International Journal of Communications


ISSN: 1998-4480
Volume 7, 2013

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Issue 1, Volume 7, 2013


Title of the Paper: Marketing and Communications Tools in Service Sector in Times of Crisis

 

Authors: Martina Jurikova, Olga Juraskova, Josef Kocourek

Pages: 1-9

Abstract: The aim of this article is to demonstrate the correlation of changes in economic performance of the Czech Republic in 21st century with respect to company´s marketing and communications activities, especially in the area of services. Based on the original research carried out by the authors at 231 service providers and results of conjunctural research and ad hoc studies, this article reveals the intensity and time delay in reactions of the service sector to the recession in the process industry as well as the level of implementation of marketing services in the time of the world economic crisis. It also points out the trends in marketing communications that react to decreased citizens´ purchasing power on one hand and lower marketing budgets on the other. The final part provides space for deduction regarding the possibilities of development and limits, barriers to effective application of marketing and marketing communications (not only) in services.


Title of the Paper: Waiting Time Distribution for an Active Queue Management Algorithm

 

Authors: Andrzej Chydzinski

Pages: 10-17

Abstract: The active queue management algorithms are designed for the Internet routers and their goal is to drop incoming packets before the actual buffer overflow occurs – in this way they notify the TCP senders about the necessity to reduce their sending rates and prevent the link from congestion. Most of the known active queue management algorithms drop incoming packets randomly, with probability that depends on the queue size observed upon packet arrival. In this paper we present calculations of the distribution of the waiting time for such active queue management algorithms, i.e. algorithms whose dropping probability is a function of the queue size. In particular, we give a formula for the transform of the waiting time distribution as well as a formula for the average waiting time. The mathematical results are accompanied with examples of numerical calculations.


Title of the Paper: Quasi-Optimal and Optimal Generalized Mutually Orthogonal ZCZ Sequence Sets Based on an Interleaving Technique

 

Authors: Hideyuki Torii, Masaaki Satoh, Takahiro Matsumoto, Makoto Nakamura

Pages: 18-25

Abstract: The present paper proposes methods for constructing quasi-optimal or optimal generalized mutually orthogonal zerocorrelation zone (GMO-ZCZ) sequence sets. Zero-correlation zone (ZCZ) sequence sets have been studied as spreading sequences for approximately synchronized code-division multiple-access (ASCDMA) systems. A mutually orthogonal ZCZ (MO-ZCZ) sequence set is composed of several small ZCZ sequence sets, and two arbitrary sequences that belong to different small ZCZ sequence sets are orthogonal. Moreover, in a GMO-ZCZ sequence set, two arbitrary sequences that belong to different small ZCZ sequence sets have a zero-correlation zone instead of being orthogonal. In the present paper, we propose two methods for constructing GMO-ZCZ sequence sets. One is a method for constructing quasi-optimal GMO-ZCZ sequence sets using perfect sequences and orthogonal codes, and this method is a generalized version of our previously proposed method. The other is a method for constructing optimal GMO-ZCZ sequence sets using discrete Fourier transform (DFT) matrices and orthogonal codes. The proposed methods can generate new GMO-ZCZ sequence sets that cannot be obtained from known methods.


Issue 2, Volume 7, 2013


Title of the Paper: Theoretical Modeling and Simulation of a Chaos-Based Physical Layer for WSNs

 

Authors: Stevan Berber, Shu Feng

Pages: 27-34

Abstract: In this paper the theoretical model and simulation of the physical layer for wireless sensor networks (WSNs) application is presented. The spreading sequences used are generated from the chaotic generators design using Chebyshev maps that increases the security in signal transmission. Signal propagation in WSNs assumes heavy influence of fading and inter-symbol interference. To mitigate this fading influence the application of chip interleaving technique is applied. For the case of fading presence in the channel and the case of interleaver application, the theoretical expressions for the bit error rate (BER) in closed form are derived. The system simulators are developed that confirmed theoretical findings. The signal processing procedures in the transmitter and receiver blocks are presented in discrete time domain that makes the design of devices directly implementable in DSP technology, which was one of the aims of this research.


Title of the Paper: Optical Access Network based on OCDMA Systems: Transmission and Security Performance

 

Authors: Hesham A. Bakarman, T. Eltaif, P. S. Menon, M. Muqaibel, Shabudin Shaari

Pages: 35-41

Abstract: In this article we aim to investigate the theoretical and simulation analysis of the next-generation optical access network based on optical code division multiple access (OCDMA) technique. Hence, incorporating this technique with passive optical network (PON) will enable the system to support higher bandwidth compared to the standard PON. In this paper, an overview of optical OCDMA features such as increasing system capacity, physical layer network security, and improving the system performance were presented. The transmission performance of PON network based on OCDMA technique has been theoretically investigated using balanced detection scheme when modified quadratic congruence (MQC) codes were assigned as a signature sequence codes for the subscribers. Consequently, the effects of the contributed noises have been considered. These noises are phase-induced intensity noise (PIIN), shot noise and thermal noises. In addition, the system of 25 subscribers was simulated with MQC codes at the C band for the upstream signal with channel spacing 50 GHz. In addition, the system was simulated using modified prime code for multi premises network.Variation in the results was studied when fiber length and data rate were varied and different transmission power was applied. The system shows good results in terms of the bit error rate (BER), and suppression of multiple access interference (MAI). Furthermore, the security performance of the coding technique, at the physical layer, has been investigated based on the code properties for the MQC. As the code size is increased, both the complexity for the eavesdropper to detect high spectral chip pulse signal to noise ratio (SNR) and the system capacity are increased.


Title of the Paper: Voice over Internet Protocol in Wireless Mesh Networks with Opportunistic Network Coding

 

Authors: Erik Pertovt, Kemal Alic, Aleš Švigelj, Mihael Mohorcic

Pages: 42-53

Abstract: In wireless networks, network coding can be used to enhance the performance of the network. By combining multiple packets into one encoded packet the network throughput is increased and the delay is lowered. In this paper, we perform the evaluation of the Voice over Internet protocol (VoIP) application in wireless mesh networks (WMNs) using network coding. For VoIP, various codecs can be used based on the Quality of Service (QoS) requirements to perform digitalization, encoding and packetization of the analog voice signal. We use various codecs and apply opportunistic network coding to observe how the network coding influences the average network delay and jitter. Moreover, we analyze the VoIP performance at the level of individual calls in order to compare the performance of calls with the International Telecommunication Union-Telecommunication (ITU-T) QoS recommendations. Network delay, End-to-End (ETE) packet delay, and packet delay variation, are investigated for each call. One of the main QoS requirements is that ETE packet delay and packet delay variation should be lower than thresholds recommended by ITU-T organization, as packets have to be transmitted through the network in real time.


Issue 3, Volume 7, 2013


Title of the Paper: Adaptive Cascade Hybrid Configurations for Linear Array Beamforming

 

Authors: Walter Orozco-Tupacyupanqui, Mariko Nakano-Miyatake, Hector Perez-Meana

Pages: 55-66

Abstract: This paper presents the analysis of three proposed Least Recursive Mean Square (LRMS) hybrid cascade configurations for beamforming based on the Least Mean Square (LMS) and the Recursive Least Square (RLS) algorithm. It involves the use of the former single algorithm as a pre-filter and the latter one as a post-filter stage. Furthermore, the steering vector of the linear array is used as the interface between these two adaptive filters to form the hybrid cascade structure and generate the impinging signal to the post-filter block. The mathematical analysis of these new schemes is based on the orthogonality principle to prove the convergence to the optimal Wiener solution. Computer simulations have been performed to show the validity, reliability and limitations that these structures have in their capacity of recovering the desired signal corrupted by noise. In addition, the speed of these configurations is determined by the number of required iterations to reach the minimum square value of the learning curve.


Title of the Paper: Band-Notched UWB Annular Slot Antenna with Enhanced Bandwidth by Using EBG Via Holes

 

Authors: Ayman Ayd R. Saad, Deena A. Salem, Elsayed Esam M. Khaled

Pages: 67-74

Abstract: In this paper, a design of a proximity-fed planar annular slot antenna with standard band-notched characteristic for ultra-wideband (UWB) applications is demonstrated. The band-notch is realized by nearly a half-wavelength split-ring parasitic element printed around the radiating patch. The patch is excited via a proximity-fed strip line with an arrangement of EBG via holes. The voltage standing wave ratio (VSWR) of the proposed antenna is less than 2.0 in the frequency band from 2.82 to 10.74 GHz, while showing a very sharp band-rejection performance at 5.51 GHz which preserved for IEEE 802.11a and HIPERLAN/2 services. The antenna is designed, simulated, and implemented. Measured data and simulated results show good agreements along with equivalent circuit results which obtained using Vector Fitting technique. The proposed antenna provides good gain flatness, high efficiency and omnidirectional field pattern over its whole frequency band excluding the rejected band. The results show that the proposed antenna is suitable for UWB applications.


Title of the Paper: Modeling and Simulation of a Physical Layer for WSNs Based on Binary Sequences

 

Authors: Stevan Berber, Yuan Yuan, Bongsue Suh

Pages: 75-82

Abstract: The theoretical model and results of simulation of a communication system representing the physical layer of wireless sensor networks are presented in this paper. The spreading sequences used are generated according to the standard specification for low rate wireless sensor networks. Due to the sever influence of fading on signal transmission in this kind of networks, the chip interleaving technique is investigated as the mean for fading mitigation in the channel. The theoretical derivations for bit error rate (BER) in closed form are derived for the case when noise, noise and fading and interleavers are present in the communication system. It is proved that the BER can be significantly improved in fading channel using the interleaver/deinterleaver technique. The theoretical analysis, derivations of the closed form BER expressions and simulations are based on discrete time domain representation of all signals in the system. These discrete time domain system representations of signals allow direct implementation of the developed system in digital technology which was one of the aims of this research. Following the theoretical model, simulators were developed and the results of simulation confirmed the derived theoretical expressions.

 


Issue 4, Volume 7, 2013


Title of the Paper: Analysis of Radio Propagation Models for Smart City Applications

 

Authors: Andrej Hrovat, Toma┼ż Javornik

Pages: 83-92

Abstract: In this paper we give a thorough study of radio propagation models suitable for smart city applications and select two channel models for coverage prediction of wireless sensor networks for two typical propagation environments often occurs in smart city applications, namely the open area plane earth model for open areas and the four slope channel model for street canyons and tunnels. The measurement campaigns performed at three carrier frequencies applied for wireless sensor networks in Europe i.e. 400 MHz, 868 MHz and 2.4 GHz, reveals, that in open areas the plane earth model fits the measurements better than two slope model and four slope channel model gives sufficiently high accurate path loss prediction in tunnels and street corridors.


Title of the Paper: A New Hybrid Approach for Symbol Rate Detection Using Simulated Annealing and Cyclic Autocorrelation

 

Authors: James E. Whitney II, Richard A. Carr

Pages: 93-97

Abstract: Cyclic Autocorrelation has been proposed as a technique for symbol rate detection in cognitive radios. However, cyclic autocorrelation can be inefficient due to the need to perform an autocorrelation of the received signal at different cyclic frequencies followed by an exhaustive search over the entire search space in order to find the cyclic frequency that produces the maximum autocorrelation. In this paper the simulated annealing algorithm is used as a preprocessor to the cyclic autocorrelation algorithm in order to estimate the symbol rate of M-Ary phase shift keyed (MPSK) signals. The Simulated annealing algorithm is used to traverse the search space in order to find the optimum cyclic frequency without performing and exhaustive search.


Title of the Paper: Exploring Campus Netflow for Managing Network

 

Authors: Hung-Jen Yang, Miao-Kuei Ho, Lung-Hsing Kuo, Hsieh-Hua Yang, Hsueh-Chih Lin

Pages: 98-108

Abstract: The purpose of this study was to monitoring and modeling netflows on a campus in Taiwan. There is a need to understand the netflow on a flow base for maintain and managing purpose. Random sampled campus was first identified. The netflow of the campus was monitored and collected for analysis. Based upon statistical test results, weekday flow characteristics were identified. A model of netfolw according to the protocols was also created. It is concluded that there exists significant characteristics of weekday netflow and certain predictable behavior between total amounts of flow and domain service. The characteristics revealed by this study should be consider as the fundamental information for managing campus networks.


Title of the Paper: A Redundant Communications Solution for Critical Infrastructure Protection and SCADA Systems

 

Authors: Jyri Rajamäki, Jari Ahokas, Paresh Rathod

Pages: 109-117

Abstract: Securing an electricity distribution network is equally crucial to securing other critical infrastructure (CI) components. Many critical infrastructure components are operating and controlling by Supervisory Control and Data Acquisition (SCADA) systems. Very SCADA system is also controlling the power network. In the modern infrastructure, these SCADA controlled systems are connecting to standard corporate networks for various reasons. Critical infrastructure and SCADA systems require higher resilient communication channels compared to the corporate network. This infrastructure and the system also demand equally high level of security along with a corporate network. Organizations must use standard base network as a part of solution in order to have resilient communications networks. These combined networks such as TETRA, 3G, LTE, ADSL and satellite have varied level of bandwidth and built-in security features. Recently the additional feature such as a live video stream transported on the critical infrastructure and SCADA networks. These data are transporting in the same logical communications channels without disturbing the SCADA command traffic. This paper aims to propose a new model to combine these networks to produce a highly resilient and secure communications network. The proposed communication system is built-on the Distributed Systems intercommunication Protocol (DSiP) that combines the contradicting requirements to a uniform and easily maintained system. The same requirements apply to ‘Multi-Agency Cooperation in Cross-border Operations (MACICO)’ project, part of an International Celtic Plus project. The proposed DSiP system is reusable for various needs and is adaptable to future network technologies.