technologies to control applications is expected to provide advantages in control applications, such as increasing the flexibility, reducing the wiring or getting information for sensors that are difficult to connect (e.g. those located in moveable devices). However, wireless communications are still under scrutiny since there are several challenges that must be solved. These challenges involve: (1) reliability, i.e. limiting message delays and lowering message dropouts; (2) finding the optimal sampling period, since it may affect the behavior of the control systems, having influence at the stability; (3) feeding power to the wireless devices. So, this work aims at analyzing the benefits and drawbacks of using wireless technologies in control applications.
8 Lee mas
Abstract—Wireless technologies have rapidly evolved and are becoming ubiquitous. An increasing number of users attach to the Internet using these technologies; hence the performance of these wireless access links is a key point when considering the performance of the whole Internet. In this paper we present a measurement-based analysis of the performance of an IEEE 802.16 (WiMAX) client and an UMTS client. The measurements were carried out in a controlled laboratory. The wireless access links were loaded with traffic from a multi-point video- conferencing application and we measured three layer-3 metrics (One-Way-Delay, IP-Delay-Variation and Packet Loss Ratio). Additionally we estimate the performance of a WiFi and Ethernet client as a reference. Our results show that Ethernet and WiFi have comparable performances. Both the WiMAX and the UMTS links exhibited an asymmetric behavior, with the uplink showing an inferior performance. We also assessed the causes of the discretization which appears in the jitter distributions of these links.
6 Lee mas
An implementation of an expert system to provide unbiased informa- tion about the most suitable technology for specific applications in healthcare. The prototype is developed as a web tool to be used in ordinary personal computers. The idea is to provide with relevant in- formation to health care administration specialists such that they can make appropriate decisions about the selection and implantation of WIT (Wireless Identification Technologies). The expert system prototype can provide expert advise to help critical decision makers in health- care facilities, health professionals, innovators, and entrepreneurs to select the most suitable technology for the specific application.The system uses membership functions to fire four different figure of merit or indicators: technical feasibility, cost, commercial availability and proven documentation. The advising results are consistent to proven application projects and show high performance dominance using UHF Active RFID for high demanding applications such as new born monitoring and patient assistance. Other non-critical applications such as cabinet monitoring and garement owner ID can be developed using HF or UHF Passive RFID technologies at various frequencies. This prototype follows an effort to create a fundamental platform that could facilitate and stimulate the adoption of WIT in the healthcare industry. Key Words: WIT, wireless technologies, expert system prototype, health care.
10 Lee mas
The massive growth in the number of connected wireless devices leads to an increasing demand for network connectivity, better performance and larger bandwidth. These technologies have been traditionally applied in UAVs for their control (piloting), but the possibility of incorporate onboard cameras, microphones and sensors requires the use other wireless technologies with the appropriate bandwidth, reliability and range. Due to their excellent performance, UAVs are becoming a useful tool in different disciplines. These devices, sometimes also known as drones, provide multidisciplinary applications in areas such as mapping, rescue, and leisure, which are the main focusing areas in this final year project.
66 Lee mas
In order to be able to measure the quality of the received signal, we must take into account the interfering signals. By interfering signals, we mean those undesired signals received by different network elements that make it harder to receive the expected signal properly. In the context of this work, it is necessary to quantify the power of interfering signals both in wireless terminals (C and D) and APs. We have to take into consideration several issues for this. First, we have assumed that there are only interferences coming from other Wi-Fi devices, but not from any other wireless technologies that may be also using the 2.4-GHz frequency band. It would not be difficult to extend our interference model, but we have decided not to do so, because these interferences are unconnected to the problem that we are presenting here. Second, provided that distance also affects interference signals, those interferences coming from sources far enough from the reception point so that they fall below the receiver’s sensitivity have been dismissed, according to the interference graph presented in Section 2.2. Third, it is commonly accepted that data traffic in access networks is very asymmetric, i.e., the downstream clearly dominates the upstream . Indeed, this asymmetry has shaped the ADSL (Asymmetric Digital Subscriber Line) and cable design. For that reason, we have assumed that uplink traffic of wireless devices (D) is negligible in comparison with the traffic transmitted by APs, so they are not included in the graph. However, note that this assumption has only been made for wireless devices (D) different from cameras, as IP-based cameras’ (C) data traffic will be mainly upstream.
22 Lee mas
These emerging wireless technologies can give benefits in cost-reduction, and reliability in industrial applications as well as opportunities in improving operational performance. But there is still work in progress to achieve usable technologies which meet industrial requirements. Firstly we will present an overview of the current and future wireless technologies from a standardization point of view. Secondly we will analyze the work to be done in the design and implementation in the industrial environments, such as in the utilities installations (power plants, sub-stations, factories). Finally we will present our current experimentations and future works within hybrid technology networking fields.
16 Lee mas
Flexible infrastructures and systems are fundamental to ensuring that wireless content—ranging from ringtones to m-greetings to broadband TV programming—can be supported by the same solution. Core issues to consider are that content itself comes in many forms with different characteristics—such as "static" content like a screensaver that does not change once published, as opposed to an evening news clip that needs to be refreshed every half hour. Even video itself has different characteristics. A music video is typically a larger file because of the action that is captured, whereas a simple news read of headlines is generally a smaller content file. A flexible solution needs to account for these differences, and also address the growing opportunity of user-created content, such as mBlogs and video messaging that may be used in place of camcorders within the next few years.
9 Lee mas
monitoring. This acquired data is locally processed, stored, and shared with other nodes so that information can be used by the whole network. Wireless Sensor Networks are built by several nodes (from dozens to several hundred depending on the application). Each node typically has four modules: (a) a microcontroller, (b) a radio transceiver with an internal or an external antenna, (c) one or more sensors, and (d) an energy source (usually batteries or an energy-harvesting system). A WSN node has several constraints in terms of size, cost, energy consumption, memory, and computational capabilities. The potential fields of application for WSNs arise from home control to military scenarios, vehicular networks, or critical information infrastructure protection. For that reason, WSNs are increasingly introduced into our daily lives. The number of devices connected is expected to grow from 2 billion in 2014 to 8 billion in 2020.
215 Lee mas
The recent switch from analog to digital TV broadcast around the world has led to the development of communications standards that consider the use of TV White Spaces (TVWS). One of such standards is the IEEE 802.22 wireless regional area network (WRAN), which considers the use of TVWS to achieve better propagation characteristics and longer transmission distances. Thus, this emerging technology presents an opportunity to provide connectivity and data based services from urban to rural areas. Some kind of services that could greatly benefit from the provision of data links between urban and rural areas are those related to telemedicine and m-‐health. Nevertheless, provisioning of a certain quality of service (QoS) level is of paramount importance to enable proper telemedicine service delivery from urban (e.g. an urban hospital) to rural locations (e.g. a rural clinic). In this context, QoS provisioning for telemedicine applications over wireless networks present a major challenge to be addressed in order to fulfill the potential that rural wireless telemedicine has to offer. In this thesis, a cross-‐layer approach combining Medium Access Control (MAC) and Application (APP) layers is presented, with the aim of reducing blocking probability and interruption probability in telemedicine services operating over IEEE802.22/WRANs. At the APP layer, telemedicine traffic profiles based on utilization rates are defined. On the other hand, at the MAC layer
126 Lee mas
locations. They have been mainly used for location estimation in wireless local area networks (WLAN), but they would appear to be attractive also for WSN. In this technique, in addition to anchor nodes (e.g. access points in WLANs) and non- anchor nodes, a large number of sample points (e.g. sniffing devices) are distributed throughout the coverage area of the WSN. At each sample point, a vector of RSS is obtained, with the i th entry corresponding to the i th anchor’s transmitted signal. Of course, many entries of the signal strength vector may be zero or very small, corresponding to anchor nodes at larger distances (relative to the transmission range or sensing radius) from the sample point. The collection of all these vectors provides (by extrapolation in the vicinity of the sample points) a map of the whole region. The collection constitutes the RSS model, and it is unique with respect to the anchor locations and the environment. The model is stored in a central location. By referring to the RSS model, a non-anchor node can estimate its location using the RSS measurements from anchors. However, the main problem of this approach is sensitivity to environmental changes. In that case, the system must be re-calibrated, i.e., new vector of RSS have to be collected.
191 Lee mas
Algal cell walls separate the inside cell content from the environment to protect the cell against desiccation, pathogens, and predators while still allowing exchange of compounds. Toward application of algae biomass as a sustainable resource, disruption of this cell wall (¼cell disruption) is an essential pretreatment step to maximize prod- uct recovery in downstream processes of the algae biorefinery. Also for direct use of algae in feed or food, cell rupture is required to increase the bioavailability of algae constituents. Depending on the cell wall structure, the size, and the shape of algae, cell disruption can be challenging. A variety of cell disruption methods is currently avail- able, and new approaches are being elaborated in parallel. Since downstream processing is responsible for a large part of the operational costs in the whole produc- tion chain, cell disruption technologies should be low cost and energy efficient and result preferably in high product quality. This chapter provides information on cell wall types and gives an overview of physical-mechanical and (bio-)chemical cell dis- ruption technologies with attention to development stage, energy efficiency, product quality, costs, emerging approaches, and applicability on large scale.
22 Lee mas
Experimental research has always been related to wired and wireless communications. Today, it is commonly conjectured that computer simulations are sufficient for evaluating wireless communications systems. Although computer simulations are indeed necessary and recommendable for this purpose, they only reflect the simulation environment instead of the actual scenarios where the systems operate. Therefore, it is also desirable to evaluate wireless communications systems in realistic and representative scenarios, keeping the required efforts within reasonable limits. Different strategies can be followed to undertake such assessment tasks. Among them, the testbed approach constitutes a simple and at the same time flexible enough solution based on the software-defined radio concept in which only the fundamental operations are carried out in real-time. The remaining tasks are implemented in high-level programming languages using floating point operations executed by general-purpose processors. Such a concept fits perfectly with the needs for the experimental assessment of wireless communications systems, while keeping the costs, manpower and a priori required knowledge within reasonable limits, making testbeds affordable even for small research groups with scarce resources, as in our case.
181 Lee mas
En cambio, una red Infraestructure BSS se distingue de una IBSS por el uso de un dispositivo especial llamado access point (AP, Punto de Acceso). Este dispositivo es un intermediario en toda conexión entre dos estaciones cualquiera, incluyendo las comunicaciones entre dos estaciones wireless pertenecientes al mismo BSS. En este caso, el nodo wireless origen transmite la trama al access point, que a su vez la retransmite al nodo wireless destino. Además, funciona como un intermediario entre los dispositivos en el medio cableado y los que se encuentran en el medio inalámbrico. El área de una red infraestructura está definida por el alcance del access point, lo que significa que todas las estaciones deben estar dentro su área de cobertura, no existiendo alguna restricción con respecto a la distancia entre las estaciones que componen un mismo BSS. Aunque dos estaciones no puedan comunicarse directamente porque están fuera del alcance, si lo podrán hacer a través del access point al que están asociados.
112 Lee mas
El snooping (simulación) inalámbrico y el sniffing (rastreo) de paquetes son términos comunes para las escuchas. El usar encriptación y evitar protocolos que son fácilmente escuchados puede combatir las escuchas. Los analizadores de protocolos inalámbricos comerciales como AiroPeek, AirMagnet, o Sniffer Wireless se pueden usar para escuchar las WLANs. Las escuchas inalámbricas se pueden usar para ver el tráfico de la red y descubrir los SSIDs en uso, las direcciones MAC válidas o para determinar si la encriptación está siendo usada. El reconocimiento inalámbrico a menudo es llamado wardriving. Los utilitarios usados para explorar las redes inalámbricas pueden ser activos o pasivos. Las herramientas pasivas, como Kismet, no transmiten información mientras están detectando redes inalámbricas.
60 Lee mas
This paper reports a joint work by the Solar Energy Group (FCEIA - IFIR) and the Intelligent Wireless Sensor Networks Group (FCEIA) for the implementation of a network of sensors to make measurements of UVI. The aim of the work described in this paper was to investigate the feasibility of the proposed project and analyze, design and build a prototype sensor node suitable for the measurement of UVI and also as a basis for the future establishment of a network of sensors for measuring UVI in the special conditions mentioned, this is: in Argentine Antarctica, on workers exposed for long periods to sunlight and in snow sports, among others. The rest of the publication is organized as follows, section 2 details the requirements defined for the system, Section 3 describes the design and implementation of the prototype, and Section 4 account for the operation tests performed. Finally, conclusions and future work lines are reported in Section 5.
9 Lee mas
Abstract—It is commonly assumed that the energy consump- tion of wireless communications is minimized when low-order modulations such as BPSK are used. Nevertheless, the literature provides some evidence that low-order modulations are subopti- mal for short transmission distances. A thorough analysis on how the modulation scheme and transmission power must be chosen as a function of distance in order to achieve energy-efficient communications over fading channels has not been reported yet. In this paper we provide this analysis by presenting a model that determines the energy consumed per payload bit transferred without error over correlated or uncorrelated random channels. We find that each modulation scheme has a single optimal signal-to-noise ratio (SNR) at which the energy consumption is minimized. We also find that if all modulations are operated at their optimal SNR, BPSK and QPSK are the optimal choices for long transmission distances, but as the transmission distance shortens the optimal modulation size grows to 16-QAM and even to 64-QAM. This result leads to showing that for short-range communications the lifetime of a typical low-power transceiver can be increased by up to 600% by selecting the optimal constellation rather than BPSK.
92 Lee mas
Benefits: IMS allows wired and wireless service providers to deliver and bill multimedia services built on applications that leverage IP. IMS solves many of the VoIP related Internetworking issues such as fast handoff in disparate physical network technologies, such as Wi-Fi to cellular to WiMAX as a SIP based, TCP/IP traffic stream. Operators see UMA and IMS as extremely complimentary because UMA lets them to take IMS application on to Wi-Fi and IP networks. Deployments: The IMS deployments for Wireless VoIP are beginning to surface across all parts of world. China Unicom has technical trials under way. Vodafone Group (UK) has decided to go for IMS based next generation wireless services. The company will be using IMS offering from Nokia and Ericsson. Tradingcom Europe Group, Europe's telecommunications capacities trader, has selected Sonus IMS architecture as the foundation for Tradingcom's complete, end-to-end IP-based voice network.
7 Lee mas
The JetWave 4020 series is an industrial grade Dual Band IP67 802.11ac Wireless Access Point. The product is equipped with the industry leading 5.8G 802.11ac Wave 1 and 2.4G 802.11n dual radios. With its 802.11ac Beamforming, high transmission speed and dual band concurrent design, the product can support Gigabit Wireless communication performance for your network.
9 Lee mas
Por lo general la tarea que suele consumir mayor tiempo en la instalación de una red inalámbrica es paradójicamente la parte cableada que se emplea para enlazar los puntos de acceso con la red local de la empresa. Aún así se mide en días la duración de un proyecto, siempre dependiendo de su extensión. En el caso de redes fijas, no son días sino habitualmente semanas. Esto es en muchos casos un factor decisivo para ciertos proyectos. También cada vez se ven más casos de despliegues primeros o ampliaciones de infraestructura que por necesidades urgentes se inician por la construcción de una red wireless para posteriormente consolidarse con una cableada, aunque manteniendo la primera para temas de movilidad y atender los requerimientos de ciertos usuarios.
88 Lee mas
coverage of typical RFID antennas with different real passive tags, when using several transmit levels. This allows us to discover hardware limitations and determine the minimum antenna separation that should be chosen to properly cover an indoor scenario minimizing blind areas, as well as the maximum cable length that should be deployed, and therefore the introduced loss. The antenna used was a far-field Laird Technologies S8658-PR right-hand circular- polarization antenna , with 3.85 dBd gain. It was mounted at 1 m height above the floor. The two tags were a Frog 3D  and a DogBone  passive tags, which were mounted on the back of a plastic chair, separated 15 cm from each other and orientated vertically. The chair was moved towards the points depicted in Figure 4.10 always maintaining the same orientation. Figure 4.11 shows the mean RSS values obtained when transmitting at different powers (20 s at each power level, obtaining typically fourteen measurements from each tag in the favourable cases). Looking at the results it is clear that tag2 behaves better for lower transmit power and
204 Lee mas