<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>

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

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In an IEEE802.15.4 beacon-enabled wireless personal area network (WPAN), the PAN coordinator can allocate slots using contention free-GTSs (guaranteed the time slots) for admitted devices. However, due to fixed slot size, the bandwidth waste problem may arise. Hence, reference [6] proposed the multi-beacon superframe structure (MBS) to overcome this problem. However, in [6], the structure of sub-beacon intervals in a superframe is non-adaptive. Therefore, this thesis proposes an enhanced multi-beacon superframe structure (EMBS). In EMBS, a PAN coordinator employs the greedy SBI-allocation algorithm to adjust a superframe structure according to the traffic demand of admitted devices such that a superframe can consist of a number of different types of sub-beacon intervals (SBIs). Simulation results reveal that a WPAN using EMBS can attain higher bandwidth utilization than a WPAN using 802.15.4 or MBS.

The Internet of Things (IoT) concept has been realised with the advent of Machineto-Machine (M2M) communication through which the vision of future Internet has been revolutionised. IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) provides feasible IPv6 connectivity to previously isolated environments, e.g. wireless M2M sensors and actuator networks. This thesis's contributions include a novel mathematical model, energy-efficient algorithms, and a centralised software controller for dynamic consolidation of programmability features in cloud-based M2M networks. A new generalised joint mathematical model has been proposed for performance analysis of the 6LoWPAN MAC and PHY layers. The proposed model differs from existing analytical models as it precisely adopts the 6LoWPAN specifications introduced by the Internet Engineering Task Force (IETF) working group. The proposed approach is based on Markov chain modelling and validated through Monte-Carlo simulation. In addition, an intelligent mechanism has been proposed for optimal 6LoWPAN MAC layer parameters set selection. The proposed mechanism depends on Artificial Neural Network (ANN), Genetic Algorithm (GA), and Particles Swarm Optimisation (PSO). Simulation results show that utilising the optimal MAC parameters improve the 6LoWPAN network throughput by 52-63% and reduce end-to-end delay by 54-65%. This thesis focuses on energy-efficient data extraction and dissemination in a wireless M2M sensor network based on 6LoWPAN. A new scalable and self-organised clustering technique with a smart sleep scheduler has been proposed for prolonging M2M network's lifetime and enhancing network connectivity. These solutions succeed in overcoming performance degradation and unbalanced energy consumption problems in homogeneous and heterogeneous sensor networks. Simulation results show that by adopting the proposed schemes in multiple mobile sink sensory field will improve the total aggregated packets by 38-167% and extend network lifetime by 30-78%. Proof-of-concept real-time hardware testbed experiments are used to verify the effectiveness of Software-Defined Networking (SDN), Network Function Virtualisation (NFV) and cloud computing on a 6LoWPAN network. The implemented testbed is based on open standards development boards (i.e. Arduino), with one sink, which is the M2M 6LoWPAN gateway, where the network coordinator and the customised SDN controller operated. Experimental results indicate that the proposed approach reduces network discovery time by 60% and extends the node lifetime by 65% in comparison with the traditional 6LoWPAN network. Finally, the thesis is concluded with an overall picture of the research conducted and some suggestions for future work.

IEEE 802.15.4 is a standard designed for low data rate wireless personal area networks (WPANs) intended to provide connectivity to mobile devices. Such devices present considerable storage, energy, and communication constraints. However, they can be used in a variety of applications like home/office automation, environmental control and more. In order to extend the lifetime of the WPAN, we propose some changes to the standard including modifications to the Superframe Guaranteed Time Slot (GTS) distribution which can be optimized to reduce energy consumption. We implemented the proposed improvements to the IEEE 802.15.4 protocol using real sensor nodes. Specifically, we conducted an energy study of the proposed acknowledgment-based GTS descriptor distribution scheme and compared the results with the standard implementation. Experiments show that the proposed changes reduce energy consumption up to nearly 50% when 7 devices allocate guaranteed time slots descriptors during normal communication.

Wireless Sensor Networks are the main representative of pervasive computing in large-scale physical environments. These networks consist of a large number of small, wireless devices embedded in the physical world to be used for surveillance, environmental monitoring or other data capture, processing and transfer applications. Ultra wideband has emerged as one of the newest and most promising concepts for wireless technology. Considering all its advantages it seems a likely communication technology candidate for future wireless sensor networks. This paper considers the viability of ultra wideband technology in wireless sensor networks by employing an IEEE 802.15.4a low-rate ultra wideband physical layer model in the OMNET++ simulation environment. An elaborate investigation into the inner workings of the IEEE 802.15.4a UWB physical layer is performed. Simulation experiments are used to provide a detailed analysis of the performance of the IEEE 802.15.4a UWB physical layer over several communication distances. A proposal for a cognitive, adaptive communication approach to optimize for speed and distance is also presented. AFRIKAANS : Draadlose Sensor Netwerke is die hoof verteenwoordiger vir deurdringende rekenarisering in groot skaal fisiese omgewings. Hierdie tipe netwerke bestaan uit ’n groot aantal klein, draadlose apparate wat in die fisiese wêreld ingesluit word vir die doel van bewaking, omgewings monitering en vele ander data opvang, verwerk en oordrag applikasies. Ultra wyeband het opgestaan as een van die nuutste en mees belowend konsepte vir draadlose kommunikasie tegnologie. As al die voordele van dié kommunikasie tegnologie in ag geneem word, blyk dit om ’n baie goeie kandidaat te wees vir gebruik in toekomstige draadlose sensor netwerke. Hierdie verhandeling oorweeg die vatbaarheid van die gebruik van die ultra wyeband tegnologie in draadlose sensor netwerke deur ’n IEEE 802.15.4a lae-tempo ultra wyeband fisiese laag model in die OMNET++ simulasie omgewing toe te pas. ’n Breedvoerige ondersoek word geloots om die fyn binneste werking van die IEEE 802.15.4a UWB fisiese laag te verstaan. Simulasie eksperimente word gebruik om ’n meer gedetaileerde analiese omtrent die werkverrigting van die IEEE 802.15.4a UWB fisiese laag te verkry oor verskillende kommunikasie afstande. ’n Voorstel vir ’n omgewings bewuste, aanpasbare kommunikasie tegniek word bespreek met die doel om die spoed en afstand van kommunikasie te optimiseer. / Dissertation (MEng)--University of Pretoria, 2011. / Electrical, Electronic and Computer Engineering / unrestricted

An energy-aware on-demand Bluetooth scatternet formation and routing protocol taking into account network architecture and traffic pattern is proposed. The scatternet formation protocol is able to cope with multiple sources initiating traffic simultaneously as well as prolong network lifetime. A modified Inquiry scheme using extended ID packet is introduced for fast device discovery and power efficient propagation of route request messages with low delay. A mechanism employing POLL packets in Page processes is proposed to transfer scatternet formation and route reply information without extra overhead. In addition, the energy aware forwarding nodes selection scheme is based on local information and results in more uniform network resource utilization and improved network lifetime. Simulation results show that this protocol can provide scatternet formation with reasonable delay and with good load balance which results in prolonged network lifetime for Bluetooth-based wireless sensor networks. In this research, a metric-based scatternet formation algorithm for the Bluetooth-based sensor motes is presented. It optimizes the Bluetooth network formation from the hop distance and link quality perspectives. In addition, a smart repair mechanism is proposed to deal with link/node failure and recover the network connectivity promptly with low overhead. The experiments with the Intel Mote platform demonstrate the effectiveness of the optimizations. This research also investigates the scalability of ad hoc routing protocols in very large-scale wireless ad hoc networks. A comprehensive simulation study is conducted of the performance of an on-demand routing protocol on a very large-scale, with as many as 50,000 nodes in the network. The scalability analysis is addressed based on various network sizes, node density, traffic load, and mobility. The reasons for packet loss are analyzed and categorized at each network layer. Based on the observations, we observe the effect of the parameter selection and try to exhaust the scalability boundary of the on-demand routing protocol for wireless ad hoc networks.

The potential of implementing subthreshold radio frequency circuits in deep sub-micron CMOS technology was investigated for developing low-power front-ends for wireless personal area network (WPAN) applications. It was found that the higher transconductance to bias current ratio in weak inversion could be exploited in developing low-power wireless front-ends, if circuit techniques are employed to mitigate the higher device noise in subthreshold region. The first fully integrated subthreshold low noise amplifier was demonstrated in the GHz frequency range requiring only 260 μW of power consumption. Novel subthreshold variable gain stages and down-conversion mixers were developed. A 2.4 GHz receiver, consuming 540 μW of power, was implemented using a new subthreshold mixer by replacing the conventional active low noise amplifier by a series-resonant passive network that provides both input matching and voltage amplification. The first fully monolithic subthreshold CMOS receiver was also implemented with integrated subthreshold quadrature LO (Local Oscillator) chain for 2.4 GHz WPAN applications. Subthreshold operation, passive voltage amplification, and various low-power circuit techniques such as current reuse, stacking, and differential cross coupling were combined to lower the total power consumption to 2.6 mW. Extremely compact resistive feedback CMOS low noise amplifiers were presented as a cost-effective alternative to narrow band LNAs using high-Q inductors. Techniques to improve linearity and reduce power consumption were presented. The combination of high linearity, low noise figure, high broadband gain, extremely small die area and low power consumption made the proposed LNA architecture a compelling choice for many wireless applications.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-01T17:19:06Z No. of bitstreams: 1 LORENO FEITOSA DE OLIVEIRA - DISSERTAÇÃO PPGCC 2007..pdf: 5757457 bytes, checksum: b80a82ad9c8975205f58ab024e542115 (MD5) / Made available in DSpace on 2018-08-01T17:19:06Z (GMT). No. of bitstreams: 1 LORENO FEITOSA DE OLIVEIRA - DISSERTAÇÃO PPGCC 2007..pdf: 5757457 bytes, checksum: b80a82ad9c8975205f58ab024e542115 (MD5) Previous issue date: 2007-08-31 / Redes pessoais sem fio, WPANs (WirelessPersonalAreaNetworks), são redes de curto alcance, em torno de 10 m, cujo centro é o usuário. O cenário de uso geral é aquele onde dispositivos dentro da área de cobertura da WPAN comunicam-se diretamente entre si ou com recursos do mundo exterior (recursos fora da WPAN) através de pontos de acesso que ofereçam esse tipo de encaminhamento de dados. WPANs vêm ganhando atenção nos últimos anos principalmente devido ao surgimento de novas tecnologias de transmissão sem fio que viabilizam este tipo de rede, particularmente Bluetooth. De fato, o desenvolvimento das WPANs confunde-se com o desenvolvimento do Bluetooth, que tem sido usado como ponto de partida em diversos estudos e protótipos nesta área. Sendo a mobilidade de usuários a principal característica das WPANs, um número de questões surge quando se pensa no desenvolvimento de aplicações direcionadas para esse novo paradigma. Uma das principais se refere à gerência de handoff. Handoff é o processo pelo qual conexões, rotas de dados, e estados associados à provisão de algum serviço são transferidos entre pontos de acesso à medida que o usuário se move entre suas áreas de cobertura. Apesar de seu alinhamento com o modelo de rede das WPANs, Bluetooth não possui facilidades para o gerenciamento de handoffs além de suas operações padrão para localização e conexão com dispositivos próximos; inquiry e paging respectivamente. Adicionalmente, o tráfego de dados dessas operações pela interface Bluetooth possui prioridade sobre o tráfego de dados das aplicações do usuário. Essa característica possui especial impacto sobre um tipo particular de aplicações: aquelas que demandam transferências de dados em tempo-real, como aplicações de streaming. Ao tornar o canal sem fio indisponível para o tráfego de dados, seja pela temporária perda total de conexão com pontos de acesso durante handoffs ou por preempção da interface para as operações citadas, aplicações de tempo-real têm seus desempenhos comprometidos devido à quebra de requisitos temporais associados às suas trocas de dados. Nesse contexto, neste trabalho é proposto um protocolo para gerência dehandoffs em WPANs Bluetooth. O protocolo apresentado é voltado para o uso com aplicações que demandam transferências de dados em tempo-real, sendo demonstrada nesse trabalho sua adequação para esse tipo de aplicação. O protocolo apresentado foi projetado levando-se em consideração as limitações dos potenciais dispositivos clientes (pequenos dispositivos móveis com pouco poder de processamento, pouca memória, largura de banda restrita, etc). Assim, são transferidas para os pontos de acesso todas as atividades relativas às transições entre pontos de acesso dos dispositivos móveis. O protocolo apresentado descarta ainda a necessidade de sinalizações ou quaisquer outras trocas de mensagens entre dispositivos móveis e pontos de acesso durante os handoffs. Por utilizar apenas operações padronizadas do Bluetooth, viabiliza-se seu uso junto com qualquer dispositivo programável equipado com interface Bluetooth de acordo com a especificação, sendo portanto dispensada a necessidade de, por exemplo, modificar a pilha Bluetooth dos dispositivos. / Wireless personal area networks (WPANs), are a mobile short range wireless network, with typical range of 10 meters, where the user is the center. The general usage scenario is where devices within the WPANs range communicate directly to each other or with resources from the external world (outside the WPAN) through access points which offer routing service. WPANs have been gaining attention over the last few years mainly due the emergence and popularization of novel wireless communication technologies that enable this kind of network, notably Bluetooth. In fact, the development of WPANs is closely related to the development of Bluetooth, which has been used as starting point to several studies and prototypes in this field. As the user mobility is the main feature of WPANs, a number of questions arise when developing applications targeted to this new paradigm. One of the most important refers to the handoff management. Handoff is the process through which network connections, routes, and states associated to services in course are seamlessly transferred between access points as the user moves through their coverage areas. Despite its alignment with the WPAN's network model, Bluetooth has no facilities for aiding the management of handoffs besides its standard operations for querying nearby devices and connect to them, inquiry and paging respectively. Moreover, the data traffic of these operations has priority over user applications' data traffic. This property has special impact for a particular kind of application: those that require real-time data transfer, such as streaming applications. When the wireless channel is unavailable for data transfers, with temporary connection loss with access points during handoffs, or interface preemption for the inquiry and paging operations, real-time applications have their performance compromised in consequence of violation of temporal requirements. In this work, a protocol for managing handoffs in Bluetooth-based WPANs is presented. The protocol is focused on the use of applications that demand real-time data transfers. The adequacy of the protocol to this kind of application is analyzed through a case study for an audio streaming application. The protocol is designed focusing on the limitations of potential client devices (small portable devices with limited computational power, memory, bandwidth, battery life, etc). Therefore, all the handoff management operations are transferred to access points. There is no need of signaling or any other kind of coordination or message exchange between access points and mobile devices during handoffs. Due to the use of standardized Bluetooth operations, any programmable device with a standard complaint Bluetooth interface can be used without changes on any underlying software layer, such as the Bluetooth stack. It is also presented a formal modelling and validation of the protocol to ensure it behaves according to its specification. The formal model is important to understand the protocol, unanbiguous documentation, and to easy the validation of changes and extension by automatic simulation and proof of properties.