Dissertations / Theses on the topic 'Communicative Output'

The market’s challenges bring firms to collaborate with other organizations in order to create Joint Ventures, Alliances and Consortia that are defined as “Interorganizational Networks” (IONs) (Provan, Fish and Sydow; 2007). Some of these IONs are managed through a shared partecipant governance (Provan and Kenis, 2008): a team composed by entrepreneurs and/or directors of each firm of an ION. The research is focused on these kind of management teams and it is based on an input-process-output model: some input variables (work group’s diversity, intra-team's friendship network density) have a direct influence on the process (team identification, shared leadership, interorganizational trust, team trust and intra-team's communication network density), which influence some team outputs, individual innovation behaviors and team effectiveness (team performance, work group satisfaction and ION affective commitment). Data was collected on a sample of 101 entrepreneurs grouped in 28 ION’s government teams and the research hypotheses are tested trough the path analysis and the multilevel models. As expected trust in team and shared leadership are positively and directly related to team effectiveness while team identification and interorganizational trust are indirectly related to the team outputs. The friendship network density among the team’s members has got positive effects on the trust in team and on the communication network density, and also, through the communication network density it improves the level of the teammates ION affective commitment. The shared leadership and its effects on the team effectiveness are fostered from higher level of team identification and weakened from higher level of work group diversity, specifically gender diversity. Finally, the communication network density and shared leadership at the individual level are related to the frequency of individual innovative behaviors. The dissertation’s results give a wider and more precise indication about the management of interfirm network through “shared” form of governance.

The market’s challenges bring firms to collaborate with other organizations in order to create Joint Ventures, Alliances and Consortia that are defined as “Interorganizational Networks” (IONs) (Provan, Fish and Sydow; 2007). Some of these IONs are managed through a shared partecipant governance (Provan and Kenis, 2008): a team composed by entrepreneurs and/or directors of each firm of an ION. The research is focused on these kind of management teams and it is based on an input-process-output model: some input variables (work group’s diversity, intra-team's friendship network density) have a direct influence on the process (team identification, shared leadership, interorganizational trust, team trust and intra-team's communication network density), which influence some team outputs, individual innovation behaviors and team effectiveness (team performance, work group satisfaction and ION affective commitment). Data was collected on a sample of 101 entrepreneurs grouped in 28 ION’s government teams and the research hypotheses are tested trough the path analysis and the multilevel models. As expected trust in team and shared leadership are positively and directly related to team effectiveness while team identification and interorganizational trust are indirectly related to the team outputs. The friendship network density among the team’s members has got positive effects on the trust in team and on the communication network density, and also, through the communication network density it improves the level of the teammates ION affective commitment. The shared leadership and its effects on the team effectiveness are fostered from higher level of team identification and weakened from higher level of work group diversity, specifically gender diversity. Finally, the communication network density and shared leadership at the individual level are related to the frequency of individual innovative behaviors. The dissertation’s results give a wider and more precise indication about the management of interfirm network through “shared” form of governance.

Literature on performance management (PM) indicates that the concept has gained momentum in its use by organisations, with the ultimate goal of improving business performance. It is argued that PM makes significant contributions to individual employees and organisational performance by enabling expectations to be defined and agreed in terms of the role, responsibilities and accountabilities, and providing opportunities for individuals to identify their own goals and to develop their skills and competencies. However, there has been much debate as to whether PM optimises or leads to improved overall business performance as other factors other than human resources policies, such as personality, job role experiences, and structural factors, may have a detrimental influence on job performance. Moreover, several studies have shown that PM, and performance management systems (PMS) has resulted in unintended impacts, both positive and negative, in addition to those sought by organisations. This research is an investigation into the perception of managers and care assistants in private care of the elderly in care homes in Scotland on the impact of performance management systems. Use is made of both PM literature and empirical research to understand the perceived impact of the PMS with the ultimate aim of developing an enhanced PMS framework. In addition to documents review, twenty-four in-depth interviews were conducted, comprising of eight managers and sixteen care assistants drawn from eight different private care homes. The interviews focused on eight key PM elements, the PM concept, goal-setting, performance reviews, performance measurement, supporting performance, rewards system, training and development, and managing underperformance. The interview results from managers and care assistants were compared with the normative/ideal PM practice from the PM literature to determine how PMS is being implemented in the private care homes. The research findings reveal an overall positive perception towards PMS implementation by managers. However, the care assistants raised many of concerns which influenced a negative perception towards the PMS implementation. This was used as the basis for developing recommendations for an enhanced PMS framework. Therecommendations are centred around the identified two main problem areas: management/leadership style and the communication process. In addition to staff involvement in performance planning, and a fair underperformance management process, three other theories: power distance, vertical and horizontal trust, and the principal-agent problem were recommended to private care homes. This would help change the negative perception towards PMS implementation by care assistants.

Introduction Measuring consumer expectations and perceptions of service provision is supported by both practitioners and academics. The National Health Service, as a result of policy reforms and structural changes, recognises the role of the patient in health care and is gradually incorporating patient views in policy and practice. This study explores the experience of the patient and its affect on the expectations and perceptions of the service provision. Two hospitals, antenatal and postnatal groups were utilised to ascertain the views and experiences of pregnant and recently delivered women. Methodology Focus groups were held with women who had delivered, since the implementation of the Patient's Charter, to establish the expectations of the women using the service provision. Issues of priority to these women and the perception of their overall service experience were also considered. In-depth interviews were then conducted with pregnant women to identify expectations of their forthcoming delivery and subsequent in-depth interviews were conducted with the same women once they had delivered their children. This was to evaluate their perceptions and compare them with their initial expectations. Finally, key themes and recurrent ideas were tested, using hypotheses developed after the qualitative research. The questionnaire approach was to substantiate or discount the findings of the first two stages of the research. Dissemination Familiar service quality attributes were recognisable from the analysis of the comments. Although there were issues on which women agreed unanimously, many elements of the service provision were viewed differently by women with experience and women from varying categories of residential area. The results also demonstrated that the use and dependence of referent groups varied between the women and that this was imperative for communication. Statistically, the use of referent groups, substantiated through the questionnaire analysis, provided significant results to support the initial findings. Contribution Using the information from the qualitative research, a Maternity User's Matrix was developed identifying key characteristics of users' of this service provision. The significant results from the quantitative research were used to develop an existing consumer behaviour model. Using expectations, levels of satisfaction and perceptions of consumers, this research has implications for service provision, health practice, future research and service itself.

In this thesis, I adopt the anti-essentialist cultural paradigm to explore the complexity within the processes of both cultural-making and personal acculturation that may occur in an interweaving way within a local cultural arena (Holliday, 2011; 2013).More precisely, I contextualise this study in student group work as the specific cultural arena to investigate the cultural-making process towards group cohesiveness and individual group member's acculturation process. A conceptual framework is suggested after synthesising both the debates between the essentialist and the anti-essentialist cultural paradigms in the field of intercultural communication and the discussions on acculturation in the existing literature. I conceptually argue that culture is constituted by various salient aspects vis-à- vis cohesive thinking and behaviours that are always forming and re-forming. Personal acculturation can be explored through tracing the changes of an individual's cultural realities (Holliday, 2011; 2013). Both of them occur in parallel in a cultural arena (in this case, student group work).Through analysing in-depth, narrative data from 15 participants about their group work experiences, I fine-tune and enrich this conceptual framework with empirical evidence (i.e. the findings) to demonstrate complexity (i.e. uncertainty and fluidity) in the cultural-making process as well as the dynamics and unpredictability of personal acculturation (i.e. an individual presents different trends of the key aspects of acculturation). Furthermore, I also identify four types of personal acculturation trajectories by comparing all the participants' acculturation trajectories. Using this fine-tuned conceptual framework, the author of the thesis strengthens the potential links between the two separate, in parallel, but interrelated processes (e.g. cultural-making process and personal acculturation), which seem not to have been paid enough attention in the existing literature vis-à-vis the study of culture and (personal) acculturation. More importantly, the author argues that the links can be interpreted as an interplay in student group work asthe specific cultural arena.

Design continuously re-defines its meaning. Over the last years, the way designers interpret information, solve problems as well as prototype and express ideas has received increased attention from domains outside of traditional design, especially from the business world. However, much of the design thinking discourse outside of traditional design centres around a few widely-read practitioner books and only builds on a rudimentary understanding of its principles. Likewise, the academic literature only offers a few rigorous investigations of the application of design thinking in the management and innovation domain, especially when it comes to thedevelopment of novice multidisciplinary teams. Therefore, this thesis provides an evaluation of the influence of the following five key themes discussed in the design thinking literature: Team diversity, iteration, learning styles, creative confidence, and team communication. These themes were explored during a quantitative quasi-experimental research study, which was built on a novel research framework. Data wascollected from 42 German research participants over a period of 10 month. The longitudinal perspective enabled the researcher to illustrate how novices develop design thinking competencies in projects over time. While investigating team diversity, multidisciplinary teams were found to produce significantly better project outcomes than single-discipline teams. On the other hand, diversity of personality traits was not found to have a significant effect on the final performance of teams. The exploration of iteration behaviour revealed that multidisciplinary teams did not iterate significantly more than single-discipline teams. In addition, more experienced participants approached design thinking projects slightly less iteratively thannovices. Overall, the degree of iteration was not found to have a significant effect on the final team performance. Regarding the use of different learning styles, it was discovered that, teams with a balance of learning styles achieved significantly better project outcomes than less-balanced teams. In terms of learning styles, participants approached design thinking tasks mainly through rational conceptualisation rather than concrete experience. Theanalysis of individual and team confidence showed that creative confidence developed slowly and linearly over the course of a project, but only partly carried over to new project and team settings. Furthermore, no evidence was found that higher levels of creative confidence directly influenced the quality of the project outcomes. The investigation of team communication revealed that the importance of individuals in design thinking teams significantlychanged over the course of a project. Contrary to previous assumptions, high degrees of internal team cohesion were found to have a significant negative effect on project outcomes. While several of these findings clarify and reiterate existing design thinking theory, others call for an adjustment of theory and highlight the need for more rigorous research. Several recommendations are offered for practitioners, educators, and researchers on how to incorporate the presented findings into practice and future research.

The exponential increase in communications in many different languages brought about by globalization has resulted in a corresponding demand for translation to be done more quickly, but without sacrificing quality. However, there are currently not enough qualified human translators to keep up with the demand. One way in which translators are trying to cope is by turning to technology, including machine translation (MT) systems. MT has the advantage of being able to produce a large volume of translation in a very short time, but it does not always produce high-quality translations. For this reason, MT cannot replace human translation, but it can make translators' work easier by producing rough drafts. Since there are currently many MT systems on the market, there is a real need for an evaluation methodology for translators to help them choose a system that will best meet their needs. As yet, no universally accepted evaluation methodology exists. The objective of this thesis is to develop and test an evaluation methodology that average translators can use to compare off-the-shelf MT systems and select the appropriate one. (Abstract shortened by UMI.)

The thesis project underlines the importance of designing calm and subtle technologies, by exploring how mobile communicative technologies, such as cell phones, could notify their users about incoming information in a more natural, and non-intrusive manner. The aim of the thesis was to find a way for cell phones to act more appropriately in public and social settings, where they now often are considered intrusive due to their uninhibited manifestations.The thesis provides a theoretical understanding of how normative expectations of cell phone conduct are constituted and maintained within public and social settings. The theories are further grounded in practical work, where the project employ user centered design methods and techniques to, in a collaborative manner, together with users explore the research field to generate insights. Solutions have further been prototyped and evaluated together with users in their everyday settings.Taking inspiration from calm technology, the project looks into how information can be notified, in a more subtle manner in the periphery of the user’s attention. Users’ own priming abilities have been considered as a personal way to recognize the notification and to further associate it as relevant information.As a solution for intrusive cell phones, the thesis proposes Knot; a signature based notification system, which builds on friends’ abilities to recognize each other’s characteristic traits. The system consists of a notification rope, which is a free standing phone accessory that twists and turns, when new information is arriving to the user’s cell phone. It can present whom the information is from by shaping itself into the sender’s representative Knot-signature. If the user can recognize the signature, it will immediately trigger a meaningful association to the person who sent the information.The solution builds upon the restrictiveness between those who can associate a certain signature to a certain person, and those who cannot. For those who have the ability to associate to the signature, its role as a notifier will become meaningful and informative, while for others, who do not share this ability, the signature would be subtle and meaningless, and hence not interfering. The thesis exemplifies how interfaces could provide users with output in a more natural way, by considering users’ previous skills and knowledge, and primarily their priming abilities.

Aphasia is an acquired general impairment of the language processes resulting from brain damage that is frequently caused by cerebrovascular accidents (CVAs). Persons with aphasia have a history of retaining important communication competencies that have the potential for helping them succeed in using augmented communication systems. Using augmentative and alternative communication (AAC) systems by adults with aphasia has been studied, but few studies have reported successfully using AAC systems in rehabilitating adults with aphasia. New advanced technologies including the availability of devices that talk, store a lot of information, and are relatively small can give AAC the potential to affect a greater change in functional communication skills for more persons with aphasia, particularly as experience with AAC rehabilitation grows. The purpose of the present study was to determine whether an adult with severe, nonfluent aphasia could communicate independently by adding a voice output communication aid (VOCA) to his natural communication repertoire. This study also sought to answer the following question: Does the addition of a VOCA to natural expression facilitate independent communication in an adult with severe, nonfluent aphasia? One subject was drawn from the out-patient members of a recreationoriented communication treatment group which is conducted at the Portland Veterans' Affairs Medical Center. The subject had been diagnosed with severe, nonfluent aphasia by a certified Speech/Language Pathologist. This study used a single-subject, component assessment research design to explore the relative effectiveness of components in an aphasia and AAC treatment package. It compared the relative effectiveness of Promoting Aphasics' Communicative Effectiveness (PACE) only treatment using natural communication strategies with that of PACE treatment for natural strategies plus a VOCA component. The subject's attempts to convey information were videotaped and analyzed using mean scores and a split-middle method of trend estimation to determine whether performance differences existed under two treatment conditions. The data for the number of conversational turns show an increase in the number of conversational turns which confirms an overall decrease in efficiency of communication for a severely aphasic person in this structured task in the augmented condition. Second, although the data for the number of communication breakdowns, the number of repair turns, and the repair turns as a percentage of total turns show a decline which would confirm an overall increase in effectiveness, this study does not conclusively demonstrate that the use of a VOCA enhances communication in this setting for this person compared to PACE only treatment. Lastly, the data for the number of messages conveyed correctly show little change which confirms by the measure used in this study, no difference in accuracy of communication for this activity in the augmented condition.

Design and analysis of random-like codes for various multiple-input and multiple-output communication systems are addressed in this work. Random-like codes have drawn significant interest because they offer capacity-achieving performance. We first consider the analysis and design of low-density parity-check (LDPC) codes for turbo multiuser detection in multipath CDMA channels. We develop techniques for computing the probability density function (pdf) of the extrinsic messages at the output of the soft-input soft-output (SISO) multiuser detectors as a function of the pdf of input extrinsic messages, user spreading codes, channel impulse responses, and signal-to-noise ratios. Using these techniques, we are able to accurately compute the thresholds for LDPC codes and design good irregular LDPC codes. We then apply the tools of density evolution with mixture Gaussian approximations to optimize irregular LDPC codes and to compute minimum operational signal-to-noise ratios for ergodic MIMO OFDM channels. In particular, the optimization is done for various MIMO OFDM system configurations which include different number of antennas, different channel models and different demodulation schemes. We also study the coding-spreading tradeoff in LDPC coded CDMA systems employing multiuser joint decoding. We solve the coding-spreading optimization based on the extrinsic information SNR evolution curves for the SISO multiuser detectors and the SISO LDPC decoders. Both single-cell and multi-cell scenarios will be considered. For each of these cases, we will characterize the extrinsic information for both finite-size systems and the so-called large systems where asymptotic performance results must be evoked. Finally, we consider the design optimization of irregular repeat accumulate (IRA) codes for MIMO communication systems employing iterative receivers. We present the density evolution-based procedure with Gaussian approximation for optimizing the IRA code ensemble. We adopt an approximation method based on linear programming to design an IRA code with the extrinsic information transfer (EXIT) chart matched to that of the soft MIMO demodulator.

Medical implant sensor that is used to monitor the human physiology signals is helpful to improve the quality of life and prevent severe result from the chronic diseases. In order to achieve this, the wireless implant communication link that delivers the monitored signal to a multiple antennas external device is an essential portion. However, the existing conventional narrow band Medical Implant Communications System (MICS) has low data rate because of the bandlimited channel is allocated. To improve the data rate in the radio frequency communication, ultra-wide band technology has been proposed. However, the ultra-wide band technology is relatively new and requires living human to be the test subject in order to validate the technology performance. In this condition, the test on the new technology can rise ethical challenge. As a solution, we improve the data rate in the conventional narrow band MICS. The improvement of data rate on the narrow band implies the information bandwidth is larger than the allocated channel bandwidth, and therefore the high frequency components of the information can loss. In this case, the signal suffers the intersymbol-interference (ISI). Instead of that, the multiple antennas external device can receive the signal from other transmitting implant sensor which has the same operating frequency. As a result, the signal is further hampered by co-channel interference (CCI). To recover the signal from the ISI and CCI, multiple-input multiple output (MIMO) blind equalization that has source separation ability can be exploited. Cross-Correlation Constant Modulus Algorithm (CC-CMA) is the conventional MIMO blind equalization algorithm that can suppress ISI and CCI and able to perform source separation. However, CC-CMA has only been analyzed and simulated in the modulation of Phase Shift Keying (PSK). The performance of CC-CMA in multi-modulus modulation scheme such as 4-Pulse-amplitude modulation (PAM) and 16-Quadrature amplitude modulation (QAM), which has higher data rate than PSK, has not been analyzed. Therefore, our work is to analysis and optimize CC-CMA on the multi-modulus modulation scheme. From our analysis, we found that the cost function of CC-CMA is biased cost function. Instead of that, from our simulation, CC-CMA introduces an unexpected shrinking effect whereby the amplitudes of the equalizer outputs have been reduced, especially in multi-modulus modulation scheme. This shrinking effect is not severe in PSK because the decision of a PSK symbol is based on phase, but not amplitude. Unfortunately, this is severe in multi-modulus modulation scheme. To overcome this shrinking effect in multi-modulus modulation scheme, we propose Cross-Independent Constant Modulus Algorithm (CI-CMA). Based on the convergence analysis, we identify the new optimum dispersion value and mixing parameter in CI-CMA. From the simulation results, we confirm that CI-CMA is able to perform equalization and source separation in the multi-modulus modulation scheme. In order to improve the steady state performance of CI-CMA, we perform the steady state mean square error (MSE) analysis of CI-CMA using the energy preservation theorem that was developed by Mai and Sayed in 2001, and our result is more accurate than the previous work. From our analysis, only the reduction in adaptation step size can reduce the steady state MSE, but it is well known that the MSE is indeed a tradeoff with the speed of convergence. Therefore without sacrificing convergence speed, our last effort is to propose hybrid algorithms. The hybrid algorithms are done by combining a new adaptive constant modulus algorithm (ACMA), a decision directed algorithm and a cross-correlation function. From the simulation results, we found that the hybrid algorithms can show low steady state error and thereby improve the reliability of the communication link. The main achievement of this thesis is the discovery of new dispersion value through the convergence analysis.

Thesis (M.A.)--Miami University, Dept. of Speech Pathology and Audiology, 2006.<br>Title from first page of PDF document. Document formatted into pages; contains [1], v, 45 p. : ill. Includes bibliographical references (p. 35-37).

In recent years, multiple input multiple output system has raised intensive researchinterests for its huge potentials to achieve higher spectral efficiency anddata rate. However, transmitting multiple data streams through the same timeand frequency resources simultaneously leads to severe interference betweentransmitted signals. In order to solve this problem, lattice reduction is proposedas a suboptimal maximum likelihood algorithm. It aims at finding aset of better basis vectors for the channel matrix and results in satisfactoryperformance improvements compared to conventional linear detectors. But theaverage complexity of lattice reduction algorithm is too high for practical uses.This thesis studies conventional linear detection algorithms and lattice reductionaided detection algorithms for uplink receiver design. Further an iterativelattice reduction algorithm is proposed by exploiting the frequency coherence inan orthogonal frequency division multiplexing system to achieve low complexity.In this thesis, algorithm performances are verified in various scenarios throughsimulations. Results show promising performance improvements for presentedlattice reduction detection algorithms, at the cost of an acceptable complexityincrease.<br>Under de senaste åren har MIMO system fått ökat intensiva forskningsintressenför sina stora möjligheter att uppnå högre spektral effektivitet och datahastighet.Överföring av era dataströmmar i samma tid och frekvensresurser lederemellertid samtidigt till allvarlig störning mellan sända signaler. För att lösadetta problem föreslås lattice reduction som en suboptimal maximal likelihoodalgorithm. Det syftar till att hitta en uppsättning bättre basviktorer för kanalmatrisenoch resultera i tillfredsställande prestandaförbättringar jämfört medkonventionella linjära detektorer. Men den genomsnittliga komplexiteten hoslattice reduction är för hög för praktiska användningsområden. Denna avhandlingstuderar konventionella linjära detekteringsalgoritmer och lattice reductiondetekteringsalgoritmer för uplink-mottagare. Vidare föreslås en iterativ latticereduction algoritm genom utnyttjande av frekvenssamhäftningen i ett OFDMsystem.I denna avhandling verifieras utförandet av olika algoritmer i olika scenariergenom simulering. Resultat visar lovande prestandaförbättringar för presenteradecc reduction detekteringsalgoritmer, till kostnaden för en acceptabelkomplexitetsökning.

The objective of this paper is to present an efficient miniaturized antenna design and simulation of a highly isolated multi-port micro-strip antenna for multiple-input multiple-output communication (MIMO) systems. Three geometric configurations were proposed and compared to achieve an isolation of as low as –30 dB without affecting the antenna performance greatly. The antenna was designed to operate at a resonance frequency of 2.45 GHz (fc ). Ferrite material beneath each meander structure was used for miniaturization purposes as well as an FR4 substrate with a compact overall area of .75 lambda0 ×.5 lambda0 for a system board, where lambda0 is the free space wavelength. A ground plane with small etched slits was used for isolation purposes. A maximum gain of 4.6 dBi in the azimuthal plane was achieved. Index Terms: MIMO, meander antenna, four-port antenna, defected ground structure<br>Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science

Educational Psychology<br>Ph.D.<br>The Center for Disease Control estimates that one in 88 births result in a diagnosis of autism (CDC, 2012). Of those individuals diagnosed with autism approximately 25-61% fail to develop vocal output capabilities (Weitxz, Dexter, & Moore, 1997). The use of Augmentative and Alternative Communication (AAC) systems, such as Picture Exchange (PE) and Voice Output Communication Aids (VOCA) has been demonstrated as effective for those individuals to acquire a mand repertoire (Mirenda, 2003). The focus of the current study was to compare mand acquisition using PE and the iPad as a VOCA, in terms of acquisition rate and participant device preference, and with regard to collateral effects on vocalizations and disruptive behaviors. Additionally, the study evaluated the effectiveness of a teaching strategy using constant time delay with full-physical prompts (Sigafoos, Doss, & Reichel, 1989) in the acquisition of a mand repertoire using PE and the iPad as a VOCA, in five preschool aged children with autism. Finally, the devices were assessed in terms of their social validity. Three participants acquired the ability to communicate using the iPad as a VOCA more readily and two participants acquired the ability to communicate more quickly using PE, while the overall rate of independent manding was higher for four participants using the VOCA. The results of the study also indicate that the use of a constant time delay procedure with full-physical prompts was effective in the acquisition of both PE and the VOCA device. Regarding preference, four participants demonstrated a clear preference for the VOCA device and one for PE, when presented with the option to respond with either device. With respect to collateral effects, the data were largely inconclusive. For one participant there was an overall increase in vocalizations, for one participant there was an overall decrease in vocalizations, for the remaining three there was no systematic change in their rate of vocalizations during or following communication training. Regarding disruptive behaviors, an overall decrease in the occurrence was seen for two participants, for the remaining three the rates of occurrence did not change systematically following communication training. Finally, in terms of social validity, both the VOCA device and PE were found to be acceptable communication tools, with educators reporting that they would not only include such training within their classroom routines, but would also recommend its use in the future.<br>Temple University--Theses

Multiple-input multiple-output (MIMO) relay communication systems have been identified to be one of the promising solutions to high rate wireless communications. In optimizing the MIMO relay networks, the knowledge of channel state information (CSI) is essential. This thesis develops novel channel estimation algorithms for MIMO relay communication networks, considering the amplify-and-forward relaying scheme. The proposed algorithms outperform existing schemes in estimating the CSI of each hop in MIMO relay networks.

In the last years hybrid optical networking is a topic of increasing interest for graceful migration to future high capacity integrated service networks.A new hybrid network architecture is proposed to harmonize different transport technologies and to support a suitable set of services: &apos;&apos;3-Level Integrated Hybrid Optical Network&apos;&apos; (3LIHON).The aim of this thesis is to study the performance of 3LIHON focusing on examining the Quality of Service (QoS) in the output part of the node.In particular we study the performance for Statistically Multiplexed (SM) traffic.In Chapter 1 we present the motivation of our study and the current work.We give the problem definition and define the goal of the thesis.Chapter 2 shows concepts and architecture of 3LIHON. Firstly we introduce the reference classes used and the Quality of Service (QoS) requirement.Furthermore we give a complete description of 3LIHON architecture describing transport services, architecture in detail, input and output part of the node.Finally we describe the advantages of 3LIHON network.To simulate the 3LIHON architecture we use a programming language called Simula and a context class for discrete event simulation called DEMOS.In Chapter 3 firstly we describe the simulation model implemented, moreover we give a code description.We show the sources characterization and the packets characterization for all type of traffic that 3LIHON is able to handle: Guaranteed Service Transport (GST) traffic, Statistically Multiplexed (SM) Real Time (RT) traffic and Statistically Multiplexed (SM) Best Effort (BE) traffic.The code used in this work is available in Appendix C.In Chapter 4 firstly we present the simulation scenario and then the obtained results.To evaluate the accuracy&apos;s level of our results we use a 95% confidence interval and more theoretical details about that are given in Appendix A.We consider three study cases and for each of them we analyze in details the Packet Loss Probability (PLP) of Statistically Multiplexed Real Time (SM/RT) packets, the Packet Loss Probability (PLP) of Statistically Multiplexed Best Effort (SM/BE) packets and the delay of Statistically Multiplexed Best Effort (SM/BE) packets in the Best Effort queue. Some additional results used to obtain the study case called Series Two in Chapter 2 are shown in Appendix B.In Chapter 5 are presented some conclusions of this work and in Chapter 6 we show some hints that can be the sparkle for further works.

Energy usage has become an important issue in wireless communication systems. The energy-intensive nature of wireless communication has spurred concern over how best systems can make the most use of this non-renewable resource. Research in energy-efficient design of wireless communication systems show that one of its challenges is that the overall performance of the system depends, in a coupled way, on the different submodules of the system i.e. antenna, power amplifier, modulation, error control coding, and network architecture. Network architecture implementation strategies offer protocol software implementors an opportunity of incorporating low-power strategies into the design of the network protocols used for data communication. This dissertation proposes a methodology that would allow a software protocol implementor to analyze the power consumption of a wireless communication system. The foundation of this methodology lies in the understanding of the formal specification of the wireless interface network architecture which can be used to predict the performance of the system. By extending this hypothesis, a protocol implementor can use the formal specification to derive the power consumption behaviour of the wireless system during a normal operation (transmission or reception of data). A high-level formalism like state-transition graphs, can be used to track the protocol processing behaviour and to derive the associated continuous-time Markov chains. Because of their diversity, Markov reward models(MRM) are used to model the power consumption associated with the different states of a specified protocol layer. The models are solved analytically using the Mobius performance and dependability tool. Using the MRM accumulation and utilization measures, a profile of the power consumption is generated. Results from the experiments on the protocol layers show the individual power consumption and utilization of the different states as well as the accumulated power consumption of different protocol layers when compared. Ultimately, the results from the reward model solution can be used in the energy-efficient design of wireless communication systems. Lastly, in order to get an idea of how wireless communication device companies handle issues of power consumption, we consulted with the wireless module engineers at Siemens Communication South Africa and present our findings on current practices in energy efficient protocol implementation.

Recently, there has been a dramatic increase in the amount of data transmission within short range local area networks (LAN). Multimode fibre (MMF) is widely used in local area networks because of its coupling and alignment along with the low cost of related components. Graded index MMF has become common due to the reduction in pulse spreading; however, as demands for high bandwidth increase towards a future gigabit rate network, the typical MMF using conventional transmission methods will not be suitable. Meanwhile, this increasing demand for high speed data transmission will soon reach the Shannon capacity limit of single mode fibres. After multiple input and multiple output (MIMO) technology was successfully used in wireless communication, the researcher realised that the same idea could also be applied to an optical fibre network. Optical MIMO techniques are gaining interest in order to create parallel channels over orthogonal modes in a MMF or a few mode fibre (FMF). This approach could lead to a significant increase in the bandwidth distance product and be employed in the next 40Gb/s or even 100Gb/s optical fibre transmission systems. Generally speaking, optical MIMO appears to be the best solution to the bandwidth limitation problem in either short distance MMF or long distance FMF systems. This thesis focuses on designing a simple, cost-effective, and energy efficient optical MIMO system based on MMFs. This proposed system can be realised by combining radial offset launching and annular multi-segment detectors. First, in the initial work, we performed a theoretical and numerical study of the key impairments of MMFs, and the mode propagation in an MMF was analysed mathematically. The variation in electrical field intensity for linearly polarised (LP) modes in the core region of an MMF and the analytical solutions for power coupling coefficients in either radial offset launching or centre launching were presented. In addition, the modal time delays, impulse response, and transfer function were all introduced. Subsequently, the near field intensity pattern (NFP) was simulated at the output facet of the MMF, which indicated that the overall NFP suffered from blurring when it contained mode mixing, and that the intensity pattern was particularly sensitive to the random phase. According to the spatial distribution of the NFP, the annular detector can be exploited more efficiently. All of the results were calculated and plotted using the MATLAB program. Secondly, the optical MIMO model in the multimode fibre was briefly summarised, including the MIMO channel matrix H expression, a mathematical expression of optical MIMO capacity, MIMO channel estimation and an equalization method. Two metrics can be used to characterise the MIMO channel performance: condition number and crosstalk at each receiver. The numerical results demonstrated that the new type of annular multi-segment detector exhibits superior performance compared to the conventional multiple single mode fibre (SMF) detectors, making them attractive for future optical MIMO systems. Finally, the core work of this thesis can be divided into two parts: the modelling of a 10Gb/s intensity modulation direct detection (IM-DD) optical MIMO MMF system; and the modelling of an advanced 10Gb/s coherent differential phase shift keying (DPSK) MIMO FMF system. In both simulation systems, the important transmission parameters of intra-group mode mixing, modal dispersion, chromatic dispersion, and mode attenuation were considered and discussed in detail. In the IM-DD optical MIMO system, the optimization of the transceiver can be based upon the laser spot size and the power flux distribution emitted by the transmitter. Results from the simulation showed that the intra-group mode mixing had a limited impact on system performance, and due to its inability to compensate for linear impairments, the IM-DD optical MIMO was not favourable for long distance transmission systems. Nevertheless, the new type of optical fibre FMF seems to be the most promising candidate for use in long haul transmission systems. Therefore, the well-known DPSK modulation format in conjugation with the coherent detection deployed in FMF was studied. Both heterodyne and intradyne detection schemes were analysed followed by mathematical derivation and numerical simulation; the results illustrated that similar system performances can be achieved in both schemes. Meanwhile, the coherent DPSK simulation results also demonstrated that the linear impairments were almost compensated by the frequency domain MIMO equalization process, which resulted in system performance being independent to transmission distance for up to 10km. This advantage proved that the coherent optical DPSK MIMO system can be employed in long haul networks. As with an IM-DD optical MIMO system, optimization of a coherent MIMO system was also possible. However, in contrast to the optimization of an IM-DD MIMO system, a trade-off had to be made between sufficient spatial diversity at the transceiver and differential modal delay caused by modal dispersion; consequently, the numerical results showed that the proposed coherent optical DPSK MIMO gained reasonable good results without using any active device, such as a spatial light modulator and a mode converter. In conclusion, this proposed optical MIMO system provided easy implementation and integration and is feasible for use in future optical communication systems.

La radio Ultra Large Bande (ULB) promet de nouveaux marchés dans les domaines des réseaux personnels hauts débits et de capteurs. De sorte à améliorer la robustesse du lien radio et le débit, l’association des techniques MIMO à l’ULB a été envisagée. En vue d’une réalisation pratique, un challenge fondamental reste la conception des antennes qui doivent répondre aux contraintes de l’ULB et des systèmes multi-antennaires, et aux contraintes physiques et économiques. Dans ce contexte, plusieurs nouveaux designs d’antennes MIMO ULB sont proposés. Leur caractérisation s’appuie sur les paramètres conventionnels utilisés en conception d’antennes ainsi que des paramètres spécifiques à l’ULB et au MIMO. En particulier, un nouveau design compact présentant une forte isolation grâce à l’insertion d’un stub sur le plan de masse est proposé. Une nouvelle méthode de modélisation du couplage mutuel, qui présente l’avantage d’offrir de nouvelles approches pour le compenser, est également introduite<br>UWB technology has rapidly emerged in the areas of WPAN and sensors networks featuring high data rate communications. The applications of UWB are limited to very short-range communications due to the extremely low transmitted power. The combination of MIMO techniques with UWB has been considered as a solution to improve the range. However, a fundamental challenge arises for the design of antennas that faces the constraints offered by UWB systems and multi-antennas systems, and the constraints of size and cost. In this context, several new UWB-MIMO antennas are proposed. Their characterization is based on the parameters relevant to conventional antenna design and the specific parameters relevant to the UWB-MIMO antenna design. In particular, a new compact design with high isolation by inserting the inverted-Y shaped stub on the ground plane is proposed. A new method for modelling the mutual coupling, is also introduced which has the advantage of offering new approach to compensate it

Academic researchers in many disciplines are facing difficulties in disseminating their research outputs beyond the academic community. Particularly, Information Systems (IS) academic researchers have been struggling to make their research more relevant to practice. The diversity of IS research means that should be a wide audience within and beyond academia who could benefit from IS research outputs. This audience includes educators, practitioners, patients, etc. How IS relevant to practice is a central dilemma of IS research. Research relevance is classified according to dimensions such as interesting, implementable, current, accessible “Article style” by many IS scholars. These dimensions are important to be investigated as some academic papers are yet to be beneficial to an audience beyond academia. The Accessible dimension is the focus of this study where accessible means the academic papers should be readable and understood in terms of tone, style, structure, and semantics by the potential audience beyond the academic community. This study investigates the barriers that limit academic researchers in disseminating and communicating their research outputs beyond academia. This study aims to design a communication method to assist academic researchers in disseminating and communicating their research outputs beyond academia. This study consists of three phases, in the first phase a qualitative method is applied by interviewing academics in the Information System and Computing Department at Brunel University to gain a better understanding of how and why academics disseminate beyond academia. Based on communication theories a research framework is adapted to analyse and explain the interview data. In the second phase, short videos are recorded of 10 academics where each explains one of their papers. In the third phase, two different groups are interviewed to evaluate the 10 short videos in regards the Information Quality (IQ) dimensions (i.e. appropriate amount of information, format, and timeliness). By using the thematic analysis technique the academics highlighted three barriers that limit them to disseminate and communicate their research outputs beyond academia. The three barriers are the message (i.e. academic structure and language of research papers), channel (i.e. academic journal and conferences), and social system (i.e. lack of Incentives, lack of time, and lack of support). Moreover, academics emphasised the vital role of feedback loop in their communication with target audience beyond academia. The 10 short videos are designed to overcome two of these barriers (i.e. message and channels). Each short video is evaluated by its academic author on one hand and the potential audience/stakeholders of the short video from the other hand (e.g. practitioners). Thus, the academic authors of the video suggest some changes by adjusting the video structure and adding some examples for more explanations of their research papers. Also, authors concerned about format particularly the visual elements of the video which have to be completely matched with the title of the video. However, the opinions of potential audiences vary based on their information need. For example, some practitioners are concerned with the practical information, in other words, practitioners seek the applicable part of the information provided in the short video (i.e. how to apply something); and others watch the short video to increase their awareness of a particular topic. This study will assist academic researchers to focus on how to disseminate their research outputs to audience/stakeholders beyond academia using media tools (i.e. video). Also, it provides a novel method of disseminating and communicating their research outputs beyond the academic community. Moreover, this study helps to create an interaction platform that enables academic researchers to build a collaborative framework and a mutual understanding with the audience beyond academia.

<p> This paper explains a new beam-forming technique implemented in a deterministic Multiple-Input Multiple-Output (MIMO) channel model in 60 GHz millimeter wave frequency. We calculate path loss between the transmitter and receiver antenna elements in the line of sight path. Assuming that Channel State Information (CSI) is known as the deterministic values at the transmitter, the Composite Transfer Function (CTF) derived from the CSI generates orthogonal beams. The orthogonal beam allows us to reuse the frequency at the same time slot with the capability of multi-user MIMO. Our beam forming technique controls the radiated power at the transmitter in such a way that the power received at a particular receiving antenna element is 0dB, and it is suppressed to less than -60dB at other receiving elements. We study the performance of our proposed beam-forming technique by transmitting the QPSK modulated signal through the orthogonal beams, and analyzing the bit error rate curve.</p>

The objectives of this research were to: (1) augment existing research regarding the impact of information retention resulting from the application of redundant color codes; and (2) determine whether the application of color in hard-copy documents has a positive influence in business reports by non-color deficient subjects. This research was an extension of work done by Lamberski and Dwyer (1983) and Moore and Dwyer (1991). Both studies were hard copy based and focused on the impact of information retention resulting from the application of redundant color codes.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California<br>This paper addresses the air-to-ground communication problem, where multiple transmit antennas are used on the aircraft to combat multi-path interference. The channel is assumed to have a line-of-sight component and a single ground reflection. Multiple input multiple output (MIMO) techniques can be used in this situation, to increase the reliability and data rate. In this paper we discuss how the MIMO channel capacity changes, with the aircraft antenna configuration, altitude, velocity, range, and a number of other parameters. For comparison, the MIMO results are compared to systems which have single antennas at the transmitter, at the receiver, or at both ends.

RF and acoustic communications are widely used in terrestrial and underwater environments, respectively. This thesis examines the use of ultrasonic communication alternately in terrestrial applications. We first investigate the ultrasonic channel in order to observe whether reliable communication is possible among the ultrasonic nodes as an alternative to RF-based communications. Some key characteristics of the single-input-single-output (SISO) and single-inputmultiple- output (SIMO) ultrasonic channel are inspected with extensive experiments utilizing ultrasonic transmitters and receivers. Well known receiver diversity techniques are employed to combine the observations of multiple receiving ultrasonic transducers in a SIMO scheme and receiver diversity gain is attained. The thesis also covers the implementation of a receiver node by using a low-cost microcontroller.

<p> This study investigated parents&rsquo; experiences, challenges, benefits, and needs regarding their child&rsquo;s voice output communication aid (VOCA). Three mothers who had children who use a VOCA device as their primary form of communication were recruited from Goodwill of Orange County&rsquo;s Technology Exchange Center and Prentke Romich Company (PRC) and were interviewed by phone or email questionnaire. Thematic analysis of the interview data revealed four major themes: (a) benefits of VOCA use, (b) barriers to VOCA use, (c) facilitators of VOCA use, and (d) continuing needs of families. The information obtained from this study can be used to better serve families and children who use VOCAs and other AAC devices to avoid barriers (e.g., insufficient training) and abandonment and to foster more successful outcomes. Further research is necessary to continue to investigate the needs of parents in terms of their child&rsquo;s device as well as the effectiveness of device training programs.</p><p>

This thesis fits into the Multiple-Input Multiple-Output (MIMO) communication systems. Nowadays, these schemes are the most promising technology in the field of wireless communications. The use of this technology allows to increase the rate and the quality of the transmission through the use of multiple antennas at the transmitter and receiver sides. Furthermore, the MIMO technology can also be used in a multiuser scenario, where a Base Station (BS) equipped with several antennas serves several users that share the spatial dimension causing interference. However, employing precoding algorithms the signal of the multiuser interference can be mitigated. For these reasons, the MIMO technology has become an essential key in many new generation communications standards. On the other hand, Massive MIMO technology or Large MIMO, where the BS is equipped with very large number of antennas (hundreds or thousands) serves many users in the same time-frequency resource. Nevertheless, the advantages provided by the MIMO technology entail a substantial increase in the computational cost. Therefore the design of low-complexity receivers is an important issue which is tackled throughout this thesis. To this end, one of the main contributions of this dissertation is the implementation of efficient soft-output detectors and precoding schemes. First, the problem of efficient soft detection with no iteration at the receiver has been addressed. A detailed overview of the most employed soft detectors is provided. Furthermore, the complexity and performance of these methods are evaluated and compared. Additionally, two low-complexity algorithms have been proposed. The first algorithm is based on the efficient Box Optimization Hard Detector (BOHD) algorithm and provides a low-complexity implementation achieving a suitable performance. The second algorithm tries to reduce the computational cost of the Subspace Marginalization with Interference Suppression (SUMIS) algorithm. Second, soft-input soft-output (SISO) detectors, which are included in an iterative receiver structure, have been investigated. An iterative receiver improves the performance with respect to no iteration, achieving a performance close to the channel capacity. In contrast, its computational cost becomes prohibitive. In this context, three algorithms are presented. Two of them achieve max-log performance reducing the complexity of standard SISO detectors. The last one achieves near max-log performance with low complexity. The precoding problem has been addressed in the third part of this thesis. An analysis of some of the most employed precoding techniques has been carried out. The algorithms have been compared in terms of performance and complexity. In this context, the impact of the channel matrix condition number on the performance of the precoders has been analyzed. This impact has been exploited to propose an hybrid precoding scheme that reduces the complexity of the previously proposed precoders. In addition, in Large MIMO systems, an alternative precoder scheme is proposed. In the last part of the thesis, parallel implementations of the SUMIS algorithm are presented. Several strategies for the parallelization of the algorithm are proposed and evaluated on two different platforms: multicore central processing unit (CPU) and graphics processing unit (GPU). The parallel implementations achieve a significant speedup compared to the CPU version. Therefore, these implementations allow to simulate a scalable quasi optimal soft detector in a Large MIMO system much faster than by conventional simu<br>La presente tesis se enmarca dentro de los sistemas de comunicaciones de múltiples antenas o sistemas MIMO. Hoy en día, estos sistemas presentan una de las tecnologías más prometedoras dentro de los sistemas comunicaciones inalámbricas. A través del uso de múltiples antenas en ambos lados, transmisor y receptor, la tasa de transmisión y la calidad de la misma es aumentada. Por otro lado, la tecnología MIMO puede ser utilizada en un escenario multiusuario, donde una estación base (BS) la cual está equipada con varias antenas, sirve a varios usuarios al mismo tiempo, estos usuarios comparten dimensión espacial causando interferencias multiusuario. Por todas estas razones, la tecnología MIMO ha sido adoptada en muchos de los estándares de comunicaciones de nueva generación. Por otro lado, la tecnología MIMO Masivo, en la cual la estación base está equipada con un gran número de antenas (cientos o miles) que sirve a muchos usuarios en el mismo recurso de tiempo-frecuencia. Sin embargo, las ventajas proporcionadas por los sistemas MIMO implican un aumento en el coste computacional requerido. Por ello, el diseño de receptores de baja complejidad es una cuestión importante en estos sistemas. Para conseguir esta finalidad, las principales contribuciones de la tesis se basan en la implementación de algoritmos de detección soft y esquemas de precodificación eficientes. En primer lugar, el problema de la detección soft eficiente en un sistema receptor sin iteración es abordado. Una descripción detallada sobre los detectores soft más empleados es presentada. Por otro lado, han sido propuestos dos algoritmos de bajo coste. El primer algoritmo está basado en el algoritmo Box Optimization Hard Detector (BOHD) y proporciona una baja complejidad de implementación logrando un buen rendimiento. El segundo de los algoritmos propuestos intenta reducir el coste computacional del conocido algoritmo Subspace Marginalization with Interference Suppression (SUMIS). En segundo lugar, han sido investidados detectores de entrada y salida soft (SISO, soft-input soft-output) los cuales son ejecutados en estructuras de recepción iterativa. El empleo de un receptor iterativo mejora el rendimiento del sistema con respecto a no realizar realimentación, pudiendo lograr la capacidad óptima. Por el contrario, el coste computacional se vuelve prohibitivo. En este contexto, tres algoritmos han sido presentados. Dos de ellos logran un rendimiento óptimo, reduciendo la complejidad de los detectores SISO óptimos que normalmente son empleados. Por el contrario, el otro algoritmo logra un rendimiento casi óptimo a baja complejidad. En la tercera parte, se ha abordado el problema de la precodificación. Se ha llevado a cabo un análisis de algunas de las técnicas de precodificación más usadas. En este contexto, se ha evaluado el impacto que el número de condición de la matriz de canal tiene en el rendimiento de los precodificadores. Además, se ha aprovechado este impacto para proponer un precodificador hibrido. Por otro lado, en MIMO Masivo, se ha propuesto un esquema precodificador. En la última parte de la tesis, la implementación paralela del algoritmo SUMIS es presentada. Varias estrategias sobre la paralelización del algoritmo han sido propuestas y evaluadas en dos plataformas diferentes: Unidad Central de Procesamiento multicore (multicore CPU) y Unidad de Procesamiento Gráfico (GPU). Las implementaciones paralelas consiguen una mejora de speedup. Estas implementaciones permiten simular para MIMO Masivo y de forma más rápida que por simulación convencional, un algo<br>La present tesi s'emmarca dins dels sistemes de comunicacions de múltiples antenes o sistemes MIMO. Avui dia, aquestos sistemes presenten una de les tecnologies més prometedora dins dels sistemes de comunicacions inalàmbriques. A través de l'ús de múltiples antenes en tots dos costats, transmissor y receptor, es pot augmentar la taxa de transmissió i la qualitat de la mateixa. D'altra banda, la tecnologia MIMO es pot utilitzar en un escenari multiusuari, on una estació base (BS) la qual està equipada amb diverses antenes serveix a diversos usuaris al mateix temps, aquests usuaris comparteixen dimensió espacial causant interferències multiusuari. Per totes aquestes raons, la tecnologia MIMO ha sigut adoptada en molts dels estàndars de comunicacions de nova generació. D'altra banda, la tecnologia MIMO Massiu, en la qual l'estació base està equipada amb un gran nombre d'antenes (centenars o milers) que serveix a molts usuaris en el mateix recurs de temps-freqüència. No obstant això, els avantatges proporcionats pels sistemes MIMO impliquen un augment en el cost computacional requerit. Per això, el disseny de receptors de baixa complexitat és una qüestió important en aquests sistemes. Per tal d'aconseguir esta finalitat, les principals contribucions de la tesi es basen en la implementació d'algoritmes de detecció soft i esquemes de precodificació eficients. En primer lloc, és abordat el problema de la detecció soft eficient en un sistema receptor sense interacció. Una descripció detallada dels detectors soft més emprats és presentada. D'altra banda, han sigut proposats dos algorismes de baix cost. El primer algorisme està basat en l'algorisme Box Optimization Hard Decoder (BOHD) i proporciona una baixa complexitat d'implementació aconseguint un bon resultat. El segon dels algorismes proposats intenta reduir el cost computacional del conegut algoritme Subspace Marginalization with Interference Suppression (SUMIS). En segon lloc, detectors d'entrada i eixidia soft (SISO, soft-input soft-output) els cuals són executats en estructures de recepció iterativa han sigut investigats. L'ocupació d'un receptor iteratiu millora el rendiment del sistema pel que fa a no realitzar realimentació, podent aconseguir la capacitat òptima. Per contra, el cost computacional es torna prohibitiu. En aquest context, tres algorismes han sigut presentats. Dos d'ells aconsegueixen un rendiment òptim, reduint la complexitat dels detectors SISO òptims que normalment són emprats. Per contra, l'altre algorisme aconsegueix un rendiment quasi òptim a baixa complexitat. En la tercera part, s'ha abordat el problema de la precodificació. S'ha dut a terme una anàlisi d'algunes de les tècniques de precodificació més usades, prestant especial atenció al seu rendiment i a la seua complexitat. Dins d'aquest context, l'impacte que el nombre de condició de la matriu de canal té en el rendiment dels precodificadors ha sigut avaluat. A més, aquest impacte ha sigut aprofitat per a proposar un precodificador híbrid , amb la finalitat de reduir la complexitat d'algorismes prèviament proposats. D'altra banda, en MIMO Massiu, un esquema precodificador ha sigut proposat. En l'última part, la implementació paral·lela de l'algorisme SUMIS és presentada. Diverses estratègies sobre la paral·lelizació de l'algorisme han sigut proposades i avaluades en dues plataformes diferents: multicore CPU i GPU. Les implementacions paral·leles aconsegueixen una millora de speedup quan el nombre d'àntenes o l'ordre de la constel·lació incrementen. D'aquesta manera, aquestes implementacions permeten simular per a MIMO Massiu, i de forma més ràpida que la simulació convencional.<br>Simarro Haro, MDLA. (2017). Effi cient algorithms for iterative detection and decoding in Multiple-Input and Multiple-Output Communication Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86186<br>TESIS

Approved for public release; distribution is unlimited<br>A multiple frequency quaternary phase shift keyed signal is generated using a complex Fast Fourier Transform on an industry standard personal computer and is output using direct memory access through a digital to analog converter. The output is permitted at rates of up to the maximum direct memory access rate of the computer. An assembly language program loop, direct hardware output, and high level language output are compared as alternate solutions to the problem of outputting a data stream contained in the computer primary memory.<br>http://archive.org/details/highspeedoutputi00chil<br>Lieutenant, United States Navy

Free-space optical (FSO) communication has recently gained a lot of interest as an attractive solution for high-rate last-mile terrestrial applications. FSO has many attractive features including the use of unlicensed parts of the electromagnetic spectrum, ease of deployment, cost efficiency, high security, and high data rates. There are however challenges in the design of FSO communication systems. Specifically, the weather-dependent optical wireless channel introduces attenuation and intensity variations known as turbulence-induced fading, which impose severe challenges for reliable data transmission. Meanwhile, the limitation in transmit power due to eye-safety regulations adds yet another design constraint. In this thesis, we first consider the performance analysis of FSO systems subject to Gamma-Gamma fading. The Gamma-Gamma probability density function (pdf) includes a modified Bessel function that precludes simple closed-form expressions. We employ a series representation of the modified Bessel function and derive closed-form expressions for the pairwise error probability (PEP) of FSO systems. We then study the performance of multiple-input multiple-output (MIMO) FSO systems for general space-time codes (STCs) for both direct and coherent/differential detection. We develop comprehensive models for both detection schemes and also use the derived models for a fair comparison between different detection schemes. For performance analysis only, we limit the number of transmit apertures to two and derive the asymptotic PEP in closed form. Moreover, design criteria are established which are used to prove the quasi-optimality of repetition and Alamouti STCs for direct and coherent/differential detection in Gamma-Gamma fading, respectively. Finally, we investigate dual-hop and multi-hop FSO systems employing electrical and all-optical relays. Erbium-doped fiber amplifiers (EDFAs) are assumed for all-optical relaying and comprehensive signal and noise models are then derived. We show that all-optical relays outperform electrical relays unless the number of relays is very large. Furthermore, we conclude that, for a fixed source-destination distance, performance improves as the number of hops increases up to a certain point. Adding more relays will then result in performance degradation for both amplification schemes.

In the forthcoming broadband wireless communications, channel equalisation and estimation solutions are required to be robust against frequency selective fading channels and have a low signal processing complexity. This thesis investigates iterative frequency-domain channel equalisation and estimation for single-carrier (SC) multi-input multi-output (MIMO) wireless communication systems, aiming to outperform iterative time-domain channel equalisation and estimation with a low complexity.

This thesis proposes novel blind and semi-blind receivers for Multiple-Input Multiple-Output (MIMO) wireless communication systems employing Orthogonal Frequency Division Multiplexing (OFDM) or Single-Carrier Frequency Domain Equalisation (SCFDE) modulation. MIMO systems can achieve higher data rates than Single-Input Single-Output (SISO) systems while the use of OFDM and SC-FDE is motivated by their simple equalisation of frequency selective channels. Furthermore, the blind or semi-blind operation increases the bandwidth efciency compared to traditional training based receivers, which is particularly interesting in MIMO systems since they require more training data than SISO systems. Blind and semi-blind equalisation in this work is performed using the statistical tool of Independent Component Analysis (ICA), which relies on the independence of the source streams. First, novel blind receivers for MIMO OFDM systems are proposed. Two linear receivers, which have different complexity / performance tradeoffs are presented. The indeterminacies of ICA estimates are handled by post-processing of the estimates, which relies on precoding of the source streams. Subsequently, these receivers are combined with Layered Space-Frequency Equalisation (LSFE), which results in performance close to the case with perfect Channel State Information (CSI) at the receiver. Reduced-complexity versions are also considered, which are essential for OFDM systems employing a large number of subcarriers. Furthermore, performance and computational complexity comparisons with other published blind receivers show the superiority of the proposed methods. Next, semi-blind receivers for MIMO OFDM systems are proposed, which are derived from the blind methods above. The advantage of operating semi-blindly is that the indeterminacies of the ICA estimates are avoided. Furthermore, better performance than in the blind case is obtained at low to moderate Signal to Noise Ratios (SNRs) and Doppler frequency shifts, using a training overhead of 2%. However, for high SNRs or Doppler frequency shifts as well as with reduced-complexity versions convergence to a solution extracting the sources in the wrong order can occur, which results in an error floor, since no post-processing to handle these ICA indeterminacies is used. Finally, semi-blind receivers for MIMO SC-FDE systems using linear equalisation and LSFE are investigated. To the author's knowledge this is the first published application of ICA to MIMO SC-FDE systems. Since in SC-FDE systems the frequency domain signals are Gaussian, ICA is applied in time domain while a computationally efficent frequency domain equalisation is employed. The resulting receiver is shown to achieve performance close to the perfect CSI case for moderate to high SNRs, using a training overhead of only 0:05%. Furthermore, convergence to a wrong solution as in the semi-blind OFDM case has not been observed, which can be explained by the larger solution space in SC-FDE systems than in OFDM systems.

In recent years, new visualisation techniques and devices, such as remote visualisation and stereoscopic displays, have been developed to help researchers. In a remote visualisation environment the user may want to see visualisation on a different device, such as a PDA or stereo device, and in different circumstances. Each device needs to be configured correctly, otherwise it may lead to an incorrect rendering of the output. For end users, however, it can be difficult to configure each device without a knowledge of the device property and rendering. Therefore, in a multiple user and multiple display environment, to obtain the correct display for each device can be a challenge. In this project, the focus on investigating a solution that can support end users to use different display devices easily. The proposed solution is to develop an application that can support the ad-hoc use of any display device without the system being preconfigured in advance. Thus, end users can obtain the correct visualisation output without any complex rendering configuration. We develop a client-server based approach to this problem. The client application can detect the properties of a device and the server application can use these properties to configure the rendering software to generate the correct image for subsequent display on the device. The approach has been evaluated through many tests and the results show that using the application is a useful in helping end users use different display devices in visualisation.

In todays society, a growing number of users are demanding more sophisticated services from wireless communication devices. In order to meet these rising demands, it has been proposed to increase the capacity of the wireless channel by using more than one antenna at the transmitter and receiver, thereby creating multiple-input multiple-output (MIMO) channels. Using MIMO communication techniques is a promising way to improve wireless communication technology because in a rich-scattering environment the capacity increases linearly with the number of antennas. However, increasing the number of transmit antennas also increases the complexity of detection at an exponential rate. So while MIMO channels have the potential to greatly increase the capacity of wireless communication systems, they also force a greater computational burden on the receiver. Even suboptimal MIMO detectors that have relatively low complexity, have been shown to achieve unprecedented high spectral efficiency. However, their performance is far inferior to the optimal MIMO detector, meaning they require more transmit power. The fact that the optimal MIMO detector is an impractical solution due to its prohibitive complexity, leaves a performance gap between detectors that require reasonable complexity and the optimal detector. The objective of this research is to bridge this gap and provide new solutions for managing the inherent performance-complexity trade-off in MIMO detection. The optimally-ordered decision-feedback (BODF) detector is a standard low-complexity detector. The contributions of this thesis can be regarded as ways to either improve its performance or reduce its complexity - or both. We propose a novel algorithm to implement the BODF detector based on noise-prediction. This algorithm is more computationally efficient than previously reported implementations of the BODF detector. Another benefit of this algorithm is that it can be used to easily upgrade an existing linear detector into a BODF detector. We propose the partial decision-feedback detector as a strategy to achieve nearly the same performance as the BODF detector, while requiring nearly the same complexity as the linear detector. We propose the family of Chase detectors that allow the receiver to trade performance for reduced complexity. By adapting some simple parameters, a Chase detector may achieve near-ML performance or have near-minimal complexity. We also propose two new detection strategies that belong to the family of Chase detectors called the B-Chase and S-Chase detectors. Both of these detectors can achieve near-optimal performance with less complexity than existing detectors. Finally, we propose the double-sorted lattice-reduction algorithm that achieves near-optimal performance with near-BODF complexity when combined with the decision-feedback detector.