A decade ago, wireless technology was unimaginable in its application in industrial automation as wireless had poor reliability and security in the form of time delays and frame losses. Also, lack of interoperability and standards has been a barrier for wireless applications in control system. But with recent advancements in wireless technology, and with the underlying advantages of wireless like low infrastructural costs, scalability, mobility, and ability to operate in extreme and remote environments, many are seriously considering wireless for industrial automation solutions. For wireless implementation in industries, it is important to understand its characteristics - security, update rates, data types, protocols, and latency time. Protocol being an important characteristic of any communication, is to be chosen intelligently for maximum efficiency. Because of the complexity of creating a communication protocol, existing information technology (IT) protocols such as Wi-Fi, Bluetooth, and ZigBee were used in industries. But as applications widened, and interoperability became an important factor to be considered, it was required to standardize the protocols used. ISA SP100 and WirelessHART are results of this standardizing process. For the last few years, there has been a huge discussion on which of these protocols are robust and work better, and none has emerged as clear winners. The aim of this thesis is to explore the capabilities and limitations of each of these protocols for various industrial applications. This thesis considers all these protocols and helps choose the best fit for industrial applications and includes study of security, reliability, and efficiency of these protocols. / text

Low-power wireless technology enables numerous applications in areas from environmental monitoring and smart cities, to healthcare and recycling. But resource-constraints and the distributed nature of applications make low-power wireless networks difficult to develop and understand, resulting in increased development time, poor performance, software bugs, or even network failures. Network simulators offer full non-intrusive visibility and control, and are indispensible tools during development. But simulators do not always adequately represent the real world, limiting their applicability. In this thesis I argue that high simulation timing accuracy is important when developing high-performance low-power wireless protocols. Unlike in generic wireless network simulation, timing becomes important since low-power wireless networks use extremely timing-sensitive software techniques such as radio duty-cycling. I develop the simulation environment Cooja that can simulate low-power wireless networks with high timing accuracy. Using timing-accurate simulation, I design and develop a set of new low-power wireless protocols that improve on throughput, latency, and energy-efficiency. The problems that motivate these protocols were revealed by timing-accurate simulation. Timing-accurate software execution exposed performance bottlenecks that I address with a new communication primitive called Conditional Immediate Transmission (CIT). I show that CIT can improve on throughput in bulk transfer scenarios, and lower latency in many-to-one convergecast networks. Timing-accurate communication exposed that the hidden terminal problem is aggravated in duty-cycled networks that experience traffic bursts. I propose the Strawman mechanism that makes a radio duty-cycled network robust against traffic bursts by efficiently coping with hidden terminals. The Cooja simulation environment is available for use by others and is the default simulator in the Contiki operating system since 2006.

Most mobile nodes are operated using batteries, protocols which conserve energy are of interest. The Dynamic Directional Power Control Protocol (DDPC) is a protocol that dynamically varies the energy used in directional transmission to increase the battery life of the transmitter without sacrificing connectivity with the receiver. The advantage of DDPC is that it takes into account the remaining battery power of a node before changing its transmission power. DDPC can achieve a higher network lifetime when compared to a network where nodes use a fixed transmit power level. Meanwhile DDPC dynamically reduces the energy consumed by a node in transmission. It can also reach nodes far from the transmitter by using directional antennas.

The development of new energy efficient Wireless Personal Area Network (WPAN) protocols is a big factor for the increased interest in Internet of Things (IoT). However, the many protocols with overlapping applications have led to competing standards and sensor networks using different protocols, even to perform the same tasks. If different sensors in IoT uses different protocols in the same area, a single gateway connecting to all of them must support all their protocols simultaneously. This thesis studies latency, average sending time and range for Bluetooth Low Energy (BLE), 802.15.4 and Zigbee in multiprotocol mode on the nRF52840 System on Chip (SoC). In addition, an 802.15.4-based protocol synchronizing with the BLE frames using Time Division Multiple Access (TDMA) techniques was designed and implemented. This protocol could be used in sensor networks using both the BLE and 802.15.4 protocols to assure the 802.15.4-based devices will not try to transmit during the periods the gateway is busy with other communications. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>

A evolução tecnológica das redes de telecomunicações sem fio permite que organizações de redes mais inteligentes sejam vislumbradas. É possível imaginar um sistema de telefonia formado por dispositivos móveis autônomos que não necessite de nenhuma infraestrutura pré-estabelecida para trocar informações com seus vizinhos, de acordo com o alcance do raio de transmissão. Assim, as informações poderiam ser repassadas de nó em nó, formando uma rede de múltiplos saltos. A ausência de uma entidade central também poderia melhorar a tolerância a falhas do sistema, principalmente por gerar uma redundância de caminhos possíveis entre os nós. Analisamos o desempenho desse sistema em diferentes cenários e a sensibilidade à variação de parâmetros como o raio de transmissão, interferências, a quantidade de nós e número de saltos máximo permitido (TTL), e testamos estratégias de comunicação com raio fixo, raio variável, número de vizinhos mínimo e etc., através de modelagem e simulação baseada em agentes. De maneira geral, a estratégia de transmissão com raio variável apresentou a melhor taxa de mensagens recebidas e a menor média de saltos até o destino, porém com maior nível de energia do sistema. A estratégia de raio fixo apresentou a menor energia total gasta pelo sistema para enviar as mensagens, porém, com uma taxa menor de mensagens recebidas. Além disso, avaliamos que as principais causas de perdas de pacotes estão associadas com o aumento da mobilidade, a redução do TTL e as interferências, sendo que cada uma contribui mais ou menos de acordo com o cenário estudado. / The technological development of Wireless Networks leads to more intelligent networks structures. One can imagine a mobile data system consisting of autonomous mobile devices that do not require any pre-established infrastructure to exchange information one with another, limited mainly by the transmission radius. Thus, data could be forwarded from node to node, forming a multihop network. The absence of a central entity could also improve fault tolerance by allowing redundant paths for nodes to communicate. We analyzed the performance of the system in different scenarios and system behavior regarding parameters variations such as transmission radius, interferences, the number of nodes and maximum allowed number of hops (TTL), and tested communication strategies with fixed radius, variable radius, minimum number of neighbors to transmit, etc., through modeling and simulation-based agents. In general, variable radius strategy had the best rate of incoming messages and the lowest average number of hops to the destination. However it presented the higher level of system energy. In one hand, fixed radius strategy presented the lowest total energy expended by the system to send messages, but, in the other hand, the rate of incoming messages was lower. Furthermore, we discovered the main causes of packet losses are associated with increased mobility, reducing the TTL and interference, each of which contributes more or less in accordance with the scenario.

A evolução tecnológica das redes de telecomunicações sem fio permite que organizações de redes mais inteligentes sejam vislumbradas. É possível imaginar um sistema de telefonia formado por dispositivos móveis autônomos que não necessite de nenhuma infraestrutura pré-estabelecida para trocar informações com seus vizinhos, de acordo com o alcance do raio de transmissão. Assim, as informações poderiam ser repassadas de nó em nó, formando uma rede de múltiplos saltos. A ausência de uma entidade central também poderia melhorar a tolerância a falhas do sistema, principalmente por gerar uma redundância de caminhos possíveis entre os nós. Analisamos o desempenho desse sistema em diferentes cenários e a sensibilidade à variação de parâmetros como o raio de transmissão, interferências, a quantidade de nós e número de saltos máximo permitido (TTL), e testamos estratégias de comunicação com raio fixo, raio variável, número de vizinhos mínimo e etc., através de modelagem e simulação baseada em agentes. De maneira geral, a estratégia de transmissão com raio variável apresentou a melhor taxa de mensagens recebidas e a menor média de saltos até o destino, porém com maior nível de energia do sistema. A estratégia de raio fixo apresentou a menor energia total gasta pelo sistema para enviar as mensagens, porém, com uma taxa menor de mensagens recebidas. Além disso, avaliamos que as principais causas de perdas de pacotes estão associadas com o aumento da mobilidade, a redução do TTL e as interferências, sendo que cada uma contribui mais ou menos de acordo com o cenário estudado. / The technological development of Wireless Networks leads to more intelligent networks structures. One can imagine a mobile data system consisting of autonomous mobile devices that do not require any pre-established infrastructure to exchange information one with another, limited mainly by the transmission radius. Thus, data could be forwarded from node to node, forming a multihop network. The absence of a central entity could also improve fault tolerance by allowing redundant paths for nodes to communicate. We analyzed the performance of the system in different scenarios and system behavior regarding parameters variations such as transmission radius, interferences, the number of nodes and maximum allowed number of hops (TTL), and tested communication strategies with fixed radius, variable radius, minimum number of neighbors to transmit, etc., through modeling and simulation-based agents. In general, variable radius strategy had the best rate of incoming messages and the lowest average number of hops to the destination. However it presented the higher level of system energy. In one hand, fixed radius strategy presented the lowest total energy expended by the system to send messages, but, in the other hand, the rate of incoming messages was lower. Furthermore, we discovered the main causes of packet losses are associated with increased mobility, reducing the TTL and interference, each of which contributes more or less in accordance with the scenario.