A wireless sensor network is designed to monitor events and report this information to a central location, or sink node. The information is required to efficiently travel through the network. It is the job of the routing protocol to officiate this process. With transmissions consuming the majority of the energy available to a sensor node, it becomes important to limit their usage while still maintaining reliable communication with the sink node. The aim of the research covered in this dissertation was to adapt the flat and hierarchical architectures to create a new hybrid that draws on current protocol theories. The designed and developed protocol, Hybrid Energy Efficient Routing (HEER) protocol, builds upon the initial groundwork laid out by the previously developed Simple Energy Efficient Routing (SEER) protocol designed by C.J. Leuschner. Another aspect of the work was to focus on the current lack of credibility that is present in the WSN research community. The validity of SEER was examined and tested and this led to the main focus of this research, ensuring that HEER proves to be valid. The HEER protocol for wireless sensor networks is designed such that it is computationally simple, limits the number of transmissions, employs a cross-layer approach, is reliable, is energy-aware, has limited support for mobile nodes, is energy efficient, and most importantly is credible. Sensor nodes are extremely limited when it comes to their available energy resources. To maximise the node and network lifetimes requires the designed algorithm to be energy aware and as efficient as possible. A cross-layer design approach is followed which allows for the different layers of the OSI model to interact. The HEER protocol limits the number of transmissions that are used for network operation. This is achieved by using a minimal amount of messages for network setup and by selecting the optimal route. Route selection is calculated using hop count, current energy available, energy available on the receiving node, and lastly the energy required to reach the destination node. HEER combines and expands upon the method used by SEER for route selection. Network lifetime for networks of large sizes is increased, mainly due to more efficient routing of messages. The protocol was kept computationally simple and energy efficient, thus maintaining network survivability for as long as possible. / Dissertation (MEng)--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

The number of potential applications for wireless sensor networks is immense. These networks may consist of large numbers of low cost, low power, disposable sensor nodes that can be deployed inside or close to phenomena to be monitored. The nature of these networks necessitates specific design requirements, of which energy efficiency is paramount. The limited available energy of sensor nodes is mainly drained during communication and computational processing. An energy efficient routing protocol can limit the number of message transmissions and the computational complexity of finding routing paths. Many routing protocols have been proposed for wireless sensor networks. Most of them are computationally complex, require a large number of messages to be transmitted or require that sensor nodes possess certain hardware capabilities in order to function. The objective of this dissertation was to develop a Simple Energy Efficient Routing (SEER) protocol for wireless sensor networks that is computationally simple, reduces the number of transmitted messages and does not impose any hardware prerequisites. The new routing protocol, which was developed during this research, uses a flat network structure for scalability and source initiated communication along with event-driven reporting to reduce the number of message transmissions. Computational simplicity is achieved by using a simple method for routing path selection. The SEER protocol selects the next hop for a message by choosing a neighbour that has a smaller or equal hop count to the current node. If multiple neighbours satisfy this requirement, the neighbour with the highest remaining energy is chosen as the next hop. Each node in the network has a table containing the hop count and remaining energy of each of its neighbours. Periodic messages sent through the network update these neighbour tables. SEER uses a novel approach to select the next hop of a message during routing. The protocol increases the lifetime of the network dramatically, compared to other similar routing protocols. This improvement is directly related to the reduction in the number of transmissions made by each node. The simplicity of the protocol reduces the required computational processing compared to other protocols, and at the same time makes this one of the few available protocols that does not impose hardware requirements on nodes in order to function. / Dissertation (MEng (Computer Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

Made available in DSpace on 2016-06-02T19:05:56Z (GMT). No. of bitstreams: 1 4225.pdf: 931319 bytes, checksum: 2be2e5e88eb314cf8769dabd2749e671 (MD5) Previous issue date: 2011-06-27 / Financiadora de Estudos e Projetos / The usage of wireless sensor network is increasingly being applied to people s everyday lives everywhere: from energy consumption in households and buildings in general, to vital signs in assistive medicine, infrastructure monitoring, chemical or biological product leaking detection in industries, better surveillance, environmental monitoring, among many others. WSN can be deployed in different densities next to several thousands of nodes. However, the development of WSN solutions are limited mainly by energy resource restriction. The great challenge to WSN solutions is to increase the network longevity while guaranteeing data delivery, reliability and accuracy in an environment prone to different types of failures. The largest source of energy consumption is data transmission. Thus, solutions to WSN needs to avoid intense communication keeping energy consumption balance and so the network longevity. In applications in which high density of nodes is necessary, sensing process can produce a large amount of data which are similar or redundant, due to the special proximity among the nodes. This spatial proximity can be explored in routing solutions to reduce the amount of messages transmitted throughout the network. This work presents the Spatial Correlation Aware Routing Protocol - SCARP , which makes use of spatial correlation to reduce the number of network transmissions. With SCARP, the WSN is configured in cells and nodes of each cell are selected, in an alternated way, to transmit similar or redundant data, and so reducing the number of transmitted messages. This traffic reduction results in less energy consumption and longer network longevity. Evaluation results show that SCARP outperforms similar solutions described in the literature, such as DAARP, which uses clustering and aggregation. SCARP has a positive performance even for large node density scenarios. / Redes de Sensores Sem Fio (RSSFs) estão sendo cada vez mais utilizadas na vida diária das pessoas em aplicações que incluem desde monitoramento de gasto de energia em residências e prédios em geral, até monitoramento de sinais vitais para medicina assistida, monitoramento de infraestruturas físicas, vazamentos de produtos químicos ou biológicos em indústrias, vigilância para melhoria de segurança, monitoramento ambiental, dentre inúmeras outras. RSSFs podem ser implantadas em diferentes densidades podendo chegar a milhares de nós. No entanto, o desenvolvimento de soluções baseadas em RSSFs é limitado, principalmente, por recursos restritos dos nós sensores, em especial recursos energéticos. O grande desafio de soluções para RSSFs é aumentar a longevidade da rede e, ao mesmo tempo, garantir a entrega, confiabilidade e precisão dos dados coletados diante de um ambiente propício a falhas de diferentes tipos. A maior fonte de consumo de energia é a transmissão de mensagens. Assim, soluções de RSSF têm que evitar comunicação intensa, mantendo o balanceamento do consumo de energia e, assim, a longevidade da rede. Em aplicações onde é necessária alta densidade de nós sensores, o processo de sensoriamento pode produzir grande quantidade de dados similares ou redundantes devido à proximidade espacial entre esses nós. Esta proximidade espacial pode ser explorada em soluções de roteamento para reduzir a quantidade de mensagens transmitidas pela rede. Este trabalho apresenta o algoritmo de roteamento SCARP (Spatial Correlation Aware Routing Protocol), que faz uso da correlação espacial para reduzir o número de transmissões pela rede. Com o SCARP, a RSSF é configurada em células e nós de cada célula são escolhidos, de maneira alternada, para transmitir dados similares ou redundantes, reduzindo assim o número de mensagens transmitidas. Essa redução de tráfego resulta em menor consumo de energia e maior longevidade da rede. Resultados de avaliação de desempenho mostram que SCARP supera soluções semelhantes descritas na literatura como o DAARP, que utiliza clusterização e agregação de dados, e mantém o desempenho positivo mesmo em situações de grande densidade de nós.

Wireless Sensor Networks (WSN) may consist of hundreds or even thousands of nodes and could be used for a multitude of applications such as warfare intelligence or to monitor the environment. A typical WSN node has a limited and usually irreplaceable power source and the efficient use of the available power is of utmost importance to ensure maximum lifetime of each WSN application. Each of the nodes needs to transmit and communicate sensed data to an aggregation point for use by higher layer systems. Data and message transmission among nodes collectively consume the largest amount of the energy available in a WSN. The network routing protocols ensure that every message reaches the destination and has a direct impact on the amount of transmissions to deliver a messages successfully. To this end the transmission protocol within the WSN should be scalable, adaptable and optimized to consume the least possible amount of energy to suite different network architectures and application domains. This dissertation proposes a Mobile Tolerant Hybrid Energy Efficient Routing Protocol (MT-HEER), where hybrid refers to the inclusion of both flat and hierarchical routing architectures as proposed by Page in the Hybrid Energy Efficient Routing Protocol (HEER). HEER was previously developed at the University of Pretoria and forms the starting point of this research. The inclusion of mobile nodes in the WSN deployment proves to be detrimental to protocol performance in terms of energy efficiency and message delivery. This negative impact is attributable to assuming that all nodes in the network are statically located. In an attempt to adapt to topological changes caused by mobile nodes, too much energy could be consumed by following traditional network failure algorithms. MT-HEER introduces a mechanism to pro-actively track and utilise mobile nodes as part of the routing strategy. The protocol is designed with the following in mind: computational simplicity, reliability of message delivery, energy efficiency and most importantly mobility awareness. Messages are propagated through the network along a single path while performing data aggregation along the same route. MT-HEER relies on at least 40% of the nodes in the network being static to perform dynamic route maintenance in an effort to mitigate the risks of topological changes due to mobile nodes. Simulation results have shown that MT-HEER performs as expected by preserving energy within acceptable limits, while considering the additional energy overhead introduced by dynamic route maintenance. Mobile node tolerance is evident in the protocol's ability to provide a constant successful message delivery ratio at the sink node with the introduction and increase in the number of mobile nodes. MT-HEER succeeds in providing tolerance to mobile nodes within a WSN while operating within acceptable energy conservation limits. AFRIKAANS : Koordlose Sensor Netwerke mag bestaan uit honderde of selfs duisende nodes en kan gebruik word vir 'n legio van toepassings soos oorlogs intellegensie of om die omgewing te monitor. 'n Tipiese node in so 'n netwerk het 'n beperkte en soms onvervangbare energie bron. Die effektiewe gebruik van die beskikbare energie is dus van uiterste belang om te verseker dat die maksimum leeftyd vir 'n koordlose sensor network behaal kan word. Elkeen van die nodes in the network moet die waargeneemde data aanstuur oor die netwerk na 'n versamelings punt vir latere gebruik deur applikasie vlak stelsels. Informasie en boodskap transmissie tussen die nodes is wel een van die aktiwiteite wat die meeste energie verbruik in the netwerk. Die roeterings protokol verseker dat die boodskappe die eindbestemming behaal en het 'n direkte impak op die hoeveelheid transmissies wat kan plaas vind om dit te bewerkstellig. Die roeterings protokol moet dus skaleerbaar, aanpasbaar en verfyn word om die minste moontlike energie te verbruik in verskillende toepassings velde. Hierdie verhandeling stel 'n Bewegings Tolerante Hybriede Netwerk Roeterings Protokol vir Koordlose Sensor Netwerke (“MT-HEER”) voor. In hierdie konteks verwys hybried na die samesmelting van beide plat en hierargiese roeterings beginsels soos voor gestel deur Page in Hybriede Netwerk Roeterings Protokol (“HEER”). HEER was ontwikkel by die Universiteit van Pretoria en vorm die begin punt van hierdie navorsing. Die insluiting van bewegende nodes in 'n Koordlose Sensor Netwerk toon 'n negatiewe tendens in terme van energie effektiwiteit en suksesvolle boodskap aflewerings by die eindbestemming. Die grootste rede vir hierdie negatiewe tendens is die aanname deur gepubliseerde werke dat alle nodes in die netwerk staties is. Te veel energie sal vermors word indien tradisionele fout korregerende meganismes gevolg word om aan te pas by die bewegende nodes. MT-HEER stel 'n meganisme voor om die bewegende nodes te gebruik as deel van die roetering strategie en gevolglik ook hierdie nodes te volg soos hulle beweeg deur die netwerk. Die protokol is ontwikkel met die volgende doelstellings: rekenkundig eenvoudigheid, betroubare boodskap aflewering, energie effektiwiteit en bewustheid van bewegende nodes. Boodskappe word langs 'n enkele pad gestuur deur die netwerk terwyl boodskap samevoeging bewerkstellig word om die eind bestemming te bereik. MT-HEER vereis wel dat ten minste 40% van die netwerk nodes staties bly om die dienamiese roeterings instandhouding te bewerkstellig. Simulasie toetse en resultate het bewys dat MT-HEER optree soos verwag in gevalle waar daar bewegende nodes deel uit maak van die netwerk. Energie bewaring is binne verwagte parameters terwyl die addisionele energie verbruik binne rekening gebring word om te sorg vir bewegende nodes. Die protokol se toleransie teen bewegende nodes word ten toon gestel deur die vermoë van die protokol om konstant 'n hoë suksesvolle bookskap aflewerings verhouding te handhaaf. MT-HEER behaal die uitgesette doel om 'n toleransie teen bewegende nodes beskikbaar te stel, terwyl die protokol steeds funksioneer binne verwagte energie besparings limiete. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted