Showing papers in "Journal of telecommunications and information technology in 2004"

Site selection for waste disposal through spatial multiple criteria decision analysis

Abstract: This article deals with the application of spatial multiple criteria evaluation concepts and methods to support the decision-making process for site selection for waste disposal. The process makes use of a recently developed Spatial Multiple Criteria Evaluation (SMCE) module, integrated into ITC’s existing geographic information system called “ILWIS”. This module supports several compensatory and non-compensatory approaches, allowing inclusion of the spatial and thematic priority of decision makers. To demonstrate the process, a landfill site selection problem around the town of Chinchina, located in the Central Cordillera of the Andes in Colombia (South America), is used as an example. Based on different objectives, a spatial data set is being made available consisting of several maps (slope, land use, geological, landslide distribution etc.) that is used for modeling the site selection process. This study makes use of the planning and decision making framework that is developed at ITC in two major phases. In phase one, Spatial Multiple Criteria Evaluation is used to find potential sites (“design of alternative solutions”). In phase two, the potential sites are evaluated using technical and socio-economic attributes to make the final recommendation of the site (“choice of alternative options”).

Closed-form 2D modeling of sub-100 nm MOSFETs in the subthreshold regime

Abstract: Closed-form 2D modeling of deep-submicron and sub-100 nm MOSFETs is explored using a conformal mapping technique where the 2D Poisson equation in the depletion regions is separated into a 1D long-channel case and a 2D Laplace equation. The 1D solution defines the boundary potential values for the Laplacian, which in turn provides a 2D correction of the channel potential. The model has been tested for classical MOSFETs with gate lengths in the range 200–250 nm, and for a super-steep retrograde MOSFET with a gate length of 70 nm. With a minimal parameter set, the present modeling reproduces both qualitatively and quantitatively the experimental data obtained for such devices.

Boolean feedback functions for full-length nonlinear shift registers

Abstract: In the paper a heuristic algorithm for a random generation of feedback functions for Boolean full-length shift register sequences is presented. With the help of the algorithm one can generate n-stage Boolean full-length shift register sequences for (potentially) arbitrary n ≥ 6. Some properties of the generated feedback functions are presented. Keywords— cryptography, shift registers, Boolean functions.

Exploring agent-based wireless business models and decision support applications in an airport environment

Abstract: This paper describes an intelligent communication and decision support system for providing wireless services in an airport environment. A novel agent-based business model is proposed and the value chain is analysed for wireless applications. This system is studied and developed within the scope of the IST ADAMANT project, where the Athens International Airport (AIA) is used as the trial environment. First of all, a set of advanced, realistic decision support application scenarios enhancing the airport facilities both for the passengers and for the airport staff is identified. Most of the applications can be summarised as location-based personalised services. They refer both to airport internal users and to passenger users. In order to provide these services, location-sensitive service level agreements (SLAs) and radio resource management (RRM) are introduced. The design of such a system is envisaged based on a generic, multi-agent architecture, which is also presented in this paper. Keywords—wireless application, multi-agent system, wireless business model, wireless SLA, radio resource management.

Towards broadband global optical and wireless networking

Abstract: We present a novel non-conventional approach to the future optical and wireless hybrid transport network that is capable of supporting the dominating kinds of traffic, i.e., voice/real-time, wireless and packet traffic, in a single transport network. The proposed model combines different technologies as connection and connectionless networks, optical cable and wireless (microwave/millimetre wave or optical wireless) and it is suitable for a variety of purposes and services in order to achieve global broadband networking features. Our new networking model contains an extension to the wireless world in order to achieve mobility and personalisation of the connection. It consists of an upgrade of real-time traffic with a microwave modulated optical wave, in order to carry out conventional mobile wireless via optical fibres though long distances and without a significant distortion. The whole available bandwidth can be fully exploited in the hybrid network. In the IP part of the network, quality of service can be differentiated for various classes of packets and network reliability/survivability can be categorised for the whole hybrid network. This substitutes the complete and revolutionary shifting to packet traffic, that many promote, with smooth evolutionary upgrades.

Application of a hash function to discourage MAC-layer misbehaviour in wireless LANs

Abstract: Contention-based MAC protocols for wireless ad hoc LANs rely on random deferment of packet transmissions to avoid collisions. By selfishly modifying the probabilities of deferments greedy stations can grab more bandwidth than regular stations that apply standard-prescribed probabilities. To discourage such misbehaviour we propose a protocol called RT-hash whereby the winner of a contention is determined using a public hash function of the channel feedback. RT-hash is effective in a full hearability topology, assuming that improper timing of control frames is detectable and that greedy stations do not resort to malicious actions. Simulation experiments show that RT-hash protects regular stations’ bandwidth share against various sophisticated greedy strategies of deferment selection; as such it may contribute to MAC-layer network

Methods for evaluation packet delay distribution of flows using Expedited Forwarding PHB

Abstract: The paper regards problem of providing statistical performance guarantees for real-time flows using Expedited Forwarding Per Hop Behavior (EF PHB) in IP Differentiated Services networks. Statistical approach to EF flows performance guarantees, based on calculation of probability that end-to-end packet delay is larger than certain value, allows larger network utilization than previously proposed deterministic approach. In the paper different methods of packet delay distribution evaluation are presented and compared. Considered cases comprise evaluation of delay distribution models for the core network and evaluation of end-to-end packet delay in the network consisted of edge node and chain of core nodes. Results obtained with aid of analytical models are compared with simulation results. Keywords—packet delay distribution, Expedited Forwarding PHB, Differentiated Services, Service Level Specification,

ASimJava: a Java-based library for distributed simulation

Abstract: The paper describes the design, performance and applications of ASimJava, a Java-based library for distributed simulation of large networks. The important issues associated with the implementation of parallel and distributed simulation are discussed. The focus is on the effectiveness of different synchronization protocols implemented in ASimJava. The practical example–computer network simulation–is provided to illustrate the operation of the presented software tool. Keywords—parallel computations, parallel asynchronous simulation, computer networks simulation.

Critical modeling issues of SiGe semiconductor devices

Abstract: We present the state-of-the-art in simulation of silicon-germanium (SiGe) semiconductor devices. The work includes a detailed comparison of device simulators and current transport models. Among the critical modeling issues addressed in the paper, special attention is focused on the description of the anisotropic majority/minority electron mobility in strained SiGe grown on Si. We use a direct approach to obtain scattering parameters (S-parameters) and other derived figures of merit of SiGe heterojunction bipolar transistors (HBTs) by means of small-signal AC-analysis. Results from two-dimensional hydrodynamic simulations of SiGe HBTs are presented in good agreement with measured data. The examples are chosen to demonstrate technologically important issues which can be addressed and solved by device simulation.

Process and device requirements for mixed-signal integrated circuits in broadband networking

Abstract: The paper describes the present status of the broadband wireline infrastructure consisting of the backbone core, metro rings, access network, local and storage area networks. Examples of various mixed-signal integrated circuits are described. Based on these considerations required process and device performance is extrapolated.

Data analysis and flow graphs

Abstract: In this paper we present a new approach to data analysis based on flow distribution study in a flow network. Branches of the flow graph are interpreted as decision rules, whereas the flow graph is supposed to describe a decision algorithm. We propose to model decision processes as flow graphs and analyze decisions in terms of flow spreading in the graph. Keywords—data mining, data independence, flow graph, Bayes’ rule.

Fairness considerations with algorithms for elastic traffic routing

Abstract: The bit rate of modern applications typically varies in time. We consider the traffic elastic if the rate of the sources can be controlled as a function of free resources along the route of that traffic. The objective is to route the demands optimally in sense of increasing the total network throughput while setting the rates of sources in a fair way. We propose a new fairness definition the relative fairness that handles lower and upper bounds on the traffic rate of each source and we compare it with two other known fairness definitions, namely, the max-min and the proportional rate fairness. We propose and compare different routing algorithms, all with three types of fairness definitions. The algorithms are all a tradeoff between network throughput, fairness and computational time. Keywords—elastic traffic, routing, fairness, maximum throughput, algorithms, ILP, heuristics.

Probes for fault localization in computer networks

Abstract: Fault localization is a process of isolating faults responsible for the observable malfunctioning of the managed system. This paper reviews some existing approaches of this process and improves one of described techniques—the probing. Probes are test transactions that can be actively selected and sent through the network. Suggested innovations include: mixed (passive and active) probing, partitioning used for probe selection, logical detection of probing results, and adaptive, sequential probing. Keywords—fault localization, probes, computer networks, partitions, logic design.

Labeling of signals in optical networks and its applications

Abstract: The paper is a review and comparative analysis of most common techniques proposed to attach additional data or identification information to digital signals in optical fiber networks by purely optical means. Such “labels” or “headers” can be attached either to continuous bit streams, e.g., in SDH networks or to optical packets. They enable to monitor, route and identify signals in transparent optical networks, especially those with optical wavelength multiplexing, allow management and supervision of remote optical amplifiers and can be used in optical switching systems. Other applications of this relatively unknown technology include monitoring of optical path dispersion, equalization of channels in DWDM systems and detection of intrusion or jamming in highly secure networks. Keywords—optical fiber transmission, transparent optical network, pilot tone, network management, overhead data channel, optical fiber dispersion, optical label.

Analysis of bandwidth reservation algorithms in HIPERLAN/2

Abstract: This paper focuses on performance of channel access methods in the HIPERLAN/2 standard. It discusses commonly used approaches to bandwidth allocation and presents a modified algorithm for effective bandwidth management based on pre-scheduled resource grants. Simulation results show that the new algorithm ensures much higher throughput compared to the standard method. Keywords—HIPERLAN/2, MAC, bandwidth allocation, QoS.

Influence of Common Path on Availability of Ring Network

Abstract: This paper analyses availability of the ring network which uses the Path Protection switching (Sub-Network Connection Protection, SNCP). Influence of the on the ring network availability is analyzed. Data regarding failures of optical fiber cables and equipment used for calculations have been obtained during years-long observation of SDH network in HT Mostar as well as from manufacturers.

New approach to power semiconductor devices modeling

Abstract: The main problems occurring during high power device modeling are discussed in this paper. Unipolar and bipolar device properties are compared and the problems concerning high time-constant values related to the diffusion phenomena in the large base are explained. Traditional and novel concepts of power device simulation are presented. In order to make accurate and modern semiconductor device models widely accessible, a website has been designed and made available to Internet users1, allowing them to perform simulations of electronic circuits containing high power semiconductor devices. In this software, a new distributed model of power diode has been included. Together with the existing VDMOS macromodel library, the presented approach can facilitate the design process of power circuits. In the future, distributed models of IGBT, BJT and thyristor will be added.

An adaptive hidden Markov model for indoor OFDM based wireless systems

Abstract: Detailed physical layer simulation of orthogonal frequency division multiplexing (OFDM) systems requires programs that execute too slowly due to long coherence time of the indoor mobile channel. Evaluation of higher layers of such systems is simplified if suitable models for reproduction of channel errors statistics are available. An adaptive hidden Markov model (HMM) for indoor OFDM based systems that accurately reproduces error statistics of the real system with less computational effort than the exact simulation is presented in this paper. The standard HMM methodology has been modified in order to reproduce the periodicity in the error positions of the OFDM systems. The proposed model is validated by comparison of three statistical parameters: number of errors, length of the errors run and length of the error—free intervals in a frame of bits. Keywords—hidden Markov model, OFDM, multicarrier transmission.

Scattering mechanisms in MOS/SOI devices with ultrathin semiconductor layers

Abstract: Main scattering mechanisms affecting electron transport in MOS/SOI devices are considered within the quantum-mechanical approach. Electron mobility components (i.e., phonon, Coulomb and interface roughness limited mobilities) are calculated for ultrathin symmetrical DG SOI transistor, employing the relaxation time approximation, and the effective electron mobility is obtained showing possible mobility increase relative to the conventional MOSFET in the range of the active semiconductor layer thickness of about 3 nm.

Ultrathin oxynitride films for CMOS technology

Abstract: In this work, a review of possible methods of oxynitride film formation will be given. These are different combinations of methods applying high-temperature oxidation and nitridation, as well as ion implantation and deposition techniques. The layers obtained using these methods differ, among other aspects in: nitrogen content, its profile across the ultrathin layer, ... etc., which have considerable impact on device properties, such as leakage current, channel mobility, device stability and its reliability. Unlike high-temperature processes, which (understood as a single process step) usually do not allow the control of the nitrogen content at the silicon-oxynitride layer interface, different types of deposition techniques allow certain freedom in this respect. However, deposition techniques have been believed for many years not to be suitable for such a responsible task as the formation of gate dielectrics in MOS devices. Nowadays, this belief seems unjustified. On the contrary, these methods often allow the formation of the layers not only with a uniquely high content of nitrogen but also a very unusual nitrogen profile, both at exceptionally low temperatures. This advantage is invaluable in the times of tight restrictions imposed on the thermal budget (especially for high performance devices). Certain specific features of these methods also allow unique solutions in certain technologies (leading to simplifications of the manufacturing process and/or higher performance and reliability), such as dual gate technology for system-on-chip (SOC) man-

Load-Balanced Route Discovery for Mobile Ad hoc Networks

Abstract: This paper presents Flow-Aware Routing Protocol (FARP), a new routing strategy designed to improve load balancing and scalability in mobile ad hoc networks FARP is a hop-by-hop routing protocol, which introduces a flow-aware route discovery strategy to reduce the number of control overheads propagating through the network and distributes the flow of data through least congested nodes to balance the network traffic FARP was implemented in Glomosim and compared with AODV To investigate the load distribution capability of FARP new performance metrics were introduced to measure the data packet flow distribution capability of the each routing protocol The simulation results obtained illustrate that FARP achieves high levels of throughput, reduces the level of control overheads during route discovery and distributes the network load more evenly between nodes when compared to AODV This paper also describes a number of Alternative strategies and improvements for the FARP I INTRODUCTION

An exact algorithm for design of content delivery networks in MPLS environment

Abstract: Content delivery network (CDN) is an efficient and inexpensive method to improve Internet service quality. In this paper we formulate an optimisation problem of replica location in a CDN using MPLS techniques. A novelty, comparing to previous work on this subject, is modelling the network flow as connection-oriented and introduction of capacity constraint on network links to the problem. Since the considered optimisation problem is NP-complete, we propose and discuss exact algorithm based on the branch-and-cut and branch-and-bound methods. We present results of numerical experiments showing comparison of branch-and-cut and branch-and-bound methods. Keywords—content delivery network, optimization, branch-and-

Multicriteria analysis for behavioral segmentation

Abstract: Behavioral segmentation is a process of finding the groups of clients with similar behavioral patterns. The basic tool for segmentation is a clustering algorithm. However, the clusters generated by the algorithm depend on the preprocessing steps as well as parameters of the algorithm. Therefore, there are many possibilities of dividing the clients into segments and it is a subjective process. In this paper we will focus on application on multicriteria analysis for selecting the best partition of clients into segments. Keywords—segmentation, clustering, multicritera analysis, telecommunications.

High-field current transport and charge trapping in buried oxide of SOI materials under high-field electron injection

Abstract: Mechanisms of the generated positive charge and the charge trapping during the high-field electron injection at constant voltage regime in buried oxide (BOX) of silicon-on-insulator (SOI) structures fabricated by UNIBOND and single implanted separation by implanted oxygen (SIMOX) technologies are studied by capacitance–voltage characteristics. It is found, that considerable positive charge is accumulated near the buried oxide/substrate interface independently from direction of the injection (from film or from silicon substrate) for both kinds of structures. Comparison of the theory and experimental data allows to suggest that in the case of the UNIBOND buried oxide a positive charge is generated by two mechanisms—anode hole injection and band-to-band impact ionization. In the case of the SIMOX SOI material at the high-field electron injection in the buried oxide the anode hole injection with defect creation at precursor sites in the strained structure of oxide network is supposed to appear. It is shown, that the positive charge in the UNIBOND BOX can be completely annealed at a temperature of 400 °C while in the SIMOX BOX it is much more stable and the annealing temperature increases with the electron injection electric field rising.

Seamless roaming between UMTS and IEEE 802.11 networks

Abstract: Mobile Internet access is currently available mainly using 2G/3G cellular telecommunication networks and wireless local area networks. WLANs are perceived as a local complement to slower, but widely available cellular networks, such as existing GSM/GPRS or future UMTS networks. To benefit from the advantages offered by both radio access networks, a mobile user should be able to seamlessly roam between them without the need to terminate already established Internet connections. The goal of this paper is to present an overview of the profitability of performing vertical handovers between UMTS and IEEE 802.11b using Mobile IP. Several simulations have been carried out using NS-2, which prove that handovers from IEEE 802.11b to UMTS can, under certain circumstances, be profitable not only when there is no more IEEE 802.11b coverage. Simulation results show that a mobile user should be able to roam between these networks depending on the current available channel bandwidth and quality, generated traffic type and number of users in both of

User services of tactical communications in the digital age

Abstract: Increasing demands on an extensive amount of digital data and information flows for C4I is forcing the modern armies to freeze and omit EUROCOM based tactical area communications system and to develop new concepts based on the adoption of modern communication systems such as ISDN, ATM described in the TACOMS Post 2000 Final Report II in NATO. ASELSAN, as a leading company in the military electronics arena, is following and participating all the activities of TACOMS Post 2000 together with Turkish Ministry of Defense. Turkey’s tactical area communications system TASMUS is a mature and fielded system, which will satisfy future communication needs of the 21st century C4I systems. In this paper, we describe the basic features and user services of TASMUS. With the support of simultaneous voice and data capabilities, TASMUS aims to form mobile, survivable, flexible and secure network to support all the present and future communication requirements of the tactical commanders. Using the near real time data communications feature, TASMUS is also significant for the network-centric warfare applications such as tactical sensor and weapon systems, besides the communication needs of the Turkish Army. Keywords— tactical communications, IP, X.25, C4I systems.

Silicon microelectronics: where we have come from and where we are heading

Abstract: The paper briefly presents the history of microelectronics and the limitations of its further progress, as well as possible solutions. The discussion includes the consequences of the reduction of gate-stack capacitance and difficulties associated with supply-voltage scaling, minimization of parasitic resistance, increased channel doping and small size. Novel device architectures (e.g. SON, double-gate transistor) and the advantages of silicon-germanium are considered, too.