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Register a new userOn Frequency Optimisation for Power Saving in WSNs: Finding Optimum Hardware Timers Frequencies
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Added by
Andreea Picu
Publication date
2012
fields
Informatics Engineering
and research's language is
English
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Wireless Sensor Networks research and demand are now in full expansion, since people came to understand these are the key to a large number of issues in industry, commerce, home automation, healthcare, agriculture and environment, monitoring, public safety etc. One of the most challenging research problems in sensor networks research is power awareness and power-saving techniques. In this masters thesis, we have studied one particular power-saving technique, i.e. frequency scaling. In particular, we analysed the close relationship between clock frequencies in a microcontroller and several types of constraints imposed on these frequencies, e.g. by other components of the microcontroller, by protocol specifications, by external factors etc. Among these constraints, we were especially interested in the ones imposed by the timer service and by the serial ports transmission rates. Our efforts resulted in a microcontroller configuration management tool which aims at assisting application programmers in choosing microcontroller configurations, in function of the particular needs and constraints of their application.
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One of the major challenges in design of Wireless Sensor Networks (WSNs) is to reduce energy consumption of sensor nodes to prolong lifetime of finite-capacity batteries. In this paper, we propose Energy-efficient Adaptive Scheme for Transmission (EAST) in WSNs. EAST is an IEEE 802.15.4 standard compliant. In this scheme, open-loop is used for temperature-aware link quality estimation and compensation. Whereas, closed-loop feedback process helps to divide network into three logical regions to minimize overhead of control packets. Threshold on transmitter power loss (RSSIloss) and current number of nodes (nc(t)) in each region help to adapt transmit power level (Plevel) according to link quality changes due to temperature variation. Evaluation of propose scheme is done by considering mobile sensor nodes and reference node both static and mobile. Simulation results show that propose scheme effectively adapts transmission Plevel to changing link quality with less control packets overhead and energy consumption as compared to classical approach with single region in which maximum transmitter Plevel assigned to compensate temperature variation.
Wireless Sensors Networks (WSNs) have a big application in heterogeneous networks. In this paper, we propose and evaluate Advanced Low-Energy Adaptive Clustering Hierarchy (Ad-LEACH) which is static clustering based heterogeneous routing protocol. The complete network field is first divided into static clusters and then in each cluster separate Ad-LEACH protocol is applied. Our proposed protocol is inherited from LEACH with a cluster head selection criteria of Distributed Energy-Efficient Clustering (DEEC). This enables Ad-LEACH to cope with the heterogeneous nature of nodes. Due to small static clusters, each node reduces its broadcast message power because it only has to cover a small area. We perform simulations in MATLAB to check the efficiency of Ad-LEACH. The Simulation results show that Ad-LEACH outperforms LEACH and DEEC in energy efficiency as well as throughput.
The median webpage has increased in size by more than 80% in the last 4 years. This extra complexity allows for a rich browsing experience, but it hurts the majority of mobile users which still pay for their traffic. This has motivated several data-saving solutions, which aim at reducing the complexity of webpages by transforming their content. Despite each method being unique, they either reduce user privacy by further centralizing web traffic through data-saving middleboxes or introduce web compatibility (Webcompat) issues by removing content that breaks pages in unpredictable ways. In this paper, we argue that data-saving is still possible without impacting either users privacy or Webcompat. Our main observation is that Web images make up a large portion of Web traffic and have negligible impact on Webcompat. To this end we make two main contributions. First, we quantify the potential savings that image manipulation, such as dimension resizing, quality compression, and transcoding, enables at large scale: 300 landing and 880 internal pages. Next, we design and build Browselite, an entirely client-side tool that achieves such data savings through opportunistically instrumenting existing server-side tooling to perform image compression, while simultaneously reducing the total amount of image data fetched. The effect of Browselite on the user experience is quantified using standard page load metrics and a real user study of over 200 users across 50 optimized web pages. Browselite allows for similar savings to middlebox approaches, while offering additional security, privacy, and Webcompat guarantees.
In this research work, we advise gateway based energy-efficient routing protocol (M-GEAR) for Wireless Sensor Networks (WSNs). We divide the sensor nodes into four logical regions on the basis of their location in the sensing field. We install Base Station (BS) out of the sensing area and a gateway node at the centre of the sensing area. If the distance of a sensor node from BS or gateway is less than predefined distance threshold, the node uses direct communication. We divide the rest of nodes into two equal regions whose distance is beyond the threshold distance. We select cluster heads (CHs)in each region which are independent of the other region. These CHs are selected on the basis of a probability. We compare performance of our protocol with LEACH (Low Energy Adaptive Clustering Hierarchy). Performance analysis and compared statistic results show that our proposed protocol perform well in terms of energy consumption and network lifetime.
Polarised radio synchrotron emission from interstellar, intracluster and intergalactic magnetic fields is affected by frequency-dependent Faraday depolarisation. The maximum polarised intensity depends on the physical properties of the depolarising medium. New-generation radio telescopes like LOFAR, SKA and its precursors need a wide range of frequencies to cover the full range of objects. The optimum frequency of maximum polarised intensity (PI) is computed for the cases of depolarisation in magneto-ionic media by regular magnetic fields (differential Faraday rotation) or by turbulent magnetic fields (internal or external Faraday dispersion), assuming that the Faraday spectrum of the medium is dominated by one component or that the medium is turbulent. Polarised emission from bright galaxy disks, spiral arms and cores of galaxy clusters are best observed at wavelengths below a few centimeters (at frequencies beyond about 10 GHz), halos of galaxies and clusters around decimeter wavelengths (at frequencies below about 2 GHz). Intergalactic filaments need observations at meter wavelengths (frequencies below 300 MHz). Sources with extremely large intrinsic $|RM|$ or RM dispersion can be searched with mm-wave telescopes. Measurement of the PI spectrum allows us to derive the average Faraday rotation measure $|RM|$ or the Faraday dispersion within the source, as demonstrated for the case of the spiral galaxy NGC 6946. Periodic fluctuations in PI at low frequencies are a signature of differential Faraday rotation. Internal and external Faraday dispersion can be distinguished by the different slopes of the PI spectrum at low frequencies. A wide band around the optimum frequency is important to distinguish between varieties of depolarisation effects.
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