 802.11 is one of the
most widely adopted mechanisms for wireless LANs. It defines both physical
(PHY) and medium access control (MAC) layer protocol however; it provides
limited data confidentiality and has cumbersome procedure for key exchange. In
response IEEE introduced a port based network access control standard 802.1x
to authenticate and authorize devices interconnected various IEEE 802 LANs.
802.1x only defines authentication not the actual authentication method which
allows the developers to construct their own algorithm and consequently a lot
of wireless vendors implemented their own 802.1x adaptation such as MD5
Message Digest 5 , TLS (Transport Layer Security) , TTLS (Tunneled TLS) ,
PEAP (Protected Extensible Authentication Protocol), LEAP (Lightweight
Extensible Authentication Protocol) and others. This versatility in 802.1x
adaptations has made it difficult for the WLANs users to choose an
appropriate mechanism in relation to performance and security of networks. An
effort has been made in [1] to carry out comparative analysis of IEEE
authentication methods in different security combinations. This work
supplements the efforts cited in [1] and incorporates more results in added
network configurations. The paper finally recommends the users an appropriate
IEEE authentication methods depending upon the need, requirements and
security concerns.
Keywords: Authentication, Packet, Round Trip Time, Security,
Throughput, Wireless LANs, 802.1x.
Title
of the Paper: Requirements for a New Resource Reservation Model in Hybrid
Access Wireless Network
DOWNLOAD FULL PDF
Authors:
Tudor Palade, Emanuel Puschita
Abstract: The wireless systems entered a phase characterized by the
integration of the existing platforms into hybrid access wireless IP
architectures. The requests of the real time applications ran in heterogeneous
environments need the presence of a mechanism for resource negotiation and
management. The paper suggests the design and implementation of an
inter-domain QoS mechanism in a hybrid access wireless IP architecture using
mobile agents. The hybrid access wireless IP architecture intends to
integrate wireless spatial and terrestrial wide area networks, and wireless
metropolitan and local area networks. The demands imposed to the inter-domain
QoS mechanism recommend the use of mobile agents as an alternative to the
classical method of resource reservation and QoS parameters transfer. In
order to provide the quality of services, mobile agents act on behalf of the
user. Inter-domain QoS support proposed by this mechanism needs the
accomplishment of three phases: resource negotiation, resource allocation,
and resource management. Each phase is associated to a corresponding specific
profile. The purpose of the mobile agents is to determine the selection of a
corresponding profile according to the negotiated set of QoS parameters.
Keywords: Resource Reservation, QoS Mechanisms, Hybrid Wireless Access
Title
of the Paper:
The System Transfering between Laser-Satellites
DOWNLOAD FULL PDF
Authors:
Marketa Smejkalova Mazalkova
Abstract: Laser inter-satellite communication is on the verge of becoming a
reality. It will be a key building block for wide-area space data networks of
the future. Design methodologies treating these as complex engineering
systems, and the technique to break down the systems into interacting but
logically separate subsystems for design and analysis, will be suggested. The
paper involves the introduction into laser inter-satellite communication
system. The paper includes briefly analysis, optimization and subsystems
design (three independent links) and system level development of signal
transferring between two GEO satellites. Research opportunities in this area
include development of laser beam acquisition, tracking and pointing
techniques and algorithms, development of computer aided analysis link budget
for the free space channel, systems engineering (analysis and design) of
optical transmission development of high efficiency flight qualifiable
solid-state lasers, fast fine-pointing mirrors high update-rate acquisition
and tracking cameras and very low-noise high-quantum efficiency receiver.
Keywords: Acquisition, tracking, data transfer, laser, satellite
systems, laser communication, space channel
Title of
the Paper: Network Architectures Exploiting Multiple HAP Constellations
for Load Balancing
DOWNLOAD FULL PDF
Authors:
Tine Celcer, Ales Svigelj, Mihael Mohorcic
Abstract: This paper addresses network architectures in a constellation of
high altitude platforms (HAPs) with overlapping coverage areas, focusing on
the additional network elements/functionalities required to make use of load
balancing mechanisms. According to the location within the network and the
complexity of additional equipment/ functionality the paper proposes two
different architectures. In the case of the basic utilisation of multiple
HAPs a new equipment/functionality is installed only at the user premises,
supporting load balancing only for the connections initialised from the HAP
user network to the Internet (i.e. the outbound connections). In the case of
advanced utilisation of multiple HAPs a new equipment/functionality is needed
both at the user premises and in the HAP network, thus supporting load
balancing in both directions. For the performance evaluation of load
balancing mechanisms we built a simulation model supporting typical
applications such as e-mail, file transfer, web browsing and IP telephony. Simulation
results confirm that in the case of traffic load close to the congestion load
balancing mechanism significantly improves the performance of selected
reference applications. In order to asses the feasibility of the proposed
network architectures in a multiple HAP system, and to confirm that carefully
designed and pointed directional user antennas allow establishment of
multiple access links for load balancing and to improve resilience of the
network, we also investigate HAP visibility distribution across the coverage
area for a single HAP system and a system comprising 4 HAPs.
Keywords: High Altitude Platforms, network architectures, load
balancing, multiple HAP constellation
Title
of the Paper: Using Randomized Association ID to Detect and Prevent
Spoofed PS-Poll Based Denial of Service Attacks in IEEE 802.11 WLANs
DOWNLOAD FULL PDF
Authors:
Zaffar I. Qureshi, Baber Aslam, Athar Mohsin, Yonus Javed
Abstract: Wireless Local Area Networks (WLAN) provide connectivity along with
flexibility at low cost. Appreciating the exponential growth in this area,
the Institute of Electrical and Electronics Engineers (IEEE) ratified IEEE
standard 802.11
in 1999 which was widely accepted as
the defacto industry standard for interconnection of portable devices. Due to
the scarcity of battery power in portable devices operating in WLANs, IEEE
802.11 directly addressed the issue of Power Saving (PS) and defined a whole
mechanism to allow stations (STA) to go into sleep mode without losing
information, as Access Point (AP) keeps buffering the messages directed to
the sleeping STA. Growing use of IEEE 802.11 lead to the identification of
flaws in security specifications of the standard known as Wired Equivalent
Privacy (WEP). These flaws were addressed by the introduction of
amendments/enhancements. However, IEEE‟s
security enhancements failed to achieve desired objectives especially
availability, which is the main concern of any network administrator. Identity
theft due to unauthenticated management and control frames left a window open
for hackers to launch successful Denial of Service (DoS) attacks. The PS
functions of 802.11 present several identity based vulnerabilities,
exploiting which, an attacker can spoof a polling message on behalf of STA
and cause AP to discard buffered packets of the client while it is asleep. As
a result, an attacker can block victim STA from receiving frames from AP,
thus launching a successful DoS attack. The mechanism proposed in [1]
addresses the issue of spoofed PS-Poll based DoS attack and proposes a robust
solution to this problem. Although the proposed solution was a novel idea;
however it was only a mathematical analysis, not verified or tested by
implementation on hardware or through simulation. In this extended version of
the paper, an endeavor has been made to implement the theoretical idea and
validate the mathematical calculations through simulation.
Keywords: Wireless security, Denial of service DoS, 802.11, Power
Saving PS, PS-Poll, Association ID
Title
of the Paper: Design of Broad-Beam Microstrip Reflectarray
DOWNLOAD FULL PDF
Authors:
Piyaporn Krachodnok, Rangsan Wongsan
Abstract: The reflectarray’s elements arrangement for generating an arbitrary
phase distribution in the antenna aperture and thus a wide beamwidth of the
far field pattern is presented. The desired phase delay of reflectarray
elements, which duplicated the same radiating aperture as backscatters, is
determined on the construction of the curvature of a shaped backscatter
surface with the help of Snell's law for beam forming to cover a broad area. The
Method of Moments (MoM) and the infinite-array are applied to calculate
reflection phase characteristics. The phase and radiation pattern synthesis
method for microstrip reflectarray that has to illuminate a predefined
circular area are presented by using a variety of discretization of
elementary geometrical functions such as, triangular, quadratic, circular,
gaussian, cosine, squared cosine, and parabolic distributions. These
backscatter functions are discussed in terms of merits and demerits to find
appropriate radiation characteristics such as radiation pattern, -3 dB
beamwidth, and maximum gain for utilization in Wireless Local Area Network
(WLAN) application. The optimized feed distance is calculated from the
aperture efficiency by considering feed blockage efficiency and the influence
of the feed position on the -3 dB beamwidth and gain performance has been
investigated. Having confirmed the validity of this approach, the X-band
antenna prototype is designed and developed. This reflectarray is tested
experimentally and shows good performance.
Keywords: reflectarray, phase array, broad-beam antenna
Title
of the Paper: Binomial and Monotonic Behavior of the Probability of
Undetected Error and the 2-r-Bound
DOWNLOAD FULL PDF
Authors:
Wacker H. D., Boercsoek J.
Abstract: Proper linear codes play an important role in error detection. They
are characterized by an increasing probability of undetected error pue(ε,C) and
are considered “good for error detection”. A lot of CRCs commonly used to
protect data transmission via a variety of field busses are known for being
proper. In this paper the weight distribution of proper linear codes on a
binary symmetric channel without memory is investigated. A proof is given
that its components are upper bounded by the binomial coefficients in a
certain sense. Secondly an upper bound of the tail of the binomial is given,
and the results are then used to derive estimates of pue(ε,C). If a
code is not proper, it would be desirable to have at least subintervals,
where pue(ε,C)
increases, or where it satisfies the 2-r-bound. It is for this
reason that next the range of monotonicity and of the 2-r-bound is
determined. Finally, applications on safety integrity levels are studied.
Keywords: Binary Symmetric Channel, Proper Linear Code, CRC,
Probability of Undetected Error, Weight Distribution, Binomiality,
Monotonicity, 2-r-bound, Dual Distance, Safety Integrity Level
Title
of the Paper: 802.11 Disassociation DoS
Attack Simulation
using Verilog
DOWNLOAD FULL PDF
Authors:
Baber Aslam, Monis Akhlaq, Shoab A. Khan
Abstract: A number of Denial of Service (DoS) attacks in IEEE 802.11 are due
to unauthenticated/ unencrypted management and control frames. Current IEEE
802.11 simulators deal with Physical and MAC layers and do not include the
exchange of management and control frames, thus making it difficult to
simulate an attack (DoS) and its possible solution. A basic IEEE 802.11
network simulator using Verilog is presented. Basic aim is to design a
simulator using a hardware description language (HDL) such as Verilog, since
the functions and protocols described in state machines are best simulated
using a HDL. Besides simulation of a simple wireless network, the paper also
presents simulation of a spoofed MAC disassociation DoS attack and one of its
possible solutions. The proposed simulator includes the communication setup
process and can be used for simulating other DoS attacks and their possible
solutions.
Keywords: Network Simulator, IEEE 802.11, Verilog, Wireless LAN, Link
layer simulation.
Title
of the Paper: An Efficient Scheduling Mechanism for Simulating Concurrent
Events in Wireless Communications Based on an Improved Priority Queue (PQ)
TDM Layered Multi-Threading Approach
DOWNLOAD FULL PDF
Authors:
P.
M.
Papazoglou, D.
A.
Karras, R.
C.
Papademetriou
Abstract: The physical activities of a real wireless network are represented
by events which are the main components of a discrete event simulation (DES)
system and are produced by its event generator during simulation time. Each
network service (e.g. voice, data and video) constitutes an event for a
particular mobile user. A critical component within the simulation system,
called scheduler, runs by selecting the next earliest event, executing it
till completion, and returning to execute the next event. Calendar queue is
the state of the art implementation of the scheduler among the most popular
networking simulation tools such as ns-2. However, Calendar queue
time-stamping mechanism presents drawbacks in the case of complex dynamical
systems, like wireless networks, where probability of events concurrency is
large. In such a case sequential time-stamping of calendar queue scheduling
does not reflect real network events occurrence and generation. It should be
remarked that there are very few reports if any in the literature concerning
research on events scheduling mechanisms in such real time systems. On the
other hand, multi-threading technology offers advanced capabilities for
modelling concurrent events. The main goal of this paper is to illustrate
that multithreading architectures provide the means for designing efficient
schedulers in the simulation of wireless networks resource allocation but,
also, several critical issues such as deadlocks, synchronization and
scheduling must be effectively faced. In this paper, a stable simulation
model is presented based on a novel layered thread architecture and on an
alternative network event scheduling mechanism, called the Priority Queue
(PQ) – Time Division Multiplexing (TDM) Layered Multithreading mechanism,
which supports concurrent events as compared to the state of the art approach
which supports only sequential events. Moreover, specific drawbacks of the
JVM multi-threading platform such as thread execution unpredictability are
also faced and presented.
Keywords: cellular network, simulation, event scheduling, concurrent
events, multi-threading
Title
of the Paper: Simulation for Different Order Solitons in Optical Fibers
and the Behaviors of Kink and Antikink Solitons
DOWNLOAD FULL PDF
Authors:
Mohammad Mehdi Karkhanehchi, Mohsen Oliaee
Abstract: Solitons are obtained by interaction effect of nonlinear effect and
dispersion, so that nonlinear differential equation, KDV, is indicated to
this matter. To understand how solitons are created and propagated, this
equation has to be solved. The solution describes first, second and third
order solitons family. Transmission relation is found by inverse scattering
transform (IST) method. Also, the dynamic behavior of the Kink and Antikink
solitons has been investigated by Sine- Gorden equation in physical systems. This
equation has significant role in various physical branches. In optical fiber,
Kink and Antikink solitons keep their forms when they propagate in fiber
length. Because of indirect loss effect on nonlinear higher order, numerical
simulation of those solitons is necessary. Therefore, Sine- Gorden equation
has to be solved analytically.
Keywords: solitons, optical fiber, nonlinear optics, KDV equation,
Sine-Gorden equation, optical communication
Issue 4, Volume 7, April 2008
Title
of the Paper: Automatic Extraction Method of Airport Object in Aerial
Imagery
DOWNLOAD FULL PDF
Authors:
Guang Yang, Bai Zhang, Xiaojuan Wang, Zongming Wang, Guoxin Wu
Abstract: Along with the progress of each basic theories in the picture
science, the numerical picture processing technique gets the extensive
application in each section of national economy, moreover, it has become
study hotspot that is automatic identify in panchromatic aerial image. A kind
of MF method to extract airport in aerial image was put forward on analysing
template match and characteristic extraction. It brought forward a template
match method to resolve that because of the information covering to have
great capacity in aviation photograph, the hair stabs ordering more, operating
great, and so on. It obtained the better result.
Keywords: Threshold segmentation, Remote sensing image, Panchromatic
aerial image, Airport object, Image segmentation, Template match,
Characteristic extraction.
Title
of the Paper:
Human Exposure Assessment in the Vicinity of 900 MHz GSM Base Station Antenna
DOWNLOAD FULL PDF
Authors:
Mimoza Ibrani-Pllana, Luan Ahma, Enver Hamiti,
Ruzhdi Sefa
Abstract: Daily exposure to GSM electromagnetic fields has raised public
concern of possible adverse health effects to people living in the vicinty of
base station antennas. International guidelines and standards established for
limiting human exposure to electromagnetic fields are given in two
categories: Basic restrictions (SAR, induced current density, and induced
power density) and Reference levels (free space electric field intensity,
magnetic field intensity and power density). In order to check compliance for
both categories, in this papers are presented measurements of incident
electric field and obtained results are used for numerical prediction of SAR.
Measurements of field strength and power flux density are performed on
locations few meters away from base station antenna, in different levels,
with and without usage of mobile phones, during day and in peak hours of GSM
system usage. Results are compared with ICNIPR Guidelines, IEEE and CENELEC
standards.
Keywords: base station antennas, field strength, power density, GSM,
measurement
Title
of the Paper: Analysis of Non-Linear Response in DS-CDMA Satellite Systems
DOWNLOAD FULL PDF
Authors:
Mario Reyes-Ayala, Edgar Alejandro Andrade-Gonzalez, Jose Alfredo Tirado-Mendez, Hildeberto Jardon Aguilar
Abstract: This paper shows an algorithm to calculate synchronous DS-CDMA
satellite links with non-linear response amplifiers, where the probability
error, active device parameters, harmonics, intermodulation products and
back-off compensation, are used to evaluate the performance of the system. The
analysis of carrier to interference ratio is carried out for N-carrier
up-link, where a single carrier uses DS-CDMA.
Keywords: Harmonics, Intermodulation, DS-CDMA, link budget, HPA,
carrier to interference ratio.
Title
of the Paper: Analytic Solution of Nadir Attitude Pointing for LEO
Microsatellite
DOWNLOAD FULL PDF
Authors:
A.
M. SI Mohammed, M. Benyettou, A. Boudjemai Y. Hashida, M.
N. Sweeting
Abstract: An Analytic solution of Nadir attitude pointing equation of gravity
gradient satellite stabilised is presented. The attitude equation is Euler linearised
equation for near Nadir pointing axially symmetric satellite including only
gravity gradient torque and assuming other torques such as magnetic torque,
aerodynamic torque, solar radiation pressure torque and controller are
constants. The obtained analytical solution was compared to numerical
solution of satellite attitude equation.
Keywords: LEO, Microsatellite, Alsat-1, Analytic, Nadir, Attitude,
Simulation.
Title
of the Paper: An Adaptive Weighted Cluster Based Routing (AWCBRP) Protocol
for Mobile Ad-hoc Networks
DOWNLOAD FULL PDF
Authors:
S.
Karunakaran, P.
Thangaraj
Abstract: Nodes of Wireless Adhoc networks have restricted bandwidth resource,
and comprise high mobility. It has a high link breakage rate and so
partitioning rate of the network is considerably high. Routing in MANET’s is
very complex because of node mobility and limited communication resource. Topology
changes and breakage of exiting paths occurs repeatedly due to the mobility
of nodes. A routing protocol should quickly adapt to the topology changes and
efficiently search for new paths with minimal power consumption. We propose
an adaptive weighted cluster based routing for mobile ad-hoc networks which
amends swiftly to the topological changes and establishes the routing
efficiently. In our proposed approach, the cluster head selection is
performed by assigning a weight value based on the factors Energy Level,
Connectivity and Stability. We show by simulations, that the performance of
our proposed protocol surpasses the existing adhoc routing protocols in all
aspects.
Keywords: Ad-hoc networks, MANETs, Clustering, Multipath, Routing.
Title
of the Paper: Combination of Service Learning and Pre-Service Teacher
Training via Online Tutoring
DOWNLOAD FULL PDF
Authors:
Chun Hung Lin, Eric Zhi Feng Liu, Hwa Wei Ko, Shan Shan Cheng
Abstract: During the teacher training process, service learning is an
important element which can improve per-service teachers’ teaching skills and
increase their understanding about their students. This study integrated the
concept of service learning into pre-service teacher training via online
instruction. Fifty-four pre-service teachers participated in this program.
X-learning system, an online tutoring system was provided by Chunghwa
Telecom. Each pre-service teacher taught one rural area student by X-learn
system. Through video record, interviews, and reflective journal, this study
demonstrated how the pre-service teachers taught their students in online
instruction, and what benefit the pre-service teachers gained from
participating in this program.
Keywords: Online instruction, Service learning, Pre-service teacher
training, E-tutor, One-on-one tutoring, X-learn system
Title
of the Paper: Bandwidth Management Method for Heterogeneous Wireless
Network
DOWNLOAD FULL PDF
Authors:
Hui-Min Huang, Ying-Hong Wang
Abstract: The integration of heterogeneous networks is a trend of Fourth
Generation (4G) systems. But with more integrating network technologies,
bandwidth management is more complicated. This paper proposes a bandwidth
management method, called Bandwidth Management and Disposition (BMD). The BMD
calculates the Reword Point (RP) to quantify the Mobile Host’s (MH) requests,
and calculates the Upgrade Rank (UR) or Downgrade Rank (DR) to quantify the
upgraded or downgraded sequence of bandwidth, respectively. In the future,
when a new service type or network technology is created, the proposed system
functions also can be directly applied. This paper analyzes the BMD is more
feasible than the other existed methods. The simulated results also
demonstrate the functionality of the BMD. The incremental rate of achieved
request is 12.52% and rate of bandwidth usage is 2.4% when the system with
BMD. We conclude that the proposed system facilitates further development of
wireless communication networks.
Keywords: bandwidth management, heterogeneous wireless network,
hierarchical mobility management, Radio Access Technology (RAT), Reword Point
(RP), Bandwidth Management and Disposition (BMD)
Title
of the Paper: Modified Pulse 2.45 Fractal Microstrip Antenna
DOWNLOAD FULL PDF
Authors:
M. Ismail, H. Elsadek, E. A. Abdallah, A. A. Ammar
Abstract: In this paper, the idea of space-filling properties of the fractal
is used to minimize the area of a microstrip rectangular patch antenna
operating at 2.45GHz. The first iteration is in the form of a pulse and the
study includes the first four iterations. It is found that the second
iteration is the most suitable one because the third and fourth iterations
have inferior antenna parameters. The size reduction in this case is about
15.1%. In order to further reduce the antenna size many trials have been
carried out. These trials include adding a shorting wall, adding an air gap,
adding a shorting wall and an air gap together, adding a shorting wall (or
pins) together with an air gap and inverting the patch. As a consequence
46.12 % reduction in size is obtained with reasonable antenna gain. The
designed antennas were fabricated on Teflon dielectric substrates and good
agreement is found between simulated and measured results.
Keywords: Fractal, Microstrip antenna, Space-filling, and Size
reduction.
Title
of the Paper: Using TETRA for Remote Control, Supervision and Electricity
Metering in an Electric Power Distribution System
DOWNLOAD FULL PDF
Authors:
Igor Ozimek, Tomaz Javornik, Gorazd Kandus, Milan Svajger
Abstract: An important part of the communication infrastructure in systems
that cover large geographic areas and require maintenance and management of
devices on remote locations - such as electric power distribution systems -
is mobile radio communication. This is especially important on remote
locations with no other communication means available. Besides the
traditional voice communication, the new digital PMR systems also support
various modes of data communication including the IP protocol. This offers
new possibilities for remote data applications. In our paper, the
possibilities of using a TETRA system for remote data applications such as
remote control and supervision of breakers and disconnectors, and remote
electric meter reading, are analyzed for the case of the electric power
distribution company Elektro Ljubljana, d.d.
Keywords: electric power distribution, remote metering, automated
circuit breakers, PMR, TETRA
Title
of the Paper: Collaborative Middleware on Symbian OS via Bluetooth MANET
DOWNLOAD FULL PDF
Authors:
Feng Gao,
Martin Hope
Abstract: In this paper we explore the possibility of using Bluetooth in the
development of a Mobile Ad-Hoc Network (MANET) suitable for transmitting data
between Symbian OS based Smartphone’s. We also analyse the problems that
Bluetooth presents when considering existing MANET routing protocols. Then,
we present the design of a collaborative application engine by making
allowances for the restrictions associated with Bluetooth and finally we
review our current progress and consider future work.
Keywords: Bluetooth, Wireless, Collaboration, Symbian OS, MANET
|
