3,452 research outputs found

    Micro power management of active 802.11 network interfaces

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    Micro power management (muPM), a standard-compliant MAC level solution to save power for active 802.11 interfaces is developed. muPM enables an 802.11 interface to enter unreachable power-saving modes even between MAC frames, without noticeable impact on the traffic flow. To control data loss, muPM leverages the retransmission mechanism in 802.11 and controls frame delay to adapt to demanded network throughput with minimal cooperation from the access point. Extensive simulation has been conducted to systematically investigate an effective and efficient implementation of muPM. A prototype muPM on an open-access wireless hardware platform has been presented. Measurements show that more than 30% power reduction for the wireless transceiver can be achieved with muPM for various applications without perceptible quality degradation

    Ό\muNap: Practical Micro-Sleeps for 802.11 WLANs

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    In this paper, we revisit the idea of putting interfaces to sleep during 'packet overhearing' (i.e., when there are ongoing transmissions addressed to other stations) from a practical standpoint. To this aim, we perform a robust experimental characterisation of the timing and consumption behaviour of a commercial 802.11 card. We design Ό\muNap, a local standard-compliant energy-saving mechanism that leverages micro-sleep opportunities inherent to the CSMA operation of 802.11 WLANs. This mechanism is backwards compatible and incrementally deployable, and takes into account the timing limitations of existing hardware, as well as practical CSMA-related issues (e.g., capture effect). According to the performance assessment carried out through trace-based simulation, the use of our scheme would result in a 57% reduction in the time spent in overhearing, thus leading to an energy saving of 15.8% of the activity time.Comment: 15 pages, 12 figure

    Flat Cellular (UMTS) Networks

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    Traditionally, cellular systems have been built in a hierarchical manner: many specialized cellular access network elements that collectively form a hierarchical cellular system. When 2G and later 3G systems were designed there was a good reason to make system hierarchical: from a cost-perspective it was better to concentrate traffic and to share the cost of processing equipment over a large set of users while keeping the base stations relatively cheap. However, we believe the economic reasons for designing cellular systems in a hierarchical manner have disappeared: in fact, hierarchical architectures hinder future efficient deployments. In this paper, we argue for completely flat cellular wireless systems, which need just one type of specialized network element to provide radio access network (RAN) functionality, supplemented by standard IP-based network elements to form a cellular network. While the reason for building a cellular system in a hierarchical fashion has disappeared, there are other good reasons to make the system architecture flat: (1) as wireless transmission techniques evolve into hybrid ARQ systems, there is less need for a hierarchical cellular system to support spatial diversity; (2) we foresee that future cellular networks are part of the Internet, while hierarchical systems typically use interfaces between network elements that are specific to cellular standards or proprietary. At best such systems use IP as a transport medium, not as a core component; (3) a flat cellular system can be self scaling while a hierarchical system has inherent scaling issues; (4) moving all access technologies to the edge of the network enables ease of converging access technologies into a common packet core; and (5) using an IP common core makes the cellular network part of the Internet

    Implementing and Evaluating a Wireless Body Sensor System for Automated Physiological Data Acquisition at Home

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    Advances in embedded devices and wireless sensor networks have resulted in new and inexpensive health care solutions. This paper describes the implementation and the evaluation of a wireless body sensor system that monitors human physiological data at home. Specifically, a waist-mounted triaxial accelerometer unit is used to record human movements. Sampled data are transmitted using an IEEE 802.15.4 wireless transceiver to a data logger unit. The wearable sensor unit is light, small, and consumes low energy, which allows for inexpensive and unobtrusive monitoring during normal daily activities at home. The acceleration measurement tests show that it is possible to classify different human motion through the acceleration reading. The 802.15.4 wireless signal quality is also tested in typical home scenarios. Measurement results show that even with interference from nearby IEEE 802.11 signals and microwave ovens, the data delivery performance is satisfactory and can be improved by selecting an appropriate channel. Moreover, we found that the wireless signal can be attenuated by housing materials, home appliances, and even plants. Therefore, the deployment of wireless body sensor systems at home needs to take all these factors into consideration.Comment: 15 page

    FastM: Design and Evaluation of a Fast Mobility Mechanism for Wireless Mesh Networks

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    Although there is a large volume of work in the literature in terms of mobility approaches for Wireless Mesh Networks, usually these approaches introduce high latency in the handover process and do not support realtime services and applications. Moreover, mobility is decoupled from routing, which leads to inefficiency to both mobility and routing approaches with respect to mobility. In this paper we present a new extension to proactive routing protocols using a fast mobility extension, FastM, with the purpose of increasing handover performance in Wireless Mesh Networks. With this new extension, a new concept is created to integrate information between neighbor wireless mesh routers, managing locations of clients associated to wireless mesh routers in a certain neighborhood, and avoiding packet loss during handover. The proposed mobility approach is able to optimize the handover process without imposing any modifications to the current IEE 802.11 MAC protocol and use unmodified clients. Results show the improved efficiency of the proposed scheme: metrics such as disconnection time, throughput, packet loss and control overhead are largely improved when compared to previous approaches. Moreover, these conclusions apply to mobility scenarios, although mobility decreases the performance of the handover approach, as expected

    Count three for wear able computers

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    This paper is a postprint of a paper submitted to and accepted for publication in the Proceedings of the IEE Eurowearable 2003 Conference, and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library. A revised version of this paper was also published in Electronics Systems and Software, also subject to Institution of Engineering and Technology Copyright. The copy of record is also available at the IET Digital Library.A description of 'ubiquitous computer' is presented. Ubiquitous computers imply portable computers embedded into everyday objects, which would replace personal computers. Ubiquitous computers can be mapped into a three-tier scheme, differentiated by processor performance and flexibility of function. The power consumption of mobile devices is one of the most important design considerations. The size of a wearable system is often a design limitation

    Mobile Networking

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    We point out the different performance problems that need to be addressed when considering mobility in IP networks. We also define the reference architecture and present a framework to classify the different solutions for mobility management in IP networks. The performance of the major candidate micro-mobility solutions is evaluated for both real-time (UDP) and data (TCP) traffic through simulation and by means of an analytical model. Using these models we compare the performance of different mobility management schemes for different data and real-time services and the network resources that are needed for it. We point out the problems of TCP in wireless environments and review some proposed enhancements to TCP that aim at improving TCP performance. We make a detailed study of how some of micro-mobility protocols namely Cellular IP, Hawaii and Hierarchical Mobile IP affect the behavior of TCP and their interaction with the MAC layer. We investigate the impact of handoffs on TCP by means of simulation traces that show the evolution of segments and acknowledgments during handoffs.Publicad

    Energy efficiency in wireless communications for mobile user devices

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    MenciĂłn Internacional en el tĂ­tulo de doctorMobile user devices’ market has experi-enced an exponential growth worldwide over the last decade, and wireless communications are the main driver for the next generation of 5G networks. The ubiquity of battery-powered connected devices makes energy efficiency a major research issue. While most studies assumed that network interfaces dominate the energy consumption of wireless communications, a recent work unveils that the frame processing carried out by the device could drain as much energy as the interface itself for many devices. This discovery poses doubts on prior energy models for wireless communications and forces us to reconsider existing energy-saving schemes. From this standpoint, this thesis is de-voted to the study of the energy efficiency of mobile user devices at multiple layers. To that end, we assemble a comprehensive en-ergy measurement framework, and a robust methodology, to be able to characterise a wide range of mobile devices, as well as individual parts of such devices. Building on this, we first delve into the en-ergy consumption of frame processing within the devices’ protocol stack. Our results identify the CPU as the leading cause of this energy consumption. Moreover, we discover that the characterisation of the energy toll ascribed to the device is much more complex than the previous work showed. Devices with complex CPUs (several frequencies and sleep states) require novel methodologies and models to successfully characterise their consumption. We then turn our attention to lower levels of the communication stack by investigating the behaviour of idle WiFi interfaces. Due to the design of the 802.11 protocol, together with the growing trend of network densification, WiFi devices spend a long time receiving frames addressed to other devices when they might be dormant. In order to mitigate this issue, we study the timing constraints of a commercial WiFi card, which is developed into a standard-compliant algorithm that saves energy during such transmissions. At a higher level, rate adaptation and power control techniques adapt data rate and output power to the channel conditions. However, these have been typically studied with other metrics rather than energy efficiency in mind (i.e., performance figures such as throughput and capacity). In fact, our analyses and sim-ulations unveil an inherent trade-off between throughput and energy efficiency maximisa-tion in 802.11. We show that rate adaptation and power control techniques may incur inef-ficiencies at mode transitions, and we provide energy-aware heuristics to make such decisions following a conservative approach. Finally, our research experience on simula-tion methods pointed us towards the need for new simulation tools commited to the middle-way approach: less specificity than complex network simulators in exchange for easier and faster prototyping. As a result, we developed a process-oriented and trajectory-based discrete-event simulation package for the R language, which is designed as a easy-to-use yet pow-erful framework with automatic monitoring capabilities. The use of this simulator in net-working is demonstrated through the energy modelling of an Internet-of-Things scenario with thousands of metering devices in just a few lines of code.El mercado de los dispositivos de usuario mĂłviles ha experimentado un crecimiento exponencial a nivel mundial en la Ășltima dĂ©cada, y las comunicaciones inalĂĄmbricas son el principal motor de la siguiente generaciĂłn de redes 5G. La ubicuidad de estos dispos-itivos alimentados por baterĂ­as hace de la eficiencia energĂ©tica un importante tema de investigaciĂłn. Mientras muchos estudios asumĂ­an que la interfaz de red domina el consumo energĂ©tico de las comuni-caciones inalĂĄmbricas, un trabajo reciente revela que el procesado de tramas que se lleva a cabo en el disposi-tivo podrĂ­a gastar tanta energĂ­a como la propia interfaz para muchos dispositivos. Este descubrimiento plantea dudas sobre los anteriores modelos energĂ©ticos para comunicaciones inalĂĄmbricas y nos obliga a reconsid-erar los esquemas de ahorro energĂ©tico existentes. Desde este punto de vista, esta tesis estĂĄ dedicada al estudio de la eficiencia energĂ©tica de dispositivos de usuario mĂłviles en mĂșltiples capas. Para ello, se construye un completo sistema de medida de energĂ­a, y una metodologĂ­a robusta, capaz de caracterizar un amplio rango de dispositivos mĂłviles, asĂ­ como partes individuales de tales dispositivos. A partir de esto, en primer lugar se profundiza en el consumo energĂ©tico del procesamiento de tramas en la pila de protocolos de los dispositivos. Nuestros resul-tados identifican a la CPU como principal causa de tal consumo. AdemĂĄs, se descubre que la caracterizaciĂłn de la cuota energĂ©tica adscrita al dispositivo es mucho mĂĄs compleja que lo mostrado por el trabajo ante-rior. Los dispositivos con CPU complejas (mĂșltiples frecuencias y modos de apagado) requieren nuevas metodologĂ­as y modelos para caracterizar su consumo de manera existosa. En este punto, volvemos nuestra atenciĂłn hacia niveles mĂĄs bajos de la pila de comunicaciones para investigar el comportamiento de las interfaces WiFi en estado inactivo. Debido al diseño del protocolo 802.11, junto con la tendencia creciente hacia la densifi-caciĂłn de las redes, los dispositivos WiFi pasan mucho tiempo recibiendo tramas destinadas a otros dispos-itivos cuando podrĂ­an estar apagados. Para mitigar este problema, se estudian las limitaciones temporales de una tarjeta WiFi comercial, lo que posteriormente se utiliza para desarrollar un algoritmo conforme con el estĂĄndar que es capaz de ahorrar energĂ­a durante dichas transmisiones. A un nivel mĂĄs alto, las tĂ©cnicas de adaptaciĂłn de tasa y control de potencia adaptan la tasa de datos y la potencia de salida a las condiciones del canal. No obstante, estas tĂ©cnicas han sido tĂ­picamente es-tudiadas con otras mĂ©tricas en mente (i.e., figuras de rendimiento como la tasa total y la capacidad). De hecho, nuestros anĂĄlisis y simulaciones desvelan un conflicto entre la maximizaciĂłn de la tasa total y la efi-ciencia energĂ©tica en 802.11. Se muestra que las tĂ©cni-cas de adaptaciĂłn de tasa y control de potencia pueden incurrir en ineficiencias en los cambios de modo, y se proporcionan heurĂ­sticos para tomar tales decisiones de un modo conservador y eficiente energĂ©ticamente. Finalmente, nuestra experiencia investigadora en mĂ©todos de simulaciĂłn nos hizo conscientes de la necesidad de nuevas herramientas de simulaciĂłn comprometidas con un enfoque intermedio: menos especificidad que los complejos simuladores de re-des a cambio de facilidad y rapidez en el prototipado. Como resultado, se desarrollĂł un paquete de simu-laciĂłn por eventos discretos para el lenguaje R orien-tado a procesos y basado en trayectorias, el cual estĂĄ diseñado como una herramienta fĂĄcil de utilizar a la par que potente con capacidad de monitorizaciĂłn au-tomĂĄtica integrada. El uso de este simulador en redes se demuestra mediante el modelado en energĂ­a de un escenario de la Internet de las Cosas con miles de dis-positivos de medida en tan solo unas pocas lĂ­neas de cĂłdigo.Programa Oficial de Doctorado en IngenierĂ­a TelemĂĄticaPresidente: Juan Manuel LĂłpez Soler.- Secretario: Francisco Valera Pintor.- Vocal: Paul Horatiu Patra
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