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With the surge in smartphones and tablets, the future of wireless cellular communication systems is marked by a drastic change in user behaviour triggered by the unbridled growth of bandwidth hungry applications. This challenge as well as the limited spectral resources drives the need to further improve resource allocation schemes for cellular networks. This thesis focuses on resource allocation in self organised cellular networks. A distributed self organised channel assignment scheme has been proposed that is shown to achieve perfect orthogonality among neighbouring sectors and reveals the importance of localised rules in designing distributed self organised systems. We define a sectorial neighbourhood based on intercell interference consideration and apply a local coordination among these sectors to achieve a self organised assignment. This unique solution for spectrum assignment strategy is demonstrated as a dynamic spectrum allocation scheme as well as a combination of both the dynamic and static spectrum allocation schemes, verified by system level simulations. The marked improvement in system performance is however not evident for users located at cell edges. Due to the performance of these cell edge users, a self organised fractional frequency reuse scheme whose allocation adapts to the system dynamics is proposed. Current solutions that employ a Fractional Frequency Reuse (FFR) are first analysed to challenge the assumption of fixed cell edge region and power allocation irrespective of the unique user distribution in each cell and its neighbours. We define a unique property for each sector based on its user distribution called its Centre of Gravity (CoG). With the CoG, each sector is classified into states that enables us to apply cellular automata theory that results in a self organised fractional frequency reuse scheme. For mulithop communication links however, intercell interference analysis becomes more complicated due to interference introduced by relay nodes. We finally investigate FFR schemes in multihop communication links comparing the performance of existing FFR schemes in multihop links in terms of their spectral efficiency and area spectral efficiency. A new FFR scheme specifically tailored for multihop links is thus proposed by applying a reuse scheme both in the cell centre and edge regions but rotated at an angle of 1200 in the centre region. Furthermore, the sectorial neighbourhood principle introduced earlier is further applied to ensure intercell interference is further minimised.

In this thesis, I present the studies on fabrication, spectral and polarisation characterisation of fibre gratings with tilted structures at 45º and > 45º (namely 45º- TFGs and ex 45º-TFGs throughout this thesis) and a range of novel applications with these two types of grating. One of the major contributions made in this thesis is the systematic investigation of the grating structures, inscription analysis and spectral and polarisation properties of both types of TFGs. I have inscribed 45º-TFGs in standard telecom and polarisation maintaining (PM) fibres. Two wavelength regions of interest have been explored including 1.55 µm and 1.06 µm. Detailed analysis on fabrication and characterisation of 45º-TFGs on PM fibres have also been carried out for the first time. For ex 45º- TFGs, fabrication has been investigated only on low-cost standard telecom fibre. Furthermore, thermal responses have been measured and analysed showing that both types of TFG have low responsivity to temperature change. More importantly, their refractive index (RI) responses have been characterised to verify the high responsivity to surrounding medium. Based on the unique polarisation properties, both types of TFG have been applied in fibre laser systems to improve the laser performance, which forms another major contribution of the research presented in this thesis. The integration of a 45º-TFG to the Erbium doped fibre laser (EDFL) enables single polarisation laser output at a single wavelength. When combing with ex 45º-TFGs, the EDFL can be transformed to a multi-wavelength switchable laser with single polarisation output. Furthermore, by utilising the polarisation property of the TFGs, a 45º-TFG based mode locked fibre laser is implemented. This laser can produce laser pulses at femtosecond scale and is the first application of TFG in the field of nonlinear optics. Another important contribution from the studies is the development of TFG based passive and active optical sensor systems. An ex 45º-TFG has been successfully developed into a liquid level sensor showing high sensitivity to water based solvents. Strain and twist sensors have been demonstrated via a fibre laser system using both 45°- and ex 45º-TFG with capability identifying not just the twist rate but also the direction. The sensor systems have shown the added advantage of low cost signal demodulation. In addition, load sensor applications have been demonstrated using the 45º-TFG based single polarisation EDFL and the experimental results show good agreement with the theoretical simulation.

Interface metaphor is a widely used design technique for interactive computer systems. The advantages of using interface metaphors derive from their ability to promote active learning, which enables a user to transfer knowledge from a familiar real world domain, to an unfamiliar computing domain. Interface metaphor is not currently used for the design of automated phone services, and it was the aim of this thesis to examine whether interface metaphor could improve the usability of speech-activated automated mobile phone services. A human-centred design methodology was followed to generate, select, and develop potential metaphors, which were used to implement metaphor-based phone services. An experimental methodology was then used to compare the usability of the metaphor-based services with the usability of currently available number-based phone services. The first experiment examined the effect of three different interface metaphors on the usability of a mobile city guide service. Usability was measured as a range of performance and attitude measures, and was supplemented by telephone interview data. After three consecutive days of usage, participants both preferred, and performed better with, the service that was based on an office filing system metaphor. Experiment two was conducted over a six week period, and investigated the effect of users' individual differences, and the context of use, on the usability of both the office filing system metaphor-based service, and a non-metaphor service. The results showed that performance with the metaphor-based service was significantly better than performance with the non-metaphor service. The usability of the metaphor-based service was not significantly affected by users' individual characteristics and aptitudes, whereas the number-based service was, suggesting that metaphor-based services may be more usable for a wider range of potential users. Usability levels for both services were found to be consistent across both private and public locations of use, suggesting that speech-activated mobile phone services provide a flexible means of information access. Experiment three investigated the strategies used by participants when interacting with mobile phone services, specifically the visualisation strategy that was used by two thirds of the metaphor-based service participants in experiment two. In addition to the attitude and performance measures used for experiments one and two, face-to face interviews were conducted with participants. The results indicated that significantly more participants visualised the metaphor-based services relative to a non-metaphor service, and that visualisation of the service structure led to significant performance improvements. This thesis has demonstrated the usability benefits of interface metaphor as a design technique for speech-based mobile phone services. These benefits of metaphor appear to derive from their ability to provide a mental model of the phone service that can be visualised, and their ability to accommodate the individual differences of users.

The investigation is concerned with various synchronous multiplexing and demultiplexing processes suitable for use with serial baseband data-transmission systems. The multiplexed signals are transmitted in orthogonal groups over a channel which introduces additive white Gaussian noise but no signal distortion. Techniques are considered for increasing both the capacity and tolerance to additive noise, when the number of multiplexed signals may vary with time, and may exceed the maximum number of orthogonal multiplexed signals.

Hitherto, historians have assumed that once a submarine telegraph cable had been laid, it would provide 50 to 70 years of reliable service. As one who has practical experience of engineering in a professional capacity, I found this order of reliability difficult to believe. I therefore set out to try to determine how reliable or otherwise this new technology actually was and how it was maintained. These questions had not been asked before and proved more difficult to answer than might have been predicted because much of the information was concealed, deliberately or otherwise, by the cable operating companies. However there were key clues such as the number of cable repair ships afloat and multiple textbooks on cable maintenance. Having unearthed useful data from the archives of the Eastern Telegraph Company (ETC) and of the Telegraph Construction and Maintenance Company, I conclude that the submarine telegraph cables during the period from the first experimental attempts in 1850 up until the Great War were not as reliable as previously assumed. On average, a voyage to repair these cables was required once per annum per 500 nautical miles of cable and this rate remained constant from 1873, when the ETC was formed, up until 1914, the end of my period of research. During this period the system which was composed of a submarine cable connecting two telegraph stations appeared increasingly reliable and efficient because of improvements in the technology at the cable stations and the duplication of many cables which allowed rerouting of communications when malfunctions occurred. I also conclude that data was concealed by the operating companies for commercial reasons. If this concealment had been less, then the genesis of the discipline of reliability engineering in the 1940s might have been developed 50 years earlier.

Bibliography: leaves 102-104 / viii, 115 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1986

Η VDSL αποτελεί την πιο σύγχρονη DSL τεχνική. Σε αυτή τη Διπλωματική Εργασία γίνεται μελέτη της ρύθμισης ισχύος εκπομπής της VDSL. Ως καινούργια τεχνολογία η VDSL καλείται να συνυπάρξει με τους διάφορους προκατόχους της (POTS, ISDN, HDSL, ADSL) με αποτέλεσμα να παρενοχλείται αλλά και να παρενοχλεί τα υπόλοιπα συστήματα. Στα πρώτα κεφάλαια της εργασίας περιγράφονται θεωρητικά η VDSL, οι πηγές παρενόχλησης της, οι διάφοροι περιορισμοί στους οποίους υπόκειται και διάφορες τεχνικές ρύθμισης της ισχύος εκπομπής της VDSL. Ακολουθεί η προσομοίωση σε περιβάλλον Matlab μίας τεχνικής ρύθμισης, του water- filling αλγόριθμου. Τα περιεχόμενα αυτής της εργασίας κατανέμονται στα ακόλουθα κεφάλαια: Στα κεφάλαιο 1 γίνεται μια σύντομη ιστορική αναδρομή στο τηλεφωνικό δίκτυο και μια μικρή περιγραφή του περιβάλλοντος του δικτύου πρόσβασης. Στο δεύτερο κεφάλαιο περιγράφονται λεπτομερώς οι διάφορες πηγές θορύβου που παρενοχλούν την VDSL. Στο τέλος του κεφαλαίου, δίνονται τα διάφορα μοντέλα θορύβου όπως έχουν τυποποιηθεί από τον ETSI αλλά και τα μοντέλα που χρησιμοποιήθηκαν κατά την προσομοίωση. Στο τρίτο κεφάλαιο γίνεται μια λεπτομερής περιγραφή της VDSL. Δίνονται τα μπλοκ διαγράμματα των VDSL1 και VDSL 2, το μοντέλο αναφοράς ο τύπος διαμόρφωσης και οι κώδικες γραμμής. Το τέταρτο κεφάλαιο ασχολείται με την ρύθμιση ισχύος εκπομπής. Περιγράφονται και συγκρίνονται οι διάφορες τεχνικές ρύθμισης. Στο ίδιο κεφάλαιο γίνεται περιγραφή του περιβάλλοντος της DSL και τελικά αναλύεται ο water- filling αλγόριθμος. Στο πέμπτο κεφάλαιο γίνεται προσομοίωση του αλγόριθμου σε περιβάλλον Matlab και παρουσιάζεται ο ψευδό- κώδικας του προγράμματος που χρησιμοποιήθηκε. Στη συνέχεια παραθέτονται οι αρχικοποιημένες μεταβλητές που χρησιμοποιήθηκαν κατά την εκτέλεση του προγράμματος, καθώς και τα αποτελέσματα που προέκυψαν. Στο τέλος της εργασίας αναλύονται τα αποτελέσματα της προσομοίωσης. / VDSL is the state of the art of DSL techniques. This diploma paper considers power emission adjusting of VDSL. As a new technology VDSL must be able to coexist with former technologies (POTS, ISDN, HDSL, ADSL). The result of this coexistence is the disturbance from and to the other technologies. The first part of this paper describes VDSL technology, noise sources, constraints that are being forced to VDSL and power emission management techniques. The second part presents a simulation in Matlab environment of a power adjustment technique called Water- filling algorithm. In more details the diploma paper is organized in the following chapters: In chapter 1 we present the history of the telephone network and a brief description of DSL environment. Chapter 2 refers to the noise sources that interfere with VDSL. In the end of chapter 2 we present some noise models standardized by ETSI and the models which were used through the simulation. In the third chapter we give a detailed description of VDSL representing block diagrams of VDSL1 and VDSL2, the reference model, the type of modulation and the line codes that VDSL uses. In chapter 4 we analyze power emission adjustment. After a comparison of several adjustment techniques we analyze water- filling algorithm. In the fifth chapter we implement the simulation of the algorithm in Matlab and we present a pseudo- code of the used program. Afterwards we give the initial values of the program and represent the results. At the end of the diploma paper we quote our conclusions.

This thesis investigates the generation and radio-over-fibre (RoF) transport of unlicensed 60 GHz millimetre-wave (mm-wave) frequency band. The investigated benefits of transmission schemes applicable for the mm-wave generation include optical carrier suppression (OCS), optical frequency multiplication (OFM) and remote heterodyne detection (RHD). For the in-door cabling of the mm-wave transmission, a low-cost polymer optical fibre (POF) along with bend-insensitive single mode fibre (BI-SMF) has been investigated for short-range networks. Transporting mm-wave generated signals over POF and BI-SMF cables based on OCS scheme showed results with the highest spectral efficiency and least inter-symbol interference over a 2.5 Gbit/s data delivery. Based on this thesis analysis, OCS simulation of POF showed the most reliable power penalty performance and receiver sensitivity at 30-m whilst the BI-SMF fiber produced equal observations at 150-m and more. In observing the free space links of delivering the RoF signal, the attenuation on the received signal power for both POF and BI-SMF was insignificant but expected, as the simulation assumed complete and total collimation of the light beams onto the aperture of the photodetector. OCS scheme for mm-wave generation and transport was explored based on the cost effectiveness of using one external modulator compared to other generation schemes that utilised more than one external modulator. OFM scheme was simulated to transport LTE and Wi-Fi signals along with 60 GHz RF band through both SMF and MMF-POF/BI-SMF cables. OFM transport scheme produced the highest attenuation on LTE, Wi-Fi and mm-wave signals carrying 100 Mbit/s data as simulated POF lengths increased. The best performance POF length was observed at 10-m. The application of offset launch technique at the coupling of SMF and POF showed insignificant improvement on signal bandwidth. The free space OFM transmission also demonstrated negligible change to the received signal power. This reinforces the attributes of deploying OWC system in an in-door environment. In other investigation, the simulated successful delivery of mm-wave signal using RHD scheme modulated and transported 10 Gbit/s data signal over POF and BI-SMF cables. Additional observed unrecorded result also showed BI-SMF cable maintained a 2% reduction of received power for 450-m fiber cable from 150-m. The attributes to RHD includes its low operating power system application and delivery of localised 60 GHz signal for uplink RoF transmission. The conceptualised design of Gigabit data delivery for indoor customer applications either through POF or BI-SMF cable, transporting various wireless channels has been presented in this thesis for the design of a robust next generation Broadband access network to reinforce the fiber-inside-the-home (FiTH) deployment.