No. 3 (2014)
Published:
2014-09-30
ARTICLES FROM THIS ISSUE
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Ubiquity of Client Access in Heterogeneous Access Environment
Abstract
With popularization of mobile computing and diverse offer of mobile devices providing functionality comparable to personal computers, the necessity of providing network access for such users cannot be disputed. The requirement is further reinforced by emergence of general purpose mobile operating systems which provide their full functionality only with network connectivity available and popular XaaS (Everything as a Service) approach. In this situation and combined with the fact that most Internet-based services are able to function efficiently even in best effort environment, requirement of ubiquity of network access becomes one of the most important elements of today’s computing environment. This paper presents a general overview of the the vast group of mechanisms and technologies utilized in modern attempts to efficiently provide ubiquity on network access in heterogeneous environment of today’s access systems. It starts with division of users interested in ubiquitous network access into broad groups of common interest, complete with their basic requirements and access characteristics, followed by a survey of both already popular and new wireless technologies suitable to provide such access. Then a general discussion of most important challenges which must be addressed while attempting to fulfill the above goal is provided, addressing topics such as handover control and mobility management.
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Evaluation of the Delay-Aware NUM-Driven Framework in an Internetwork Environment
Abstract
Nowadays, due to emergence of cloud services, even the basic uses of personal computers may require the access to the Internet. In this paper modifications to Delay-Aware Network Utility Maximization System (DANUMS) are presented, which enable it to be deployed in an internetwork environment. The proposed solution consists of DANUMS and WiOptiMo systems, which cooperate by exchanging measurements of transmitted traffic in order to improve the network utility. Additionally, WiOptiMo enhances mobility by providing facilities for soft handover. Experiments presented in this paper illustrate the benefits gained from the integrated system application.
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New Threats and Innovative Protection Methods in Wireless Transmission Systems
Abstract
Many improvements in the field of wireless communication can be observed nowadays. Some developments are gradual, others are revolutionary. It is obvious that each innovation in the area may lead to new security threats and vulnerabilities. Such technologies and transmission methods as: Near Field Communication (NFC), Visible Light Communication (VLC), handover, mesh networks, 5G cellular network, mobile IPv6, beamforming, cooperative beamforming, Multiple Input Multiple Output (MIMO), Orthogonal Frequency Division Multiple Access (OFDMA), transmission in Extra High Frequency (EHF) band are very important from the security point of view. In order to preserve high level of security one needs to identify, analyse and classify distinctive sets of threats and vulnerabilities as well as some emerging data protection opportunities related to innovative wireless transmission methods and technologies. This identification, analysis and classification is a main purpose of the paper. It will focus on cryptography in wireless systems, security vs. energy tradeoffs, physical layer security. For example, common problems related to cryptography may be solved with a use of physical layer security. Data confidentiality may be fulfilled with a use of beamforming and jamming, authentication may be performed with a use of out-of-band authentication model.
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Lessons Learned from WiMAX Deployment at INEA
Abstract
Home broadband access is continuously demanding more bandwidth fueled by video streaming, entertainment and gaming applications. In 2010, a company INEA decided to roll-out new WiMAX-based services aimed to meet the needs of home users across theWielkopolska region of western Poland. It was decided to follow the 802.16e standard and the Time Division Duplexing (TDD) mode that oer the ability to adjust the downlink/uplink ratio and thus are well suited for data transmission. After an extensive testing period of equipment from various vendors, engineers at INEA have chosen the Motorola (currently Cambium Networks) PMP320 solution because it is compact and its components are space- and energy-ecient. The company choice was also influenced by its simple operation, management and installation, which ensured low costs of ownership. So far, this deployment has provided fast and aordable connectivity for Internet and telephony services to around 5,500 households across the 30,000 sq. km region. After 3 years of experience, INEA would like to share the lessons learned from this roll-out.
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DVB-T Channels Measurements for the Deployment of Outdoor REM Databases
Abstract
In this paper the analysis of the spectrum occupancy in the TV band is provided based on the outdoor measurements campaigns carried out in Poznań, Poland in 2013 and 2014. The goal of this work is to discuss the stability and other important features of the observed spectrum occupancy in the context of outdoor Radio Environment Maps database deployment. Reliable deployment of these databases seems to be one of the critical points in practical utilization of the TV White Spaces for cognitive purposes inside buildings and in densely populated cities. The results obtained for outdoor scenario are briefly compared with the previous measurements conducted indoors in Barcelona, Spain, and in Poznań, Poland.
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Adaptive Algorithms Versus Higher Order Cumulants for Identification and Equalization of MC-CDMA
Abstract
In this paper, a comparative study between a blind algorithm, based on higher order cumulants, and adaptive algorithms, i.e. Recursive Least Squares (RLS) and Least Mean Squares (LMS) for MultiCarrier Code Division Multiple Access (MC-CDMA) systems equalization is presented. Two practical frequency-selective fading channels, called Broadband Radio Access Network (BRAN A, BRAN B) normalized for MC-CDMA systems are considered. In the part of MC-CDMA equalization, the Zero Forcing (ZF) and the Minimum Mean Square Error (MMSE) equalizer techniques were used. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the blind algorithm gives approximately the same results obtained by adaptive algorithms. However, the proposed algorithm presents the advantage to estimate the impulse response of these channels blindly except that the input excitation is non-Gaussian, with the low calculation cost, compared with the adaptive algorithms exploiting the information of input and output for the impulse response channel estimation.
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QoS Equalization in a W-CDMA Cell Supporting Calls of Infinite or Finite Sources with Interference Cancelation
Abstract
In this paper, a multirate loss model for the calculation of time and call congestion probabilities in a Wideband Code Division Multiple Access (W-CDMA) cell is considered. It utilizes the Bandwidth Reservation (BR) policy and supports calls generated by an infinite or finite number of users. The BR policy achieves QoS equalization by equalizing congestion probabilities among calls of different service-classes. In the proposed models a multiple access interference is considered, and the notion of local blocking, user's activity and interference cancelation. Although the analysis of the proposed models reveals that the steady state probabilities do not have a product form solution, the authors show that the calculation of time and call congestion probabilities can be based on approximate but recursive formulas, whose accuracy is verified through simulation and found to be quite satisfactory.
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On IPv6 Experimentation in Wireless Mobile Ad Hoc Networks
Abstract
With the growing interest towards the Internet of Things IPv6-based mobile ad hoc networks (MANETs) become a key enabling technology offering the possibility of automated, unsupervised network configuration and operation. Such a functionality calls for an accurate and reliable testing of the newly proposed solutions, which is challenging due to the dynamic, decentralized and ad hoc nature of MANETs. In this work selected topics are presented on performing IPv6 protocols experimentation in wireless, IPv6-only mobile ad hoc networks – including both simulation – and testbed-based evaluation. Based on the authors experience with the evaluation of the extended IPv6 Neighbor Discovery protocol (ND++) proposed during the course of research, the selection of an opensource simulation environment is presented and a comparison between simulation and emulation experimentation methods is provided. Benefits and drawbacks of both these methodologies for testing IPv6 solutions are depicted. Moreover, the important aspects of topology and mobility considerations are considered. Finally the authors propose a testing approach that would allow for a detailed and accurate evaluation by means of open-source, easily accessible and low-cost methodologies
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Review of Simulators for Wireless Mesh Networks
Abstract
The research of computer networks construction of models that reflect the current audited environment to carry out practical research is extremely dicult and often involves signicant costs. Hence, the popularity of simulation tools that help developers to determine as early as at the stage of the simulation whether a given solution can be deployed in a real network. However, over time many dierent simulation tools have been developed, each with dierent characteristics, dierent uses, dierent strengths and weaknesses. It is the task of the researcher then to select, before starting the actual research, one of the available simulators in accordance with the needs and adopted criteria of evaluation. In the article the authors present issues related to the simulation tools and the main advantages of simulation as well as their drawbacks. To help researchers select an appropriate simulation environment, the authors present statistical information gathered during a literature survey of a number of research articles from the most popular publishers in which the selected simulators were used in initial system design.
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Priority Based Routing for Forest Fire Monitoring in Wireless Sensor Network
Abstract
Recently, forest fire monitoring system in wireless sensor networks has received much attention. The conventional scheme receives fire alert data quickly to inform about fire forest event. However, since two or more nodes may detect a fire, high priority fire detection data frequently collide. In this paper, a new forest fire monitoring system is proposed in order to reduce high priority fire detection data dropped rate, by specifying a high priority received data immediately after fire detection and just before the destruction by fire. Furthermore, the node only transmits high priority data to a node, which has a low possibility of destruction by fire for low end-to-end delay of high priority fire detection data. The simulation results show that proposed scheme can reduce high priority data dropped ratio and the end-to-end delay, and have less effect of wind direction compared with the conventional scheme.
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On-demand QoS and Stability Based Multicast Routing in Mobile Ad Hoc Networks
Abstract
Finding a connection path that remains stable for suciently longer period is critical in mobile ad hoc networks due to frequent link breaks. In this paper, an on-demand Quality of Service (QoS) and stability based multicast routing (OQSMR) scheme is proposed, which is an extension of ad hoc on-demand multicast routing protocol (ODMRP) to provide QoS support for real time applications. The scheme works as follows. Each node in the network periodically estimates the parameters, i.e., node and link stability factor, bandwidth availability, and delays. Next step is creation of neighbor stability and QoS database at every node by using estimated parameters. The last sequence is multicast path construction by using, route request and route reply packets, and QoS and stability information, i.e., link/node stability factor, bandwidth and delays in route information cache of nodes, and performing route maintenance in case of node mobility and route failures. The simulation results indicate that proposed OQSMR demonstrates reduction in packet overhead, improvement in Packet Delivery Ratio (PDR), and reduction in end-to-end delays as compared to ODMRP, and Enhanced ODMRP (E-ODMRP).
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Design of a Superconducting Antenna Integrated with a Diplexer for Radio-Astronomy Applications
Abstract
This paper presents the design of a compact frontend diplexer for radio-astronomy applications based on a self complementary Bow-tie antenna, a 3 dB T-junction splitter and two pass-band fractal lters. The whole diplexer structure has been optimized by using an evolutionary algorithm. In particular the problem of the diplexer design is recast into an optimization one by dening a suitable cost function which is then minimized by mean of an evolutionary algorithm namely the Particle Swarm Optimization (PSO). An X band diplexer prototype was fabricated and assessed demonstrating a good agreement between numerical and experimental results.
