Impurity Induced Layer Disordering (IILD) of a GaAs/AlGaAs Multi Quantum Well (MQW) structure is known to produce a change in the refractive index dependent on the polarisation of the propagating mode. This index change can be used to provide lateral confinement in stripe optical waveguides, which are an essential component in any integrated optical circuit. Silicon implantation has been used to disorder GaAs/AlGaAs MQWs and the effects of implantation dose, encapsulant and annealing conditions on the disordering process have been investigated using Photoluminescence (PL). It was observed that deep level emissions accompanied the disordering and the results suggest that the degree of intermixing and the deep level emissions were determined by several competing processes. Calculation of the deep level/band-edge integrated intensity ratio for these emissions, provided an indication of the suitability of the process for the fabrication of disorder delineated stripe waveguides, where a correlation between the propagation loss of the waveguides and the integrated intensity ratio was observed. Buried stripe optical waveguides fabricated using Si+ IILD has been demonstrated for the first time in this work. Waveguide assessment using end-fire coupling was performed with the propagation losses and modal dimensions determined. The lowest loss of a waveguide fabricated by IILD presented in this thesis is 21.9dBcm-1 and it is suggested that the deep level states observed using PL are a significant source of attenuation of the propagating mode in the side walls of the waveguides.

Many emerging applications based on wireless networks involve distributed control. This implies high requirements on reliability, but also on predictable maximum delay. Further, for applications, it is vital to use off-the-shelf components, both due to cost constraints and requirements on interoperability with existing networks. This, in turn, implies that concurrent transmissions and multiuser detection are seldom possible. Instead, half-duplex time-division multiple access (TDMA) is typically used. Aiming to reduce the packet error rate given a deadline (a set of TDMA time-slots), this thesis proposes a relaying scheme, which can be implemented on top of off-the-shelf components. The relaying scheme selects the best sequence of relayers, given the number of time-slots allowed by the deadline, such that the resulting error probability is minimized at the targeted receiver(s). The scheme differs from existing work in that it considers both unicast as well as broadcast and assumes that all nodes can overhear each other, as opposed to separating source nodes, relay nodes and destination nodes into three disjoint sets. A full analysis of the resulting error probability is provided and complementary numerical results show that the proposed relay sequencing strategy significantly improves reliability given a certain maximum delay, or alternatively, reduces the delay, given a certain target reliability requirement. To illustrate the performance improvements of relay sequencing, it is incorporated in a platooning application. If the decision regarding which relayer to assign in each time-slot can be taken online, just before the transmission, much can be gained. To this end, a low-complexity algorithm is developed, which is shown to be highly likely to find the optimal combination of relaying nodes that minimizes the resulting error probability at the targeted receiver(s). Data packets in wireless automation networks is typically small. To enable timely and reliable all-to-all broadcast in such systems, relay sequencing using packet aggregation is proposed. The strategy assigns relayers to time slots, as well as determines which packets to aggregate in each slot, using the proposed low-complexity algorithm. To further increase the reliability, a clustering scheme is proposed. When a relayer in the sequence fails to overhear a correct copy, a backup relayer in the cluster takes over. This work thereby enables ultra-reliable communications with maintained end-toend delay using low-complexity techniques and off-the-shelf components.

M.Ing. / In this thesis we investigated the characterization of wireless communication channels. The characterization of the channel itself focused on the analog as well as the discrete domains. This was done to provide a more complete treatment than that which is usually found in the literature (which normally focuses" on either one of the domains). We also provide a discussion on the basic issues that arise when trying to characterize a wireless communication channel. The analog characterization proceeded by means of the impulse response of the chan­ nel. We calculated the scattering function of the channel as well as the Delay and Doppler Power Spectra. From the wideband data we also derived the equivalent Narrowband en­ velope and phase and investigated the probability density functions of these. We also implemented the GMSK modulation scheme, used in the GSM system, in software. This included a simulation of the additive white Gaussian noise channel as well as the Rayleigh fading channel, the two most common assumed models. A complete discussion is provided on this implementation. The implementation above was used to obtain discrete channel models of GMSK on a Rayleigh fading channel. This also provided us with the opportunity to compare the performance of three of the most common discrete channel models : the Gilbert model, the Gilbert-Elliott model and the Fritchman model. Lastly we obtained equations that describe the behaviour of the Gilbert model's parameters as a function of average signal­ to-noise ratio.

M.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

M.B.A. / The first mobile cellular telephone was established In St. louis (Missouri. USA) in 1946. In a few years time Europe followed with a similar service. These systems were based on technology developed during the World War 2 (Vodacom Corporate Profile:1999/2000:1). Between 1950 and 1960, cellular radio evolved to become automatic and Its costs dropped due to the Introduction of transistor technology. During the 1970's large scale integration and development of micro-processors enabled more complex systems development (Vodacom Corporate Profile :1999/2000:1 ). In 1988 the European Telecommunications Standard Institute (ETSI) was created. This Institute enabled network operators and telecommunications equipment manufacturers to become Involved In the specification of Global System for Mobile Communications (GSM) (Vodacom Corporate Profile :199~/2000:1 ). The GSM standard of communication was launched In Europe in 1992. This standard Is widelyused In European and African countries...

No description available.

The amount of data required to be processed in real-time embedded system is steadily increasing. This has caused industries to search for alternatives for reliable time-sensitive network communication. IEEE set of standards for Time-Sensitive Networking (TSN) is an attractive option for achieving this. It leverages the advantages of IEEE standards for Ethernet, such as high bandwidth and low hardware cost, while introducing deterministic behaviour. Simulation tools are used to facilitate verification and analysis of TSN networks. However, even simulation-assisted design of large complex networks is a challenging process. To alleviate this issue, this thesis investigates how TSN simulation can be improved by automatic generation of network configurations. So far, many different simulation frameworks have been developed in academia. This thesis builds on the OMNeT++ simulation framework and NeSTiNg simulation model. We prototype an automatic TSN configuration tool capable of generating configuration automatically through a graphical user interface (GUI). The purpose of the prototype is to demonstrate the feasibility of automatic configuration in TSN and how it eases design complexity. Furthermore, to verify the proposed tool a use case inspired by the vehicle industry is modelled. It is concluded that automatic configuration improves usability in five key areas, such as: (1) facilitating recollection of the network, (2) enabling automatic configuration, (3) increasing user-friendliness of a TSN simulation platform with a GUI, (4) increasing efficiency and usability of a TSN simulation platform, and (5) minimizing user error. The results gained in this thesis justify the usability of automation and could provide insights for future research and development of TSN simulation tools.

No description available.

Within the Internet of Things (IoT) a need for new IP-compatible communication technologies has grown stronger during the last few years as the need to connect these IoT networks to the Internet has become increasingly more important. In this report, we evaluate IPv6 over the TSCH mode of IEEE 802.15.4e (6TiSCH) with the purpose of observing how different values for the enhanced beacon (EB) period affect certain network metrics such as delay, energy consumption, join time, and throughput. The EB period is a periodic message used in the Time Slotted Channel hopping (TSCH) protocol used to advertise the network. Our goal is to evaluate the effect of different EB periods on the network and determine if there would be a benefit of integrating SDN to change the EB period dynamically. To fulfill our goal, we will evaluate the effect of the change in EB period on the network metrics. This would be an indication that the 6TiSCH network benefits from an integration with SDN. The reason that we would draw this conclusion is because SDN would be capable of predicting the state of the network and from that update the EB period for the 6TiSCH network. Our results indicate that a lower EB period has a positive effect on join times in the network while a longer EB period has a positive effect on the end-to-end delay. Our results display a promising future for future research on the integration of SDN and 6TiSCH.

Nutidens tåg har en livslängd på ungefär 40 år, och många av de tåg vi har i drift är runt 20 år. Under denna tid har mycket utveckling skett inom insamling och analys av diagnostik som dessa äldre tåg inte har kunnat ta del av. Detta projekt startades med syftet att skapa ett system som kan kopplas till databussarna i dessa äldre tåg, samt expanderas med extra sensorer, och därefter samla data, konvertera den till ett mer användbart format, och skicka den effektivt och kryptografiskt säkert till en central server för insamling och analys. En förstudie genomfördes för att kartlägga vilka system som finns i äldre tåg, samt vilka nuvarande standarder som finns och skulle kunna användas för våra syften. Från den samlade informationen i förstudien designades ett system med en eller flera noder i varje tåg som samlade ihop både cyklisk processdata och sporadiska meddelanden från tågets databuss. Dessa skickades sedan till en central server via en säker VPN-tunnel. Den mottagna cykliska och sporadiska datan sparades sedan i en round-robin databas respektive en loggfil, varifrån den kunde avläsas. Systemet implementerades i en testmiljö och visade sig fungera utan problem. Vi kunde inte implementera systemet i ett riktigt tåg, men våra test visar att den övergången borde kunna hanteras med minimala problem.