Digital communication networks incorporating mobile data terminals

The use of digital communication systems is increasing very rapidly. This is due to lower system implementation cost compared to analogue transmission and at the same time, the ease with which several types of data sources (data, digitised speech and video, etc.) can be mixed. The emergence of packet broadcast techniques as an efficient type of multiplexing, especially with the use of contention random multiple access protocols, has led to a wide-spread application of these distributed access protocols in local area networks (LANs) and a further extension of them to radio and mobile radio communication applications. In this research, a proposal for a modified version of the distributed access contention protocol which uses the packet broadcast switching technique has been achieved. The carrier sense multiple access with collision avoidance (CSMA/CA) is found to be the most appropriate protocol which has the ability to satisfy equally the operational requirements for local area networks as well as for radio and mobile radio applications. The suggested version of the protocol is designed in a way in which all desirable features of its precedents is maintained. However, all the shortcomings are eliminated and additional features have been added to strengthen its ability to work with radio and mobile radio channels. Operational performance evaluation of the protocol has been carried out for the two types of non-persistent and slotted non-persistent, through mathematical and simulation modelling of the protocol. The results obtained from the two modelling procedures validate the accuracy of both methods, which compares favourably with its precedent protocol CSMA/CD (with collision detection). A further extension of the protocol operation has been suggested to operate with multichannel systems. Two multichannel systems based on the CSMA/CA protocol for medium access are therefore proposed. These are; the dynamic multichannel system, which is based on two types of channel selection, the random choice (RC) and the idle choice (IC), and the sequential multichannel system. The latter has been proposed in order to supress the effect of the hidden terminal, which always represents a major problem with the usage of the contention random multiple access protocols with radio and mobile radio channels. Verification of their operation performance evaluation has been carried out using mathematical modelling for the dynamic system. However, simulation modelling has been chosen for the sequential system. Both systems are found to improve system operation and fault tolerance when compared to single channel operation.

Transmission of data under multipath transmission conditions

The explosive growth in microprocessor technology and the increasing use of computers to store information has increased the demand for data communication channels. Because of this, data communication to mobile vehicles is increasing rapidly. In addition, data communication is seen as a method of relieving the current congestion of mobile radio telephone bands in the U.K. Highly reliable data communication over mobile radio channels is particularly difficult to achieve, primarily due to fading caused by multipath interference. In this thesis a data communication system is described for use over radio channels impaired by multipath interference. The thesis first describes radio communication in general, and multipath interference In particular. The practical aspects of fading channels are stressed because of their importance in the development of the system. The current U.K. land mobile radio scene is then reviewed, with particular emphasis on the use of existing mobile radio equipment for data communication purposes. The development of the data communication system is then described. This system is microprocessor based and uses an advanced form of automatic request repeat (ARQ) operation. It can be configured to use either existing radio-telephone equipment, totally new equipment specifically designed for data communication, or any combination of the two. Due to its adaptability, the system can automatically optimise itself for use over any channel, even if the channel parameters are changing rapidly. Results obtained from a particular implementation of the system, which is described in full, are presented. These show how the operation of the system has to change to accomodate changes in the channel. Comparisons are made between the practical results and the theoretical limits of the system.

Cryptographic techniques for personal communication systems security

The advent of personal communication systems within the last decade has depended upon the utilization of advanced digital schemes for source and channel coding and for modulation. The inherent digital nature of the communications processing has allowed the convenient incorporation of cryptographic techniques to implement security in these communications systems. There are various security requirements, of both the service provider and the mobile subscriber, which may be provided for in a personal communications system. Such security provisions include the privacy of user data, the authentication of communicating parties, the provision for data integrity, and the provision for both location confidentiality and party anonymity. This thesis is concerned with an investigation of the private-key and public-key cryptographic techniques pertinent to the security requirements of personal communication systems and an analysis of the security provisions of Second-Generation personal communication systems is presented. Particular attention has been paid to the properties of the cryptographic protocols which have been employed in current Second-Generation systems. It has been found that certain security-related protocols implemented in the Second-Generation systems have specific weaknesses. A theoretical evaluation of these protocols has been performed using formal analysis techniques and certain assumptions made during the development of the systems are shown to contribute to the security weaknesses. Various attack scenarios which exploit these protocol weaknesses are presented. The Fiat-Sharmir zero-knowledge cryptosystem is presented as an example of how asymmetric algorithm cryptography may be employed as part of an improved security solution. Various modifications to this cryptosystem have been evaluated and their critical parameters are shown to be capable of being optimized to suit a particular applications. The implementation of such a system using current smart card technology has been evaluated.

An analysis of the effectiveness of a behavioural based safety intervention in a UK paper mill

This research examines a behavioural based safety (BBS) intervention within a paper mill in the South East of England. Further to this intervention two other mills are examined for the purposes of comparison — one an established BBS programme and the other an improving safety management system through management ownership. BBS programmes have become popular within the UK, but most of the research about their efficacy is carried out by the BBS providers themselves. This thesis aims to evaluate a BBS intervention from a standpoint which is not commercially biased in favour of BBS schemes. The aim of a BBS scheme is to either change personnel behaviours or attitudes, which in turn will positively affect the organisation's safety culture. The research framework involved a qualitative methodology in order to examine the effects of the intervention on the paper mill's safety culture. The techniques used were questionnaires and semi structured interviews, in addition to observation and discussions which were possible because of the author's position as participant observer. The results demonstrated a failure to improve any aspect of the mill's safety culture, which worsened following the BBS intervention. Issues such as trust, morale, communication and support of management showed significant signs of negative workforce response. The paper mill where the safety management system approach was utilised demonstrated a significantly improved safety culture and achieved site ownership from middle managers and supervisors. Research has demonstrated that a solid foundation is required prior to successfully implementing a BBS programme. For a programme to work there must be middle management support in addition to senior management commitment. If a trade union actively distances itself from BBS, it is also unlikely to be effective. This thesis proposes that BBS observation programmes are not suitable for the papermaking industry, particularly when staffing levels are low due to challenging economic conditions. Observers are not available when there are high hazard situations and this suggests that BBS implementation is not the correct intervention for the paper industry.

The design of fault tolerant software for loosely coupled distributed systems

Requirements for systems to continue to operate satisfactorily in the presence of faults has led to the development of techniques for the construction of fault tolerant software. This thesis addresses the problem of error detection and recovery in distributed systems which consist of a set of communicating sequential processes. A method is presented for the `a priori' design of conversations for this class of distributed system. Petri nets are used to represent the state and to solve state reachability problems for concurrent systems. The dynamic behaviour of the system can be characterised by a state-change table derived from the state reachability tree. Systematic conversation generation is possible by defining a closed boundary on any branch of the state-change table. By relating the state-change table to process attributes it ensures all necessary processes are included in the conversation. The method also ensures properly nested conversations. An implementation of the conversation scheme using the concurrent language occam is proposed. The structure of the conversation is defined using the special features of occam. The proposed implementation gives a structure which is independent of the application and is independent of the number of processes involved. Finally, the integrity of inter-process communications is investigated. The basic communication primitives used in message passing systems are seen to have deficiencies when applied to systems with safety implications. Using a Petri net model a boundary for a time-out mechanism is proposed which will increase the integrity of a system which involves inter-process communications.

Perceptions of technological change : the attitude of managers towards group technology in the United States food equipment industry

In the center of today's continued and rapid technological change and ever competitive environment of the next millennium, manufacturers must realize that unless they are ready to consider and evaluate new technologies brought onto them, they may fail to adequately respond to the challenges that lie ahead of them. This research was designed to determine the consistency of the perceptions of technical and non-technical administrators, in manufacturing environment, towards technological change and group technology as an advanced manufacturing system. This research has included a review of literature with references to technological change, justification and implementation processes, and various manufacturing systems including group technology and its benefits. This research has used the research method of empirical analysis (quantitative) and case studies (qualitative) to research perceptions of technical and non-technical administrators towards technological change and group technology. Sixty-four (64) technical and fifty-one (51) nontechnical administrators from fifty (50) manufacturing organizations in the United States of America responded to the mail survey questionnaire used in this research. Responses were analyzed using the Repeated Measures ANOVA procedure to compare mean responses of each group. Two correlation analyses, Cronback Coefficient Alpha and Pearson Correlation Coefficient, were also performed to determine the reliability of the questionnaire as well as the degree of correlation of perceptions between these two groups. This research, through the empirical analysis, has found that perceptions of the technical and non-technical administrators towards group technology were not consistent. In other words, they did not perceive the benefits of group technology in the same manner to the overall organizational performance. This finding was significant since it provided the first clear and comprehensive view of the technical and non-technical administrators' perception towards group technology and technological change, in Food Equipment Manufacturer Industry, in United States of America. In addition, a number of cases were analyzed and the results have supported those of the quantitative analysis. Therefore, this research not only has provided basic data, which was unavailable prior to this investigation, but it also provided a basis for future studies.

Study of management decision making by ward sisters in a hospital and the effects on decision making after the implementation of a decision support sytem

This thesis considers management decision making at the ward level in hospitals especially by ward sisters, and the effectiveness of the intervention of a decision support system. Nursing practice theories were related to organisation and management theories in order to conceptualise a decision making framework for nurse manpower planning and deployment at the ward level. Decision and systems theories were explored to understand the concepts of decision making and the realities of power in an organisation. In essence, the hypothesis was concerned with changes in patterns of decision making that could occur with the intervention of a decision support system and that the degree of change would be governed by a set of `difficulty' factors within wards in a hospital. During the course of the study, a classification of ward management decision making was created, together with the development and validation of measuring instruments to test the research hypothesis. The decision support system used was rigorously evaluated to test whether benefits did accrue from its implementation. Quantitative results from sample wards together with qualitative information collected, were used to test this hypothesis and the outcomes postulated were supported by these findings. The main conclusion from this research is that a more rational approach to management decision making is feasible, using information from a decision support system. However, wards and ward sisters that need the most assistance, where the `difficulty' factors in the organisation are highest, benefit the least from this type of system. Organisational reviews are needed on these identified wards, involving managers and doctors, to reduce the levels of un-coordinated activities and disruption.

An institutional perspective on management accounting change in the public sector : a case study from Canada

This thesis reports on a four-year field study conducted at the Saskatchewan regional office of the Department of Indian Affairs and Northern Development, a large department of the Government of Canada. Over the course of the study, a sweeping government-wide accounting reform took place entitled the Financial Information Strategy. An ethnographic study was conducted that documented the management accounting processes in place at the regional office prior to the Financial Information Strategy reform, the organization’s adoption of the new accounting system associated with this initiative, and the state of the organization’s management accounting system once the implementation was complete. This research, therefore, captures in detail a management accounting change process in a public sector organization. This study employs an interpretive perspective and draws on institution theory as a theoretical framework. The concept of loose coupling and insights from the literature on professions were also employed in the explanation-building process for the case. This research contributes to institution theory and the study of management accounting change by recognizing conflicting institutional forces at the organizational level. An existing Old Institutional Economics-based conceptual framework for management accounting change is advanced and improved upon through the development of a new conceptual framework that incorporates the influence of wider institutional forces, the concepts of open and closed organizational systems and loose coupling, and the recognition of varying rates of change and institutionalization of organizational activity sets. Our understanding of loose coupling is enhanced by the interpretation of institutional influences developed in this study as is the role of professionalization as a normative influence in public sector organizations.

Enhancing delivery of health behaviour change interventions in primary care: a meta-synthesis of views and experiences of primary care nurses

Objective To systematically find and synthesise qualitative studies that elicited views and experiences of nurses involved in the delivery of health behaviour change (HBC) interventions in primary care, with a focus on how this can inform enhanced delivery and adherence to a structured approach for HBC interventions. Methods Systematic search of five electronic databases and additional strategies to maximise identification of studies, appraisal of studies and use of meta-synthesis to develop an inductive and interpretative form of knowledge synthesis. Results Nine studies met the inclusion criteria. Synthesis resulted in the development of four inter-linking themes; (a) actively engaging nurses in the process of delivering HBC interventions, (b) clarifying roles and responsibilities of those involved, (c) engaging practice colleagues, (d) communication of aims and potential outcomes of the intervention. Conclusion The synthesis of qualitative evidence resulted in the development of a conceptual framework that remained true to the findings of primary studies. This framework describes factors that should be actively promoted to enhance delivery of and adherence to HBC interventions by nurses working in primary care. Practice implications The findings can be used to inform strategies for researchers, policymakers and healthcare providers to enhance fidelity and support delivery of HBC interventions.

The design and implementation of a portable operating system for microcomputers

Communication and portability are the two main problems facing the user. An operating system, called PORTOS, was developed to solve these problems for users on dedicated microcomputer systems. Firstly, an interface language was defined, according to the anticipated requirements and behaviour of its potential users. Secondly, the PORTOS operating system was developed as a processor for this language. The system is currently running on two minicomputers of highly different architectures. PORTOS achieves its portability through its high-level design, and implementation in CORAL66. The interface language consists of a set of user cotnmands and system responses. Although only a subset has been implemented, owing to time and manpower constraints, promising results were achieved regarding the usability of the language, and its portability.

The interaction between the implementation of an occupational health and safety management system and safety culture:a case study in the rubber industry

A prominent theme emerging in Occupational Health and Safety (OSH) is the development of management systems. A range of interventions, according to a prescribed route detailed by one of the management systems, can be introduced into an organisation with some expectation of improved OSH performance. This thesis attempts to identify the key influencing factors that may impact upon the process of introducing interventions, (according to B88800: 1996, Guide to Implementing Occupational Health and Safety Management Systems) into an organisation. To help identify these influencing factors a review of possible models from the sphere of Total Quality Management (TQM) was undertaken and the most suitable TQM model selected for development and use in aSH. By anchoring the aSH model's development in the reviewed literature a range ofeare, medium and low level influencing factors were identified. This model was developed in conjunction with the research data generated within the case study organisation (rubber manufacturer) and applied to the organisation. The key finding was that the implementation of an OSH intervention was dependant upon three broad vectors of influence. These are the Incentive to introduce change within an organisation which refers to the drivers or motivators for OSH. Secondly the Ability within the management team to actually implement the changes refers to aspects, amongst others, such as leadership, commitment and perceptions of OSH. Ability is in turn itself influenced by the environment within which change is being introduced. TItis aspect of Receptivity refers to the history of the plant and characteristics of the workforce. Aspects within Receptivity include workforce profile and organisational policies amongst others. It was found that the TQM model selected and developed for an OSH management system intervention did explain the core influencing factors and their impact upon OSH performance. It was found that within the organisation the results that may have been expected from implementation of BS8800:1996 were not realised. The OSH model highlighted that given the organisation's starting point, a poor appreciation of the human factors of OSH, gave little reward for implementation of an OSH management system. In addition it was found that general organisational culture can effectively suffocate any attempts to generate a proactive safety culture.

Maintenance of communication in primary classrooms : some evidence for the role of elicitation and code-switching in English medium schools in Kenya, with implications for teaching

This is a study of specific aspects of classroom interaction primary school level in Kenya. The study entailed the identification of the sources of particular communication problems during the change-over period from Kiswahili to English medium teaching in two primary schools. There was subsequently an examination of the language resources which were employed by teachers to maintain pupil participation in communication in the light of the occurrence of possibility of occurrence of specific communication problems. The language resources which were found to be significant in this regard concerned firstly the use of different elicitation types by teachers to stimulate pupils into giving responses and secondly teachers' recourse to code-switching from English to Kiswahili and vice-versa. It was also found in this study that although the use of English as the medium of instruction in the classrooms which were observed resulted in certain communication problems, some of these problems need not have arisen if teachers had been more careful in their use of language. The consideration of this finding, after taking into account the role of different elicitation types and code-switching as interpretable from data samples had certain implications which are specified in the study for teaching in Kenyan primary schools. The corpus for the study consisted of audio-recordings of English, Science and Number-Work lessons which were later transcribed. Relevant data samples were subsequently extracted from transcripts for analysis. Many of the samples have examples of cases of communication breakdowns, but they also illustrate how teachers maintained interaction with pupils who had yet to acquire an operational mastery of English. This study thus differs from most studies on classroom interaction because of its basic concern with the examination of the resources available to teachers for overcoming the problem areas of classroom communication.

West German bank advertising and the East German public:a study in intercultural advertising communication

In the wake of German unification, initial advertising by many West German companies in the new federal states (the former German Democratic Republic - GDR) proved largely ineffective and many advertisers were forced to change their approach to this new market. The advertising task proved even more complicated for banks, because banking existed only at the most basic level in the former GDR. Furthermore, under the old regime, "capitalist" banks represented the very antithesis of the GDR's founding ideology. This analysis of advertising by West German banks - in particular Dresdner Bank - in the new federal states brings together elements of discourse and communication theory, particularly Relevance Theory [Sperber and Wilson 1986], with the overall objective of designing a model of intercultural advertising communication. A series of simple association tasks based on texts from pre-Wende advertisements was completed by a sample of advertisees (as they are called in the study) in Leipzig. The research shows the lack of relevance between the advertiser's understanding of concepts such as "credit", "bank" etc. and the associations which these concepts have for the sample of advertisees. Further analysis reveals that this lack of relevance occurs because advertisers and advertisees assign differing contexts to these concepts when they communicate through advertising. The study concludes that these different contexts, governed by the contrasting ideological, economic and linguistic environments of the advertisers and advertisees, interfere with the effective communication of the advertising message.

Strategies for agricultural change and the UK balance of payments

The world food crisis, Britain's reliance on imported food and feedstuffs and balance of payments difficulties were some of the factors which lent weight to the call for increased self-sufficiency in Britain's agriculture in the 1970s. This project considers two main areas: an investigation of the impact of radical agricultural change, designed to increase self-sufficiency, on the balance of payments; and, an appraisal of the potential role of the food industry within a radically different food system. The study proceeded by: an examination of the principles of agricultural policy and its development in Britain; an overview of the mechanism and meaning of the balance of payments; a consideration of the debate on agricultural import saving; the construction of radical agricultural strategies; the estimation of effects of the strategies, particularly to the balance of. payments; the role of the food industry and possible innovations within the strategies; a case study of textured vegetable proteins; and, the wider implications of implementation of radical agricultural alternatives. Two strategies were considered: a vegan system, involving no livestock; and, an intermediate system, including some livestock and dairy cattle. The study concludes that although agricultural change could in principle make a contribution to the balance of payments, implementation of agricultural change cannot be justified for this purpose alone. First, balance of payments problems can be solved by more appropriate methods. Second, the UK' s balance of payments problem has disappeared for the time being owing to North Sea oil and economic recession. Third, the political and social consequences of the changes investigated would be unacceptable. Progress in UK food policy is likely to be in the form of an integrated food and health policy.

Semantics of query-driven communication of exact values

We address the question of how to communicate among distributed processes valuessuch as real numbers, continuous functions and geometrical solids with arbitrary precision, yet efficiently. We extend the established concept of lazy communication using streams of approximants by introducing explicit queries. We formalise this approach using protocols of a query-answer nature. Such protocols enable processes to provide valid approximations with certain accuracy and focusing on certain locality as demanded by the receiving processes through queries. A lattice-theoretic denotational semantics of channel and process behaviour is developed. Thequery space is modelled as a continuous lattice in which the top element denotes the query demanding all the information, whereas other elements denote queries demanding partial and/or local information. Answers are interpreted as elements of lattices constructed over suitable domains of approximations to the exact objects. An unanswered query is treated as an error anddenoted using the top element. The major novel characteristic of our semantic model is that it reflects the dependency of answerson queries. This enables the definition and analysis of an appropriate concept of convergence rate, by assigning an effort indicator to each query and a measure of information content to eachanswer. Thus we capture not only what function a process computes, but also how a process transforms the convergence rates from its inputs to its outputs. In future work these indicatorscan be used to capture further computational complexity measures. A robust prototype implementation of our model is available.