by Tam Wing-Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 55-57). / Abstracts in English and Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / 哲學碩士論文摘要 --- p.iii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Research Background --- p.2 / Chapter 1.2 --- Contribution of the Thesis --- p.5 / Chapter 1.3 --- Organization of the Thesis --- p.6 / Chapter Chapter 2 --- Content Repurposing System Architecture --- p.7 / Chapter 2.1 --- Introduction to ICAP-based Content Repurposing System --- p.7 / Chapter 2.2 --- Generic Service-enabling Platform --- p.8 / Chapter 2.3 --- Rule Engine --- p.10 / Chapter 2.4 --- ICAP-enabled Application Server --- p.10 / Chapter 2.5 --- Store-and-forward Transcoding and Streamed Transcoding --- p.11 / Chapter Chapter 3 --- Transcoding Techniques --- p.18 / Chapter 3.1 --- Text Transcoding --- p.19 / Chapter 2.2 --- Image Transcoding --- p.20 / Chapter 3.3 --- Audio Transcoding --- p.23 / Chapter 3.4 --- Video Transcoding --- p.25 / Chapter Chapter 4 --- Adaptation Policy --- p.28 / Chapter 4.1 --- Delay Analysis of Content Repurposing System --- p.30 / Chapter 4.2 --- Store-and-forward Transcoding for Image Files --- p.31 / Chapter 4.2.1 --- Distribution of Input Web Images --- p.34 / Chapter 4.2.2 --- Transcoding Web images to WBMP --- p.34 / Chapter 4.2.3 --- Adaptation policy of Transformation to WBMP --- p.36 / Chapter 4.2.4 --- Adaptation policy of JPEG images --- p.36 / Chapter 4.3 --- Streamed Transcoding for Audio/Video Files --- p.39 / Chapter 4.3.1 --- Audio Transcoding --- p.41 / Chapter 4.3.2 --- Video Transcoding --- p.42 / Chapter 4.4 --- Case Study --- p.43 / Chapter 4.4.1 --- Weak Device with Insufficient Bandwidth --- p.43 / Chapter 4.4.2 --- Weak Device with Sufficient Bandwidth --- p.43 / Chapter 4.4.3 --- Strong Device with Insufficient Bandwidth --- p.44 / Chapter Chapter 5 --- Conclusion --- p.54 / Bibliography --- p.55

Multipath fading is one of the major practical concerns in wireless communications. A multipath transmission takes place when a transmitted signal arrives at a receiver by two or more paths of different delay. Such multiple paths may be due to atmospheric reflection or refraction, or reflections from buildings or other objects. A multipath fading channel is usually modeled as a time-variant tapped delay system. RAKE receiver can be used to detect the signal from the multipath fading channel. However, the number of delay taps, the time delay of each path, and the tap weight for each delay path need to be determined. The objective of this thesis is to explore the possibility of using the advance signal processing algorithms to estimate the number of delays, the time delay of each path, and the tap weight for each delay path in multipath channels and to investigate the performance of the RAKE receiver based on chip rate channel estimates in a realistic mobile environment. Simulations show that the new approach outperforms the existing approaches.

Due to the enormous capacity and performance gains associated with the use of antenna arrays in wireless multi-input multi-output (MIMO) communication links, it is inevitable that these technologies will become an integral part of future systems. In order to assess the potential of such beam-oriented technologies, direct representation of the dispersion of multipath fading channel in angular and temporal domains is required. This representation can only be achieved with the use of spatial channel models. This thesis thus focuses on the issue of spatial channel modeling for cellular systems and on its use in the characteri- zation of multipath fading channels. The results of this thesis are presented mainly in five parts: a) modeling of scattering mechanisms, b) derivation of the closed-form expressions for the spatio-temporal characteristics, c) generalization of the quantitative measure of angular spread, d) investigation of the effect of mobile motion on the spatio-temporal characteris- tics, and e) characterization of fast fading channel and its use in the signature sequence adaptation for direct sequence code division multiple access (DS-CDMA) system. The thesis begins with an overview of the fundamentals of spatial channel modeling with regards to the specifics of cellular environments. Previous modeling approaches are dis- cussed intensively and a generalized spatial channel model, the 'Eccentro-Scattering Model' is proposed. Using this model, closed-form mathematical expressions for the distributions of angle and time of multipath arrival are derived. These theoretical results for the picocell, microcell and macrocell environments, when compared with previous models and available measurements, are found to be realistic and generic. In macrocell environment, the model incorporates the effect of distant scattering structures in addition to the local ones. Since the angular spread is a key factor of the second order statistics of fading processes in wireless communications, the thesis proposes a novel generalized method of quantifying the angular spread of the multipath power distribution. The proposed method provides almost all parameters about the angular spread, which can be further used for calculating more accurate spatial correlations and other statistics of multipath fading channels. The degree of accuracy in such correlation calculations can lead to the computation of exact separation distances among array elements required for maximizing capacity in MIMO systems or diversity antennas. The proposed method is also helpful in finding the exact standard deviation of the truncated angular distributions and angular data acquired in measurement campaigns. This thesis also indicates the significance of the effects of angular distribution truncation on the angular spread. Due to the importance of angular spread in the fading statistics, it is proposed as the goodness-of-fit measure in measurement campaigns. In this regard, comparisons of some notable azimuthal models with the measurement results are shown. The effect of mobile motion on the spatial and temporal characteristics of the channel is also discussed. Three mobile motion scenarios are presented, which can be considered to be responsible for the variations of the spatio-temporal statistical parameters of the multipath signals. Two different cases are also identified, when the terrain and clutter of the mobile surroundings have an additional effect on the temporal spread of the channel during mobile motion. The effect of increasing mobile-base separation on the angular and temporal spreads is elaborated in detail. The proposed theoretical results in spatial characteristics can be extended to characterizing and tracking transient behavior of Doppler spread in time-varying fast fading channels; likewise the proposed theoretical results in temporal characteristics can be utilized in designing efficient equalizers for combating inter-symbol interference (ISI) in time-varying frequency-selective fading channels. In the last part of the thesis, a linear state-space model is developed for signature sequence adaptation over time-varying fast fading channels in DS-CDMA systems. A decision directed adaptive algorithm, based on the proposed state-space model and Kalman filter, is presented. The algorithm outperforms the gradient-based algorithms in tracking the received distorted signature sequence over time-varying fast fading channels. Simulation results are presented which show that the performance of a linear adaptive receiver can be improved significantly with signature tracking on high Doppler spreads in DS-CDMA systems.

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Estimating the carrier frequency from a modulated waveform is one of the most important functions of a coherent signal receiver. Good performance and low bit error rates are obtained by coherent demodulation. Therefore, exact knowledge of the received signal carrier frequency is critical for communication systems. Also due to the spectral crowding, a high probability of channel interference can be observed. Under moderate carrier frequency offsets, data-aided estimators have been developed which have a high accuracy of estimation. However, for high frequency offsets the frequency estimator does not have the information of data or timing. In this thesis we propose a parametric based carrier frequency estimation of GMSK, which has improved performance over ad-hoc methods (delay and multiply) and has high resolution capability. In this thesis three methods are implemented over GMSK data to improve the performance and their results compared with the standard delay and multiply method. Two of these methods are parametric based estimators and one is a fast frequency estimator. Parametric based estimators were chosen partly due to their high resolution capabilities and mainly for their proven performance. Parametric based estimators were seen to have high computational load, and hence an alternate fast frequency estimator was implemented. The tradeoffs involved with respect to computational load and performance were shown. The contributions of this thesis include the verification of the validity of applying a parametric based approach on GMSK data, and compare the performances of parametric methods and fast frequency estimator. It is showii that such an approach has a better performance compared to non-data aided ad-hoc delay. and multiply methods. A closed loop configuration of the open loop parametric methods is suggested in the end. / Graduation date: 2004 / Best scan available. Figures are light on the original.

Due to the rapid growth of wireless technology, there has been a growing interest in the capabilities of ad hoc networks connecting mobile phones, PDAs and laptop computers. The distributed and self-configurable capabilities of ad hoc networks make them very attractive for some applications such as tactical communication for military, search and rescue mission, disaster recovery, conferences, lectures, etc. In this thesis, we describe several new time scheduling algorithms for multihop packet radio networks; MaxThrou, MinDelay, ECTS (Energy Conserving Transmission Scheduling) and LA-TSMA (Location-Aided Time-Spread Multiple-Access). The MaxThrou and MinDelay algorithms focus on maximizing the system throughput and minimizing the delay bound by using constant weight codes. In these algorithms, each mobile host is assigned a word from an appropriate constant weight code of length n, distance d and weight w. The host can send a message at the j[superscript th] slot provided the assigned code has a 1 in this j[superscript th] bit. The MaxThrou and MinDelay scheduling algorithms are better than the previously known algorithms in terms of the minimum throughput per node and/or the delay bound. Since most of mobile hosts are operated using the scarce battery, and the battery life is not expected to increase significantly in the near future, energy efficiency is a critical issue in ad hoc networks. The ECTS algorithm conserves the power using strategies that allow the network interface to use the low power sleep mode instead of the idle mode, and also eliminates data collisions by introducing Request-To-Send (RTS) and Clear-To-Send (CTS) control slots. Simulation study shows that the ECTS algorithm outperforms previously known protocols. Due to the increasing popularity of mobile networking systems, the scalability becomes a significant new challenge for ad hoc network protocols. To provide a scalable solution for mobile ad hoc networks, we introduce the LA-TSMA algorithm. Instead of assigning a globally unique TSV to each host as done in previous topology-transparent scheduling algorithms, the proposed algorithm assigns a locally unique TSV to each host. In LA-TSMA, a territory is divided into zones, and the mobile hosts located in different zones can be assigned the same TSV. / Graduation date: 2003

This master’s thesis has been written within the field of Electrical Engineering at the Department of Science and Technology, Linköping University. The work has been carried out at Ericsson’s site in Linköping during the spring of 2010. The purpose of this master thesis was to construct a model which could capture and present the utilization rate of test equipment at a telecom company in general. Since this field has not been studied very much in the past, it was decided to study a model from the production industry and try to reuse some of the basic ideas from this model. From this generic model a recommendation is given as to how the model could be used by implementing a Common Utilization Tool, which could be used to store, configure and present utilization data from all types of equipment in Ericsson’s test environment. This common utilization tool will use measurement modules that will both collect and classify the state of the equipment and deliver the result to a common database. To this Common Utilization Tool a measurement module has been implemented which samples Base Station Controllers (BSC) in Ericsson’s test environment state; used, unused and down. This implementation is also validated against real measured data from testers to conclude if the results are accurate.

Thesis (MCIS - Computer and Information Sciences) -- AUT University, 2008. / Includes bibliographical references. Also held in print ( xi, 105 leaves : ill. ; 30 cm.) in the Archive at the City Campus (T 621.382 LOL)

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

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 203-208).