Polarization Mode Dispersion induces polarization dependent propagation. Consequently it generates a multiple imaging of the light pulse carrying the information. Its first order appears as a dual path fading channel of Maxwellian statistics. It results in harmful impairments that prevent the upgrade and installation of high bit-rate systems. The random process PMD exhibits a strong frequency dependence, so that its amelioration requires channel by channel, non-linear, adaptive mitigation. Electronic mitigation appears as a very attractive solution to overcome the limit set by the PMD. Consequently, we considered the implementation of these solutions at the receiver in the electrical domain. We verified that these linear and non-linear equalization techniques can greatly reduce the power penalty due to PMD. Equalization's performance depends highly on the type of systems considered. For the two main types of systems: thermal noise limited systems and systems exhibiting ASE (systems using optical amplifiers), we demonstrated and quantified the induced improvement (measured as power penalty reduction). The most sophisticated technique that we considered (NLC+FDE) handles any kind of first order PMD within a 4 dB margin in the thermal noise limit. This extended to a 11 dB margin in the presence of ASE. This comes from the limitation set by the signal dependence of the noise. In fact, these DSP techniques do a better job at reducing very high penalty. Consequently, for a power and ISI limited link, it may be required to associate to electronic solutions optical compensation in order to reach acceptable performance. On the other hand, for links having large power margin or exhibiting reasonable PMD, electronic techniques appear as an easy, inexpensive and convenient solution. We derived in this work the bounds to NLC performance in the presence of ASE. Therefore, we extended the usual results of the thermal noise limit to the particular case of signal dependent noise. We also made clear that optical systems, because of their noise specificities can not be studied or designed as others links. Notions such as eye opening, SNR and ISI need to be carefully defined and adapted to this case. We have provided in this work PMD dependent power penalty map for known systems. Given the link's statistics and characteristics, one can determine, following our structure, which mitigation techniques allow upgrade. / Master of Science

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The relative anti-jam (AJ) performance of several diversity combiners are investigated. The modulation is 8-ary frequency-shift-keying (FSK), the demodulation process consists of energy detection of the eight frequency bins at each hop and the subsequent combining of detector outputs. Three combiners are considered : the linear combiner, where the detector outputs of each hop (corresponding to the same frequency bin) are summed without any processing; the self-normalized combiner, where the eight detector outputs of any particular hop are normalized so that they add to unity; and the max-normalized combiner, where the eight detector outputs of any hop are divided by the maximum value among those eight outputs. Results indicate that under worst-case tone jamming, the selfnormalized combiner performs the best, the max-normalized combiner second best, and the linear combiner performs the worst among the three.

RF positioning methods have various tradeoffs that make them suitable for differing applications. This thesis identifies the most prominent positioning methods and deter-mines their suitability for context aware applications in pub-lic spaces using a number of different factors. This thesis first explores the physical characteristics of GPS, GSM, 802.11 and Bluetooth focusing on coverage and accuracy in both a historical and forward looking context. Next, it explores what it means for an application to be context aware and how that translates into building applications that are used in the context of public places. This thesis then reflects on the intersection of the two and explores some challenges related to practical implementations. In order to further explore these challenges, it assesses a high accuracy use case of merging Bluetooth positioning with augmented reality and virtual reality applications. We find that in the last decade Bluetooth has made rapid advancements in relation to competing technologies, but it is still far from ideal in all situations, especially when the situation requires extremely high accuracy.

The cascading or concatenation of error control codes is a well-established technique in digital communications. This type of code can yield excellent bit error rate performance. Concatenated codes that contain short memory convolutional codes are applicable to many communication links. The applications include the various combinations of modulations with memory, channels with memory and coding with memory. The Viterbi decoder is the decoder of choice for these concatenated coding schemes. Unfortunately, Viterbi decoders produce only hard decisions. The Viterbi decoders near the channel (inner decoders) therefore do not send all the available symbol information (soft decisions) to the outer decoders. Also, there are no practical decoders that produce this symbol information. The result is an unrealized coding gain. The principal contribution of this dissertation is to present a new decoder design that can be used as an inner decoder in a concatenated convolutional coding scheme. This decoder is a modified Viterbi decoder that generates soft decisions. The decoder has been named the Maximum Likelihood Paths Comparison (MLPC) decoder. The MLPC decoder uses a subset of the operations performed by a normal Viterbi decoder and therefore it is practical. The performance of the new decoder in a communication link is determined by simulation. The link uses a concatenated code that contains two convolutional codes. Both codes have a base code constraint length of 7 and rates of 1/2. The outer code is punctured to a few higher rates. Various results from these simulations are presented. The bit error rate performance of the code is excellent. The code performance also matches the theoretical upper bit error rate bound very closely for the signal-noise-ratios simulated. The complexity of the overall concatenated code system is compared to the complexity of a single convolutional code with equal performance. Using certain reasonable assumptions, the complexity of the concatenated code is roughly an order of magnitude less than the complexity of the single code.

The nature of sociability in the digital world has attracted much attention, with theories of the network society describing the formation of networked connections across distant geographies. Policymakers are optimistic about the potential for these new forms of connectivity to overcome some of the longstanding disadvantages of rural life. However, a prerequisite for full and meaningful participation in the network society is equal access to digital infrastructure, and a persistent urban–rural divide in this regard has been documented across Britain. The thesis argues that the meaning of the divide has been under-investigated with the result that our understanding of rural sociability in contemporary society is theoretically underdeveloped. This is addressed through a study of sociability in rural Britain, which adopts a “facet methodology” approach, examining the research problem from different angles using a range of methods. The first facet of the research compares the perceptions of rural and urban Internet users through an analysis of the Oxford Internet Survey. The second facet conducts a social network analysis of the online connections formed by a group of bloggers in the Scottish islands. The third facet explores the discursive interactions of the same set of bloggers through a thematic analysis of their writings. Together, the methods shed light on key aspects of the research problem. The findings reveal that people living in the country's rural areas are experiencing a different relationship with digital technology from urban residents. Rather than occupying peripheral or inferior positions in the network society, however, they are cultivating unique forms of digital sociability, informed by particular influences and motivations that set their social behaviour apart from the networked norm. Throughout the thesis, an understanding of the place of rural in the digital world is elaborated and the network society is shown to be differentiated across multiple dimensions.

D. Ing. / The digital transmission of information necessitates the compensation for disturbances introduced by the channel. The compensation method usually used in digital communications is error correcting coding. The errors usually encountered are additive in nature, i.e. errors where only symbol values are changed. Understandably, the field of additive error correcting codes has become a mature research field. Remarkable progress has been made during the past 50 years, to such an extent that near Shannon capacity can be reached using suitable coding techniques. Sometimes the channel disturbances may result in the loss and/or gain of symbols and a subsequent loss of word or frame synchronisation. Unless some precautions were made, a synchronisation error may propagate and corrupt large blocks of data. Typical precautions taken against synchronisation errors are: out-of-band clock signals distributed to the transmission equipment in a network; stringent requirements on clock stability and jitter; limits on the number of repeaters and regeneration to curb jitter and delays; line coding to facilitate better clock extraction; and - use of framing methods on the coding level. Most transmission systems in use today will stop data transmission until reliable synchronisation is restored. El multiplexing systems are still the predominantly used technology in fixed telephone line operators and GSM operators, and recovering from a loss of synchronisation (the FAS alarm) typically lasts approximately 10 seconds. Considering that the transmission speed is 2048 KB/s, a large quantity of data is lost in during this process. The purpose of this study is therefore to broaden the understanding of insertion/deletion correcting binary codes. This will be achieved by presenting new properties and coding techniques for multiple insertion/deletion correcting codes. Mostly binary codes will be considered, but in some instances, the results may also hold for non-binary codes. As a secondary purpose, we hope to generate interest in this field of study and enable other researchers to continue to deeper explore the mechanisms of insertion and/or deletion correcting codes.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering / This dissertation verifies a Computer Simulation Package for modeling pulse transmission over digital subscriber loops. Multigauge sections on subscriber cables can be studied. The model used for each section incorporates skin, proximity and eddy current effects. The model allows important quantities such as near end echo and overall transmission distortion of pulses to be.predicted. An experimental facility has been established in the laboratory for the purpose of validating the results produced by the simulator with results obtained over real cables. The experimental facility has as far as possible been automated by making use of computer controlled equipment for direct setup or the experiment, data transfer, and analysis. The results obtained from the pulse propagation program and that obtained from measurements are in close. agreement, rendering the Computer Simulation Package useful for analysing the performance of multi gauge digital subscriber loops. / AC 2018

Tsang Tin-Tak. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 78-80). / Abstract also in Chinese. / Chapter CHAPTER ONE: --- INTRODUCTION --- p.2 / Literature Survey --- p.3 / Project overview --- p.4 / Chapter CHAPTER TWO: --- SENSOR --- p.6 / Chapter 2.1. --- Background --- p.6 / Chapter 2.1.1. --- Piezoresistive effect --- p.6 / Chapter 2.1.2. --- Wheatstone bridge --- p.7 / Chapter 2.2. --- Strain Gauge --- p.10 / Chapter 2.2.1. --- Experimental setup for strain gauge --- p.11 / Chapter 2.2.2. --- Position of the strain gauge --- p.12 / Chapter 2.2.3. --- Selection of the value for the resistor to complete the bridge --- p.13 / Chapter 2.3. --- Pressure sensor --- p.15 / Chapter 2.3.1. --- Structure of pressure sensor die --- p.15 / Chapter 2.3.2. --- Modeling of the pressure sensor die --- p.17 / Chapter 2.3.3. --- Alternative application of the pressure sensor die --- p.20 / Chapter CHAPTER THREE: --- WIRELESS TRANSMISSION --- p.24 / Chapter 3.1. --- Introduction --- p.24 / Chapter 3.2. --- Analogue Transmission --- p.25 / Chapter 3.2.1. --- Transmitter (MC2833) --- p.26 / Chapter 3.2.2. --- Receiver (MC13135) --- p.29 / Chapter 3.3. --- Digital transmission --- p.30 / Chapter 3.3.1. --- Advantage of using Digital transmission --- p.30 / Chapter 3.3.2. --- Digital Transmitter and receiver 1 (H2000 & RX2020) --- p.30 / Chapter 3.3.3. --- Digital Transmitter and receiver 2 (TX2) --- p.32 / Chapter 3.4. --- Comparison between the three sets of transmitter --- p.34 / Chapter 3.4.1. --- Analogue Vs Digital --- p.34 / Chapter 3.4.2. --- Number of components (Complexity) --- p.35 / Chapter 3.4.3. --- Excepted size --- p.35 / Chapter 3.4.4. --- Transmitting distance --- p.36 / Chapter 3.4.5. --- Power supply --- p.36 / Chapter 3.4.6. --- Conclusion --- p.36 / Chapter 3.5. --- The detail investigation of HX2000 and RX2020/RX2056 --- p.37 / Chapter 3.5.1. --- Transmitting distance --- p.37 / Chapter 3.5.2. --- Shape of the received signal --- p.37 / Chapter 3.5.3. --- Orientation of the chips --- p.39 / Chapter 3.5.4. --- Conclusion for the transmitter --- p.39 / Chapter CHAPTER FOUR: --- ENCODING AND DECODING CIRCUIT --- p.40 / Chapter 4.1. --- Introduction --- p.40 / Chapter 4.2. --- Serial binary converter (MAX 1240) --- p.40 / Chapter 4.2.1. --- Features of MAX1240 --- p.41 / Chapter 4.2.2. --- Implementation of MAX1240 --- p.43 / Chapter 4.2.3. --- Method to decode the signal generated by MAX1240 --- p.46 / Chapter 4.3. --- Voltage-to-Frequency Converter (AD654) --- p.52 / Chapter 4.3.1. --- Advantages of using AD654 as the A/D converter --- p.54 / Chapter 4.3.2. --- Disadvantages of using AD654 as the A/D converter --- p.55 / Chapter 4.3.3. --- Method to read the frequency --- p.56 / Chapter 4.4. --- Frequency counter --- p.57 / Chapter 4.4.1. --- Schmitt trigger NAND-gate --- p.58 / Chapter 4.4.2. --- Ripple counter --- p.61 / Chapter 4.4.3. --- Implementation of the counter --- p.63 / Chapter 4.5. --- Conclusion --- p.66 / Chapter CHAPTER FIVE: --- INTERGATION OF THE THREE COMPONENTS --- p.67 / Implementation of the Circuit --- p.67 / Chapter 5.2. --- The result before transmission --- p.70 / Chapter 5.2.1. --- Analysis and Discussion for the experimental result (before transmission) --- p.72 / Chapter 5.3. --- The result after transmission --- p.74 / Chapter 5.3.1. --- Analysis and Discussion for the experimental result (after transmission) --- p.76 / Chapter CHAPTER SIX: --- SUMMARY --- p.77 / BIBLIOGRAPHY --- p.78

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 159-167).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 118-130).