<p>In this thesis centralized routing methods for wireless sensor networks have been studied. The aim has been to prolong network lifetime by reducing the energy consumed by sensor-node communication.</p><p>Wireless sensor networks are rapidly becoming common in application areas where information from many sensors is to be collected and acted upon. The use of wireless sensor networks adds flexibility to the network, and the cost of cabling can be avoided.</p><p>Wireless sensor networks may consist of several hundreds of small devices, equipped with sensors (e.g. acoustic, seismic or image) that form a wireless network. Each sensor node collects information from its surroundings and sends it to a base station, either from sensor node to sensor node, or directly to the base station.</p><p>We have made simulations that show that asymmetric communication with multihop extends the lifetime of large wireless sensor networks. We have also investigated the usefulness of enforcing a minimum separation distance between cluster heads in a cluster based wireless sensor network. The results show that our sensor network performs up to 150% better when introducing a minimum separation distance between cluster heads. The simulations also show that the minimum separation distance resulting in the lowest energy consumption in our network varies with the number of clusters. We have also made an initial study of maximum lifetime routing in sparse wireless sensor networks to be able to see how different heuristic routing algorithms influence the energy consumption of individual sensor nodes, and thus the lifetime of a sparse sensor network. We have also compared the maximum lifetime of the heuristic algorithms to the maximum lifetime of an optimal routing solution. These simulations showed that for some types of applications the choice of heuristic algorithm is more important to prolong network lifetime, than for other types of applications.</p>

In this thesis centralized routing methods for wireless sensor networks have been studied. The aim has been to prolong network lifetime by reducing the energy consumed by sensor-node communication. Wireless sensor networks are rapidly becoming common in application areas where information from many sensors is to be collected and acted upon. The use of wireless sensor networks adds flexibility to the network, and the cost of cabling can be avoided. Wireless sensor networks may consist of several hundreds of small devices, equipped with sensors (e.g. acoustic, seismic or image) that form a wireless network. Each sensor node collects information from its surroundings and sends it to a base station, either from sensor node to sensor node, or directly to the base station. We have made simulations that show that asymmetric communication with multihop extends the lifetime of large wireless sensor networks. We have also investigated the usefulness of enforcing a minimum separation distance between cluster heads in a cluster based wireless sensor network. The results show that our sensor network performs up to 150% better when introducing a minimum separation distance between cluster heads. The simulations also show that the minimum separation distance resulting in the lowest energy consumption in our network varies with the number of clusters. We have also made an initial study of maximum lifetime routing in sparse wireless sensor networks to be able to see how different heuristic routing algorithms influence the energy consumption of individual sensor nodes, and thus the lifetime of a sparse sensor network. We have also compared the maximum lifetime of the heuristic algorithms to the maximum lifetime of an optimal routing solution. These simulations showed that for some types of applications the choice of heuristic algorithm is more important to prolong network lifetime, than for other types of applications.

Internet of Things utvecklas och växer konstant. Det blir allt vanligare att applikationer och enheter kopplas samman via nätverk. En av teknikerna som används för att trådlöst sammankoppla enheter är Bluetooth Low Energy. Preferenser för kvaliteten i en kommunikation kan variera. Det är därför viktigt att utföra prestandamätningar för att veta vilka fördelar och nackdelar en nätverksteknik har.  Detta examensarbete handlar om prestandamätningar vid datasändningar mellan mobila enheter och trådlösa sensorer, och övervakning av parametrar som fås under mätningarna. En metod med monitoreringspaket inspirerad från tidigare forskning, utformades och implementerades i ett system för Bluetooth Low Energy, vilken därefter har utvärderats.  Resultatet blev att två system skapades som visade dataförluster, fördröjningsvariation och genomströmning, löpande på en mobil enhet. Det ena systemet använde metoden med monitoreringspaket. Det andra systemet använde en egengjord metod som gjorde mätningar med hög precision, men som ställde högre krav på funktioner och prestanda på sensornoden, och på den mobila enheten. Experiment med hjälp av systemen utfördes och resulterande värden analyserades. / Internet of Things develops and grows constantly. It becomes increasingly common that applications and units are connected through a network. One of the technologies used for wirelessly linking together units is Bluetooth Low Energy. Preferences for the quality of a connection can vary. It is therefore important to conduct measurements of performance in order to know advantages and disadvantages that a networking technology has.  This thesis is about measurements of performance during data transfers between mobile devices and wireless sensors, as well as monitoring parameters that are given during the measurements. One method using monitoring packets inspired from previously made research, were designed and implemented in a system for Bluetooth Low Energy, which was then evaluated. The result was that two systems were created that presented data loss, delay variation and throughput, continuously on a mobile device. One system used the method with monitoring packets. The other system used a self-made method which made measurements with high precision, but that places higher demands on functions and performance of the sensor node, and on the mobile device. Experiments were conducted by using the systems and resulting values were analyzed.

Trådlösa sensornät (eng. Wireless Sensor Networks, WSN) är ett snabbt växande teknikområde med många applikationer. Ett typiskt WSN består av en mängd små billiga och energisnåla enheter, så kallade sensornoder, som mäter någon miljöparameter och via radio skickar ett datapaket med uppmätt värde till en basstation som ofta är kopplad till en PC. Informationen kan därefter analyseras eller redovisas grafiskt för användaren. Sensornätverkets storlek kan variera från några få noder på en liten yta till nätverk med tusentals noder som täcker flera kvadratkilometer stora områden. Ett avsnitt om trådlösa sensornät ingår i kursen Data- och telekommunikationsteknik II, DA122T, vid Malmö högskola. Denna rapport presenterar ett examensarbete med att utveckla laborationer och studiematerial om sensornät till kursen.Utrustningen som används i laborationerna är ett paket innehållande sex sensornoder, en basstation och nödvändig programvara. Tillverkare är Crossbow Technology, världens ledande företag inom WSN.Resultatet av arbetet är två laborationshandledningar, beskrivning av utrustning som används i laborationerna samt en rapport – Introduktion till WSN. Handledningarna och det övriga materialet är skrivna på svenska.Den första laborationen, i vilken man bygger ett enkelt WSN, ger studenten förståelse för principen hos trådlösa sensornät och för hur hårdvaran och programvaran samverkar med varandra. I den andra laborationen lär sig studenten programmera sensornoder för att sedan studera kommunikationen mellan noderna och basstationen samt undersöka olika nätverkstopologier. / Wireless sensor networks, WSN, is a rapidly growing field of technology with many applications. A typical WSN consists of many small, inexpensive and energy-saving devices, called sensor nodes. These nodes measure an environmental parameter and the radio sends a data packet with the measured value to a base station, which is often connected to a PC. The information can then be analyzed and presented graphically to the user. A sensor network's size can vary from a few nodes in a small area to a network with thousands of nodes that covers several square kilometers of area. A section on wireless sensor networks is part of the course in Computer and telecommunication technologies II, DA122T, at Malmö University. This thesis reports on the development of study material for the practical laboratory motes on sensor networks for the course. The equipment used in the practical experiments is a package containing six sensor nodes, a base station and the necessary software. The manufacturers are Crossbow Technology, the world's leading company of WSN products. The results of the work are two practical exercises, a description of the equipment used in practical experiments and a report – Introduction to WSN. These guides and other materials are written in Swedish. The first lab in which to build a simple WSN, gives students an understanding of the principle of wireless sensor networks and how the hardware and software interacts with each other. In the second exercise, students will learn to program the sensor nodes to study the communication between the nodes and the base station and to explore the different network topologies.