Zigbee-based intra-car wireless sensor networks: a case study

There is a growing interest in eliminating the wires connecting sensors to the microprocessors in cars due to an increasing number of sensors deployed in modern cars. One option for implementing an intra-car wireless sensor network is the use of ZigBee technology. In this article we report the results of a ZigBee-based case study conducted in a vehicle. Overall, the results of the experiments and measurements show that ZigBee is a viable and promising technology for implementing an intra-car wireless sensor network.     

Reliability issues with multiprocessor distributed databasesystems: a case study

The results and the methodology used in the reliability analysis of a call-handling database system are presented. Those areas where the reliability modeling methods and analysis techniques need to be extended to cover all causes of outages are identified, especially when dealing with novel architectures, such as the next-generation switch. The analysis indicates that for this architecture, node configurations with one redundant processor meet the hardware-allocated downtime objective. However, some configurations do not meet this objective when hardware failure rates, repair times, and other parameters such as uncoverage are increased. Some of these parameters can be controlled by the maintenance policies of the support organization, but the critical ones are mainly defined by the reliability and quality programs that equipment suppliers have in place. Reliability and quality analyses can be used to address the many areas in a supplier's program that affect product reliability     

Techno-economic evaluation of narrowband and broadband accessnetwork alternatives and evolution scenario assessment

The paper presents the main results obtained within the Research in Advanced Communications in Europe (RACE) project: 2087 TITAN regarding minimum-risk introductory routes for new narrowband and broadband services in the residential and small business market. The project developed a methodology and a tool for techno-economic evaluation of advanced narrowband and broadband telecommunications networks and services. Results from four extensive access network studies are presented. For the narrowband services, optical access and radio in the local loop have been assessed and compared to conventional copper layout in a greenfield environment. Access network upgrade strategies for emerging new broadband services have been evaluated in three studies, with technological options ranging from enhanced copper to hybrid-fiber-coax (HFC) and broadband passive optical networks. An extensive study on different broadband access network upgrade alternatives for public network operators (PNOs) were carried out, taking into account the diversity of conditions met today by European countries. In another study, the effect of competition In the access network was modeled assuming two main operators sharing the market. Broadband upgrade alternatives were evaluated for a new cable operator, competing with the dominant public network operator. In addition, video-on-demand (VoD) and Internet access upgrades have been analyzed. The paper demonstrates the viability of techno-economic studies for the access network, including in-depth analysis of the time-dependence of component cost, tariffs, service penetrations and market shares     

Reliability evaluation of wireless sensor networks using an enhanced OBDD algorithm

An enhanced ordered binary decision diagram (EOBDD) algorithm is proposed to evaluate the reliability of wireless sensor networks (WSNs), based on the considerations of the common cause failure (CCF) and a large number of nodes in WSNs. The EOBDD algorithm analyzes the common cause event (CCE) and the network structure when CCE takes place according to the stochastic graph and the CCF model of WSNs. After constructing the ordered binary decision diagram (OBDD) of the original network with node expansion, it uses a set of OBDD variables (SOV) to guide reliability computations along this OBDD. The two steps about OBDD can decrease the cost of OBDD constructions and storage. Furthermore, the efficient OBDD structure and Hash tables can greatly decrease redundant computations of isomorphs. The experiment results show that the EOBDD can be used to evaluate the reliability of WSN efficiently.     

Reliability of local area networks with bus and ring topologies

The reliability of local area networks with bus and ring topologies with a simple transfer medium are critically analysed. A double transfer medium is used to increase reliability. The efficiencies of these approaches are compared.     

仿真研究无线多跳网络跨层协议设计的优劣

为了改善无线多跳网络的性能，很多研究表明跨层协议设计比OSI模型更适合无线网络。本文分析了无线多跳网络的特征及对各协议层的影响，给出了跨层协议设计对网络性能的改善以及它可能带来的问题，并针对速率自适应MAC协议和网络层路由协议之间的相互影响给出了仿真实例，结果证明跨层协议设计要充分考虑不同协议之间的相互影响，合理规划、谨慎实施，否则网络的性能不升反降。     

Reliability and cost: Questions for the engineer

In designing a subsystem for a major system, a design engineer is often faced with a number of options, ranging from an inexpensive subsystem with low reliability to a highly reliable subsystem, usually costing considerably more. The basic question which we address in this paper is how to choose among these competing subsystems. This paper utilizes both reliabilities and costs to find the subsystems with the lowest overall expected cost. These concepts are then applied to k-out-of-n: G subsystems. A computer program has been developed to assist the design engineer in exploring and graphing the relative expected costs of competing subsystems over a range of values.     

Reliability of mesh and torus topologies in the presence of faults

Mesh and torus topologies have been used to implement various multicomputer architectures. Faults in these networks significantly degrade their performance. In this paper, a new Markov model is used to derive a closed form analytical solution for the terminal reliability of the mesh and 2‐dimensional torus. The effect of the added links in the torus on reliability is studied. Networks of various dimensions are analyzed, and all the analytical results are verified by computer simulations. Although the mesh‐connected topology is considered in this paper, the analysis can be readily adopted for any network topology. This revised version was published online in June 2006 with corrections to the Cover Date.     

Design study for a CDMA-based third-generation mobile radio system

This paper focuses on a CDMA design study for future third-generation mobile and personal communication systems such as FPLMTS and UMTS. In the design study, a rigorous top down approach is adopted starting from the most essential objectives and requirements of universal third-generation mobile systems. Emphasis is laid on high flexibility with respect to the implementation of a wide range of services and service bit rates including variable rate and packet services. Flexibility in frequency and radio resource management, system and service deployment, and easy operation in mixed-cell and multioperator scenarios are further important design goals. The system concept under investigation is centered around an open and flexible radio interface architecture based on asynchronous direct-sequence CDMA with three different chip rates of approximately 1, 5, and 20 Mchip/s. The presented CDMA system concept forms the basis for an experimental test system (testbed) which is currently under development. This experimental system concept has been jointly established by the partners in the European RACE project R2020 (CODIT). The paper describes the radio transmission scheme and appropriate receiver principles and presents first performance results based on simulations     

Reliability evaluation of a Moran reservoir

The author develops a model to evaluate the reliability measures of a Moran reservoir with respect to the reservoir level (that is, with respect to the occurrence of reservoir emptiness), and with respect to the continuity of the output flow (i.e. with respect to the occurrence of no output flow). For a binary input, the most usual case in practice, simple explicit formulas are derived. Some numerical examples are given for illustration     

Reliability analysis of component-level redundant topologies for solid-state fault current limiter

Experience shows that semiconductor switches in power electronics systems are the most vulnerable components. One of the most common ways to solve this reliability challenge is component-level redundant design. There are four possible configurations for the redundant design in component level. This article presents a comparative reliability analysis between different component-level redundant designs for solid-state fault current limiter. The aim of the proposed analysis is to determine the more reliable component-level redundant configuration. The mean time to failure (MTTF) is used as the reliability parameter. Considering both fault types (open circuit and short circuit), the MTTFs of different configurations are calculated. It is demonstrated that more reliable configuration depends on the junction temperature of the semiconductor switches in the steady state. That junction temperature is a function of (i) ambient temperature, (ii) power loss of the semiconductor switch and (iii) thermal resistance of heat sink. Also, results’ sensitivity to each parameter is investigated. The results show that in different conditions, various configurations have higher reliability. The experimental results are presented to clarify the theory and feasibility of the proposed approaches. At last, levelised costs of different configurations are analysed for a fair comparison.     

Power-area evaluation of various double-gate RF mixer topologies

In this letter, we analyze the suitability of the double gate MOSFETs (DG MOSFETs) for RF-mixer applications from the point of optimizing the transconductance gain, power consumption, and area. Mixer topologies using the 0.13-/spl mu/m conventional MOSFETs, simultaneously driven DG MOSFETs (SDDG) and the independently driven DG MOSFETs (IDDG) are compared using extensive device simulations. In the frequency range 1-40 GHz, our simulation results show that the mixer circuits realized using the SDDG technologies show an order of magnitude lower power-area product, for a given transconductance gain, compared to the conventional and the IDDG technologies.     

Reliability prediction using nondestructive accelerated-degradationdata: case study on power supplies

This paper describes a conceptual framework for reliability evaluation from nondestructive accelerated degradation data (NADD). A numerical example of data sets from power supply units for electronic products is presented using this framework. The authors model NADD as a collection of stochastic processes for which the parameters depend on the stress levels. The relationship between these parameters and the associated stresses is explored using regression. The failure-time of power-supply units is modeled by the Birnbaum-Saunders distribution, for which the confidence bounds and tolerance limits can be easily obtained     

无线通信产品的可靠性预计与实现

针对消费类电子产品的可靠性预计方法Bellcore-SR332的缺陷,提出一种以产品现场返还数据进行失效率建模,以产品开发过程中各可靠性活动的结果作为输入变量的可靠性预计方法,从而弥补可靠性预计与产品开发过程结合的不足,为可靠性预计提供更为真实、准确的预计方法。同时,结合可靠性理论知识在无线通信产品返还数据分析的结合,提出一套符合无线通信产品的返还率预测方法。     

Multimedia quality transmission evaluation over wireless networks: a survey

In recent years, usage of multimedia applications has increased dramatically, especially after the evolution of 3G and 4G technologies. Moreover, the development of new user devices, such as laptops, Smartphone, etc. increased very steeply and rapidly, to support different types of services and different means of communication satisfying user’s needs. Here, the challenge is how to make those services available to users with a high quality; we speak here about quality of service (QoS) and quality of experience. In this survey, we examine different characteristics of wireless networks to determine the enhancements introduced by each technology. Particularly, we focus on the benefits and limitations of three main technologies which are WiMAX, UMTS and LTE, and the role of each one in increasing QoS satisfaction for multimedia application. A comparison is also done between researches already published in Multimedia quality evaluation over wireless networks topic, taking into account some considerations, such QoS parameters, used simulator, assessed applications, etc. All those help us to extract the strengths and limitations of those researches.     

Modeling uncertainties for passive microwave precipitation retrieval: evaluation of a case study

Physically based microwave spaceborne techniques for rainfall retrieval are usually trained by simulated cloud-radiation databases (CRDs) composed of cloud profiles and associated brightness temperatures (TBs). When generating the database, the evaluation of the associated modeling uncertainties is crucial for retrieval error estimation. However, this is extremely complex due to the large number of free parameters. In this work, a possible methodology for taking into account CRD-related modeling uncertainties is proposed. The methodology-fairly general-is here applied to a limited dataset (a cloud-model resolved numerical output of a tropical cyclone). The modeling errors are obtained from systematic TB sensitivity tests associated to several parameters: particle sizes, temperature, ice content, sea surface wind speed, viewing angle, footprint size, radiative transfer schemes, melting phase, and particle shape. TB uncertainties are eventually summarized in a modeling error covariance matrix representing the intrinsic variability of the generated CRD. For comparison with real observations, the TBs are simulated at the spatial resolution, viewing geometry and frequencies of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). The matrix is evaluated with respect to TMI data in terms of an indicator called database matching index. Since they are based on a single case study and suffer from the lack of direct coupling of the radiative transfer with the cloud-resolving model, the provided results should not be considered an exhaustive evaluation of cloud-radiation modeling errors. Nevertheless, they may be considered a valuable starting point for error characterization, since extensions to larger databases could definitely improve modeling error budgets.     

Reliability and lifetime modeling of wireless sensor nodes

The accuracy of system reliability analysis depends not only on system-level model construction, but also on realistic estimation of failure parameters at the component-level. In this paper, we model and evaluate the reliability and lifetime of a wireless sensor node under three typical working scenarios, contributing toward the accurate reliability analysis of wireless sensor network systems. According to the medium access control (MAC) protocols, the three working scenarios are defined based on the sensor node modes (sleep and active) and the mechanism of alternating between the modes. Reliability and lifetime of wireless sensor nodes under these three scenarios are illustrated and compared through numerical examples.     

Reliability and performance of a true enhancement mode HIGFET for wireless applications

Freescale’s true enhancement mode (EMODE) HIGFET is a high performance single supply technology used for wireless power amplifiers. It is the first technology of its kind to be produced in a high volume manufacturing environment. The EMODE HIGFET intrinsic reliability was evaluated using a conventional three temperature DC accelerated stress test. The device used for these tests has a total gate width of 0.6 mm, a gate length of 0.8 μm, and a die thickness of 3 mils. The device has no through-wafer vias, is representative of the unit cell for larger devices, and was processed using a production mask set.For targeted applications with a system life of 5 years, the first expected failure at 150 °C for the 1 ppm level was determined to be 82 years at a 90% lower confidence level, which exceeds the reliability requirements for subscriber unit power amplifiers by a wide margin. This work demonstrates that EMODE HIGFET devices are high performance RF devices with intrinsic reliability well in excess of anticipated system requirements.     

Context-based wireless mesh networks: a case for network virtualization

Wireless Mesh Networks (WMNs) have gained increasing attention as an attractive means to provide connectivity in complement to access as offered by regular Internet Service Providers (ISPs). Such a grass-root technique, however, often suffers from detrimental operating conditions and poor quality. Network virtualization, on the other hand, has been widely advocated as a possibility to overcome what has often been referred to as the ossification of the Internet. Combining the concept of network virtualization with WMN technology, therefore, appears to be promising and desirable. It is envisioned that well managed multiple Virtual Networks (VNs) may overcome shortcomings of WMNs on the one hand, and extend the reach of the Internet beyond its current confinement into the realm and control of the user on the other hand. In this paper, we argue for a context-based approach for an effective means to extend multi-VNs from the Internet domain into WMN environments. We describe both mobility and preferences as context models in order to create virtualized WMNs based on these types of context models. As a result, it is envisioned to achieve a comprehensive connectivity coverage, accompanied by high assurance in network quality. We further present a distributed solution to manage multi-VNs, and a mobility-aware context use case to demonstrate the usefulness of our approach.     

Modelling the energy cost of a fully operational wireless sensor network

Several applications have been proposed for wireless sensor networks, including habitat monitoring, structural health monitoring, pipeline monitoring, precision agriculture, active volcano monitoring, and many more. The energy consumption of these applications is a critical feasibility metric that defines the scope and usefulness of wireless sensor networks. This paper provides a comprehensive energy model for a fully functional wireless sensor network. While the model uses toxic gas detection in oil refineries as an example application, it can easily be generalized. The model provides a sufficient insight about the energy demand of the existing or proposed communication protocols.