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Issue 1, Volume 10,
January 2011
Title
of the Paper:
Improved Power Control MAC Protocol for
wireless Ad Hoc Networks
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Authors:
Yaser Mahmood, A. Hamid, D. K. Lobiyal
Abstract: In this paper, we propose an Improved Power Control MAC (IPCM)
protocol which improves the throughput and yields energy saving. This protocol
sends all the packets RTS, CTS, DATA and ACK with optimal transmit power,
which save the energy, makes spatial reuse of the wireless channels, and
achieves the maximum throughput. On the other hand, the power of the data
packets is periodically raised to a suitable level (Pai) to avoid the
interference but not to the maximum so that it will not create unnecessary
contention between nodes. The power level of Pai is based on finding the
optimum carrier sensing range that increase the network capacity and reduce
the interference effect of the ongoing transmission. Our simulation results
show that IPCM protocol scheme can achieve high reduction in energy
consumption and also improves the throughput efficiency compared to the other
schemes.
Keywords: Ad hoc networks, IEEE 802.11, MAC protocol, power control, IPCM,DCF
Title
of the Paper:
Resource Allocation for QoS-Aware OFDMA
Cellular Networks with Cooperative Relaying
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Authors:
Xiaoyan Huang, Yuming Mao, Fan Wu, Supeng Leng
Abstract: This paper proposes a QoS-aware resource allocation scheme, called
as cooperative resource allocation scheme (CoRA), for relay-based OFDMA
systems with both QoS and Best-effort (BE) users. Using CoRA, cooperative
transmission between the Base-station (BS) and the Relay-station (RS) is
employed to fulfill the requirements of QoS users. Moreover, resource
scheduling is allowed not only at the BS but also at each RS to fully exploit
time-varying channel state and multiuser diversity, so as to achieve efficient
radio resource utilization. The design of subchannel and power allocation in
CoRA can be formulated as a non-linear combinatorial optimization problem,
which aims at maximizing the system utility while satisfying the data rate
requirements of QoS users and the separate transmission power constraints at
both BS and RSs. To address the prohibitively high computational complexity in
solving the optimization problem, we decompose the global optimization problem
in CoRA into subchannel allocation and power control sub-problems as a
suboptimal solution. Numerical results demonstrate that our proposed CoRA
scheme is able to significantly improve the network performance in terms of
power saving, user utilities, system throughput, as well as the number of
admitted users.
Keywords: Cooperative transmission, Subchannel allocation, Power control,
Quality-of-service
Title
of the Paper:
Feedforward Networks Based Straightforward
Hierarchical Routing in Solar Powered Wireless Sensor Networks
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Authors:
R. Nallusamy, K. Duraiswamy
Abstract: Wireless sensor networks play an important role in monitoring and
collecting data from difficult geographical terrains. They find useful
applications in various fields ranging from environmental monitoring to
monitoring parameters within patients in hospitals. Constraints such as
limited battery life and less processing capability of the sensors make the
routing of WSNs a tedious and challenging task. A great emphasis is laid on
the development of alternate sources of power and energy efficient routing
protocol to maximize network life. This paper proposes clustering and shortest
path based straight forward routing for solar powered wireless sensor
networks. For clustering k-means clustering algorithm is proposed. A
feedforward neural network based shortest path routing is proposed for routing
within clusters. The simulation results show that the proposed neural networks
provide quick solutions for route calculation comparing to other existing
neural networks.
Keywords: Solar powered wireless sensor networks, Feedforward neural networks,
Shortest path routing, and k-means clustering
Title
of the Paper:
Strategic Management Using VoIP Technology: a
Case Study in a Call Center Company
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Authors:
Marcelo E. Fernandes, Carlos R. C. Lima, Juliano Schimiguel
Abstract: The ability of voice transmission over TCP/IP package, also called
Voice over IP or VoIP, allows voice integration and data in just one
structure; this enables a very cheap communication among remote locations. The
main goal of this article is to analyze and demonstrate VOIP applications in
the corporate market networks, their advantages and applications on the
feasibility of tooling use in the corporate world. The method applied in this
article is qualitative, semi-structured as a unique case study. The studied
company is called KONTAK, a Brazilian organization of the call center segment
located in the east region of “Sao Paulo”. Intrinsic to the business, the
major operation costs are related to telephony management. The results show a
reduction in the calling costs among branches, customers and suppliers
obtained after the implementation of this technology, as well as a better
control of operational processes and organization management strategy in terms
of the voice and data technology management. The business feasibility is
evidenced by the return on investment (ROI) reached by the company due to this
technology.
Keywords: Voice over IP, Connection, Protocol, Transmission, Telephony
Issue 2, Volume 10,
February 2011
Title
of the Paper:
Allocation Algorithm for Optimizing MC-CDMA
Over Correlated Channel
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Authors:
Hassan El Ghazi, Hamza Dahmouni, Nawal Bounouader
Abstract: In this paper, we address the problem of MAI (Multiple Access
Interference) degrading the performance of a downlink MC-CDMA system in a
frequency selective fading channel. Our objective is to develop a code
allocation strategy subject to use any code family and any equalizer. This
allocation problem is formulated as a minimization problem of a cost function
related to MAI. Firstly, we build the cost function from an approximation of
the analytical expressions of the MAI power for MRC, EGC and MMSE
equalization. Then we propose an iterative algorithm based on the min-max
criterion to select the spreading code of the active users. Simulation results
show the efficiency of our allocation strategy versus key parameters, in
particular the correlation degree between the faded subcarriers.
Keywords: MC-CDMA, channel frequency correlation function, MAI minimization, MAI
power approximation, spreading code allocation
Title
of the Paper:
Generalization and Optimization of Feature
Set for Accurate Identification of P2P Traffic in the Internet using Neural
Network
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Authors:
S. Agrawal, B. S. Sohi
Abstract: P2P applications supposedly constitute a substantial proportion of
today's Internet traffic. The ability to accurately identify different P2P
applications in internet traffic is important to a broad range of network
operations including application-specific traffic engineering, capacity
planning, resource provisioning, service differentiation, etc. In this paper,
we present a Neural Network approach that precisely identifies the P2P traffic
using Multi-Layer Perceptron (MLP) neural network. It is general practice to
reduce the cost of classification by reducing the number of features,
utilizing some feature selection algorithm. The reduced feature set produced
by such algorithms are highly data-dependent and are different for different
data sets. Further the feature set produced from one data set does not yield
good results when tried upon other data sets. We propose an optimum and
universal set of features which is independent of training and test data sets.
The proposed feature set has enabled us to achieve significant improvement in
performance of the MLP classifier. The few features in the proposed feature
set results in a significant reduction in training time, while maintaining the
performance, thereby making this approach suitable for real-time
implementation.
Keywords: Peer-to-Peer (P2P), Traffic classification, Flow features, Multi-Layer
Perceptron (MLP) Neural Network
Title
of the Paper:
Web-based IP telephony Penetration System
Evaluating Level of Protection from Attacks and Threats
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Authors:
Miroslav Voznak, Filip Rezac
Abstract: This article deals with detection of threats in IP telephony, the
authors developed a penetration testing system that is able to check up the
level of protection from security threats in IP telephony. SIP is being widely
used in building VoIP networks. Unlike the traditional telephone networks VoIP
networks does not have a closed communication which makes communication medium
vulnerable to all kinds of attacks from the in truders. The SIP server is a
key component of VoIP infrastructure and often becomes the aim of attacks and
providers have to ensure the appropriate level of security. We have developed
web-based penetration system which is able to check the SIP server if can face
to the most common attacks. The developed application is distributed as an
open-source and is equipped with four modules. The result is reported to the
particular e-mail and information supplemented to the report should help to
improve the overall protection of the SIP server. The developed application
represents effective tool which is able to point out the weaknesses of the
tested system.
Keywords: IP telephony, UDP flood, SIP server, Penetration test, Flood attack,
SIPVicious, Vulnerability
Issue 3, Volume 10,
March 2011
Title
of the Paper:
Performance Analysis of Dual Selection-Based
Macrodiversity System over Channels Subjected to Nakagami-m Fading and Gamma
Shadowing
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Authors:
Nikola M. Sekulovic, Edis S. Mekic, Dragana S. Krstic, Aleksandra D.
Cvetkovic, Martina Zdravkovic, Mihajlo C. Stefanovic
Abstract: This paper studies wireless communication system following
microdiversity to mitigate the effects of short-term fading and macrodiversity
processing to reduce shadowing effects. N-branch maximal-ratio combining (MRC)
is implemented at the micro level (single base station) and selection
combining (SC) with two base stations (dual diversity) is implemented at the
macro level. Model in the paper assumes a Nakagami-m density function for the
envelope of the received signal and a gamma distribution to model the average
power to account for shadowing. Analytical expressions for the probability
density function (PDF), cumulative distribution function (CDF) and moments of
signal after micro- and macrodiversity processing are derived. These
expressions are used to study important system performance criteria such as
the outage probability, average bit error probability (ABEP), average output
signal value and amount of fading (AoF). Various numerical results are
graphically presented to illustrate the proposed mathematical analysis and to
show the effects of various system parameters to the system performance, as
well as enhancement due to use of the combination of micro- and
macrodiversity.
Keywords: Gamma shadowing, Macrodiversity, Microdiversity, Nakagami-m fading
Title
of the Paper:
Small Size Defected Ground Structure (DGS)
Coupled Resonator Band Pass Filters with Capacitor Loaded Slot Using FDTD
Method
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Authors:
Adel Abd Elrahman, Adel Zein Eldein, Ahmed Abd Elmonem, Hesham Fathi
Abstract: This paper presents a design of a small size second and third order
band pass coupled resonator filters by using finite difference time domain
method (FDTD). Two of the proposed filters consist of compact folded DGS
resonators, the other consists of compact rectangular DGS resonators and a
lumped capacitor is combined within the slot of each filter. The insertion of
lumped capacitor within resonators increases the effective capacitance, and
reduces the resonant frequency, so the dimensions of the filter will reduce
and the performance of the filter will be improved by enhancing the energy
stored in the resonator. The resonance bandwidth is decreased leading to
increasing the resonator quality factor. A second order band pass filter with
centre frequency of 2.4 GHz has been designed, fabricated and measured. The
filter has a wide stop band with a rejection higher than 20 dB up to more than
10 GHz. Insertion loss of less than 0.7 dB is achieved within the pass band.
Another second order band pass filter with centre frequency of 3.1 GHz has
been designed, fabricated, and measured. The filter has a wide stop band with
a rejection higher than 20 dB up to more than 10 GHz. Insertion loss of less
than 0.8 dB has been achieved within the pass band. It is found that, the
experimental results agree well with the EM-simulation and FDTD simulation
results. Finally, a third order band pass filter with center frequency of
2.4GHZ with single transmission zero at 2.61 GHz is designed and simulated.
The filter has pass band from 2.3 to 2.52 GHz and wide stop band with
rejection higher than 20 dB up to more than 8GHZ, and insertion loss lower
than 1 dB is achieved within pass band.
Keywords: Band Pass Filter, Coupled resonator filter, Defected ground structure,
Lumped capacitor, FDTD
Title
of the Paper:
Radio Access Network Power Management
Considering Radio over Fiber Technique for 4G Mobile System
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Authors:
Jalal J. Hamad Ameen, Widad Ismail, Sevia M. Idrus
Abstract: Radio over fiber technique was suggested as excelent candidates for
4G radio access network considering large number mobile users. With higher
number of base stations, a microwave link presents more disadvantages across
base stations in relation to power management, interference effect, atmosphere
effects, and maintenance. In this paper, the radio over fiber power management
technique is introduced. It transmits and receives signals with lower losses
and dispersion effect through the fiber link. The signal quality is improved
with the parameters optimization for practical applications. It proposed
better power level for 4G mobile base stations with the expected coverage
area, as well as power control and signal improvement for the system.
Keywords: Radio over fiber , 4G mobile system, radio access network, power
manaegment, fiber dispersion
Issue 4, Volume 10,
April 2011
Title
of the Paper:
Video Summary Application over Cross-layer
Designed Wireless Networks Using Multi-carrier CDMA
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Authors:
Srimathi Mathialagan, S. Shanmugavel
Abstract: Cross-layer design has become an emerging trend in the wireless
network for efficient video transmission. In this paper, a cross-layer design
approach is proposed for multi-user scenario by using multiple-input multiple-
output antennas (MIMO) at the physical layer. The impact of multi-user system
on the bit error rate performance is presented in Rayleigh fading channels.
The cross-layer adaptation across physical layer, data link layer and
application layer works well in multi-user environment. Results reveal that
proposed cross-layer design attain 15 % distortion gain.
Keywords: Cross-layer design, Quality-of-service (QoS), Multiple-input
multiple-output (MIMO), Multi-carrier code-division multiple-access (MC-CDMA),
Automatic repeat request (ARQ), Adaaptive modulation coding(AMC)
Title
of the Paper:
Energy Efficient Constant Cluster Node
Scheduling Protocol for Wireless Sensor Networks
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Authors:
R. Saravanakumar, S. G. Susila, J. Raja
Abstract: The Wireless sensor network (WSN) consisting of a large number of
sensors are effective for gathering data in a variety of environments. Since
the sensors operate on battery of limited power, it is a great challenging aim
to design an energy efficient routing protocol, which can minimize the delay
while offering highenergy efficiency and long span of network lifetime. In
this paper, we first completely analyzes the basic distributed clustering
routing protocol LEACH (Low Energy Adaptive Clustering Hierarchy), then
proposed a new routing protocol and data aggregation method in which the
sensor nodes form the constant cluster and the cluster-head elected based on
the residual energy of the individual node calculation with constant
clustering and the node scheduling scheme is adopted in each cluster of the
WSNs. In the node scheduling scheme (ACTIVE and SLEEP mode) the energy
efficiency is increased near to 50% than LEACH protocol and lifetime of the
networks also increased. Simulation results using MATLAB are shows that the
proposed routing protocol significantly reduces energy consumption and
increase the total lifetime of the wireless sensor network compared to the
LEACH protocol.
Keywords: Constant cluster, energy efficiency, LEACH protocol, node scheduling,
network lifetime, wireless sensor networks
Title
of the Paper:
Optimal Design of Virtual MIMO for WSN
Performance Improvement?
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Authors:
Kan Baoqiang, Lei Zhao, J. H. Fan, J. Y. Wang
Abstract: In this paper, we studied the performance of bit error rate(BER) for
a virtual multiple-input multiple-output (MIMO) based communications
architecture. As a case, wireless sensor networks with clusters were
considered. Then an optimal transmitting power(TP) scheme for cooperative
sensor nodes was presented. Specifically, by minimizing BER of the Nt?1
virtual MIMO system, we derived the closed-form of the optimal TP for each
cooperating node in one cluster. Through simulations , we compared this
strategy with an equal TP assignment method. Its performance enhancement was
verified by extensive simulations under different scenes. At the aim to energy
efficient, a thorough explanation of optimally choosing number of cooperating
nodes was also delivered by the aid of mathematical analysis as well as
simulation verifications.
Keywords: Energy efficiency, virtual MIMO, wireless sensor networks (WSNs)
Issue 5, Volume 10,
May 2011
Title
of the Paper:
Effect of Constraint Length and Code Rate on
the Performance of Enhanced Turbo Codes in AWGN and Rayleigh Fading Channel
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Authors:
T. Gnanasekaran, V. Aarthi
Abstract: Turbo coding (TC) has been adopted as a channel coding scheme for
several 3G mobile systems, in particular 3GPP (Third Generation Partnership
Project) and in upcoming 4G standards for high data rates. Turbo decoder uses
Maximum A posteriori Probability (MAP), or Soft Output Viterbi Algorithm
(SOVA) because it produces error correction near to Shannon’s limit. A simple
but effective technique to improve the performance of the decoding algorithms
is to scale the extrinsic information exchanged between two decoders. Modified
Log MAP (MMAP) and Modified SOVA (MSOVA) algorithms are achieved by fixing an
arbitrary value of scaling factor for inner decoder (S2) and an optimized
value for the outer decoder (S1). We proposed to enhance the performance of
MMAP and MSOVA by optimizing both the scaling factors S1 and S2, thus
achieving low bit error rate (BER). This paper investigates the effects of
constraint length and code rate on the performance of the enhanced Turbo
codes. A comprehensive analysis of the algorithms considering different
channel conditions and iterations are also presented.
Keywords: Constraint Length, Extrinsic information, MAP, Scaling Factor, SOVA,
Turbo codes
Title
of the Paper:
An Optimal Gain Control Scheme for Digital
On-Channel Repeater with Feedback Interference Canceller in Digital
Terrestrial Television Broadcasting Networks
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Authors:
Chang Liu, Miao He, Wei Xia
Abstract: In this paper, a new gain control scheme is proposed for a digital
on-channel repeater (DOCR) with a feedback interference canceller (FIC) in
Digital Terrestrial Television Broadcasting (DTTB) networks. In the proposed
scheme, a variable attenuator is placed behind the amplifier of the DOCR and
the least mean square (LMS) adaptive algorithm is implemented in the FIC to
estimate the feedback channel. The proposed scheme consists of two stages. In
the first stage, the variable attenuator is fixed on a high attenuation level
for a sufficient time with the purpose of avoiding oscillation at start-up of
the DOCR. In the second stage, based on the non-oscillation condition derived
in Section II, the attenuation level can be decreased at intervals until the
aimed gain is approached. Simulations show that the proposed scheme increases
the convergence speed of the adaptive algorithm and saves the adjusting time
of approaching the aimed gain compared with the conventional gain control
scheme.
Keywords: DTTB, digital on-channel repeater (DOCR), feedback interference
canceller (FIC), oscillation, gain control, least mean square (LMS) algorithm
Title
of the Paper:
User Based Resource Scheduling for
Heterogeneous Traffic in the Downlink of OFDM Systems
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Authors:
G. Indumathi, S. Vijayarani, K. Murugesan
Abstract: Besides avoiding inter-symbol interference and leading to high
capacity, wireless orthogonal frequency division multiplexing (OFDM) provide
fine granularity for resource allocation since they are capable of dynamically
assigning sub-carriers to multiple users and adaptively allocating transmit
power. The current dominate layered networking architecture, in which each
layer is designed and operated independently, results in inefficient and
inflexible resource use in wireless networks due to the nature of the wireless
medium, such as time-varying channel fading. Thus, we need an integrated
adaptive design across different layers. In this paper, we focus on resource
allocation and scheduling in wireless multiuser OFDM networks based on joint
physical and medium access control (MAC) layer optimization. An adaptive
cross-layer design for the downlink multiuser OFDM systems, to maximize the
weighted sum capacity of all users, where each user has multiple heterogeneous
traffic queues simultaneously is proposed. A packet dependent (PD) scheduling
scheme is employed at the MAC layer, which determines the packet transmission
order by assigning different weights to different packets, and is shown by
simulations more efficient than the previous methods where all packets in a
queue have the same weight. The weight design in PD scheduling considers the
delay, size and quality of service (QoS) priority level of packets. Each user
weight employed in resource allocation at the physical (PHY) layer is obtained
by summing up the weights of selected packets for the user. We also deeply
investigate the various resource scheduling schemes for comparisons.
Keywords: Cross-layer design, quality of service, packet scheduling, orthogonal
frequency division multiplexing systems
Issue 6, Volume 10,
June 2011
Title
of the Paper:
Reducing Wastage Capacity in OVSF Based CDMA
Networks using Dynamic Rake Combiners
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Authors:
Davinder S. Saini
Abstract: Orthogonal variable spreading factor (OVSF) codes in CDMA networks
are designed to handle quantized data rates. Handling non-quantized data rates
in such networks leads to code capacity wastage if traditional single code
assignment is used. Although, the use of multiple codes reduce this wastage
capacity but the use of large number of fixed rake combiners per call increase
cost and complexity of the system. I propose zero wastage designs in which the
rake combiner’s usage is made dynamic and the amount of rake combiners used
depend upon the rate type, with more combiners given to the rate which
deviates significantly from the quantized one. The average number of rakes per
call is arbitrarily assumed, and if the rakes used for a particular call are
less than the average (which happens for quantized or near quantized calls),
the unused rakes can be used by future calls. The performance is significantly
improved compared to the fixed rate systems. The amount of codes used on
average is less than the codes required for existing multi code designs. In
the reduced wastage capacity design, which is a special case of zero wastage
designs, some wastage can be tolerated for simplicity and less equipment cost.
Keywords: OVSF codes, CDMA, wastage capacity, code assignment, quantized and
non-quantized rates
Title
of the Paper:
Influence of Laser Linewidth and Modulation
Level for Coherent Optical OFDM with Punctured LDPC Codes
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Authors:
Chang-Jun Ahn, Takeshi Kamio, Hisato Fujisaka, Kazuhisa Haeiwa
Abstract: Recently, coherent optical OFDM (CO-OFDM) has been proposed for
optical networks to combat chromatic dispersion. CO-OFDM system has been
successfully processed and recovered for transmitted signals without optical
chromatic dispersion compensation. However, in optical links, the available
optical power is limited due to fiber nonlinearity, and power consumption. As
previously reported, we focused on the minimizing the optical power and have
proposed CO-OFDM with punctured LDPC codes and variable amplitude block codes
to overcome the above-mentioned problems. In this paper, we focus on the
implementation of the proposed CO-OFDM and evaluate the influence of laser
linewidth and modulation level for coherent optical OFDM with punctured LDPC
codes.
Keywords: OFDM, LDPC, RCPC codes, Puncturing codes, linewidths
Title
of the Paper:
Inter Cluster Distance Management Model with
Optimal Centroid Estimation for K-Means Clustering Algorithm
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Authors:
M. Vijayakumar, S. Prakash, R. M. S. Parvathi
Abstract: Clustering techniques are used to group up the transactions based on
the relevancy. Cluster analysis is one of the primary data analysis method.
The clustering process can be done in two ways such that Hierarchical clusters
and partition clustering. Hierarchical clustering technique uses the structure
and data values. The partition clustering technique uses the data similarity
factors. Transactions are partitioned into small groups. K-means clustering
algorithm is one of the widely used clustering algorithms. Local cluster
accuracy is high in the K-means clustering algorithm. Inter cluster
relationship is not concentrated in the K-means algorithm. K-means clustering
algorithm requires the cluster count as the major input. The system chooses
random transactions are initial centroid for each cluster. Cluster accuracy is
associated with the initial centroid estimation process. The random
transaction based centroid selection model may choose similar transactions. In
this case the cluster accuracy is limited with respect to the distance between
the centroid values. The proposed system is designed to improve the K-means
clustering algorithm with efficient centroid estimation models. Three centroid
estimation models are proposed system. They are random selection with distance
management, mean distance model and inter cluster distance model. Cosine
distance measure and Euclidean distance measure are used to estimate
similarity between the transactions. Three centroid estimation models are
tested with two distance measure schemes. Precision and recall and fitness
measure are used to test the cluster accuracy levels. Java language and Oracle
database are selected for the system development.
Keywords: Clustering, Data Partitioning, K-means Clustering, Initial Centroid,
Inter cluster distance model, optimal Centroid
Issue 7, Volume 10,
July 2011
Title
of the Paper:
Improvement of Li-Hwang’s Biometrics-based
Remote User Authentication Scheme using Smart Cards
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Authors:
Cheng-Chi Lee, Rui-Xiang Chang, Lung Albert Chen
Abstract: Recently, Li and Hwang proposed an efficient biometrics-based remote
user authentication scheme without storing the password tables. Their scheme
uses random numbers to solve the problem of synchronized clocks. It also
enables the user to freely choose or change their passwords. At the same time,
they claimed that their scheme provides security, reliability and efficiency.
However, we found that Li and Hwang’s scheme is vulnerable to denial of
service attacks. Therefore, in this paper we propose an improved scheme to
solve this weakness.
Keywords: User authentication, password, biometrics, smart cards, security,
cryptography
Title
of the Paper:
Impact of Physical Layer Impairments on the
All-to-All Broadcast in Wavelength Routed Optical Networks
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Authors:
M. Sabrigiriraj, M. Meenakshi
Abstract: All-to-all broadcast is to disseminate a unique message from each
node to every other node of the network. This paper investigates the impact of
some of the physical layer impairments on the optical all-to-all broadcast in
linear array, bidirectional ring and hypercube networks. The physical layer
impairments include Amplified Spontaneous Emission (ASE) noise, switch induced
crosstalk and demux/mux crosstalk. In all networks, the result shows that for
shorter lightpaths, the ASE noise and demux/mux crosstalk are found to be much
less as they traverse through few fiber links. Longer lightpaths due to their
larger stretch experiences higher accumulated ASE noise and demux/mux
crosstalk. In addition, lightpaths of a hypercube network suffer switch
induced crosstalk at all the nodes along its path. A few measures to reduce
the impact of transmission impairments are suggested since the control signals
in a network should be highly reliable.
Keywords: All-to-all broadcast; Physical layer impairments; crosstalk
Title
of the Paper:
Design and Analysis of Ultra Wide Band
Planar Monopole Antenna
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Authors:
M. K. A. Rahim, T. Masri, H. A. Majid, O. Ayop, F. Zubir
Abstract: A novel two layered UWB antenna is proposed and designed to resonate
at the full range of UWB frequencies’ spectrums from 3.1 GHz up to 10.6 GHz,
well below -14.0dB reference levels of return loss. The size of the UWB
antenna is small, with width of 31.0 mm and length of 25.0 mm, and the two
layers of FR4 board thickness are 0.5 mm (top layer) and 1.6 mm (bottom
layer).The antenna radiates omni-directionally with different intensities at
different directivities within the UWB frequency spectrums. The dual layered
configuration gives the antenna additional options of being integrated with
additional structures in order to perform a band rejection of a certain
targeted band of frequencies, if required. The UWB antenna has also been
fabricated using the same dimensions on a single layer 1.6 mm thick FR4 board
and it still gives similar excellent performance.
Keywords: UWB antenna, planar antenna, monopole antenna, omnidirectional, short
range communication
Issue 8, Volume 10,
August 2011
Title
of the Paper:
A Novel Strategy for High Throughput in Ad
Hoc Networks using Potential Transmission Count (PTC) Metric
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Authors:
Arun Kumar Singh, Neelam Srivastava, J. B. Singh
Abstract: A multi-hop wireless network is a network of computers and devices
(nodes) which are connected by wireless communication links. The links are
most often implemented with digital packet radios. Because each radio link has
a limited communications range, many pairs of nodes cannot communicate
directly, and must forward data to each other via one or more cooperating
intermediate nodes. The PTC of a route is the total number of packet
transmissions and retransmissions required to send a packet across the route,
assuming that each link in the route retransmits the packet until it is
successfully received across the link. PTC is designed for links with
link-layer acknowledgments (ACKs) and retransmissions, as provided by IEEE
802.11 radios. The PTC metric for a route is calculated using measurements of
the lossless of each link in the route. Routing protocols select routes with
the minimum PTC. For short routes, the minimum- PTC route is the
maximum-throughput route; for longer routes, the minimum- PTC route is still a
high-throughput route. The design of the PTC metric does not depend on a
particular routing protocol; PTC improves the throughput of both Dynamic
Source Routing (DSR), an on-demand source routing protocol, and
Destination-Sequenced Distance-Vector (DSDV) routing, a proactive table-driven
distance-vector routing protocol. We also present a set of design changes and
implementation techniques that allow DSR and DSDV to work well with PTC.
Keywords: Multi-hop, Ad-Hoc, Hop Count Metric, 802.11b, PTC, Radio Packets
Title
of the Paper:
Performance Evaluation of Full Rate
Space-Time Block Code for Multiple Input Single Output (MISO) Wireless
Communication System
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Authors:
Fahima Tabassum, Mahbubul Alam, Md. Imdadul Islam, M. R. Amin
Abstract: To enhance the capacity of a multiple input single output (MISO)
system in wireless communications, the most widely used channel coding
technique is the space time block coding (STBC). The outstanding orthogonal
full rate STBC proposed by Alamouti is the most successful one and also very
simple to implement, where only two transmit antennas and one receive antenna
are used. As the number of antennas is increased beyond two, the orthogonality
of the STBC is lost. Recent literature proposes a scheme known as the
quasi-orthogonal STBC for full rate communication. It has been found that for
½ and ? rate, the orthogonality of the code can be maintained. In this paper,
we propose a system with a full rate orthogonal STBC for four symbols and
eight transmit antenna MISO case. After comparing the performance of the
proposed system with the existing models, we have found that the proposed
scheme is the best in context of the probability of bit error (BER)
consideration.
Keywords: Rayleigh fading, Walsh matrix, quasi orthogonality, AOD, SNIR,
Kronecker product
Title
of the Paper:
An Area Segmentation Strategy for Adaptive
Transmission to Achieve Near-Uniform High Quality Coverage in 30 GHz Fixed
Wireless Cellular Systems in Tropical Regions
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Authors:
Suwadi, Gamantyo Hendrantoro, Wirawan
Abstract: This paper presents an area-segmented adaptive transmission strategy
aiming at providing near-uniform high quality coverage in terms of
availability and average spectral efficiency across the coverage area in
broadband fixed wireless access (BFWA) systems operating at 30 GHz. The
strategy considers implementation during rain in tropical regions with heavy
rain rates of fixed 64-QAM, adaptive modulation (AM), adaptive coded
modulation (ACM) with or without cell-site diversity with selection combining
(SC), to be implemented in different ring-shaped segments around each base
transceiver station (BTS). The results of synthetic storm-based evaluation
show that near-uniform high quality coverage in tropical regions can be
achieved using this strategy. Discussions are made upon the implementation of
the area segmentation strategy in cellular configurations having square cells
with different spacings between BTSs.
Keywords: Adaptive transmission, Coverage, Fixed wireless Cellular, Rain
attenuation, Millimeter-wave
Issue 9, Volume 10,
September 2011
Title
of the Paper:
PAPR Reduction in OFDM System using Adapting
Coding Technique with Pre distortion Method
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Authors:
Chhavi Sharma, Shiv Kumar Tomar, A. K. Gupta
Abstract: In this paper we propose the Peak to Average Power ratio reduction
(PAPR) in OFDM using adapting coding technique with pre-distortion method to
decrease the nonlinear distortion and to improve the power efficiency of the
non-linear high power amplifier (HPA). In the proposed method adaptive coding
is used for error correction as well as PAPR reduction. The pre-distorter
improves the bit error rate performance of the system.
Keywords: Complementary cumulative distribution function (CCDF), Peak to average
power ratio (PAPR), High power amplifier (HPA), Orthogonal frequency division
multiplexing (OFDM)
Title
of the Paper:
Energy Aware Multiple Constraints Multipath
QoS Routing Protocol with Mobility Prediction for MANET
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Authors:
M. Senthilkumar, S. Somasundaram
Abstract: This paper presents a source based reactive protocol called “Energy
aware Multipath QoS Routing Protocol with Mobility Prediction (EMQRPMP)” for
MANET. It is the enhanced version of the existing protocol called “Power aware
Multiple QoS constraints Routing Protocol with Mobility Prediction (PMQRPMP)”.
It considers quality of service constraints namely delay, delay-jitter,
bandwidth, and cost for each link on ‘n’ available paths and selects ‘k’
routing paths between a source and a destination during path discovery.
EMQRPMP checks bandwidth constraint during route request to minimize control
overhead. It also checks power constraint for each node for selecting paths
with good battery backup. EMQRPMP uses our new mobility prediction mechanism
to find the link expiry time and determines the stability of link expiry time
for each link between two adjacent nodes of each path during route reply. It
executes path maintenance procedure when the link between two nodes is cut
off. EMQRPMP considers the reservation of a backup path during link failure
thus reducing control overhead. After finding multiple paths, the source
distributes routing load on all the selected paths using an intelligent load
distribution algorithm as to increase throughput in MANET.
Keywords: Energy level, Multipath Routing, QoS, Protocol, Mobility Prediction,
MANET
Title
of the Paper:
A New Topology for Telecom and Broad Band
Services in Spars, Remote and Hilly Areas
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Authors:
P. K. Chopra, R. Manchanda, R. Mehrotra, S. Jain
Abstract: Technological development and mass scale deployment of mobile
telephony in the last 15-20 yrs has made telecom services an essential
commodity for the modern age society. Affordable and wide spread availability
of telecom services is giving impetus to digitalization of all the contents
and leading to convergence of telecom, media and broadcasting. This phenomenon
is further accelerating the demand for higher bandwidth, while at the same
time there is a limitation in the availability of additional spectrum and is
posing problems due to increased power consumption by telecom systems, ill
effects of excessive electromagnetic radiations and scarcity of backbone for
carrying telecom traffic. To overcome the above problems there is a need for
defining new topologies for telecom and broadband deployment befitting the
terrain and population density, particularly in the thinly populated, remote
and hilly areas where making available regular power supply for operating
telecom infrastructure round the clock and installing backbone infrastructure
in the conventional way is impractical and not cost effective. A study is
attempted to define a new telecom network deployment topology that would
reduce the power and backbone backup required by almost 50 times while at the
same time, increase and make available broadband connectivity on demand and
also reduce the ill effect of electromagnetic radiations in a phenomenal
manner. The authors have attempted to vary the capacity and coverage, of
telecom services provided, based on the requirement, and have also
phenomenally increased the coverage provided by the mother BTS by increasing
its height by almost 10 times by placing it in a tethered balloon. While this
would provide uniform umbrella coverage with low traffic capacity over a large
area i.e., upto 5000 Sq Kms, enhanced capacity would be provided in pockets
under this umbrella in populated residential area (villages) and office
complexes by installing very low power BTSs which are equivalent system
capable of being operated using alternate sources of energy like wind, solar
etc and also cause negligible electromagnetic radiation pollution. The
umbrella coverage provided by the mother BTS will communicate with these low
power BTSs and will also provide backhaul connectivity.
Keywords: BTS, Flexible Tower, Communication, CDMA
Issue 10, Volume
10, October 2011
Title
of the Paper:
A Sustained QoS Solution by Contention
Adaptation in IEEE 802.11e Wireless LANs
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Authors:
Chia-Chuan Liang, Shih-Wei Pan, Jung-Shyr Wu
Abstract: The most significant issue in 802.11 contention based networks is to
prevent collisions and to ensure connection quality. Researchers have shown an
increased interest in collision aware back-off algorithms. However, collision
aware back-off algorithms are still failed to ensure strict priority for the
high priority traffic. Especially in the heavy loading network, a large number
of unsuccessful collisions of low priority traffic are the leading cause of
the performance degradation of high priority traffic. Our scheme aims to share
the transmission channel efficiently and to provide the strict priority
contention scheme. Our approach is derived from the Enhanced Distributed
Channel Access (EDCA) induced in the IEEE 802.11e standard. Relative
priorities adjust the average size of the CW of each traffic class according
to both applications requirements and network conditions. We demonstrate the
effectiveness of our solution by comparing with existing approaches through
extensive simulations. Results show that our scheme improves the throughput of
higher priority traffic as well when traffic load is heavy. Furthermore, our
scheme is simple and easy to implement.
Keywords: 802.11e, Back-off, EDCF, Contention Window, Collision, QoS
Title
of the Paper:
A Secure Dominating Set based Routing and
Key Management Scheme in Mobile Ad Hoc Network
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Authors:
R. Pushpalakshmi, A. Vincent Antony Kumar
Abstract: In Mobile Ad hoc Network (MANET) nodes communicate with each other
using shared wireless medium. Due to their distributed nature and dynamic
topology, MANET is less secured than wired network. To enhance the security of
MANET, it is important to establish routing path based on the trustworthiness
of each node in the network. Most existing routing protocols in MANET mainly
focus at finding efficient routing path. To deal with the effect of malicious
node, trustworthiness of node can be taken into consideration in routing
decision making. A routing protocol based on distributed dominating set based
clustering algorithm is presented in this paper. The dominator set is formed
based on the trust ability of the node and probability of future contact of
the node in the network. This paper present a adaptive neuro fuzzy logic
controller to evaluate the trust level of each node and a composite key
management technique used for effective key management within cluster.
Simulation results show that proposed routing protocol provides efficient
routing path that bypass malicious nodes in the network.
Keywords: Mobile Ad hoc network, dominating set, fuzzy controller, trust
valuation, key management, secure routing
Title
of the Paper:
Non-Split Balancing Higher Order Tree for
Multi-Privileged Groups
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Authors:
A. Muthulakshmi, R. Anitha, M. Sumathi
Abstract: In group communication scenario, key management is important to
preserve forward and backward secrecy. In order to achieve it keys need to be
changed during user join/leave which is done by an operation called rekeying.
In a centralized key management scheme, the server thereafter passes the new
keys to the existing users who are affected via unicasts and multicasts. The
number of unicasts and multicasts decide the rekeying cost. B-trees and NSBHO
trees help to reduce the rekeying cost as compared to the binary trees. This
paper discusses the use of these trees in Multi-privileged environment
providing the algorithms for user join/leave as well as rekeying algorithms in
both the cases. The bounds for the heights of the trees have been given and
also the rekeying costs in the three cases have been addressed.
Keywords: Multi-privileged group; rekeying; balanced tree;B-tree, NSBHO tree
Issue 11, Volume
10, November 2011
Title
of the Paper:
Two-Dimensional Models of Cylindrical
Monopole Plasma Antenna Excited by Surface Wave
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Authors:
Jun Wei Lv, Ying Song Li, Zi Li Chen
Abstract: The numerical calculation model of cylindrical monopole plasma
antenna excited by surface wave is proposed in the paper. The wave propagation
model of the plasma antenna is also investigated. The models are both analyzed
in two-dimension and calculation equations of models are given and deduced.
The detailed analysis of models and the calculation results have been
obtained. The two models are testified through the specific experiments. The
results show that the measured results agree well with the calculated ones
which help to verify validity of the proposed models.
Keywords: Monopole Cylindrical Plasma Antenna; Surface Wave; Two-Dimensional
Model; Numerical Calculation
Title
of the Paper:
A Review of Routing Protocols for Mobile Ad
Hoc Networks
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Authors:
Anuj K. Gupta, Harsh Sadawarti, Anil K. Verma
Abstract: A number of routing protocols has been proposed in recent years for
possible use of Mobile Ad Hoc Networks in various application areas such as
military, govt. etc. In this paper we have presented a comprehensive review of
these protocols with a particular focus on their security aspects. Further we
have presented a comparison of some of the existing Routing Protocols of
MANETs. The base criteria for comparison is routing methodologies and the
information used to make routing decisions. All the protocols have to meet
five security requirements: confidentiality, integrity, authentication,
non-repudiation and availability, with respect to which the analyses of secure
versions of proposed protocols are discussed.
Keywords: Routing Protocols, Network attacks & Defense, AODV, DSDV, DSR, SRP,
TORA, ZRP
Title
of the Paper:
Markov Models and Their Use for Calculations
of Important Traffic Parameters of Contact Center
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Authors:
Erik Chromy, Jan Diezka, Matej Kavacky, Miroslav Voznak
Abstract: The appropriate model and consecutive design is the basis for
building of successful Contact center. Excessive complexity of model can be
sometimes contra-productive. The main goal of this work is to analyze of
Markov model M/M/m/infinity properties in Contact center environment. This
model offers wide range of important traffic parameters calculations of the
system, while keeping transparent and simple structure – the key factor in
design of Contact center. The second part of the paper deals with the
modelling of contact center equipped with Interactive Voice Response (IVR)
system. IVR system is modeled by Markov model M/M/infinity/infinity. It
results in the less number of needed agents in contact center.
Keywords: M/M/m/infinity, M/M/infinity/infinity, Erlang C formula, Automatic
Call Distribution, Interactive Voice Response, Quality of Service
Issue 12, Volume
10, December 2011
Title
of the Paper:
SC and SSC Diversity Reception over
Correlated Nakagami-m Fading Channels in the Presence of CCI
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Authors:
Mihajlo Stefanovic, Dragana Krstic, Stefan Panic, Jelena Anastasov, Dusan
Stefanovic, Sinisa Minic
Abstract: Performance analysis of switched-and-stay combining (SSC) and
selection combining (SC) diversity receivers operating over correlated
Nakagami-m fading channels in the presence correlated Nakagami-m distributed
co-channel interference (CCI) is presented. Novel infinite series expressions
are derived for the output signal to interference ratio's (SIR’s) probability
density function (PDF) and cumulative distribution function (CDF).
Capitalizing on them standard performance merasures criterion like outage
probabilty (OP) and average bit error probability (ABEP) for modulation
schemes such as noncoherent frequency-shift keying (NCFSK) and binary
differentially phase-shift keying (BDPSK) are efficiently evaluated. In order
to point out the effects of fading severity and the level of correlation on
the system performances, numericaly obtained results, are graphically
presented and analyzed
Keywords: Switched-and-Stay Combining, Selection Combining, Nakagami-m fading
channels, Co-Channel Interference, Outage Probability, Average Bit-Error
Probability
Title
of the Paper:
An Optimized Ku-Band Corrugated Feed Horn
Antenna Design for a Cassegrain Reflector using Multi-Objective Particle Swarm
Optimization
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Authors:
Mohammad Asif Zaman, Md. Gaffar, Md. Abdul Matin
Abstract: In this paper, a Ku-band corrugated feed horn antenna for a
Cassegrain reflector is designed and optimized. The horn dimension parameters
are optimized so that it has a radiation pattern with a specific beamwidth
which would illuminate the sub-reflector of the Cassegrain antenna with the
desired taper. It is also required that the horn must have low S11 parameter
and low cross-polarization levels. Multi-objective particle swarm optimization
is performed to optimize the horn dimensions to meet these requirements. The
radiation characteristics of the optimized horn are analyzed using computer
simulation. The far-field radiation pattern of the Cassegrain reflector for
the optimized feed horn is also discussed and compared with the case of an
un-optimized horn.
Keywords: Cassegrain reflector, Corrugated horn antenna, Multi objective
particle swarm optimization
Title
of the Paper:
PerNEWQUE: An Active Queue Management
Algorithm for Controlling Unresponsive Flows
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Authors:
Santhi V, A. M. Natarajan
Abstract: In order to design the congestion control scheme in the routers, an
Active Queue Management (AQM) is proposed. This is used to control congestion
at the router, where packets are dropped before queue become full. A new
framework of AQM, namely NEWQUE with Per-flow Scheduling (PerNEWQUE) active
queue management algorithm supporting explicit congestion notification (ECN),
is proposed by extending scheduling nature in NEWQUE AQM. It is developed with
the aim of strengthen the robustness of Internet against unresponsive flows.
The objective of the new algorithm is to detect and penalize the unresponsive
flows like UDP flows from responsive flows like TCP flows. The PerNEWQUE AQM
is implemented with help of NS2 simulator. The simulation shows that the
proposed design outperforms other AQM schemes in terms of reduction of
throughput, link utilization and increasing percentage packet loss of
unresponsive flows.
Keywords: Active Queue Management, Congestion control, Explicit Congestion
Notification (ECN), Unresponsive flow, TCP, UDP
Title
of the Paper:
Synthesis of Linear Antenna Array using
Genetic Algorithm with Cost Based Roulette to Maximize Side lobe Level
Reduction
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Authors:
T. S. Jeyali Laseetha, R. Sukanesh
Abstract: This paper discusses the deployment of Genetic algorithm
optimization method for synthesis of antenna array radiation pattern in
adaptive beam forming. The synthesis problem discussed is to find the weights
of the antenna array elements that are optimum to provide the radiation
pattern with maximum reduction in the side lobe level. This technique proved
its effectiveness in improving the performance of the antenna array.
Keywords: Adaptive Beam forming, Side lobe level, Genetic Algorithm, Linear
Antenna Array, Pattern Synthesis, Convergence, Array Factor
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