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In this paper it is presented a new open source tool for evaluating data fusion systems, mainly related to the maritime surveillance domain. This tool provides specific utilities for designing and simulating synthetic maritime environments to assists in the fusion development process, like designing vessels trajectories, placing different types of sensors, simulating vessels dynamics, or simulating sensors detections. This synthetic information can be used to feed a data fusion system to evaluate its response in a reproducible way under different conditions. This tool can be used to optimize the data fusion evaluation process, since testing a fusion system is a quite complex task, as the fusion output depends on the combination of multiple algorithms, configurations, measures, timing, and so on. Then, having reproducible synthetic environments can be quite useful when evaluating fusion results, system performance in dense scenarios, vessel trajectories with different dynamics, sensor coverages, and so on. This tool has been used with success for evaluating different fusion systems, and now it is presented as an open source tool, so it can be easily adapted to different environments, be used by other researchers, or extended by the community. This paper presents how it is built, the underlying algorithms, and presents some example use cases. [ABSTRACT FROM AUTHOR]

Research interest on Information Centric Networking (ICN) has been sharply growing. Although new architectures, algorithms, and analytical models have been proposed, their evaluation remains often isolated and not rigorously verified by the research community. This paper initially portrays the composition of open source software tools available for ICN, certifying the predominance of Content Centric Networking (CCN)/Named Data Networking (NDN) simulators. Then, inspired by similar works related to the P2P field, it surveys related research papers to qualify the ICN literature produced so far, finding that a large fraction of contributions either uses custom, proprietary, and unavailable software, or even plainly fails to mention any information in this regard. By adopting a rigorous methodology, in the second part of the paper four simulators, namely ndnSIM, ccnSim, CCNPL-Sim , and Icarus , are cross-compared under several key aspects. Our findings confirm both their accuracy with respect to reference theoretical models in simple settings, and their consistency in more complex scenario. Additionally, our analysis can both assist researchers in the choice of the tool that best fits their needs, and provide guidelines to avoid common pitfalls in the ICN performance evaluation. [ABSTRACT FROM AUTHOR]

RSVP represents one of the most discussed network protocols in the last decade. Although there are a large number of papers that refer to the scalability problem of the protocol, only a very limited subset of those analyze the performance of RSVP. Up to this point no real evaluation exists on the efficiency and applicability of the scalability extensions proposed for RSVP. This paper presents a simulation study of RSVP and its scalability extensions in OPNET Modeler. The results obtained are put in context of the previous work done on the scalability of RSVP. It is found that the Summary Refresh extension considerably improves the performance of the protocol both in terms of message processing and message generation. An important finding of the present paper is that the scalability of RSVP is not directly linked to the specifications of the protocol and its extensions as such, but rather to the design choices of the actual implementation under evaluation. [ABSTRACT FROM AUTHOR]

Experimental data can aid in gaining insights about a system operation, as well as determining critical aspects of a modeling or simulation process. In this paper, we analyze the data acquired from an extensive experimentation process in a serverless Function as a Service system (based on the open source Apache Openwhisk) that has been deployed across 3 available cloud/edge locations with different system setups. Thus, they can be used to model distribution of functions through multi-location aware scheduling mechanisms. The experiments include different traffic arrival rates, different setups for the FaaS system, as well as different configurations for the hardware and platform used. We analyze the acquired data for the three FaaS system setups and discuss their differences presenting interesting conclusions with relation to transient effects of the system, such as the effect on wait and execution time. We also demonstrate interesting trade-offs with relation to system setup and indicate a number of factors that can affect system performance and should be taken under consideration in modeling attempts of such systems. • Experimental data analysis of 3 different setups of a FaaS system. • Insights into the transient effects of the system. • Considerations in terms of modeling approaches. • Explore interesting conclusions regarding the system setup and its trade-offs • Examine hidden factors influencing performance. [ABSTRACT FROM AUTHOR]

Abstract: Testing algorithms with real cars is a mandatory step in developing new intelligent abilities for future transportation systems. However, this step is sometimes hard to accomplish especially due to several problems. It is also difficult to reproduce the same scenario several times. Besides, some critical and/or real world forbidden scenarios cannot be tested. Thus, the comparison of several algorithms using the same experimental conditions is hard to realize. Considering that, it seems important to use simulation tools to perform scenarios with realistic conditions. The main problem with these tools is their distance from real conditions, since they deeply simplify the reality. This paper presents the architecture of the simulation/prototyping tool named Virtual Intelligent Vehicle Urban Simulator (vivus). The goal of vivus is thus to overcome the general drawbacks of classical solutions by providing the possibility of designing a vehicle virtual prototype with simulated embedded sensors and physical properties. Experiments made on linear platoon algorithms are exposed in this paper in order to illustrate the similarities between simulated results and those obtained with real cars. [Copyright &y& Elsevier]

Abstract Cloud based architectures present many challenges, ranging from poorly dimensioned hardware to lengthy wait times and resource balancing issues. Most of these problems can be mitigated by using proper performance evaluation techniques, depending on the accuracy of the model abstracting the real system. The adoption of a formalism over another to describe the considered infrastructure plays a crucial role in achieving this goal. In this sense, multiformalism proves itself to be a powerful modeling approach describing each system component according to the most suitable representation. This paper presents a novel modeling method oriented to the prediction of cloud architectures performance, suitable for joining the advantages of high level modeling abstractions and of the detail of a specialized simulator. Generalized Stochastic Petri Nets are used to describe the workload and the behavior of users and applications, while Cloudsim, a well known cloud infrastructure simulator, is adopted for the cloud part. A case study of a simplified Edge Computing application is presented to demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract As the paradigm shift toward Software as a Service (SaaS) continues to gain momentum, there is a growing focus on the performance of SaaS clouds from both academia and industry. In this paper, we evaluate the performance of a SaaS cloud under various tardiness bounds and different levels of workload computational demand variability. The workload consists of bag-of-tasks jobs, which are scheduled on the underlying virtualized host environment. The jobs have soft deadlines and different levels of variability in their computational demands. A multi-tier SLA is employed, which imposes a soft and a hard tardiness bound on each job. Furthermore, the employed pricing scheme is based on the provided level of Quality of Service (QoS). The performance of the SaaS cloud is evaluated by simulation, in an attempt to shed light on how it is affected by the tardiness bound and the computational demand variability of the workload. [ABSTRACT FROM AUTHOR]

Abstract: Network protocols and their efficiency are extremely important to the research community. Evaluating the performance of these protocols has thus also becoming extremely important. However, it is difficult to conduct physical experiments on the performance of these systems, especially wireless networks. Therefore, network simulators, such as ns-2, QualNet and OPNET, have been widely used to evaluate the performance of network protocols, and thus the accuracy of network simulators is critical to the research community. In this paper, we consider the incorrect simulation results generated by the current ns-2 implementation employed in numerous research works. The cause which for the purposes of this paper will be called the incorrect error frame assumption (IEFA), is the incorrect handling of frames from stations located between the carrier sense and transmission ranges of the receiver in the two-ray ground propagation model. Although this model is known to be oversimplified to the extent that it does not consider such critical phenomena as cumulative interference and noise levels, it is the most popular model for simulating wireless networks. Moreover, the incorrect assumption has been widely adopted in the research community, such that the simulation scenarios are limited or the results of simulations are significantly affected by the IEFA. The issue is therefore in need of investigation and clarification. In this paper, we present a detailed description of the IEFA problem and a probabilistic analysis of the problem to determine its root cause. We suggest an implementation that fixes the IEFA and present the current bit-error model for the ns-2 simulator. We then conduct simulations to show how the problem impacts the simulation results from the MAC to the application layers. [Copyright &y& Elsevier]

Abstract: This paper presents a new method of estimating the rotor resistance of an induction motor. This method is based on model reference adaptive system approach. The rotor resistance changes dramatically with temperature and frequency. The rotor resistance variation has a great influence on the FOC performance of an IM since the actual slip frequency deviates from their set value by rotor resistance variations. Therefore, the compensation of the parameter variation is vital especially in FOC of an IM. Three different methods of rotor resistance estimations, namely, electromagnetic torque equation, reactive power and active power equations, are discussed in this paper. Author proposes the third technique, which is an improvement over the two strategies Although all three schemes estimate the rotor resistance effectively, the proposed technique is superior to others in providing faster estimation approach. Simulation results of all three methods will be provided in order to confirm the superiority of proposed method. [Copyright &y& Elsevier]

Performance evaluation is integral to the vast majority of research on Vehicle-to-Vehicle (V2V) technology enabled connected cars. To validate ideas and concepts, researchers have been continuously striving towards the higher accuracy of simulation-based performance evaluation. However, many state-of-the-art network simulators lack comprehensive physical (PHY) layer models. More often, simplified representations of vehicular channel characteristics are used to achieve a trade-off between accuracy and performance. Vehicular channel modeling is a highly complex task because of its unique properties, for example, higher carrier frequency, rapid fluctuations in vehicular channels due to moving scatterers, and propagation in horizontal plane instead of a vertical plane with diffraction and reflection. Efficiently incorporating vehicular channel details into a single network simulator is infeasible; instead, a chain of simulation tools are used together. In this paper, we proposed a two-stage simulation framework which combines several layers of simulation tools into two distinct stages. During the first stage, a Geometry-based vehicular propagation model is used to characterize received signal strength among transmitter-receiver pairs. For this purpose, metropolitan area-wide 2.5D building geometry data and vehicular mobility traces are employed to represent the real-world environment. Subsequently, the output from the first stage is collected and fed as an input to the network simulator. Through extensive simulation-based studies, we analyze the difference between the proposed framework and standard propagation models implemented in the network simulator and their impact on the network-level performance metrics such as packet loss rate (PLR), throughput, latency, and jitter. [ABSTRACT FROM AUTHOR]

Today, cities are facing new issues with the increase of the population and the massive urbanization. One of them is the mobility as the cities were not designed to support such increase. Improving mobility in smart cities, becomes an important challenge to avoid traffic jam and improving sustainability by reducing greenhouse effect. This contributes as well to having better life for citizen. Even with rich infrastructures, the vehicles behavior could decrease the traffic flow. This is why figure out how the mobility is done on the highways can give more details on how it can create traffic jams and then several solutions could be proposed to contribute to the improvements. This is the goal of this study. In this paper, a new stochastic model based on Markov chain is proposed, which represents the behaviors of overtaking on the highways. A full description of the model is given with numerical resolution to calculate several rewards such as delays and congestion. Intensive simulations were carried out to compare both simulations and analytical model results and to provide results for more complex configurations. [ABSTRACT FROM AUTHOR]

Ns-3 simulator provides a great platform for experimental studies on different communication technologies and network topologies, and it is already used by many researchers all around the world. Unfortunately, its current TCP implementation is outdated and not ready for being used as reference platform for TCP-centered research, relegating ns-3 to play a background role in favor of its predecessor, ns-2. This paper presents the update process of ns-3 TCP module, that offers to TCP developers and researchers a consistent and RFC-compliant platform to base their works on. The method involves the addition of a new congestion-based state machine, the split of congestion control out from the socket core, and the development of a very detailed and complete testing framework, which can be easily extended. Performance tests follow the description, comparing RAM usage and execution time between ns-3 releases. Also, a case study over high-delay links on the interaction between the Transmission Control Protocol (TCP) and CoDel, an Active Queue Management algorithm born to control queuing delay, is presented. [ABSTRACT FROM AUTHOR]

Vehicular Ad hoc NETworks (VANETs) have attracted much attention in the last decade. Many routing protocols have been proposed for VANETs and their performance is usually evaluated and compared using simulation-based studies. However, conducting reliable simulation studies is not a trivial task since many simulation parameters must be configured correctly. The selected parameters configuration can considerably affect the simulation results. This paper presents a methodology for conducting reliable simulations of routing protocols in VANETs urban scenarios. The proposed methodology includes relevant simulation aspects such as measurement period, selection of source–destination pairs for the communication traffic flows, number of simulations, mobility models based on road city maps, performance metrics and different analyses to evaluate routing protocols under different conditions. The proposed methodology is validated by comparing the simulation results obtained for Ad Hoc On-Demand Distance Vector (AODV) routing protocol with and without using the proposed methodology. The obtained results confirm that by using the proposed methodology, we can achieve more reliable simulations of VANETs routing protocols. [ABSTRACT FROM AUTHOR]

A body sensor network (BSN) is a type of network for Internet of Things. A BSN typically consists of tens (dozens) of biosensor nodes distributed on/in the human body, and these autonomous nodes can form a wireless network to measure physiological signals and execute intelligent treatment automatically. BSNs have wide application prospects in intelligent healthcare. Because physiological signals measured and processed by BSNs involve patient privacy, security mechanisms must be developed to secure BSNs, and therefore the adoption of available key negotiation protocols is fundamental. Due to stringently limited operation resources, BSNs require these protocols to be highly energy efficient. Recent development has discovered that certain physiological signals can be used for efficiently negotiating common keys among biosensor nodes. These signals and fuzzy technology are used to design lightweight key negotiation protocols, and many solutions have been proposed. In this paper, we explore and classify these solutions, and evaluate their performance by analyzing their merits and drawbacks. Finally, we present open research issues that should be solved in the future. [ABSTRACT FROM AUTHOR]

Large-scale urban systems simulations are complex and with a large number of active simulation entities the computational workload is extensive. Workstation computers have only limited capabilities of delivering results for large-scale simulations. This leads to the problem that many researchers and engineers have to either reduce the scope of their experiments or fail to execute as many experiments as they would like in a given time frame. The use of high-performance computing (HPC) infrastructure offers a solution to the problem. Users of such simulations are often domain experts with no or little experience with HPC environments. In addition users do not necessarily have access to an HPC. In this paper we propose an architecture for a cloud-based urban systems simulation platform which specifically aims at making large-scale simulations available to typical users. The proposed architecture also addresses the issue of data confidentiality. In addition we describe the Scalable Electro-Mobility Simulation (SEMSim) Cloud Service that implements the proposed architecture. [ABSTRACT FROM AUTHOR]

In this paper we identify basic design issues of Mobile Crowdsensing Systems and investigate some characteristic challenges. We define the basic components of an MCS – the Task, the Server and the Crowd – and investigate the functions describing/governing their interactions. We identify three qualitatively different types of Tasks; (a) those whose added utility is proportional to the size of the Task, (b) those whose added utility is proportional to the progress of the Task and (c) those whose added utility is reversely proportional to the progress of the Task. For a given type of Task, and a finite Budget, the Server makes offers to the agents of the Crowd based on some Incentive Policy. On the other hand, each agent that receives an offer decides whether it will undertake the Task or not, based on the inferred cost (computed via a Cost function) and some Join Policy. In their policies, the Crowd and the Server take into account several aspects, such as the number and quality of participating agents, the progress of execution of the Task and possible network effects, present in real-life systems. We evaluate the impact and the performance of selected characteristic policies, for both the Crowd and the Server, in terms of Task execution, Budget efficiency and Workload balance of the Crowd. Experimental findings demonstrate key performance features of the various policies and indicate that some policies are more effective in enabling the Server to efficiently manage its Budget while providing satisfactory incentives to the Crowd and effectively executing the system Tasks. Interestingly, incentive policies that take into account the current crowd participation achieve a better trade-off between Task completion and budget expense. [ABSTRACT FROM AUTHOR]

For virtual machine based traffic simulation platforms, the paper proposes a software framework that performs trace-based dynamic translation. Through monitoring the runtime execution status of bytecodes and translating frequently executed bytecodes, also known as hot spots, into equivalent native machine codes, the framework considerably improves the performance of virtual machine based traffic simulation platforms up to ten times or more, as the experiments showed. For the first time, the presented work clearly exhibits that a seamless combination of the two technologies - dynamic translation and virtual machine could lead to a new generation of applicable traffic simulation platforms. Such a platform not only offers high flexibility in terms of traffic model simulation, but also preserves the ability of conducting numerical computation-intensive simulations generally found in real-life industrial projects. [ABSTRACT FROM AUTHOR]

A functional product is an integrated package consisting of hardware, software and a service support system that provides a customer with a certain function and is sold under a performance-based contract that includes a functional availability guarantee. For the availability performance, prediction, optimisation and management of risk are therefore important concerns during product development. This paper describes a software tool that can generate an integrated model of a functional product from its design details and analyse it through simulation to provide availability performance information. The model's application to the analysis of a real industrial system is demonstrated. Such tools are important for the development and widespread adoption of functional products. The resulting analysis gave an indication of a suitable guaranteed functional availability level for the product and could be used to compare the performance of different design options. [ABSTRACT FROM AUTHOR]

In this paper, we develop a simulation model to study the performance of clinic operations based on the settings of a typical VA primary care clinic with complex characteristics. The clinic serves three different types of patients, namely, regular appointment patients, walk-in patients, and nurse-only patients, and they each have different patient flow routes. The model captures the patient flow characteristics of the studied clinic, and it is validated by comparing the simulation results with the real key performance measures obtained from in the clinic. The system performance is mainly measured by two metrics: one is how the clinic makes efficient use of its resources, and the other is how long the patients need to wait for services. A scenario analysis is conducted which adopts the experiment design method for multiple factors to study the effect of six parameters on the system performance. The six parameters are walk-in arrival rate, no-show rate, post-triage rate, new patient rate, number of double booking, and nurse-only appointment rate. Based on the results, one major recommendation for the clinic is to reduce or eliminate the use of double booking because it causes the dramatic increase of patient waiting time. Also, based on the projection of the high new patient rate in the near future, it is recommended that the clinic manage the walk-in patient load by adjusting the existing admission policy. In addition, for the clinic with already high provider utilization, interventions for reducing patient no-show rate alone may further deteriorate the congestion of patient visit in the clinic. [ABSTRACT FROM AUTHOR]

A better and feasible control strategy for dynamic voltage restorers (DVR) is presented in this paper: the passivity based control (PBC) allows a better compensation performance under transient and steady state operating conditions, and provides tracking with zero error of any reference for linear and nonlinear loads. The closed-loop source-DVR-PBC-load system is asymptotically stable at all operating points, with practically very slight constraints; its transient response is faster than with classical controllers, and does not present overshoots. These characteristics do not depend on source voltage disturbances, the kind of load, or parameter variations. The PBC uses less digital operations than the PI, and does not require dq transformations. [ABSTRACT FROM AUTHOR]

Abstract: Large-scaled cluster systems have been employed in various areas by offering pools of fundamental resources. Efficient allocation of the shared resources in a cluster system is a critical but challenging issue, which has been extensively studied in the past few years. Despite the fact that existing load balancing policies, such as Random, Join Shortest Queue and size-based polices, are widely implemented in actual systems due to their simplicity and efficiency, the performance benefits of these policies diminish when workloads are highly variable and temporally correlated. In this paper, we propose a new load balancing policy, named ADuS, which attempts to partition jobs according to their present sizes and further rank the servers based on their loads. By dispatching jobs of similar sizes to the corresponding ranked servers, ADuS can adaptively balance user traffic and system load in a cluster and thus achieve significant performance benefits. Extensive trace-driven simulations using both synthetic and real traces show the effectiveness and robustness of ADuS under many different environments. [Copyright &y& Elsevier]

Abstract: Server performance is one of the critical activities in the data grid environment. A large number of applications require access to huge volumes of data from grid servers. In this case, efficient, scalable and robust grid server which can deal with large file transfer concurrent is needed. In this paper, we analyze the bottleneck of our grid servers and introduce user-space I/O scheduling, zero copy and event-driven architecture in our grid server to improve the servers’ performance. The user-space I/O scheduling can save almost 50% I/O time in a huge number of small files transfer. Grid servers can elimination CPU consumptions between kernel and user space by zero copy and cut 63% times for context switches. Event-driven architecture will save 30% CPU usage to reach the best performance by thread-driven architecture. Optimization method combination of these three above are used in our grid servers, the full-load throughput of our system is 30% more than traditional solutions and only 60% CPU consumed compared with traditional solutions. [Copyright &y& Elsevier]

Abstract: Grid computing is an evolutionary technological achievement that takes advantages of wide area communication and large scale resource sharing. Although there are several advantages, grid does not guaranty stableness of resources due to their resources’ nature, diverse failures and error conditions that may appear. Consequently, grid dependability issues arise. In this paper, a grid computing environment with star topology and direct access to resources is considered, which consists of a Resource Management System (RMS) and distributed Root Nodes (RNs). The distributed RNs are considered either as operational or as failed, though the RMS is susceptible to resource exhaustion, which can lead to software failures. The response waiting time from a distributed RN is also taken under consideration. A software rejuvenation to counteract RMS resource exhaustion is adopted, and its effect on grid environment performance is studied extensively. A non-Markovian approach is considered to model the system’s evolution in time and to evaluate the proposed performance measures. Due to the complicated structure of the system, analytic formulas for the proposed measures are not available, thus Monte Carlo simulation methods are employed. [Copyright &y& Elsevier]

Abstract: In the recent years, energy-efficiency of computing infrastructures has gained a great attention. For this reason, proper estimation and evaluation of energy that is required to execute data center workloads became an important research problem. In this paper we present a Data Center Workload and Resource Management Simulator (DCworms) which enables modeling and simulation of computing infrastructures to estimate their performance, energy consumption, and energy-efficiency metrics for diverse workloads and management policies. We discuss methods of power usage modeling available in the simulator. To this end, we compare results of simulations to measurements of real servers. To demonstrate DCworms capabilities we evaluate impact of several resource management policies on overall energy-efficiency of specific workloads executed on heterogeneous resources. [Copyright &y& Elsevier]

Abstract: The first hurdle for carrying out research on cloud computing is the development of a suitable research platform. While cloud computing is primarily commercially-driven and commercial clouds are naturally realistic as research platforms, they do not provide to the scientist enough control for dependable experiments. On the other hand, research carried out using simulation, mathematical modelling or small prototypes may not necessarily be applicable in real clouds of larger scale. Previous surveys on cloud performance and energy-efficiency have focused on the technical mechanisms proposed to address these issues. Researchers of various disciplines and expertise can use them to identify areas where they can contribute with innovative technical solutions. This paper is meant to be complementary to these surveys. By providing the landscape of research platforms for cloud systems, our aim is to help researchers identify a suitable approach for modelling, simulation or prototype implementation on which they can develop and evaluate their technical solutions. [Copyright &y& Elsevier]

Abstract: Leader election problem has been studied in the past to improve the efficiency of both distributed systems and wireless ad hoc and sensor networks. Yet, few research has been done on the leader election process for wireless mesh networks. Most of the existing leader election protocols consider wireless networks in general, without focusing on the particularities of mesh networks. Thus, these protocols are not suitable for wireless mesh networks. The lack of research on this issue has motivated us to design a leader election protocol dedicated to wireless mesh networks. In this work, we propose an efficient leader election protocol for wireless mesh network, which is based on the construction of a spanning tree that includes all wireless mesh routers. The protocol elects the node with the longest remaining battery life. In this paper, we give a detailed description of the proposed protocol, prove its correctness, discuss its message and time complexities and then evaluate its performance through simulation using ns-2. We show that our protocol is efficient and scales well with the increase in number of mesh routers and mesh clients. [Copyright &y& Elsevier]

Abstract: In this paper, an approach is developed to improve the power efficiency of Bluetooth. The better efficiency is achieved by reducing the unnecessary polling operations in the Basic Rate/Enhanced Data Rate (BR/EDR) controllers. An analysis of the current low power modes in the Bluetooth BR/EDR controller indicates that their activation requires a critical and challenging parameter negotiation phase. These parameters have a wide range of choices and as a result the associated low power modes are typically ignored by the Bluetooth application developers. The new approach is based upon multiple polling intervals. It is shown that three different polling intervals: small, medium and large are sufficient for a broad range of data traffic scenarios. As the kernel idea, each controller runs a common algorithm to choose among the three polling intervals and adaptively switches link state between the active data transfer state and idle. The state-transition rules are derived, and a system model is established based on the Hidden Markov Model (HMM), which is used to analyze and design the new Bluetooth link state-transition algorithm. The simulation and analysis demonstrates significant power saving and relatively low average end-to-end packet delay for this state-transition based approach, in comparison to the conventional polling system and the low power sniff mode. Moreover, the state-transition approach enables easier parameter setting that can be further optimized for a specific Bluetooth scenario. [Copyright &y& Elsevier]

Abstract: As a common support of M&S (Modeling and Simulation) applications, M&S language and platform can effectively improve M&S capability for complex objects and systems. This paper proposes an Intelligent system Modeling and Simulation Language (IMSL) which integrates artificial intelligence theory and M&S technology to describe intelligent model structures, behaviors, facts, knowledge, and rules. Meanwhile, an M&S platform is implemented to provide a basic support for M&S of intelligent systems, featured as its convenience, efficiency and problem solving ability. Our research work has been focused on M&S methods and language specification of intelligence systems, intelligent simulation resource libraries and integrated development environment. As an application instance, M&S of a C3I (Command, Control, Communication and Information) system is conducted to evaluate the performance of IMSL and the IMSL platform. And the simulation result proves that IMSL can work effectively in solving practical problems. [Copyright &y& Elsevier]

Abstract: This paper presents a radio paths modeling framework for simulating RF coverage in complex indoor environments. We propose an algorithm which utilizes a geometric visibility graph of a building to traverse all possible bounded radio paths. These paths are needed for the computation of signal strength captured at a given receiver location. We have implemented the suggested algorithm and conducted a set of experiments to evaluate its performance in complex environments. The main conclusion is that the new algorithm is both (i) Accurate: predicts the signal strength inside complex buildings. (ii) Runtime efficient: requires only few seconds to compute all relevant radio paths, even when operating on complex structures containing thousands of walls. [Copyright &y& Elsevier]

Abstract: The photovoltaic (PV) modules used in the building integrated photovoltaic (BIPV) system generally are installed in different orientations and angles. The performance of them is easily to be affected by partial shadows and mismatch of their electrical parameters. Some high performance power configurations have been proposed to solve these problems. This paper presents an energy efficiency analysis method to evaluate the energy efficiencies of BIPV systems with different power configurations. The principles and performance of seven types of power configurations for BIPV systems are discussed. The energy efficiency analysis model of each BIPV power configuration is built, and the simulation results of each configuration under different partial shade and electrical parameter mismatch conditions are presented to quantitatively evaluate their energy efficiencies. The evaluation results show that the AC module and photovoltaic DC building module is the optimal configuration since they have better anti-shading and anti-mismatch performances than the other power configurations. [Copyright &y& Elsevier]

Abstract: WiMAX is one of the most interesting solutions for broadband wireless access, supporting multimedia traffic and applications through an appropriate QoS management for fixed and mobile devices. Simulation tools play a central role to study network performance and to test new functionalities. In this paper we propose a new simulation module, compliant to IEEE 802.16e, which implements the five WiMAX QoS classes and handover procedures as well, so as to support investigations on QoS management during mobility in WiMAX scenarios. The developed tool has been validated and tested through exhaustive simulations, showing its conformance with the defined specifications. [Copyright &y& Elsevier]

Abstract: Grey Model (GM) deals with the systems where certain information about the systems is unknown or incomplete. GM has been successfully used in many engineering areas, including agriculture, energy, economy, and environmental engineering where prediction needs to be made with uncertain factors. Particularly, GM is widely applied in image processing and data filtering. In a GM defined by matrix series, the prediction is made by solving these matrixes through a sequence of matrix operations. To improve the simulation and prediction accuracy of GM matrix solving, a novel secondary-diagonal mean transformation Partial GM (mtP-GM) is developed in this paper. We first defined a mean transformation in the secondary-diagonal direction of the matrix series. We then defined the mtP Accumulating Generation Operation (mtP-AGO) according to the principles of AGO, matrix-AGO (m-AGO), and Partial-AGO (P-AGO). The principles of GM are followed in the modeling process, and grey impact factors of the model are encapsulated in a matrix with m 2 unknown elements. Finally, four real data sets with long-running data and multi-stream series are imported for comparing the performance of the developed mtP-GM with several other grey models, such as RGM, dtP-GM, and GM(1,1). The comparison results show that dtP-GM can obtain a better accuracy for periodic data sequences. However, our mtP-GM outperforms the other three models for non-periodic data sequences. [Copyright &y& Elsevier]

Abstract: This paper presents the simulation study of “Host based autonomous Mobile Address Translation” using NCTUns simulator. It is a network layer, end-to-end vertical handover solution, based upon modification of “Mobile IP with address Translation”. Vertical handover approaches generally require new network elements, a new layer in TCP/IP stack, or fixing a protocol at a particular layer. To enhance handover experience, recent approaches focus on reducing signalling, localizing the registration, creating hierarchies, using proxy, preparing handover in advance, predicting target network, or exploiting multicasting and path extension techniques. These approaches, however, demand change in the network infrastructure to support mobility and limit the scope of mobility. Despite end-to-end signalling, the Host based autonomous Mobile Address Translation scheme ensures minimum service disruption and distinctly allows global mobility of the mobile node without requiring any modification in the network. We have simulated the mobility of a multi-interface mobile node in a heterogeneous network environment composed of WiFi (IEEE802.11a, IEEE802.11b) and WiMAX (IEEE802.16e) access networks. Performance of the scheme is evaluated taking into account wide range of end-to-end delays between mobile node and the correspondent node, various speeds of the mobile node and different packet loss rates of the network. Based on our detailed simulation study, it has been observed that this scheme offers reduced service disruption time, packet loss and packet latency. The service disruption time is found to be significantly low (typically in the range of 10ms) compared to that of Mobile IP (which is in the order of 100ms); this makes this new scheme perfectly suitable for real time applications. Low service disruption time consequently reduces the packet loss by manyfold and the packet latency remains unaffected during and after handover due to translation of address at the source. The results suggest that this protocol is a viable vertical handover solution due to its simplicity, scalability, low overhead and ready deployability. [Copyright &y& Elsevier]

Abstract: Although most of the traffic carried over the Internet uses the Transmission Control Protocol (TCP) as the transport layer protocol, it is of paramount importance to develop models for streams that use the User Datagram Protocol (UDP), since these streams are inelastic and, consequently, they can jeopardize the acquisition of bandwidth by TCP streams. This paper introduces a traffic model for UDP streams and its performance is compared to those of other traffic models. The proposed model can be used to generate streams of aggregated UDP sources in simulation experiments. [Copyright &y& Elsevier]

Abstract: In this paper, a generalized method is proposed for the accurate simulation of equal/unequal power correlated Rayleigh fading channels to overcome the shortcomings of existing methods. Spatial and spectral correlations are also considered in this technique for different transmission conditions. It employs successive coloring for the inphase and quadrature components of successive signals using real correlation vector of successive signal envelopes rather than complex covariance matrix of the Gaussian signals which is utilized in conventional methods. Any number of fading signals with any desired correlations of successive envelope pairs in the interval [0, 1] can be generated with high accuracy. Moreover, factorization of the desired covariance matrix is avoided to overcome the shortcomings and high computational complexity of conventional methods. Extensive simulations of different representative scenarios demonstrate the effectiveness of the proposed technique. The simplicity and accuracy of this method will help the researchers to study and simulate the impact of fading correlation on the performance evaluation of various multi-antenna and multicarrier communication systems. Moreover, it enables the engineers for efficient design and deployment of new schemes for feasible wireless applications. [Copyright &y& Elsevier]

Abstract: Dynamic network reconfiguration is described as the process of replacing one routing function with another while the network keeps running. The main challenge is avoiding deadlock anomalies while keeping limitations on packet injection and forwarding minimal. Current approaches which have a high complexity and as a result have a limited practical applicability either require the existence of extra network resources, or they will affect the network performance during the reconfiguration process. In this paper we present a simple, fast and efficient mechanism for dynamic network reconfiguration which is based on regressive deadlock recovery instead of avoiding deadlock. The mechanism which is referred to as PDR guarantees a deadlock-free reconfiguration based on wormhole switching. In PDR, a particular approach is taken to handle both deadlocks and performance degradation. We propose the use of a packet injection restriction mechanism that prevents performance degradation near the saturation by controlling the network traffic. Further, in this approach, to accurately detect deadlocks, the deadlock detection mechanism is implemented and also improved by using only the local information, thereby considerably reducing false deadlock detections. In the rare cases when deadlocks are suspected, we propose a new technique that absorbs the deadlocked packet at the current node instead of dropping deadlocked packets and re-injects it later into the network. The main advantage of this method is its simplicity and also it does not require any additional buffers in intermediate nodes to handle deadlocks. It requires only some buffer space in the local node to temporarily hold the deadlocked packets removed from the network. Evaluating results reveal that the mechanism shows substantial performance improvements over the other methods and it works efficiently in different topologies with various routing algorithms. [Copyright &y& Elsevier]

Abstract: The system performance metric “availability” is a central concept with respect to the concerns of a plant’s operators and owners, yet it can be abstract enough to resist explanation at system levels. Hence, there is a need for a system-level metric more closely aligned with a plant’s (or, more generally, a system’s) raison d’être. Historically, availability of repairable systems – intrinsic, operational, or otherwise – has been defined as a ratio of times. This paper introduces a new concept of availability, called endogenous availability, defined in terms of a ratio of quantities of product yield. Endogenous availability can be evaluated using a discrete event simulation analysis methodology. A simulation example shows that endogenous availability reduces to conventional availability in a simple series system with different processing rates and without intermediate storage capacity, but diverges from conventional availability when storage capacity is progressively increased. It is shown that conventional availability tends to be conservative when a design includes features, such as in – process storage, that partially decouple the components of a larger system. [Copyright &y& Elsevier]

Abstract: Spatial partitioning is commonly used for parallel simulation of spatial–temporal systems, such as simulations of wildfires. Achieving effective spatial partitioning is a challenging task due to the dynamic behavior of the simulation models. This paper presents a partitioning method named profile-based spatial partitioning for parallel simulation of large scale wildfires. The profile-based partitioning exploits the dynamic behavior of a wildfire spread simulation model and uses it as a profile to guide the spatial partitioning for parallel simulations. Experimental results show that the profile-based partitioning can increase the degree of parallelism and improve the scalability of parallel simulations of large-scale wildfires. [Copyright &y& Elsevier]

Abstract: In this paper, we present a complete Geocasting solution for underwater sensor networks. The model named Routing and Multicast Tree based Geocasting (RMTG) has been designed for underwater sensor networks. In our previous work , we proposed and simulated the RMTG model in terms of routing, route maintenance, link stability and data dispersion inside the geocast region in static as well as in mobile network conditions. In we provided the theoretical improvement over the RMTG in terms of Geocasting for underwater sensor network by providing solutions for hole/void area detection inside the geocast region and a solution to cover the scattered nodes in the geocast region for guaranteed message delivery by means of boundary routing (that is routing by traversing all the faces of a particular geocast region). Here, the work in has been enhanced, the model is named as Routing and Multicast Tree based Geocasting with Hole Detection (RMTG-HD). A detailed analysis and performance evaluation of the proposed model has also been provided. The simulation results show that the proposed model provides an efficient distribution of data in the geocast region in terms of packet delivery ratio, boundary routing delay, hole detection delay and handling of node mobility. [Copyright &y& Elsevier]

Abstract: In the present paper we evaluate the performance of three different site allocation policies in a 2-level computational grid with heterogeneous sites. We examine the case where service demands of jobs show high variability, and we consider that schedulers are aware of the service times. A simulation model is used to evaluate performance in terms of the average response time and slowdown, under medium and high load. The impact of the various input parameters on performance is also taken into account. Simulation results show that one policy outperforms the other two that are examined, especially at high load. Furthermore, no performance degradation is observed when estimations are used instead of exact knowledge about job service times. [Copyright &y& Elsevier]

Abstract: Network-on-Chip (NoC) has been proposed as an alternative to bus-based schemes to achieve high-performance and scalability in System-on-Chip (SoC) design. Performance analysis and evaluation of on-chip interconnect architectures are widely based on simulations, which become computationally expensive, especially for large-scale NoCs. In this paper, a Network Calculus-based methodology is presented to analyze and evaluate the performance and cost metrics, such as latency and energy consumption. The 2D Mesh, Spidergong, and WK-Recursive on-chip interconnect architectures are analyzed using this methodology and results are compared with those produced using simulations. The values obtained by simulations and by analysis show similar trends in the same order of magnitude. Furthermore, WK outperforms the other on-chip interconnects in all considered metrics. [Copyright &y& Elsevier]

Abstract: The performance of modern computer systems is increasingly often limited by long latencies of accesses to the memory subsystems. Instruction-level multithreading is an architectural approach to tolerating such long latencies by switching instruction threads rather than waiting for the completion of memory operations. The paper studies performance limitations in distributed-memory block multithreaded systems and determines conditions for such systems to be balanced. Event-driven simulation of a timed Petri net model of a simple distributed-memory system confirms the derived performance results. [Copyright &y& Elsevier]

Abstract: This paper presents the engine performance and optimum injection timing for 4-cylinder direct injection hydrogen fueled engine. The 4-cylinder direct injection hydrogen engine model was developed utilizing the GT-Power commercial software. This model employed one dimensional gas dynamics to represent the flow and heat transfer in the components of engine model. Sequential pulse injectors are adopted to inject hydrogen gas fuel within the compression stroke. Injection timing was varied from 110° before top dead center (BTDC) until top dead center (TDC) timing. Engine speed was varied from 2000rpm to 6000rpm, while the equivalence ratio was varied from 0.2 to 1.0. The validation was performed with the existing previous experimental results. The negative effects of the interaction between ignition timing and injection duration was highlighted and clarified. The results showed that optimum injection timing and engine performance are related strongly to the air fuel ratio and engine speed. The acquired results show that the air fuel ratio and engine speed are strongly influence on the optimum injection timing and engine performance. It can be seen that the indicated efficiency increases with increases of AFR while decreases of engine speed. The power and torque increases with the decreases of AFR and engine speed. The indicated specific fuel consumption (ISFC) decreases with increases of AFR from rich conditions to lean while decreases of engine speed. The injection timing of 60° BTDC was the overall optimum injection timing with a compromise. [Copyright &y& Elsevier]

Abstract: This paper describes INSEE, a simulation framework developed at the University of the Basque Country. INSEE is designed to carry out performance-related studies of interconnection networks. It is composed of two main modules: a Functional Simulator of Interconnection Networks (FSIN) and a TRaffic GENeration module (TrGen), together with several other modules that extend INSEE’s functionality. The router models and topologies implemented in FSIN are included in this description. Likewise, the available methods to generate traffic are described thoroughly. Finally, the resource consumption of INSEE when managing different systems and workloads is also evaluated. INSEE has been used to conduct a variety of studies, including evaluation of novel topologies, diagnosis of causes of network congestion and evaluation of parallel scheduling algorithms. [ABSTRACT FROM AUTHOR]

Abstract: The most crucial aspect of distributed real-time systems is the scheduling algorithm, which must guarantee that every job in the system will meet its deadline. In this paper, we evaluate by simulation the performance of strategies for the dynamic scheduling of composite jobs in a heterogeneous distributed real-time system. Each job that arrives in the system is a directed acyclic graph of component tasks and has an end-to-end deadline. For each scheduling policy, we provide alternative versions which allow the insertion of tasks into idle time slots, using various bin packing techniques. The comparison study, based on different workloads and system heterogeneity levels, shows that the alternative versions of the algorithms outperform their respective counterparts. [ABSTRACT FROM AUTHOR]

Abstract: Databases form the common component of many software systems. However, performance models specifically targeted at the database design have not been extensively studied. In this paper, we propose QuePED – a queueing network performance evaluation model for database designs. QuePED provides for the performance modelling of database design constructs, including active database rules; thus, deviating from current methods that consider database designs as processing demands on the hardware architecture. We present a formal specification of QuePED and describe its application to database designs. Experimental evaluation has shown the ability of QuePED to capture the steady state performance of an implementation of the TPC-C benchmark. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a mathematical model is described and developed based on a set of algebraic equations which is capable of artificially generating normal events of the electrocardiogram (ECG) such as P-wave, QRS complex, T-wave or synthetic abnormal phenomena like ST-segment episodes (i.e. depression, elevation, and sloped ascending or descending) and repolarization abnormalities such as T-wave alternans (TWA). In order to demonstrate the flexibility of the presented model for the simulation of various ECG signals, fascicular ventricular tachycardia, rate dependent conduction block, and acute Q-wave infarctions of inferior and anterior-lateral walls are simulated. Then, using the proposed artificial ECG signal, two new developed QRS detection algorithms (Modified Hilbert transform-MHT and discrete wavelet curve length-DWCL algorithms) evolved, respectively based on the implementation of some modifications to the conventional Hilbert and discrete wavelet transforms of the ECG signal, are then evaluated. To meet this end, a mathematically-simulated ECG signal with a weak R-wave is embedded into a Gaussian noise with a wide range for variances (powers) and the MHT and DWCL algorithms are applied to the resulted signal to detect QRS complexes. In the next step, an artificial baseline wander is added to the ECG signal and the performance of the MHT and DWCL algorithms in cases of high baseline wander are studied. After conducting numerous simulations, it was concluded that for the values of signal to noise ratio (SNR) larger than −5dB and amplitudes of baseline wanders approximately less than 5 times of R-wave amplitude, the two detection algorithms will have acceptable performance while it is seen that in low (negative) SNR values, performance endurance of the DWCL based detection algorithm is higher than MHT method. The Matlab m-file script of the synthetic ECG generator will be freely available from the Appendix of this paper. [Copyright &y& Elsevier]

Abstract: The necklace hypercube has recently been introduced as an attractive alternative to the well-known hypercube. Previous research on this network topology has mainly focused on topological properties, VLSI and algorithmic aspects of this network. Several analytical models have been proposed in the literature for different interconnection networks, as the most cost-effective tools to evaluate the performance merits of such systems. This paper proposes an analytical performance model to predict message latency in wormhole-switched necklace hypercube interconnection networks with fully adaptive routing. The analysis focuses on a fully adaptive routing algorithm which has been shown to be the most effective for necklace hypercube networks. The results obtained from simulation experiments confirm that the proposed model exhibits a good accuracy under different operating conditions. [Copyright &y& Elsevier]

Abstract: Multi-core architectures have emerged as the dominant architecture for both desktop and high-performance systems. Multi-core systems introduce many challenges that need to be addressed to achieve the best performance. Therefore, benchmarking of these processors is necessary to identify the possible performance issues. In this paper, broad range of homogeneous multi-core architectures are investigated in terms of essential performance metrics. To measure performance, we used micro-benchmarks from High-Performance Computing Challenge (HPCC), NAS Parallel Benchmarks (NPB), LMbench, and an FFT benchmark. Performance analysis is conducted on multi-core systems from UltraSPARC and x86 architectures; including systems based on Conroe, Kentsfield, Clovertown, Santa Rosa, Barcelona, Niagara, and Victoria Falls processors. Also, the effect of multi-core architectures in cluster performance is examined using a Clovertown based cluster. Finally, cache coherence overhead is analyzed using a full-system simulator. Experimental analysis and observations in this study provide for a better understanding of the emerging homogeneous multi-core systems. [Copyright &y& Elsevier]

Abstract: Fault-tolerance in a communication network is defined as the ability of the network to effectively utilize its redundancy in the presence of faulty components (i.e., nodes or links). New technologies of integration now enable the design of computing systems with hundreds and even thousands of independent processing elements which can cooperate on the solution of the same problem for a corresponding improvement in the execution time. However, as the number of processing units increases, concerns for reliability and continued operation of the system in the presence of failures must be addressed. Adaptive routing algorithms have been frequently suggested as a means of improving communication performance in large-scale massively parallel computers, Multiprocessors System-on-Chip (MP-SoCs), and peer-to-peer communication networks. Before such schemes can be successfully incorporated in networks, it is necessary to have a clear understanding of the factors which affect their performance potential. This paper proposes a novel analytical model to investigate the performance of five prominent adaptive routings in wormhole-switched 2-D tori fortified with an effective scheme suggested by Chalasani and Boppana [S. Chalasani, R.V. Boppana, Adaptive wormhole routing in tori with faults, IEE Proc. Comput. Digit. Tech. 42(6) (1995) 386–394], as an instance of a fault-tolerant method widely used in the literature to achieve high adaptivity and support inter-processor communications in parallel computers. Analytical approximations of the model are confirmed by comparing them with those obtained through simulation experiments. [Copyright &y& Elsevier]