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Oulun yliopiston väitöskirjat

AN EFFICIENT ENTROPY ESTIMATION APPROACH, ACTA UNIVERSITATIS OULUENSIS C Technica 394

ISBN-13:	978-951-42-9592-8
Kieli:	englanti
Kustantaja:	Oulun yliopisto
Oppiaine:	Tekniikka, matematiikka
Painosvuosi:	2011
Sidosasu:	pehmeäkantinen
Sijainti:	Print Tietotalo
Sivumäärä:	80
Tekijät:	PAAVOLA MARKO

15.00 €

Advances in miniaturisation have led to the development of new wireless measurementtechnologies such as wireless sensor networks (WSNs). A WSN consists of low cost nodes, whichare battery-operated devices, capable of sensing the environment, transmitting and receiving, andcomputing. While a WSN has several advantages, including cost-effectiveness and easyinstallation, the nodes suffer from small memory, low computing power, small bandwidth andlimited energy supply. In order to cope with restrictions on resources, data processing methodsshould be as efficient as possible. As a result, high quality approximates are preferred instead ofaccurate answers. The aim of this thesis was to propose an efficient entropy approximation method for resource-constrained environments. Specifically, the algorithm should use a small, constant amount ofmemory, and have certain accuracy and low computational demand. The performance of the proposed algorithm was evaluated experimentally with three casestudies. The first study focused on the online monitoring of WSN communications performancein an industrial environment. The monitoring approach was based on the observation that entropycould be applied to assess the impact of interferences on time-delay variation of periodic tasks. The main purpose of the additional two cases, depth of anaesthesia (DOA) –monitoring andbenchmarking with simulated data sets was to provide additional evidence on the generalapplicability of the proposed method. Moreover, in case of DOA-monitoring, an efficient entropyapproximation could assist in the development of handheld devices or processing large amount ofonline data from different channels simultaneously. The initial results from the communication and DOA monitoring applications as well as fromsimulations were encouraging. Therefore, based on the case studies, the proposed method was ableto meet the stated requirements. Since entropy is a widely used quantity, the method is alsoexpected to have a variety of applications in measurement systems with similar requirements.

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