186,653 research outputs found
Autonomous energy efficient protocols and strategies for wireless sensor networks
No full textThe aim of this research is to develop a model of a sensor network that will endeavour to monitor a hostile environment (one where communication within the network is difficult and the network entities are under risk due to physical damage). In this context, the study identifies the following key characteristics. A wireless sensor network (WSN) is a wireless network consisting of spatially distributed devices using sensors to monitor physical or environmental conditions at different locations. In addition to one or more sensors, each node in a WSN is typically equipped with a radio transceiver or other wireless communications device, a small micro controller, and an energy source, usually a battery. The size constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth. Of these, energy is the most important since it is required for everything else. Thus, it directly influences the life-span of the nodes, hence, that of the system as a whole. Furthermore, the environment itself, where these sensor nodes are deployed, plays a big role in influencing the entire architecture of the network hardware platform and protocols that govern its smooth functioning. As a result the protocols required for governing the actions of the sensor nodes need to be designed accordingly.Against this background, this research facilitates the development of an environmental sensor network called GlacsWeb (deployed inside a glacier in Norway) which focuses on providing useful information about sub-glacial dynamics. GlacsWeb nodes are deployed under very hostile conditions. The strain from the moving ice may damage the nodes and the en-glacial water bodies may carry the nodes far out of transmission range from a centrally located base station. For these reasons GlacsWeb nodes have a high rate of failure. In order to effectively tackle this problem, this research develops GW-MAC (a Medium Access Control protocol) which focuses on efficiently connecting GlacsWeb nodes in an ad-hoc manner.Moreover, the poorly understood nature of the glacier imposes further challenges in the area of sensing. Sub-glacial behaviour appears vary across the entire large mass of ice. For this reason, there is a strong need for nodes to make autonomous decisions to adapt their observation patterns and communication patterns accordingly to ensure maximum data is gathered with minimum consumption in energy. The study, therefore, develops USAC (A Utility Based Sensing and Communication Model for an Agent-Based Sensor Network), that provides a measure of utility by combining the task of both sensing and communication by the sensor nodes. The model, at first, develops a sensing protocol in which each agent node locally adjusts its sensing rate based on the value (importance) of the data it believes it will observe. Then, it details a communication protocol that finds optimal routes for relaying this data back the network base station based on the cost of communicating (derived from the opportunity cost of using the battery power for relaying data) it.Both GW-MAC and USAC have been tested in simulation and have shown to perform better than other similar models
A utility-based sensing and communication model for a glacial sensor network
No full textThis paper reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multi-sensor networks. The specific application considered is that of GLACSWEB, a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of the network topology, the size of the network, and the degree of dynamism of the environment. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 470%, 250% and 300% respectively
GWMAC- A TDMA Based MAC Protocol for a Glacial Sensor Network
No full textWireless sensor networks demand the need to design practical and robust communication protocols to meet the application specifications. Our research focuses on designing and implementing an environmental sensor network to be used for sub-glacial study. The glacier is a very hostile environment presenting severe challenges and complications in the smooth functioning of such a network. In light of these challenges, we present a low power sensor node design and an energy-efficient medium access control protocol called GWMAC developed for a network deployed in a glacier in Norway. The general architecture of GWMAC is based on scheduling and time division multiple accesses (TDMA). We argue that for a highly dynamic network such as ours, GWMAC is more desirable over more widespread protocols such as S-MAC and LMAC. In doing so, we perform extensive series of simulations to empirically evaluate our claim. Our results illustrate that on average GWMAC can increase the network life time by at least 63%. This also has a significant effect on the amount of data that can be collected over network life time
A utility-based adaptive sensing and multi-hop communication protocol for wireless sensor networks
No full textThis article reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multisensor networks. The specific application on which we illustrate our mechanism is that of GlacsWeb. This is a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. The sensors employ a Bayesian linear model to decide their sampling rate and exploit the properties of the Kullback-Leibler divergence to place an appropriate value on the data. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of a static network topology, a dynamic network topology, the size of the network, the degree of dynamism of the environment, and the mobility of the nodes. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 78%, 133%, 100%, and 93%, respectively. Furthermore, we show that our system performs at 65%, 70%, 63%, and 70% of the theoretical optimal, respectively, despite being a distributed protocol that operates with incomplete knowledge of the environment
A Note on Generalized Indexed Norlund Summability Factor of an Infinite Series
No full textIn the present article, we have established a result on generalized indexed absolute Norlund summability factor by generalizing results of Mishra and Srivastava on indexed absolute Cesaro summabilty factors and Padhy et.al. on the absolute indexed Norlund summability
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Deploying a Sensor Network in an Extreme Environment
No full textA wireless sensor network has been designed and deployed to gather data from nodes on and inside glaciers. This paper describes the solutions to power management, radio communications, management and discusses the performance of the final system. 18 months of data have now been received, which provide an insight not only into the glacier’s behaviour but on the design decisions. The system uses custom PIC-based sensor nodes and an ARM-based base station which controls weather and differential GPS. Different versions have been installed in Norway from 2003-5 and this paper describes the lessons learnt from coping with the extreme conditions found in glaciers
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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