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Novel Algorithms and Techniques In Telecommunications, Automation and Industrial Electronics



Novel Algorithms and Techniques in Telecommunications, Automation and Industrial Electronics includes a set of rigorously reviewed world-class manuscripts addressing and detailing state-of-the-art research projects in the areas of Industrial Electronics, Technology & Automation, Telecommunications and Networking. Novel Algorithms and Techniques in Telecommunications, Automation and Industrial Electronics includes selected papers form the conference proceedings of the International Conference on Industrial Electronics, Technology & Automation (IETA 2007) and International Conference on Telecommunications and Networking (TeNe 07) which were part of the International Joint Conferences on Computer, Information and Systems Sciences and Engineering (CISSE 2007).
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Chapters (88)

In this paper, we introduce a new multivariate statistical process control chart for outliers detection using kernel local linear embedding algorithm. The proposed control chart is effective in the detection of outliers, and its control limits are derived from the eigen-analysis of the kernel matrix in the Hilbert feature space. Our experimental results show the much improved performance of the proposed control chart in comparison with existing multivariate monitoring and controlling charts.
A multidirectional spatial prediction method to reduce spatial redundancy by using neighbouring samples as a prediction for the samples in a block of data to be encoded is already included in the H.264/ AVC. The spatial prediction may be performed on sample wise DPCM instead of the block-based manner as used in the current H.264/ AVC standard. The block structure is retained for the residual difference entropy coding process. There are two approaches of spatial prediction i.e. sample prediction and block prediction. The Second approach is more efficient. It is being introduced into the H.264/ AVC standard as an enhancement. This paper is a brief survey of what is important in intra prediction and with some experimental work. The work involves running of the code of H.264.
In this dissertation, a wireless network of sensors was implemented for the monitoring of physical variables, consisting of a software-hardware platform in keeping with the design model of virtual instruments. The communication protocols used were RS232 and ZigBee; the network is made up of various modules, each one consisting of five sensors and one Zigbee transmitter. These modules, in turn, communicate wirelessly with a ZigBee receiver module that is linked up to the RS232 port of a personal computer that administers the entire system. In developing the software, we used a object-oriented programming paradigm, Java programming language, the LINUX operating system, all of which are open source; this, together with the electronic elements used, makes for a low-cost system that can be used for industrial purposes by both small and medium-sized enterprises (SMEs) enhancing both their productivity as well as their competitiveness.
In the paper, we present the agent communication standards that are implemented in the Rice simulation system for management and control of processes conducted in an electrical power network. The system models the power network using the multi-agent approach, with the agent communication flowing through a 4-layer communication protocol. We summarize the main features of the Knowledge Query and Manipulation Language (KQML) which is used as the system’ s content language. These features are then confronted with specific requirements of the area of electrical power network simulation and specific adaptations directed to system optimizations are described.
This paper describes the design and implementation of a system used for monitoring and controlling the operation of various types of DC motors. The system consists of two major components: a PC application and a hardware component controlled by a FPGA device. The role of the system implemented in the FPGA device is to acquire and process data related to the DC motor’ s operation, to control the operation of the motor and to implement a communication protocol for exchanging data with the PC application. The PC application provides to the user an interface for visualizing information related to the motor’ s operation and for interacting with the system. The PC application implements a speed controller, a speed and position controller and a series of automatic tuners for the speed controllers. The main advantage of the system is that it allows to automatically determine the control parameters for DC motors with different characteristics, and it allows to easily verify the performance of different controllers.
This paper presents the design of a web-based tele-operated control system intended for office-wide geographically remote and real time control of a mobile robot utilizing networking technologies. A comprehensive account of the design paradigm for the web based control system of the robot is presented. Experiments are successfully carried out to verify the system implemented.
An automated, robust and fast vehicle license plate recognition system has become a essential necessity for traffic control and law enforcement in the present scenario. With increasing volumes of traffic being added to Indian roads every year and rough weather conditions prevalent, the challenge has become tougher. Here, we present a novel OCR-based method for number plate recognition using the Analytical Fourier Mellin transform which is fast and yields better results as compared to basic Fourier Mellin Transform. The overall system uses an intelligent but cost-effective camera, which also uses minimal space, because the processor and the sensor are integrated in one package. They are more robust and reliable in outdoor environments, they require less maintenance and they are well suited for cost sensitive applications. Traditional correlation methods have to calculate the correlation over all possible rotations to determine the rotation angle between the template and query number plate character image when this angle is unknown. In this paper we achieve the alignment by Analytical Fourier-Mellin transform (AFMT), which can quickly align two images without re sampling errors and the high computation cost involved in conversion from log-polar to Cartesian. The Signature Technique has been used for the Number Plate Localization and Peaks to Valleys method have been used for character segmentation. As in the Indian Scenarios, the character distortion caused by dirt particles, image blurring or shadows that partially cover the license plate may cause problems. Thus, the segmentation is preferably parameterized to be sensitive to spaces. To further speed up the system, the property of symmetry of the vehicle rear and front parts are uniquely used to make the process of localization/ identification of the license plate quicker.. To ensure the identified character is not a caption a syntax analysis is subsequently performed. The experimental results with number plate correlation databases show that the proposed algorithm is effective.
The paper describes a new concept for training the neural networks, which can be concretized by using a new modified classical architecture. The idea considered to be the basis of this new architecture was taken over from learning machine, namely that for defining a concept, we need both negative and positive examples. Neural networks are models that are trained only with positive examples and allow the recognition of new examples using the learning machine. Training neural networks with negative examples aims at preventing the development of some specific features of these examples and at obtaining a better recognition of the positive examples. The architecture developed through this method is generic and can be applied to any type of neural network. For simplicity and for the need of obtaining immediate results, a multilayer perceptron was chosen for testing. The results achieved with the help of this network are encouraging and they open new possibilities of study for the future.
In the last years, the use of sophisticated controllers, i.e., components that control larger systems, has become very common. In previous papers, we introduced a general, automatic methodology for the synthesis of optimal controllers which exploits explicit model checking to generate controllers for very complex systems. However, to completely validate the usefulness of our methodology we still need to compare it with other, well-established controller generation techniques that are currently applied to a variety less complex control problems. To this aim, in this paper we present a comparative evaluation, from both a theoretical and a computational point of view, between our model checking methodology and the widely applied dynamic programming approach, using the well known inverted pendulum problem as a test case. As a result, we find that our approach is always feasible when dynamic programming can be applied, and that the generated controllers perform better than the ones obtained by dynamic programming.
This paper discusses three basic concepts: a) The behavioral management of artificial intelligence (AI) namely the intelligent multi agent systems, b) a geometric property of any object considered as an environment, and that define the average location of their weight and can completely describe the motion of any object “Uniform Mass, Common Shapes, Non-uniform Mass and a general shape” through space in terms of the translation of the center of gravity (G) of the object from one place to another and the rotation of the object about its center of gravity if it is free to rotate. c) Artificial immune system that imitates the biological theory called the immune system and the evolutionary computation called Discrimination-based Artificial Lymphocyte (that includes a Genetic Artificial Immune System GAIS): modeling the learning mechanism of Self and Non-self Discrimination for environment idiosyncrasy. The outcome of this research is an Artificial Immune System based Intelligent Multi Agent robotic that solves agent-based applications. This new and specific strategy is applied to a robot cooperation problem focusing on the center of gravity where autonomous mobile robots emulate natural behaviors of our cells and molecules and realize their group behaviors; and the results prove that our method has solved the problem successfully.
Team-Robotics is an evolving mobile embedded system comprising a set of autonomous mobile robots operating in a dynamic environment and cooperating to fulfill a particular task. Scheduling is one of the main attributes of Team-Robotics. The objective of this research is to enable software self-scheduling and its monitoring at runtime in evolving Team Robotics systems modeled as reactive autonomic systems with the Autonomic Systems Timed Reactive Model (AS-TRM) architecture. In this paper, we propose a runtime self-monitoring methodology for controlling the correctness of behavior in such a system, based on the synchronous composition of its reactive autonomic components modeled as labeled transition systems, and from the specification of system policies such as safety and liveness. The AS-TRM architecture, sustaining the real-time self-scheduling modeling, verification and monitoring, is further refined with the Autonomic System Specification Language (ASSL) - a framework for formally specifying and generating autonomic systems. With ASSL, we can specify high-level behavior policies, thus it is a highly appropriate language for specifying self-scheduling mechanism as part of the overall team-robotics system behavior.
A novel control and mechanical system design of a linear direct drive permanent magnet actuator is presented. The actuator consists of a Halbach permanent magnet array for the moving part and a two-phase air core stator winding. The magnet assembly is clamped to the stator with springs that maintain the actuator in a fixed position when no power is applied. By applying a sequence of controlled current pulses both separating and propelling forces are generated. A prototype of the actuator was built. The control system was developed and tested with the actuator prototype. The proposed control algorithms require neither high computational capacity of the hardware nor high resolution velocity information. A model was developed to assess the control system performance. The control system design and associated test results are discussed.
In this paper, we discuss the exact collision course in a dynamic environment between a wheeled mobile robot and a moving object. The paths intersection conditions in the horizontal plane are deduced based on the geometry of the paths, and the collision course is deduced based on the relative kinematics model between the robot and the moving object. The exact conditions under which the robot and the moving object are in a collision course are derived and proven rigorously. The collision course condition is expressed as a function of the robot and the moving object orientation angles and linear velocities. The method can be used for collision detection in a dynamic environment, and therefore, it can be used for collision avoidance. Several simulation examples are used for an illustration.
Antifriction bearing failure is a major factor in failure of rotating machinery. As a fatal defect is detected, it is common to shut down the machinery as soon as possible to avoid catastrophic damages. Performing such an action, which usually occurs at inconvenient times, typically results in substantial time and economical losses. It is, therefore, important to monitor the condition of antifriction bearings and to know the details of severity of defects before they cause serious catastrophic consequences. The vibration monitoring technique is suitable to analyze various defects in bearing. This technique can provide early information about progressing malfunctions. In this paper is presented a data acquisition system conceived for the analysis of the signal from two vibration transductor.
Extensive research on model-based 3D object tracking has yielded a number of effective methodologies. However, work reported in the literature on initiating tracking has been limited. This paper addresses this issue via a novel framework that can automatically find an Object-of-Interest (OI) in a dynamic scene and initiate tracking. Since OI definition is, typically, application dependent, the proposed framework is modular and customizable. It combines a real-time motion segmentor with a set of customizable interest filters to separate, highlight, and select the OIs. Furthermore, our earlier model-based object tracker is extended in this paper to utilize OI-selection data and track objects in the presence of background clutter. Thus, the overall computer-vision system presented in this paper can automatically select, model, and track the six degree-of-freedom position and orientation of an OI, whose model is not known a-priori. Proposed algorithms were verified via extensive simulations and experiments, some of which are presented herein.
The ideas of pull production managed by kanban-cards are well documented in the literature and are in practice worldwide. The advance of ICT technologies like RFID technology presents us with the opportunity to develop more advanced ICT supported electronic kanban solutions. This study defines the factors influencing the success of electronic kanban systems and describes how they should be taken into account in the planning process. The study suggests that the understanding of original pull planning philosophy is important. The shop floor practices refined in leading companies utilizing the pull production system have to taken into account while planning the practical ICT applications. The UCD process is important, since the original ideas have to be infused in shop floor information and material flow control systems where the human-computer system interaction takes place.
This paper introduces an omni-directional mobile robot for educational purposes. The robot has full omni-directional motion capabilities, thanks to its special Mecanum wheels. The paper provides some information about conventional and special wheels designs, mechanical design aspects of the Mecanum wheel and also electronics and control strategies: remote control, line follow, autonomous strategy.
Modifications to the common IFT algorithm are proposed in order to address the problem of poor internal performance that was noted in instances that are commonly encountered in industrial systems. This is caused by pole-zero cancellation as demonstrated and four proposals that achieve pole-shifting for IFT in cases where it would otherwise produce pole-zero cancellation are investigated.
This paper recommends a layered system model to overpass the gap between mobile and grid computing world. The model divides the complexities in mobile grid integration, among different components of different layers of the proposed model. The model proposes an efficient architecture which addresses the problem of scheduling and disconnection. The model addresses resource scheduling problem and principally focuses on disconnections problem of the mobile devices, battery power and economy issues.
In this paper we present a robust stability analysis for a time-delay systems, in closed loop with proportional, proportional integral and proportional derivative (P, PI and PD respectively) controllers. The frequency approach is used in order to obtain necessary and sufficient conditions for the robust stability of the characteristic equation in closed loop and to tune the controller. The time domain analysis is used to obtain sufficient stability conditions for the system in closed loop with the PI controller, with nonlinear uncertainties. Also, the results are applied to a binary column distillation and coupled tanks, process commonly used in industry applications.
This paper presents a comparative analysis of some novel approaches proposed by authors for content based image retrieval (CBIR). One of them uses Two-Segments Turning Functions (2STF) and provides searching and retrieval of the multimedia documents within digital collections. Another technique retrieves images computing similarity between wavelet coefficients of querying and preprocessed images. For this purpose the Symlet transform has been used in designed system called Image Retrieval by Neural Network and Wavelet Coefficients RedNeW. However both of approaches operate with low-level characteristics processing color regions, shapes, texture, and they do not provide the analysis of image semantics. In order to improve these systems a novel approach is proposed that combines non-sensitive to spatial variations shape analysis of objects in image with their indexing by textual descriptions as part of semantic Web techniques. In the proposed approach the user’ s textual queries are converted to image features, which are used for images searching, indexing, interpretation, and retrieval. A decision about similarity between retrieved images and user’ s query is taken computing the shape convergence and matching to ontological annotations of objects in image providing in this way definition of the machine-understandable semantics. In order to evaluate the proposed approach the Image Retrieval by Ontological Description of Shapes IRONS system has been designed and tested using some standard domains of images.
We use hybrid specification methods to capture the behavior of the perceptual system of autonomous mobile robots. A robot is divided into three main subsystems: the perceptual subsystem, the planning subsystem, and the acting subsystem. The perceptual system is itself decomposed into subsystems. We elaborate a formal description of these subsystems, and we model the communication protocol among them. A software simulation is developed to illustrate the behavior of the proposed design. The resulting model allows developers to test, verify, and simulate autonomous robot systems.
This communication proposes a basic software and hardware architecture of a controller for the X10 technology interface CM11A, oriented to the world of home automation. The implementation of the system is based in the use of programmable devices such as FPGA (Field Programmable Gate Array). With this controller an end user will be able to control and to manage a set of devices distributed in a domotics space
The robust performance of a control design scheme for sloshing suppression and container positioning during liquid transfer using robotic manipulators is studied with respect to parametric uncertainty. The control scheme combines a partial inverse dynamics controller with a heuristically tuned PID controller. Robustness is studied with respect to uncertainties on the parameters of the liquid, namely the liquid’ s density and viscosity, as well as the liquid’ s level within the tank. The range of uncertainties that can be well tolerated without critical deterioration of the closed-loop performance is determined using simulation results. Moreover, an enhancement of the control design scheme is proposed that improves robustness.
In the present work we study the application to a characteristic nonlinear process of the Step-Wise Safe Switching (SWSS) control approach for SISO plants. The process nonlinear description is considered to be unknown for control design, while its behavior is approximated by a set of SISO linear models derived through identification around corresponding operating points. The performance of the supervisory scheme is illustrated using simulation results, which are also compared with corresponding results of other approaches.
An algebraic model for interconnected dynamic systems with dead time is proposed. The model structure separates the system dynamics and connections into two sets of equations in which the dynamic equation is invariant under changes in system interconnections. Useful properties of the characteristic connection matrix of the resulting model are illustrated through applications of the theoretical results for feedback connections and for model inversion. It is shown that the former can guide the design of control structures in industrial plants before modelling their dynamics whilst the latter can optimize block diagram connections to ensure causal dynamic blocks where possible.
Teleoperation system performance suffers from the delays in communication lines. These delays are usually variable time delays. The customary wave variable technique used for constant time delays cannot provide satisfactory results to stabilize the system under variable delays. Another problem is observed in the position tracking performance of the limited-workspace teleoperation systems. Although wave variable technique is proven to track position demands successfully under constant time delays given that there is no communication failure, position tracking performance also degrades under variable delays. In this paper, a new controller is proposed to stabilize the system and enhance position tracking performance under variable time delays. This proposed controller is then applied to an identical master-slave teleoperation configuration which qualifies as a limited-workspace teleoperation system.
Studying the Manipulability index for every point within the workspace of any serial manipulator is considered one of the important problems, required for designing trajectories or avoiding singular configurations. We had to go through this problem for our project of optimizing D-H parameters of extending for Mitsubishi which is existed at our lab. First step is to get all points within the workspace envelope with different manipulability bands and to find most the high band to start forward kinematic design and optimization of additional s parameters. We have discovered a new concept in this paper ,related for one method used before in measuring kinematic Manipulability .We have made simulations supporting our method on Puma560, Mitsubishi movemaster, and six degrees of freedom manipulator.
This article is presenting a method for simultaneous localization an mapping (SLAM) of mobile robots in unknown environments. The method is using 3D range data which are acquired from a continuously inclined laser time of flight ranging sensor. In order to accelerate existing computational time-demanding Iterative Closest Point SLAM methods, the SLAM procedure is using a leveled map of the environment created from the 3D data which serves as a pre-estimation of the optimal translation and rotation in three degrees of freedom. This can eliminate the number of iterations of the final robust six degrees of freedom (6DOF) ICP registration, thus saving a lot of computational time. The criteria of the success of this method are the characteristics of the environment, especially the way the environment is structured, and the appropriate setting of the leveled map extraction. Results from the testing of the method in indoor environment are also presented.
A peer-to-peer collaboration framework for multi-sensor data fusion in resource-rich radar networks is presented. In the multi-sensor data fusion, data needs to be combined in such a manner that the real-time requirement of the sensor application is met. In addition, the desired accuracy in the result of the multi-sensor fusion has to be obtained by selecting a proper set of data from multiple radar sensors. A mechanism for selecting a set of data for data fusion is provided considering application- specific needs. We also present a dynamic peer-selection algorithm, called Best Peer Selection (BPS) that chooses a set of peers based on their computation and communication capabilities to minimize the execution time required for processing data per integration algorithm. Simulation-based results show that BPS can deliver a significant improvement in execution time for multi-radar data fusion.
The paper presents an approach to improve the dependability of software implementation of the explicit DMC (Dynamic Matrix Control) Model Predictive Control (MPC) algorithm. The investigated DMC algorithm is implemented for a control system of a rectification column - a process with strong cross-couplings and significant time delays. The control plant has two manipulated inputs and two outputs. The fault sensitivity of the proposed implementation is verified in experiments with a software implemented fault injector. The experimental results prove the efficiency of proposed software improvements.
The analog front end is one of the key elements in passive UHF RFID transponders, accounting for such diverse operations as RF-DC conversion, voltage regulation, modulation und demodulation of the incident RF wave, and voltage limiting, among others. During the design process it is therefore necessary to accurately simulate the power up process and such functions as demodulation and backscatter modulation. However, since the input impedance of the chip varies with different operating conditions, the test bench set up poses a complex task. In addition, the antenna connected to the front end plays a key role and must be adequately modeled. This paper focuses on the simulation strategy of the analog front end for an RFID transponder fabricated in standard CMOS technology working in the UHF/ SUHF range. We show how the input impedance and input power of the analog front end in its active and idle states can be precisely determined through simulation
Initial capital investment for setting up an electrical power plant is huge, and the annual operating costs of major and preventive maintenance, administration, labor, fuel consumption, etc., amount to a very large sum. Therefore, optimized operation of the power plants and accomplishment of the highest level of utilization is of utmost importance. This paper reviews the use of neural network techniques for optimal load-distribution in a network of power plant units, and using a software program. The computed results for a one-day operation of a power plant are mathematically analyzed and compared. Fuel cost is calculated by the program and compared with the Figures obtained via manual methods.
There is a growing need to block the illegal immigrants into US-Mexico border as part of ‘ war on drugs’ and for ‘ national security’ , especially after September 11, 2001 [1]. In this research, an efficient border surveillance system using video cameras and video processing units connected to a base station using a wireless network is proposed. A novel image enhancement technique is incorporated to get a quality image of the intruder even at low lighting conditions or during night. This system will send an interrupt signal to the nearby base station when an intruder is detected along with intruder’ s image for immediate law enforcement activities. A light source is also provided with automatic ‘ ON/ OFF’ capability to capture the image when it is completely dark.
This paper presents analysis, design and simulation of velocity loop PDFF controllers and }H ∞ feedback controller for permanent magnetic synchronous motor (PMSM) in the AC servo system. PDFF and H ∞ control algorithm have its own capability of achieving good performance criteria such as dynamic reference tracking and load torque disturbance rejection. The PDFF is designed and analyzed in the forward loop to provide low frequency stiffness and overcome low-frequency disturbances like friction. While in the feedback loop, H ∞controller is designed to meet system robust stability with the existence of external disturbance and model perturbations. The proposed PDFF and H ∞ controllers are designed based on the transfer function of the poly-phase synchronous machine in the synchronous reference frame at field orientation control (FOC). The parameter variations, load changes, and set-point variations of synchronous machine are taking into consideration to study the dynamic performance.
Relations between a trilattice and corresponding meet-distributive lattices are discussed. The three meet-distributive lattices illustrate the five information levels, five logical levels and five levels of constructivity respectively. While the trilattice shows connections among the sixteen truth values in general, the three meet-distributive lattices visualize specific information about the sixteen truth values with respect to information, logic and constructivity.
Mobile platforms are usually equipped with sensors for obstacle avoiding or building maps of area. In this article there is presented an algorithm based on Hough transformation. Also experiment for determining the properties of used sensor is presented.
This paper deals with a new approach of trajectory tracking for a vision based x-y robot which delivers a delayed and sampled output. A control theory of using a class of piecewise continuous systems named as piecewise continuous controllers and a specific observer enabling sampled tracking is developed. The experimental results show the effectiveness and robustness aspects of the method.
mdash MEMS (Microelectromechanical System) reliability is a very critical issue for its commercial applications. In order to measure the reliability of MEMS, a systematic reliability model is required. In this paper, we developed a MEMS reliability model for quantitative assessment of the MEMS reliability analysis. Based on this model, we analyze the reliability of both BISR (built-in-self-repairable) and non-BISR MEMS comb accelerometers under Z-axis shocking environment. Simulation results demonstrate very effective reliability enhancement due to the BISR design. The reliability model can also be applied to other MEMS devices under various failure mechanisms in a similar way.
This paper presents a technique for automatic generation of a transition network and its translation to a PLC program from the processing specifications. On the one hand the paper presents an algorithm for generating PLC code, and on the other hand the paper presents a new representation scheme expressing the high level function of the system. Thus, it is hoped that the new transition networks could become successful replacement for the current PLC languages.
DES, an old but very useful algorithm of encryption, has been endangered to be replaced in the latest years by the more advanced and competent algorithms as we can exemplify: Triple DES and AES (Advanced Encryption Standard) both from the same category - block oriented encryption algorithms. Obviously, the more advanced the technology is, the requirements for implementation are more costlier and often, the devices that support these advanced implementations are very sophisticated and hard to build or require a lot of work comparing with the classic, traditional once. From the financial as well as from implementation point of view, it would be definitely very important for the cryptography to keep using DES as long as possible, this being dictated of the ability of this encryption algorithm to remain efficient and how many resources might still have. The present study is needed to be another way to look at DES and review the other side of improvements that might be done in order to keep it up for a few more years. This might be considered a hybrid between DES and Triple DES by keeping on one side the efficiency of plain DES and taking on the other side a part of Triple DES higher security. Even if is not a “Double DES” because of the different principle used, it might be a good idea attempting to mix these two important algorithms. For the purpose of this article we will call this implementation “2K-DES”.
One-time password scheme based on infinite forward stepping hash chains and not requiring re-initialization after a certain number of authentications is proposed. It resists known for such type schemes attacks, channel failures, and server side database compromise.
This paper deals with the estimation of rapidly time-varying Rayleigh fading channels in Orthogonal Frequency Division Multiplexing (OFDM) mobile wireless systems. When the fading channel is approximated by an Autoregressive (AR) process, it can be estimated by means of Kalman filtering. Nevertheless, the AR model order has to be selected. In addition, the AR parameters must be estimated. One standard solution to obtain the AR parameters consists in first fitting the AR process autocorrelation function to the theoretical Jakes one and then solving the resulting Yule-Walker Equations (YWE). However, this approach requires the Doppler frequency which is usually unknown. To avoid the estimation of the Doppler frequency, the joint estimation of both the channel and its AR parameters can be addressed. Instead of using the Expectation-Maximization (EM) algorithm which results in large storage requirements and high computational cost, we propose to consider a structure based on two-cross-coupled Kalman filters. It should be noted that the Kalman filters are all the more interactive as the variance of the innovation of the first filter is used to drive the Kalman gain of the second. Simulation results show the effectiveness of this approach especially in high Doppler rate environments.
All research to date using wireless networks for wildlife tracking has concentrated on monitoring a single species, using large GPS enabled collars. These collars are too heavy to attach on smaller animals. Rather than omit small animals from the tracking spectrum, we show how a fusion of GPS tracking (where applicable) and an improved version of VHF tracking can result in a system which is able to track a wide range of animal species using the same underlying wireless network for information transfer. Tags are equipped with radio transceivers, which are used to both transmit and receive beacons. Received beacons are used to construct radio proximity maps which characterize co-location of various animals at different points in time. Furthermore, as the locations of some nodes are known, coarse estimates of animal locations can be determined, especially around focal points such as waterholes. We present the components of our system and discuss our prototype implementation.
IEEE 802.15.4 is a proposed standard addressing the needs of low-rate wireless personal area networks LR-WPAN with a focus on enabling the wireless sensor networks. This is an emerging application of wireless sensor networking with particular performance constraints, including power consumption, physical size, robustness and security. The two factors that are of utmost importance in the development of such networks are energy efficiency and bandwidth utilization. Greater emphasis is hence required for the design of newer MAC protocols to maximize net throughput for the available bandwidth. In this paper, we introduce a new paradigm of ‘ circularity’ by selectively sensing the medium as busy for appropriate data packets in order to obviate the costly data collisions so as to achieve maximum net throughput. Results are substantiated through NS-2 simulations, dealing with IEEE 802.15.4 beacon enabled mode for star topology network.
-Securing Wireless LAN is a task in progress, being a constant concern for every network administrator. Choosing the right wireless LAN security mechanism is a real challenge, because it depends on what level of risk is allowable. Taking also into account the performance and interoperability issues, this paper covers the main wireless LAN security protocols from both the enterprise and home user perspective.
This paper proposes a simple synchronization scheme for a new TR-UWB detection method called Time Delayed Sampling & Correlation (TDSC). The TDSC concept is based on inter-correlation between two waveforms captured by two time delayed samplers. The objective is to determine a synchronization scheme with lowest complexity for silicon integration without affecting the BER performance. A multiple correlator acquisition structure in conjunction with a training sequence and a smoothing procedure is used to estimate the signal correlation. Acquisition speed and BER performance are analyzed using IEEE UWB channel models. Results show that good performance are obtained using few correlators and fast acquisition.
In this paper we present an algorithm that allows a wireless sensor node to decide with reasonable error tolerance whether the node is within a region of interest or not. The algorithm requires a very limited amount of information exchange with neighboring nodes, making it very energy-efficient for resource-scarce sensor nodes. The sensitivity of event detection using this algorithm can be adjusted using a multiple-scale method. We show preliminary simulation results to demonstrate the effectiveness of the algorithms
In this paper, a wireless Circular Model over a generic distance-vector routing protocol is presented and analyzed. The performance of this model over the Distance Vector protocol, which is an implementation of Distributed Bellman-Ford algorithm, has been evaluated by using the simulation environment of NS-2. We conducted an extensive evaluation study for various mobility schemes in order to incorporate the behavior of nodes and the routing protocol in a real-life hotspot situation In the test-bed model, while the number of source nodes was allowed to arbitrarily vary, there was exactly one destination node, closely modeling thus real-life situations where a single hotspot/access point exists. Finally, different constant bit rates (CBR) were used in order to estimate the throughput of receiving, dropping rates, the number of lost packets, as well as the average packet delay under various traffic conditions. This study is aimed to help wireless network designers in choosing the best suited routing protocols for their networks, through making explicit performance figures for common network setups.
In this paper we are considering the performance evaluation of three routing protocols in Mobile Ad-hoc Networks (MANETs). We have tested the effect of speed, TCP types, and maximum queue length for Destination Sequence Distance Vector (DSDV) protocol, Dynamic Source Routing (DSR), and Ad-hoc On Demand Distance Vector (AODV).
In this paper we propose light-weight-agent as an efficient and effective tool for implementing data communication network bandwidth optimization and response time. The routing model for the agents is based on TSP algorithms. Performance comparison was carried out among RPC, Single Mobile Agent and tiny agents otherwise referred to as lightweight agents on the basis of bandwidth usage and response time. The performance evaluation shows the superiority of lightweight agents over the other schemes in terms of bandwidth usage and the response time.
The lack of an accepted standard approach to the provision of caller location information is a serious shortcoming in IP telephony. This paper presents a novel approach to implementing this functionality without the additional infrastructure overheads typically found in comparable efforts. The proposed system achieves caller location identification using a series of SNMP requests that could be implemented on existing networks. Initial evaluation shows potential for further development as an alternative to other proposed solutions.
-This article intends to characterize the traffic flows of SIP/ RTP and IAX protocols in the environment of IP Telephony as standard of communication in their local networks. Our study allowed us to conclude that the packages of voice have a significant impact on the amount of data injected in LANs, which makes of fundamental importance the development of tools to evaluate them.
Recent developments in wireless communications have enabled the development of low-cost, low-power wireless sensor networks (WSN) with wide applicability, including environment and vehicle-health monitoring. Minimizing energy consumption and hence maximizing the life time of the network are key requirements in the design of optimum sensor networking protocols and algorithms. Several routing protocols with different objectives have already been proposed for energy-efficient WSN applications. This paper surveys a sample of existing energy-efficient cluster-based and QoS-aware routing protocols and highlights their key features, including strengths and weaknesses
-Attackers on the Internet typically launch network intrusions indirectly by creating a long connection via intermediary hosts, called stepping-stones. One way to detect such intrusion is to check the number of intermediary hosts. Neural networks provide the potential to identify and classify network activity. In this paper, we propose an approach to stepping-stone intrusion detection that utilizes the analytical strengths of neural networks. An improved scheme was developed for neural network investigation. This method clustered a sequence of consecutive Round-Trip Times (RTTs). It was found that neural networks were able to predict the number of stepping-stones for incoming packets by the proposed method without monitoring a connection chain all the time.
To evade detection, network attackers usually launch intrusions through stepping-stones by building a long connection via intermediary hosts. In order to detect long connection chains, we first need to identify whether a host has been used as a stepping-stones. In this paper, we proposed the packet fluctuation approach to detect stepping-stones based on the range of a random walk model. Two algorithms (transformation and packet size) are proposed for this approach to distinguish the stepping-stone connections (ATTACK pairs) from the normal connections (NORMAL pairs). We also show the effectiveness of our algorithms in detecting the chaff perturbation. It is found that both algorithms are able to effectively identify the stepping-stone connections.
-With the latest advances in Information and Communication Technologies (ICT), using different technologies for electronic-payment has become a major issue in the retail market. The use of portable communication devices became particularly attractive candidates when versatility, security and simplicity features of payment technologies are considered. In this paper, we investigate the use of mobile communication devices as versatile, secure and simple micro-payment tools, which satisfy the related financial, technological, computational and managerial requirements. The versatility and security of the method comes from the use of a mobile telephone and a Variable Transaction Number (VTN) in each transaction. Experimental results have shown that, the systematic requirements for the implementation of this technology are minimal and the costs involved are very much reasonable.
-This work aims at providing a proof of concept for multiplexing in Bluetooth by using traditional Time Division and Frequency Division multiplexing overlays upon frequency hopping spread spectrum (Bluetooth Modulation) by means of a functional simulation. This overlaid multiplexing technique can simplify the point to multi-point connections, especially when there are multiple Bluetooth devices in the vicinity and using the limited ISM spectrum. The available narrow bandwidth can be better utilized in point to multi-point connections using the proposed method.
This publication gives new results in applying the theoretical knowledge based on the Laplace-Stiltes transform. The main purpose is to predict packets transmitting delay, in a network based on the Internet technology. A new method for modeling the real-time networking process is designed.
Developing network simulations is a complex task that is often performed in research and testing. The components required to build a network simulator are common to many solutions. In order to expedite further simulation development, these components have been outlined and detailed in this paper. The process for generating and using these components is then detailed, and an example of a simulator that has been implemented using this system, is detailed.
Hybrid Wireless Mesh Networks (HWMNs) based on the IEEE 802.11 are being increasingly deployed as a varied network of Mobile Ad-hoc Network (MANET) to provide users with extended coverage for wireless Internet access. HWAN, however, has a problem of too wide broadcasting of the Route Request (RREQ) in the route discovery of the Ad hoc Ondemand Distance Vector (AODV) protocol. In this paper, to enhance the performance of the AODV protocol, we have transformed it into a multipath protocol and proposed a new protocol that overcomes disadvantage of AODV by composing the neighbor table for overloaded RREQ. The neighbor table is provided in the form of metric using several items including the bandwidth. This can bring the localization effect of the nodes and we can expect a performance improvement by preventing an overloaded RREQ. Through the simulation, we could confirm better performance in packet loss rate, throughput, packet delivery ratio and routing overhead than the DSR protocol and AODV protocol.
High-performance pseudorandom number generators (PRNGs) play an important role in a variety of applications like computer simulations, and industrial applications including cryptography. High-quality PRNG can be constructed by employing cellular automata (CA). Advantage of the PRNG that employs CA includes that it is fast and suitable for hardware implementation. In this paper, we propose a two-dimensional (2-D) CA based PRNG. Our scheme uses the structure of programmable CA (PCA) for improving randomness quality. Moreover, for reducing of serial correlations among the produced pseudorandom bits, a consecutive bits replacing spacing technique is proposed. Finally, we provide experimental results to verify the randomness quality using ENT and DIEHARD test suites.
This paper presents a very efficient approach for streaming wireless video. The method is based on encoding MPEG video streams using differently encoding technique, I-P(Intra)-B(Intra). P(Intra) frames are coded using motion estimation and each one has a dependency only on to the preceding I- frame. Similarly, B(Intra) frames are coded based on a forward prediction from a previous I - frame as well as a backward prediction from a succeeding I - frame of the next Group Of Pictures (GOP). The requirements of wireless video include controlled jitter, improved packet loss characteristics and mechanism to dynamically adjust the output bit rate of the video encoder to meet the variable wireless channel throughput. Mechanisms for controlling the proposed MPEG-based streams using dynamic rate control algorithm are also presented and their effectiveness is assessed through extensive simulations. Compared with the MPEG-4 rate control algorithm, our proposed algorithm can effectively enhance loss characteristics, adjust the out video bit rate to meet the variable channel throughput channel; thereby, improve the smoothness of the video.
This paper presents interactive compression algorithms for streaming media over high speed networks. An MPEG coded media sequence is typically partitioned into small intervals called GoP (Group Of Pictures). This structure allows a simple realization of forward (normal)-pay operation but imposes several additional constraints on the other interactive functions. Implementation of the rewind operations requires that the decoder either decodes the whole GoP and store it, or it decodes the GoP up to the current frame to be displayed. Both of these techniques lead either to the requirement for large storage at the client machine (to store a fully decoded GoP) or massive decoding processing power (to fully decode a GoP at required displayed frame rate). Neither of these options is desirable. Furthermore, Fast Play (Fast Forward/ Jump Forward) functions of MPEG coded video present are problematic. When a P-/B- frame is requested, all the related previous P-/I-frames need to be sent over the network. This is likely to lead in considerable increase in communication bandwidth and decoding power compared to the normal-play mode. Several interactive algorithms are detailed with respect to server load/network bandwidth and decoder complexity. Finally an extensive comparative study has been carried out in order to determine the trade offs of the proposed approaches.
Part of a detailed study of adaptive radio techniques, the work presented in this paper focuses on the potential of MEMS (Micro-Electro-Mechanical Systems) in reconfigurable antenna array technology. After identifying the main challenges and benefits of multiple antenna systems, we have analyzed the four mechanisms in which a multiple antenna system can improve upon the throughput of a traditional wireless network: beamforming, beam-steering, transmit and receive diversity, and spatial multiplexing. In this paper we propose a unified technology for both the MEMS and the metallic pixel-patches that form the reconfigurable antenna array, thus aiming at a less expensive one, that can be unitarily controlled, as a single entity. This will in turn reduce the computational complexity of the control module. We have designed, simulated and analyzed reconfigurable MEMS antenna arrays at 40 GHz, 2.4 and 5 GHz. Reconfigurability of the operating frequency and of polarization are discussed. Based on our observations we can set the premises for new adaptive strategies.
In general terms, the public telecommunication networks in Venezuela are conformed by Access, Transport and Core Networks. The locations where does not exist telecommunications services but there are users, generally exits electrical services, which allows utilization of existing electrical systems as the access network. During the development of this research it was consulted documentation related to PLC implementations in Europe, which allowed to establish how is constituted a based PLC network, which are the elements that need to be considered, aspects related with electromagnetic compatibility, and transmission speed researched, also it was consulted the PLC systems description developed by vendors associations and organisms without profit aims, doing more specific in testing PLC systems and results. This paper presents the research results of information transmission systems over low and medium electrical power supply networks, as a last mile alternative for access to the public telecommunication network in Venezuela using PLC.
This work shows the design, simulation, and analysis of two optical interconnection networks for a Dataflow parallel computer architecture. To verify the optical interconnection network performance on the Dataflow architecture, we have analyzed the load balancing among the processors during the parallel programs executions. The load balancing is a very important parameter because it is directly associated to the dataflow parallelism degree. This article proves that optical interconnection networks designed with simple optical devices can provide efficiently the dataflow requirements of a high performance communication system.
We present the development and implementation of an algorithm for tracking the position of a mobile network node. The tracking algorithm uses distance measurements between a mobile node and multiple anchor nodes. The first stage of our algorithm calculates the initial position from distance measurements relative to three (2D) or four (3D) anchors of known position. In a second stage this initial position is improved and tracked over time by feeding a Kalman filter with new distance measurements to neighboring anchor nodes of known position. Both the algorithm and the related communication protocol have been implemented and verified in multiple scenarios by using the event driven OMNET++ network simulator.
During the last decade wireless systems has experienced tremendous demands from social market. Subscribers now want a wider choice of services, better quality, faster response times, and greater coverage, which enhance the development of wireless technology than ever before. Among these, one of the greatest concerning problems for seamless global connectivity of mobile user is mobility management. The aim of this paper is to analyze the IP based Mobility management for next generation wireless networks. By the way of mobility management it is possible to locate roaming terminals for call delivery and maintain connections with mobile terminal that changes their points of attachment. In this paper it is also discussed how several type of mobility can be solved by Mobile IP and cellular IP.
Reducing email spam has been an active industry and academic research domain for a number of years. Despite this, spam has remained an on-going world-wide problem which absorbs significant network resources in its delivery. Client-side solutions have addressed much of the end-user nuisance factor, but trace-back solutions have not succeeded in sufficiently reducing spam ingress at its source due to both the movement towards distributed spam generation and geopolitical factors. At a systems-level, part of the inherent issue in addressing global spam is the current divergence between responsibility and accountability; end-users’ are made responsible for addressing issues which the originating ISP’ s are better positioned to solve. Within this work, an overlay network-based approach is developed, which employs peer-to-peer QoS agreements in conjunction with a non-repudiation protocol for broadcast environments, to affect a low-spam overlay network. This of course does not solve the global spam issue, but does allow participating communities to move to a low-spam environment provided they are willing to accept their agreed to responsibilities.
The efficiency of any system is related to the quality of its configuration and tuning. Especially in security appliances, there exists strong relativity in performance efficiency and quality of tuning and configuration. This paper presents an approach to design a tuning engine that will dynamically configure the security devices according to the rules defined by policy makers and network administrators. The tuning engine will dynamically configure the devices to act efficiently for specific threats. It will filter the irrelevant daily alerts from different security devices. The scope of response of a security system is selected by finding out the probability of occurrence of a specific threat and the severity of that threat. Thus the tuning engine dynamically configures the response of security system according to the policies defined for different types of threat. This is an attempt to design a tuning engine which has influences from general policies, administrator settings and information during its operations. The mechanism of introducing the influence of information and policies for tuning and configuration of security devices will efficiently decrease the false alarm rates in any security system.
Presently, the INTERNET network has been considerably congested due to the excessive use of the service. Because the current TCP Reno, a protocol suite in a transport layer, doesn’ t correlate to the use in WWW scenario, the overall performances of a network are subjected to be laborious to amend. In this paper, we propose the technique to improve the performance of the TCP in a congestion condition. By using the modification algorithm based on TCP Vegas, we could showing how control parameters of TCP Vegas should be configure for achieving better both performance and better throughput.
This paper analyses an Optical WDM network model with application of Limited Range Wavelength Converters for online routing with a wavelength assignment scheme under symmetric Erlang-C traffic. Distinct wavelengths have been assigned to short and long hop connections by wavelength conversion besides attempt to reserve an identical wavelength across all nodes. Probabilistic model for traffic has been developed employing both ring and star topology networks. A mathematical model has been further devised and its call blocking probability has been enunciated. Compared performance analysis of both topologies has been presented with an investigation on collective impacts of various traffic parameters on transmission.
Portable handheld devices are emerging as strong competitors to large traditional electronic devices requiring advanced safety and security mechanisms. Lightweight cryptography is developing as an attractive public-key cryptosystem for use with many such devices, particularly when the devices are not capable of performing sufficient cryptographic operations to guarantee adequate security. The paper provides a survey, how Elliptic Curve Cryptography as a light weight security solution, is accommodating the limitations of resource constrained environments of a whole lot of new generation applications.
An ad hoc network is wireless, self-configuring network of mobile routers forming a dynamic topology. In such an environment, any malicious behavior by these routers (nodes) could greatly compromise secured routing. However, just detecting the malicious nodes is not enough to guarantee security. It should be ensured that, only trusted nodes take part in routing. In this paper, we propose a distributed dynamic trust evaluation scheme for securing DSR routing in mobile ad hoc and sensor networks. Each node periodically calculates trust for others based on its direct experience, recommendation and previous knowledge. Extensive simulation studies show that our scheme, unlike most of the previously proposed ones, efficiently adapt to fast changing trust scenario and the trust converges to values, revealed by long term behavior of the nodes. This scheme is resistant to ‘ collusion’ attack and is cautious not to punish nodes when packet is dropped due to ‘ node mobility’
Voice Encoder Schemes, Weighted Fair Queuing (WFQ) and Speech Activity Detection (SAD) techniques affect the overall Quality of Service (QoS) of Voice over Internet Protocol (VoIP) services. VoIP is one of the most discussed and rapidly emerging technologies in telecommunication. We are slowly witnessing a change in telephony from Public Switched Telephone Network (PSTN) to IP based VoIP Network. Despite the benefits being enormous, the switch to VoIP hasn’ t been swift, primarily due to various performance (delay, jitter, packet loss, echo etc.) and security issues plaguing the VoIP telephony network. To achieve minimal QoS for telephony, the voice (packets) must be delivered within 150 ms to 200 ms. This paper presents a performance model to quantifying the influence of VoIP which gives an in-depth understanding of how Voice Encoder Schemes, WFQ and SAD influence VoIP QoS from a theoretical and implementation point of views.
This paper provides a critical analysis of the recent research wok and its impact on the overall performance of a mobile Ad hoc network. In this paper, we clarify some of the misconceptions in the understating of selfishness and miss-behavior of nodes. Moreover, we propose a mathematical model that based on the time division technique to minimize the node misbehavior by avoiding unnecessary elimination of bad nodes. Our proposed approach not only improves the resource sharing but also creates a consistent trust and cooperation (CTC) environment among the mobile nodes. We believe, that the proposed mathematical model not only points out the weaknesses of the recent research work but also approximates the optimal values of the critical parameters such as throughput, transmission over head, channel capacity etc. The simulation results demonstrate the success of the proposed approach that significantly minimizes the malicious nodes and consequently maximizes the overall throughput of the Ad Hoc network than the other well known schemes.
High performance packet switching networks are being deployed to provide sufficient data bandwidth for end users 3G services such as video streaming and broadband like data services. The use of high performance networks is, therefore, essential to the success of any 3G service. However, in practice, the deployment of High performance packet switching networks is hindered due to the improper congestion control which consequently results longer delays. In this paper, we propose a new method that can effectively improve the congestion control in high performance packet switching networks. Our numerical and simulation results demonstrate that the proposed method can be implemented for both lightly and heavily loaded networks. Simulation results show that the transmission delays can also be reduced significantly that improves the over all performance of high performance packet switching networks
As ATM network is designed for broad band transmission that is high data rate (25 Mbps to 2.5 Gbps) and supports the transmission of every kind of data, congestion control and delay have been important issues for ATM networks. Data transmission is done in the form of cell (53 bytes) relay. Hence, cell sequence and the error control have to be carried out properly. ATM networks presents difficulties in effectively controlling congestion not found in other types of networks, including frame relay networks. In this paper, we present an efficient methodology for traffic management. The simulation results suggest that the proposed solution is effective for both slow and high data rate transmission.
A sensor network is made up of numerous small independent sensor nodes with sensing, processing and communicating capabilities. The sensor nodes have limited battery and a minimal amount of on-board computing power. A self-adaptive methodology that utilizes the source and path redundancy techniques to efficiently reduce the required energy consumption is proposed. The proposed methodology presents a self-adaptive strategy to optimize the number of active sensor nodes and assign equal time slots to each sensor nodes for sensing and communication with the BS. The self-adaptive property enables the proposed methodology to perform a global search for optimizing the position of active sensor nodes with respect to the location of the base station (BS). The global search performed by the proposed methodology is carried out in a complete top down manner. The proposed self-adaptive methodology, therefore, not only reduces the energy consumption of wireless sensor nodes but also effectively maximizes the lifetime of active sensor nodes. Simulation results demonstrate that the proposed methodology significantly minimizes the energy consumption and consequently increases the life time of active sensor nodes.
A mobile ad-hoe network (MANET) is a kind of self configuring network with mobile routers connected by wireless links. Misbehavior in MANET arises for several reasons such as non-intentionally when a node is faulty or it is overloaded or intentionally when a node is being selfish to save battery, bandwidth, and processing power. This paper presents a new method to stabilize the performance of the network for the active nodes even in the presence of some misbehaving nodes which do not route and forward packets send by the others correctly. This situation becomes even worst when mobile nodes do not rely on an), routing infrastructure but relay packets for each other. Specifically, we introduce two extensions to the Dynamic Source Routing (DSR) algorithm [1] to mitigate the effects of routing misbehavior: the watchdog and the pathrater [2]. Based on the watchdog and the pathrater systems, we propose a reputation trust (RT) algorithm that updates the reputation trust (RT) table of each node with the ranked values of other nodes. Simulation and numerical results show the success of the proposed method by minimizing the malicious behavior of mobile nodes and consequently improving the overall throughput of MANET.
Low-Density Parity-Check (LDPC) codes have recently received a lot of attention by their excellent error-correcting capability and have been adopted as an optional error correct coding scheme by many standards. This paper presents, reviews and discussed the implementation of LDPC codes in the upcoming WiMax (IEEE802.16e) and DVB-S2 standards. An analysis and simulation of the LDPC codes has been conducted using various code rates.
We present how weather forecasts estimating the solar radiation for the following days at a given location can be used to adjust the power consumption of a wireless network node. The node is powered by a solar panel which recharges a battery. We discuss two methods to adjust the configuration of the wireless node according to weather forecasts. We are using OLSR routing parameters and hardware adjustments to control the amount of energy needed. One method calculates the available energy, the other uses a naive Bayesian classifier to choose the optimal configuration.
The aim of IP Multimedia Subsystem (IMS) is not only to realize the convergence of the fixed or mobile networks at network level, but also to establish a uni-platform for providing services, no matter which access technology is used. However, due to limited protocol support and the other limitation of device capabilities, a majority of legacy devices (e.g. mobile phone, PDA, laptop, etc) today and in the near future lack coherent support for those services. In this paper, we propose a browser-based Thin Client IMS System Architecture to support non-IMS Client devices. The main issues considered in the paper include security, provisioning, identity management, Thin Client Inter-working, IMS Inter-working and device management. We also build the prototype to validate the design concept.
Authentication mechanisms coupled with strong encryption techniques are used for security purposes; however, at times, well-equipped intruders succeed in breaking encryption and compromising data integrity, confidentiality and trust. Kerberos is a widely used computer network authentication protocol which allows individuals communicating over an insecure network to prove their identity to one another in a secure manner. This paper presents an approach that involves temporary interruption to link server access with a new authentication protocol that delays the decryption with timed authentication. The analysis and verification of authentication properties and results of the designed protocol are presented.
We considered a self-repair network by an autonomous and strategic repair. The network is assumed to be composed of agents with a failure rate. This paper further assumes that the failure rate changes dynamically, hence modelling a dynamic environment. When the failure rate oscillates with a fixed amplitude and cycle, computer simulations indicated that there is a threshold of not only the amplitude but the cycle. When the failure rate changes with the cycle not exceeding the threshold, the strategic repair adapts to the environment and exhibits a reasonable performance.
This study describes a novel technique of using cellular automata for congestion control in wireless LANs (WLANs). Our approach relies on cooperation between central nodes in WLANs, covering the same geographical area. Such geographical areas, even in the scope of a single building, may be covered by several available wireless networks, supporting same or different WLAN standards over the same space. We propose a technique for congestion avoidance in such heterogeneous environments, based on the use of cellular automata (CA). When each mobile device attempts to join a wireless network, a decision is made by the central node, whether to accept the association attempt, or reject it, in accordance with the outcome of a CA execution. Our technique attempts to reach a social goal for a large number of WLANs of optimizing the use of central node resources. This technique is not applicable in ad hoc networks due to the inherent decentralization of resources.
In this study we measured simulated end user HTTP response times in a 802.11g WLAN. Our results show that, ceteris paribus, modeling heavy tailed file sizes at an HTTP server, results in two times worse response times as compared to modeling Web pages of lognormal file sizes. Accesses to content containing large images and embedded documents appear to result in tolerable end user response times, as long as HTTP server directories contain a small number of such large files, that is, if file sizes are modeled by a heavy tailed Pareto distribution, where minimum file sizes are 100 Kbytes or less. When file size at the server become larger, with a minimum size of 1Mbytes, response times increase substantially and may quickly become intolerable by users. Our results confirm related findings in [3] and demonstrate that studies which do not consider these findings may present too optimistic results, misrepresenting real end user delays of Web accesses.
... There is also the incremental case, in which traffic is considered to only arrive but never leave the network. The latter case is known as incremental approach and it is the most appropriate for algorithms aimed at deriving worst scenario reports or minimizing blocking probability over time [13]. Recent publications such as [14], [15], [16] and [17] have focused on network planning using incremental traffic algorithm. ...
... Incremental traffic is more suitable to mapping the network aggregate bandwidth necessities and worst-case scenario [13], which is not possible with the dynamic approach, and incremental traffic planning has been shown to derive more cost efficient network planning [14]- [17]. RMSA resolution for incremental traffic is usually devised to maintain the blocking probability of the network within a desired threshold, also related to the QoS. ...
The rapidly increasing data demand from current Internet services, such as cloud computing and high-quality video streaming, is raising the pressure on network operators to provide reliable high-speed connections while keeping costs low. Without having to rely on the bandwidth expansion of optical waveguides or modulation level efficiency, one of the ways to increase spectral efficiency of a network is by the optimal utilization of already existing resources. For elastic optical networks (EON) this can be solved by the Routing, Modulation and Spectrum Assignment (RMSA). However, another problem arises, due to the nature of computer network traffic, that makes it difficult to assess the longevity of physical components and to plan a network to serve a maximum amount of bandwidth demand for predetermined time span. To help alleviating these problems, this paper presents an investigation of a novel technique for resource planning and consume estimation based on simulations. First, traffic matrix prediction is made using recurrent neural networks (RNN) , and then simulations are ran to estimate the consumed bandwidth for a point in time. For the traffic forecasting, real traffic data has been used to train the RNN, obtained from an anonymous dataset containing the traffic history of the ABILENE and GEANT networks from the years 2004-2005, which is a relatively recent available dataset. Furthermore, heuristic algorithms are proposed to apply the RMSA to the predicted traffic, in a quasi-optimal manner, in order to minimize the use of network resources for future traffic, by releasing available capacity in the existing optical fiber links in an incremental traffic approach. The results show that the proposed RNN models are indeed capable of predicting the traffic matrices a month ahead, with low mean squared error. RMSA simulations were also performed using heuristics in order to estimate the consumed bandwidth in the context of EON networks, revealing that, for the proposed heuristics, the results favor the shortest path routing heuristic over the load balancing heuristic for a long-term bandwidth open capacity maximization and better resource savings.