Typescript (photocopy). / Digitized by Kansas Correctional Industries

Dissertation (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Though not so prominent as the wide band, high speed, mainstream development of data communication networks, cost and particular bandwidth limitations, still ensure extensive and continuing use of low-speed, half-duplex data link equipment. Most of these applications are radio based and aimed towards telemetry systems serving a wide range of utilities. Experience has shown that systems engineering for this type of installation, is seldom undertaken to a satisfactory analytical level. Investigation of published analyses of CSMA protocols in general, has indicated scope of extension of theoretical work to include system parameters for the type of protocol investigated in this dissertation. This dissertation describes the mathematical modeling of such a strategy by utilising a significantly modified, finite source, transition state-matrix approach derived from queueing theory. The contribution of the dissertation is to include system overhead parameters, such as backoff strategy, channel noise, equipment rise times, propagation- and retry delays, into the abovementioned model. The latter provides a relatively straightforward and readily applicable method for system analysis and performance prediction. A further contribution is the presentation of a software emulation with which different strategies could be simulated, allowing for adjustment of all design parameters. The simulation is intended for parallel and confimatory use with the theoretical model. A dual set of tools, theoretical and emulation based, is thus contributed to assist with the system design, performance prediction and protocol selection process. / AFRIKAANSE OPSOMMING: Alhoewel nie so prominent soos die wyeband, hoëspoed, hoofstroom ontwikkeling van datakommunikasie netwerke nie, verseker koste en spesifieke bandwydte beperkings nog die uitgebreide en voortdurende gebruik van laespoed half-dupleks data verbindingstoerusting. Meeste van die toepassings is radio gebaseer en gerig op telemetriestelsels wat deur 'n wye verskeidenheid diensverskaffers benut word. Stelselontwerp vir hierdie tipe installasies word selde op analitiese vlak benader. Ondersoek van gepubliseerde analises van kontensieprotokolle in die algemeen, het ruimte aangetoon vir die uitbreiding van bestaande teoretiese werk om stelselveranderlikes soos van toepassing op die tipe protokol in hierdie proefskrif ondersoek, in te sluit. Hierdie proefskrif beskryf die wiskundige modelering van sodanige strategie, deur gebruik te maak van 'n beduidend veranderde eindige bron, oorgangs-toestandmatriks benadering, afgelei van touteorie. Die bydrae van hierdie proefskrif is die insluiting van oorhoofse stelselveranderlikes, soos herhaal strategie, kanaalruis, toerusting stygtye, herhaal- en voortplantingsvertragings, in bogenoemde model. Laasgenoemde verskaf 'n relatief eenvoudige en maklik toepasbare metode vir stelselanalise en werkverrigtingvoorspelling. 'n Verder bydrae is die daarstelling van 'n sagteware simulasie waarmee verskillende strategieë nageboots kan word. Verstelling van alle ontwerpparameters word ondersteun. Die simulasie is bedoel vir parallelle en bevestigende gebruik tesame met die teoretiese model. 'n Dubbele, teoreties- en simulasie gebaseerde benadering, word dus aangebied vir gebruik by stelselontwerp, gedragsvoorspelling en optimale protokolseleksie.

No description available.

This paper describes the design and simulation of a network interface unit (NIU) for a picture archiving and communication system (PACS) network called PACnet. PACnet is a dual fiber optic ring network under development at the Computer Engineering Research Laboratory of the University of Arizona. This network integrates voice, data, and image communications in a hospital environment and supports a throughput rate between 200-500 megabits per second. At each node in the network, an NIU implements the Data Link Layer and Physical Layer protocols of PACnet. The initial network interface unit design for PACnet was a functional description of NIU protocols and major components. In order to construct a demonstration prototype of PACnet,the NIU description must be refined and an architecture must be specified. The NIU design is specified and simulated using the hardware description language VHDL. Simulation results provide information on NIU timing characteristics and logic families required to implement the NIU.

M.Ing. (Electrical and Electronic Engineering) / In this study, the problem of correcting burst of adjacent deletions by adapting product codes was investigated. The first step in any digital transmission is to establish synchronization between the sending and receiving nodes. This initial synchronization ensures that the receiver samples the information bits at the correct interval. Unfortunately synchronization is not guaranteed to last for the entire duration of data transmission. Though synchronization errors rarely occur, it has disastrous effects at the receiving end of transmission. These synchronization errors are modelled as either insertions or deletions in the transmitted data. In the best case scenario, these errors are restricted to single bit errors. In the worst case scenario, these errors lead to bursts of bits being incorrect. If these synchronization errors are not detected and corrected, it can cause a shift in the transmitted sequence which in turn leads to loss of synchronization. When a signal is subjected to synchronization errors it is difficult accurately recover the original data signal. In addition to the loss of synchronization, the information transmitted over the channel is also subjected to noise. This noise in the channel causes inversion errors within the signal. The objective of this dissertation is to investigate if an error correction scheme can be designed that has the ability to detect and correct adjacent bursts of deletions and random inversion errors. This error correction scheme needed to make use of a product code matrix structure. This product matrix needed to incorporate both an error correction and synchronization technique. The chosen error correcting techniques were Hamming and Reed-Solomon codes. The chosen synchronization techniques for this project were the marker technique or an adaptation of the Hamming code technique. In order to find an effective model, combinations of these models were simulated and compared. From the research obtained and analyzed in this document it was found that, depending on the desired performance, complexity and code rate, an error correction scheme can be used in the efficient correction of bursts of adjacent deletions by adapting product codes.

Promoting healthcare and wellbeing requires the dedication of a multi-tiered health service delivery system, which is comprised of specialists, medical doctors and nurses. A holistic view to a patient care perspective involves emotional, mental and physical healthcare needs, in which caring is understood as the essence of nursing. Properly and efficiently capturing and managing nursing knowledge is essential to advocating health promotion and illness prevention. This thesis proposes a document-indexing framework for automating classification of nursing knowledge based on nursing theory and practice model. The documents defining the numerous categories in nursing care model are structured with the help of expert nurse practitioners and professionals. These documents are indexed and used as a benchmark for the process of automatic mapping of each expression in the assessment form of a patient to the corresponding category in the nursing theory model. As an illustration of the proposed methodology, a prototype application is developed using the Latent Semantic Indexing (LSI) technique. The prototype application is tested in a nursing practice environment to validate the accuracy of the proposed algorithm. The simulation results are also compared with an application using Lucene indexing technique that internally uses modified vector space model for indexing. The result comparison showed that the LSI strategy gives 87.5% accurate results compared to the Lucene indexing technique that gives 80% accuracy. Both indexing methods maintain 100% consistency in the results. / by Sucharita Vijay Chichanikar. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Next, we investigate several models of TRC including the discrete memoryless TRC, the Gaussian TRC and the bandlimited Gaussian TRC, and prove an outer bound on the capacity region of each of the TRC models. In particular, the outer bound on the capacity region of the bandlimited Gaussian TRC is a theoretical outer bound on the capacity region achievable by physical-layer network coding (PNC). Furthermore, we model a cellular relay network consisting of multiple users, multiple relays and multiple base stations as a collection of two-node point-to-point systems and three-node networks, where each two-node point-to-point system consists of two bandlimited Gaussian channels and each three-node network consists of a bandlimited Gaussian TRC. We obtain performance bounds of PNC on the cellular relay network by simulation and our simulation results show that the average maximum equal-rate throughput over all users under every PNC strategy investigated is generally worse than the average equal-rate throughput over all users under some routing strategy. This is possibly due to larger interference among the nodes under the PNC strategies compared with the routing strategy. / Our investigation of wireless relay networks begins by studying the two-way relay channel (TRC), in which a user and a base station exchange their messages with the help of a middle relay. We model the TRC as a three-node point-to-point relay network and propose practical symbol-level network coding schemes for the three-node network. We obtain several rate regions achievable by the network coding schemes and show that the use of symbol-level network coding rather than routing alone always enlarges the achievable rate region. Inparticular, the use of symbol-level network coding always increases the maximum equal-rate throughput. Furthermore, we model a cellular relay network consisting of multiple users, multiple relays and multiple base stations as a collection of two-node point-to-point systems and three-node point-to-point relay networks where each point-to-point channel is modeled as a bandlimited Gaussian channel. We propose several practical symbol-level network coding schemes on the network and investigate the benefit of symbol-level network coding by simulation. Our simulation results show that the use of symbol-level network coding rather than routing alone increases the average maximum equal-rate throughput over all users. / Fong, Lik Hang Silas. / Adviser: Yeung, Wai-Ho Raymond. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 267-270). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

by Wan Wai Leung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 77-[80]). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Wireless Multimedia System --- p.1 / Chapter 1.2 --- Motivation of this thesis --- p.2 / Chapter 1.3 --- The theme of this thesis --- p.4 / Chapter 1.3.1 --- System Model and Assumptions --- p.4 / Chapter 1.3.2 --- Outline of the thesis --- p.5 / Chapter 2 --- Overview of TDMA/FDMA Digital Cellular Systems --- p.7 / Chapter 2.1 --- The Cellular Concept --- p.7 / Chapter 2.2 --- Channel Assignment Strategies --- p.9 / Chapter 2.2.1 --- Fixed Channel Assignment --- p.9 / Chapter 2.2.2 --- Dynamic Channel Assignment --- p.9 / Chapter 2.3 --- Multiple Access Techniques --- p.10 / Chapter 2.3.1 --- Introduction to Multiple Access --- p.10 / Chapter 2.3.2 --- Frequency Division Multiple Access - FDMA --- p.11 / Chapter 2.3.3 --- Time Division Multiple Access - TDMA --- p.12 / Chapter 2.4 --- A TDMA/FDMA System - GSM --- p.13 / Chapter 2.4.1 --- Global System for Mobile --- p.13 / Chapter 2.4.2 --- GSM radio subsystem --- p.13 / Chapter 3 --- Multi-rate Data in TDMA/FDMA Digital Cellular Systems --- p.17 / Chapter 3.1 --- Incorporation of Multimedia Data --- p.17 / Chapter 3.2 --- A Global Optimal Strategy --- p.19 / Chapter 3.2.1 --- Channel Rearrangement --- p.19 / Chapter 3.2.2 --- Analytical Performance Analysis of a Special Case --- p.21 / Chapter 3.2.3 --- Numerical Results --- p.24 / Chapter 3.2.4 --- Issues in Channel Rearrangement --- p.25 / Chapter 4 --- Multiple Slots Allocations --- p.26 / Chapter 4.1 --- Introduction --- p.26 / Chapter 4.2 --- No-Split Algorithm --- p.27 / Chapter 4.2.1 --- No-Split Algorithm --- p.27 / Chapter 4.2.2 --- Pros and Cons --- p.28 / Chapter 4.3 --- Best Fit Algorithm --- p.29 / Chapter 4.3.1 --- Best Fit Algorithm --- p.29 / Chapter 4.3.2 --- Optimization --- p.31 / Chapter 4.3.3 --- Pros and Cons --- p.32 / Chapter 4.4 --- Comparison of the two algorithms --- p.32 / Chapter 5 --- Buddy Algorithm --- p.37 / Chapter 5.1 --- Introduction --- p.37 / Chapter 5.2 --- Buddy System in Memory Management --- p.38 / Chapter 5.3 --- Buddy Algorithm --- p.40 / Chapter 5.3.1 --- Adaptation in slot allocation --- p.40 / Chapter 5.3.2 --- Data structure --- p.40 / Chapter 5.3.3 --- Slot allocation --- p.40 / Chapter 5.3.4 --- Slot deallocation --- p.44 / Chapter 5.4 --- Inference Property --- p.45 / Chapter 5.4.1 --- Proof of the Inference Property --- p.47 / Chapter 5.5 --- Pros and Cons --- p.49 / Chapter 6 --- Performance Study --- p.51 / Chapter 6.1 --- Introduction --- p.51 / Chapter 6.2 --- Fixed Channel Assignment --- p.52 / Chapter 6.2.1 --- System Parameters --- p.52 / Chapter 6.2.2 --- Simulation Results --- p.53 / Chapter 6.3 --- Dynmaic Channel Assignment --- p.55 / Chapter 6.3.1 --- System Parameters --- p.55 / Chapter 6.3.2 --- Simulation Results --- p.56 / Chapter 7 --- A Case Study - H.263 Video Coding --- p.59 / Chapter 7.1 --- CCITT H.263 Image Compression --- p.59 / Chapter 7.2 --- On a GSM Network --- p.60 / Chapter 8 --- Conclusion --- p.63 / Chapter A --- A General Data + Voice System with Channel Rearrangement --- p.65 / Chapter A.1 --- System Model --- p.65 / Chapter A.2 --- Markovian Analysis --- p.66 / Chapter B --- NP-Completeness Proof of the Best Fit Algorithm --- p.69 / Chapter B.1 --- CONSTRAINT SUBSET-SUM Problem --- p.69 / Chapter B.2 --- BEST-FIT Problem --- p.72 / Chapter C --- Proof of Proposition 5.2 --- p.74 / Chapter C.1 --- Upper Bound on Demand Advancement --- p.74 / Chapter C.2 --- Proof of Proposition 5.2 --- p.75 / Bibliography --- p.77

"Recently the Internet has been increasingly used for multi-party applications like video-conferencing, video-on-demand and shared white-boards. Multicast extensions to IP to support multi-party applications are best effort, often resulting in packet loss within the network. Since some multicast applications can not tolerate packet loss, most of the existing reliable multicast schemes recover each and every lost packet. However, multimedia applications can tolerate a certain amount of packet loss and are sensitive to long recovery delays. We propose a new loss recovery technique that selectively repairs lost packets based upon the amount of packet loss and delay expected for the repair. Our technique sends a special WAIT message down the multicast tree in the event a loss is detected in order to reduce the number of retransmission requests. We also propose an efficient sender initiated multicast trace-route mechanism for determining the multicast topology and a mechanism to deliver the topology information to the multicast session participants. We evaluate our proposed technique using an event driven network simulator, comparing it with two popular reliable multicast protocols, SRM and PGM. We conclude that our proposed WAIT protocol can reduce the overhead on a multicast session as well as improve the average end-to-end latency of the session."

Typescript (photocopy). / Digitized by Kansas Correctional Industries