Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Recent advances in wireless sensor networks have led to an emergence of many routing protocols. Limited battery capacity of sensor nodes makes energy efficiency a major and challenge problem in wireless sensor networks. Thus, the routing protocols for wireless sensor networks must be energy efficient in order to maximise the network lifetime. In this thesis, we developed a centralised clustering, energy-efficient routing protocol for wireless sensor networks. Our protocol consists of a cluster head selection algorithm, a cluster formation scheme and a routing algorithm for the data transmission between cluster heads and the base station. The cluster head selection algorithm is performed by the base station using global information of the network. This algorithm aiming at choosing cluster heads that ensure both the intra-cluster data transmission and inter-cluster data transmission are energy-efficient. The cluster formation scheme is accomplished by exchanging messages between non-cluster-head nodes and the cluster head to ensure a balanced energy load among cluster heads. The routing algorithm is based on the optimal transmission range for the data transmission between cluster heads and the base station using multi-hop. The performance of our routing protocol is evaluated by comparing with three existing routing protocols on a simulation platform. The simulation results show that our protocol can achieve better performance in terms of energy efficiency and network lifetime. Because of the centralised algorithm and multi-hop routing, there is a small communication overhead and transmission delay when using our protocol. Since our protocol can save energy and prolong network lifetime, it is well suited for applications where energy and network lifetime are the primary considerations and small overhead and time delay can be tolerated. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1456494 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Electrical and Electronic Engineering, 2009

Le codage espace-temps est une technique qui permet d'exploiter de façon très efficace la diversité spatiale et temporelle présente dans certains systèmes de communication, dont le canal sans fil. Le principal avantage de cette technique est une très grande efficacité spectrale. Dans nos jours, où le canal radio-mobile est de plus en plus utilisé pour transmettre tout type d'information, les méthodes permettant une utilisation plus efficace du spectre électromagnétique ont une importance fondamentale. Les algorithmes de réception connus aujourd'hui sont très complexes, même en ce qui concerne les codes espace-temps les plus simples. Cette complexité reste l'un des obstacles principaux à l'exploitation commerciale de ces codes. Cette thèse présente une étude très détaillée de la complexité, la performance, et les aspects les plus intéressants du comportement des algorithmes de réception pour des codes espace-temps, étude qui présente un moyen rapide pour une éventuelle conception des architectures adaptées à ce problème. Parmi les sujets présentés dans cette thèse, une étude approfondie de la performance de ces algorithmes a été réalisée, ayant pour objectif d'avoir une connaisance suffisante pour pouvoir choisir, parmi le grand nombre d'algorithmes connus, le mieux adapté à chaque système particulier. Des améliorations aux algorithmes connus ont aussi été proposées et analysées.

<p>In this thesis we investigate different algorithms for dynamic resource allocation in wireless networks. We introduce a general framework for modeling systems whichis applicable to many scenarios. We also analyze a specific scenario with adaptivebeamforming and show how it fits into the proposed framework. We then studytwo different resource allocation problems: Quality-of-Service (QoS) constraineduser scheduling and sum-rate maximization. For user scheduling, we select some“good” set of users that is allowed to use a specific resource. We investigatedifferent algorithms with varying complexities. For the sum-rate maximizationwe find the global optimum through an algorithm that takes advantage of thestructure of the problem by reformulating it as a D.C. program, i.e., a minimizationover a difference of convex functions. We validate this approach by showing that itis more efficient than an exhaustive search at exploring the space of solutions. Thealgorithm provides a good benchmark for more suboptimal algorithms to comparewith. The framework in which we construct the algorithm, apart from being verygeneral, is also very flexible and can be used to implement other low complexitybut suboptimal algorithms.</p>

<p>Genom hela arbetet har enkelhet och användbarhet varit ledorden. Detta för att man ska kunna implementera tjänster för en relativt liten målgrupp utan att behöva göra större investeringar. I linje med detta har möjligheter för att kunna erbjuda tjänsten till en större målgrupp och därmed få ned kostnaden per användare eftersökts.</p><p>Rapporten börjar med en studie av 3G, WLAN och Bluetooth för att läsaren ska få en grund i de tekniker på vilka tjänsterna skulle kunna implementeras. Sedan diskuteras dagens tjänster och vilka önskemål om tjänster som framkommit från diskussioner med olika parter. Slutligen exemplifieras ett antal tjänster som skulle kunna tillämpas på dagens tekniker.</p><p>Efter att ha läst rapporten skall läsaren ha fått en uppfattning hur mobila tjänster med hög överföringshastighet bör utformas för att underlätta kommunikation för funktionshindrade.</p>

<p>To predict the lifetime of wireless sensor networks before their installation is an important concern. The IEEE 802.15.4 standard is specifically meant to support long battery life time; still there are some precautions to be taken by which a sensor network system application based on the standard can be made to run for longer time periods.</p><p>This thesis defines a holistic approach to the problem of energy consumption in sensor</p><p>networks and suggests a choice of node architecture, network structure and routing</p><p>algorithm to support energy saving in the network. The idea and thrust of the thesis is that stand-alone measures such as selecting a low-power microcontroller with embedded transceiver will not alone be sufficient to achieve energy saving over the entire network. A comprehensive design study with energy saving as a primary task must be made. Focus given on the design objectives needs to look at different aspects – application code, network configuration code, routing algorithms etc to come up with an energy efficient network.</p>

<p>Wireless Sensor Network (WSN), a collection of “sensor nodes” promises to change the scientist’s approach of gathering the environmental data in various fields. Sensor nodes can be used for non-stop sensing, event detection, location sensing and local control of actuators, this concept gives surety to many latest application areas like agriculture, military, home or factory automation, logistics and so on. Remote surveillance and measurement missions can be performed by using WSNs. The hot research topic now-a-days is to make such networks remotely controllable and adaptive to the environment and mission.</p><p> </p><p>The work carried out in this thesis is the development of a surveillance application using TinyOS/nesC. The purpose of this application is to perform event-detection mission by using any one of the built-in sensor on Mica2 motes as well as a setup protocol is designed to make the WSN remotely controllable and adaptive to the mission. In this thesis, an experimental work is also performed using TinyDB to build up a surveillance system whose purpose is to detect and count the total number of person present at any time in a given room and to view the results at a remote place. Besides these two system applications, a comparative study between TinyDB and nesC is described which concludes that more hardware control can be achieved through nesC which is a more power efficient platform for long-term applications.</p>

<p>This thesis was completed as a part of the project "Microwave wireless Communication </p><p>Link". In this thesis, the requirements to develop base band part for the transceiver were </p><p>studied, including, usage of proper hardware equipment as well as software </p><p>programming. A signal injector performed as a hardware interface between the Analog </p><p>part and the Digital (base band) part of the tranceiver, whereas, a PCI card acted as a data </p><p>acquisition device for base band part. A programming language was required to build </p><p>such a software, able to successfully represent a transmitter and a receiver. All the </p><p>features were found in Labview (Laboratory Virtual Instrument Engineering Workbench) </p><p>introduced by National Instruments in 1980s. A modern version of Labview i.e. version </p><p>7.1, was used in this thesis, it views the software as a virtual instrument to automate and </p><p>measure the values passed from the connected hardware. Labview provides a graphical </p><p>development environment, which is modular and parallel in nature, and uses an efficient </p><p>G compiler. A coherent base band receiver using matched filter was implemented, and a </p><p>base band transmitter using NRZ-L digital encoding scheme and QPSK modulation </p><p>scheme was developed.</p>

<p>There has been a quick development in the wireless network area during the last decade. Mostly </p><p>these days the focus in the wireless area is on very high speed and long range applications. This </p><p>thesis describes how ZigBee is suitable for wireless sensor networks in logistic telemetry </p><p>applications for global managing and monitoring of goods. ZigBee has been developed by the </p><p>organization named as ‘ZigBee Alliance’ as a new wireless standard for the wireless solutions </p><p>based upon the IEEE 802.15.4 Standard [2]. ZigBee is a new technology as compared to the other </p><p>wireless technologies such as Bluetooth, but it has certain characteristics such as low cost, low </p><p>power, support for mesh networking e.t.c which makes its chances to be more successful than </p><p>others. </p><p> </p><p>The other aim of this thesis is to examine different issues related to ZigBee to see its fitness for </p><p>logistic telemetry applications like multi-hop routing issues, routing strategies and design </p><p>requirements. ZigBee is relatively new wireless technology, so there are great deals of promises </p><p>associated with it. In this thesis, a comparison between ZigBee and Bluetooth technologies will </p><p>also be made.</p>

<p>Wireless sensors networks are used in a variety of environments ranging from environment</p><p>monitoring such as humidity and temperature, to environments like patient monitoring, habitat</p><p>monitoring etc. Sometimes sensors are deployed in inaccessible or hazardous places, and they</p><p>are battery operated; recharging or changing the sensor’s battery is almost impossible.</p><p>In such scenarios, where the battery can not be recharged or changed, it is crucial to know in</p><p>advance how long the battery will last so that the old sensor node can be replaced by a new</p><p>one. Normally, in order to effectively utilize the battery the components of a wireless sensor</p><p>node are turned off when not needed.</p><p>This paper presents an in-depth analysis of the importance of switching sensor node</p><p>components, and its impact on the life time prediction. A new energy model is presented</p><p>which caters for the current and time consumed in switching from one mode to another. A</p><p>comparison is made between scenarios where current consumption while switching is catered</p><p>with the one where it is not catered. This was achieved by using on chip fuel gauge, with</p><p>some limitation, which was verified by using digital multimeter.</p>