WSEAS CONFERENCES. WSEAS, Unifying the Science

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10, 2011
Print ISSN: 1109-2742
E-ISSN: 2224-2864








Issue 1, Volume 10, January 2011

Title of the Paper:  Improved Power Control MAC Protocol for wireless Ad Hoc Networks


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


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


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


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


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


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


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


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


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


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


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


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?


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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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