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.

Trådlösa sensornätverk byggs upp av trådlösa sensorer, som gemensamt arbetar för att lösa en viss uppgift. Ett exempel på en sådan uppgift kan vara insamling av pollennivåer i luften över en stor yta. Sensornoderna vidarebefordrar datan sinsemellan tills den når en datainsamlingsnod någonstans i nätverket där den sedan lagras och efterbehandlas. Generellt gäller att sensornoder är små, billiga, kommunicerar trådlöst och har en väldigt lång livslängd. Traditionellt sett har sen- sornoder också antagits vara statiska (stillastående), vilket medför begränsningar om noderna bärs av exempelvis människor eller monteras på fordon. I detta examensarbete presenteras matmac , ett mac-protokoll som designats för att hantera mobila noder i trådlösa sensornätverk. En referensimplementa- tion av matmac har implementerats i operativsystemet Contiki och utvärderats med varierande konfigurationsparametrar, rörelsehastigheter och dataintensitet i simulatorn Cooja. Resultatet från utvärderingen visar att mekanismerna för mo- bilitetshantering i matmac främjar sensornodernas förmåga att pålitligt överföra data trots att de är mobila.

A Wireless Sensor Network is formed of several small devices encompassing the capability of sensing a physical characteristic and sending it hop by hop to a central node via low power and short range transceivers. The Sensor network lifetime strongly depends on the routing protocol in use. Routing protocol is responsible for forwarding the traffic and making routing decisions. If the routing decisions made are not intelligent, more re-transmissions will occur across the network which consumes limited resources of the wireless sensor network like energy, bandwidth and processing. Therefore a careful and extensive performance analysis is needed for the routing protocols in use by any wireless sensor network. In this study we investigate Objective Functions and the most influential parameters on Routing Protocol for Low power and Lossy Network (RPL) performance in Contiki (WSN OS) and then evaluate RPL performance in terms of Energy, Latency, Packet Delivery Ratio, Control overhead, and Convergence Time for the network. We have carried out extensive simulations yielding a detailed analysis of different RPL parameters with respect to the five performance metrics. The study provides an insight into the different RPL settings suitable for different application areas. Experimental results show ETX is a better objective, and that ContikiRPL provides very efficient network Convergence (14s), Control traffic overhead (1300 packets), Energy consumption (1.5% radio on time), Latency (0.5s), and Packet Delivery Ratio (98%) in our sample RPL simulation of one hour with 80 nodes, after careful configuration of DIO interval minimum/doublings, Radio duty cycling, and Frequency of application messages. / En Wireless Sensor Network består av flera små enheter som omfattar de förmåga avkänning en fysisk egenskap och skicka den hoppa med hopp till en centrala noden via låg effekt och kort sändtagare räckvidd. Det sensornätverk livslängd är starkt beroende av routingprotokoll som används. Routingprotokoll är ansvarar för att vidarebefordra trafik och göra routing beslut. Om dirigeringen beslut som fattas inte är intelligenta, kommer fler återsändningar förekomma på nätverk som förbrukar begränsade resurser trådlösa sensornätverk som energi, bandbredd och bearbetning. Därför är en noggrann och omfattande prestanda analys behövs för routingprotokoll används av alla trådlösa sensornätverk. I denna studie undersöker vi mål Funktioner och den mest inflytelserika parametrar Routing Protokoll för låg effekt och Förstörande nätverk (RPL) prestanda i Contiki (WSN OS) och sedan utvärdera RPL prestanda vad gäller av energi, fördröjning, Packet Delivery Ratio, kontroll overhead och konvergens Dags för nätverket. Vi har genomfört omfattande simuleringar som ger en detaljerad analys av olika RPL parametrar med avseende på de fem resultatstatistik. Studien ger en inblick i de olika RPL inställningar som är lämpliga för olika användningsområden. Experimentella resultat visar ETX är en bättre målsättning och att ContikiRPL ger mycket effektivt nätverk Konvergens (14s), Control trafik overhead (1300 paket), Energiförbrukning (1,5% radio i tid), Latens (0,5 s), och paket Leverans Ratio (98%) i vårt urval RPL simulering av en timme med 80 noder, efter noggrann konfiguration av DIO intervall minimum / dubbleringar, Radio plikt cykling, och frekvensen av ansökan meddelanden. / tocomputerscientist@gmail.com Mob: 0046760721720

The Internet is one of the greatest innovations ever created by mankind, and it is a technical trend that has moved into industries to facilitate automation, supervision and management in the form of IoT devices. These devices are designed to be extremely lightweight and operate in low-power and lossy networks, and therefore run a low duty cycle and CPU-clock frequency to reserve battery life. Fog nodes are located on site to minimize network delay and provide centralized processing to handle data from hundreds of connected devices in wireless sensor networks. This is the future of industrial automation. Our goal is to show the functionality of an industrial IoT network within the scope of Fog computing by implementing a closed-loop control system in Cooja. Performance evaluations considered network reliability in terms of packet delivery ratio and timeliness. We assume that wireless IoT devices are running RPL routing (one of the most common standard routing protocols for IoT applications). We implement a mobility controller at the Fog-server in order to collect measurements made by the Fog nodes and send commands to IoT devices. In this thesis work, we assume that the commands are related to the mobility pattern of mobile node (e.g. AGVs in industrial automation) in order to avoid collision. From the simulation results we can conclude that sampling rates and node density have a greater impact on performance compared to payload size. We cannot be sure that our results reflect what a real-world evaluation would imply as we are running an emulation software, even though it has a very realistic physical layer. We do however believe that with substantial testing and improvements to both Cooja and our implementation, an accurate representation can be accomplished and algorithms in Cooja can be moved to real-world implementations.

The goal of this diploma work is to study the problems of wireless sensor networks. Describe elements of sensor network and discuss how the individual sensor nodes communicate with each other. Find the way how it would be possible to determine the possition of the new added sensor node or mobile sensor node in the sensor network. The selected one algorithm of determining the possition of the sensor node will be implemented in diploma thesis. Algorithms for determining the positions of sensor nodes are divided into groups by using the methods. Selected algorithm will be tested in simulation on chosen platform.

Monitoring waterbirds have several benefits, including analyzing the number of endangered species, giving a reliable indication of public health, etc. Monitoring waterbirds in their habitat is a challenging task since the location is distant, and the collection of monitoring data requires large bandwidth. A promising technology to tackle these challenges is thought to be Wireless Multimedia Sensor Networks (WMSN). These networks are composed of small energy-constrained IoT devices that communicate together to collect data or monitor a given location. Performances in such networks are impacted by not only upper-layer protocols (transmission, routing, application layer) but also Medium Access Control (MAC) Layer. Therefore, improvement in this layer can increase the performance considerably. Traditional contention-based MAC modes like CSMA have large energy expenditure even though they have a good network performance profile. Energy-constrained devices cannot have a long lifespan with this type of MAC layer technology. Therefore, the IEEE 802.15.4e amendment proposed TSCH MAC mode which takes advantage of time-slotted access and channel hopping techniques. IETF integrated TSCH protocol into IPv6-based wireless sensor networks and standardized it as 6TiSCH which is a unique protocol stack for Low-Power and Lossy Networks (LLN). WMSN applications (e.g. Waterbirds Monitoring Application) generates heterogeneous traffic. Heterogeneous traffic can be defined as a mixture of different traffic types (light: temperature, humidity, etc. and heavy: audio, picture, video, etc.). TSCH-based WMSNs are considered a fit for this kind of traffic since they provide better performance and low power usage.  Yet, the 6TiSCH Working Group left open the scheduling of TSCH communication for industries to make TSCH more easily adaptable to any kind of application. Until now, there have been a huge number of scheduling algorithms from industries and academia. Each scheduling algorithm has a different objective that maximizes the network performance of a specific application. This thesis work studies the most recent state-of-the-art scheduling algorithms (protocols) and compares them in a unique simulation environment with heterogeneous traffic to find out which protocol performs well while maintaining low energy consumption. Particularly, this work studies a new approach in TSCH scheduling which is Reinforcement Learning based scheduling. We implemented one of the state-of-the-art RL-based schedulers in Contiki-NG and included it in our comparison of TSCH schedulers. The experiment results showed that the RL-based scheduler implemented in this work demonstrated better performance in PDR and latency compared to other scheduling protocols. However, it presented high energy usage. On the other hand, Orchestra performed well while keeping the energy expenditure of nodes at a low level.