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Lavén, Andreas. "Multi-Channel Anypath Routing for Multi-Channel Wireless Mesh Networks." Thesis, Karlstad University, Faculty of Economic Sciences, Communication and IT, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-5370.
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Increasing capacity in wireless mesh networks can be achieved by using multiple channels and radios. By using different channels, two nodes can send packets at the same time without interfering with each other. To utilize diversity of available frequency, typically cards use channel-switching, which implies significant overhead in terms of delay. Assignment of which channels to use needs to be coupled with routing decisions as routing influences topology and traffic demands, which in turn impacts the channel assignment.
Routing algorithms for wireless mesh networks differ from routing algorithms that are used in wired networks. In wired networks, the number of hops is usually the only metric that matters. Wireless networks, on the other hand, must consider the quality of different links, as it is possible for a path with a larger amount of hops to be better than a path with fewer hops.
Typical routing protocols for wireless mesh networks such as Optimized Link State Routing (OLSR) use a single path to send packets from source to destination. This path is precomputed based on link state information received through control packets. The consideration of more information than hop-count in the routing process has shown to be beneficial as for example link quality and physical layer data rate determines the quality of the end-to-end path. In multi-channel mesh networks, also channel switching overhead and channel diversity need to be considered as a routing metric. However, a major drawback of current approaches is that a path is precomputed and used as long as the path is available and shows a good enough metric. As a result, short term variations on link quality or channel switching are not considered.
In this thesis, a new routing protocol is designed that provides a set of alternative forwarding candidates for each destination. To minimize delay (from both transmission and channel switching), a forwarding mechanism is developed to select one of the available forwarding candidates for each packet. The implementation was tested on an ARM based multi-radio platform, of which the results show that in a simple evaluation scenario the average delay was reduced by 22 % when compared to single path routing.
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Naveed, Anjum Computer Science & Engineering Faculty of Engineering UNSW. "Channel assignment in multi-radio multi-channel wireless mesh networks." Awarded by:University of New South Wales. Computer Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41500.
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Channel assignment in wireless mesh network (WMN) aims at improving the network throughput by utilizing multiple orthogonal frequency channels to minimize the interference. Interference can be categorized as coordinated and non-coordinated, depending upon the relative location of the interfering links. Compared to coordinated interference, non-coordinated interference has a severe adverse impact on throughput. This thesis is based on the hypothesis that the network throughput can be improved significantly, if channel assignment minimizes non-coordinated interference with priority. We propose a static and centralized channel assignment scheme CCAS to show the effectiveness of the hypothesis. The cluster-based approach of CCAS minimizes non-coordinated interference with reduced complexity. CCAS improves the network throughput by upto 80%, compared to the existing schemes. We propose topology control scheme MATS that constructs low interference multipath network topology using a subset of links from physical topology. We report an additional improvement of upto 10% in the network throughput, when CCAS assigns channels to the links selected by MATS. In the final part of the thesis, we formulate generalized channel assignment as an optimization problem, accounting for real network traffic. The objective of the problem is to select the channels for links such that maximum incident traffic can be transmitted over the links, while ensuring a fair distribution of throughput amongst links and elimination of non-coordinated interference. For a given network and incident traffic, the solution to this problem generates the channel assignment resulting in optimal network throughput. We propose dynamic and distributed scheme LYCAS as an approximate solution to the problem. LYCAS employs MATS to construct network topology and cluster-based approach of CCAS to minimize non-coordinated interference. In addition, it periodically updates the assignment of channels to adapt to the changing traffic load. LYCAS achieves upto 68% of the optimal network throughput and upto 72% of optimal aggregate end-to-end throughput of multi-hop flows. It outperforms the existing schemes by a factor of 2.
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Amiri, Nehzad Maryam. "Channel assignment protocols for multi-radio multi-channel wireless mesh netwworks." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/104156.
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The increasing demand for large and low cost wireless coverage, ranging from campus to city wide areas, has motivated a high interest in multi-hop communications with Wireless Mesh Networks (WMN) based on IEEE 802.11s as the
most recent and significant standard.
Channel Assignment (CA) is mechanism which selects the best channels for an individual wireless node or the entire network aiming to increase the capacity of the network. Channel assignment has been extensively researched for
multi-radio WMNs, but it is still very challenging when it comes to its implementation. Although IEEE 802.11s introduces new inter-working, routing and wireless frame forwarding at the link layer, the multi channel architecture receives less attention due to many unsolved challenges that arises while mesh service set works over multiple frequencies.
This research work tries to give a solution to the needs of designing an efficient channel assignment mechanism.
As a result we have proposed a new static channel assignment based on the fact that not all wireless links are practically useful. Our mechanism prunes the network topology by removing weak wireless links and improves the network
performance by reaching a more diverse channel-radio assignation solution.
Toward designing a distributed channel assignment we propose a new game theory based formulation of channel assignment which is applicable to a realistic scenario with imperfect information at each router. We have proposed a distributed and hybrid channel assignment protocol based on the game formulation. The proposed channel assignment makes wireless router to
be able to follow the unpredictable changes in the wireless environment.
We also investigated the types of channel assignment protocols which can be adapted to the IEEE 802.11s based mesh network and improve the network good-put in terms of data delivery ratio and end-to-end delay.
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Chiu, Hon-sun, and 邵漢新. "Channel assignment and routing in multi-channel multi-interface wireless networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182050.
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Chiu, Hon-sun. "Channel assignment and routing in multi-channel multi-interface wireless networks." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182050.
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Farber, Dawn L. (Dawn Lee). "Multi-channel QRS detector." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10868.
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Golmohamadi, Marcia. "Multi-Polarized Channel Characterization." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/1026.
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Machine-to-machine (M2M) communication is becoming an important aspect of warehouse management, remote control, robotics, traffic control, supply chain management, fleet management and telemedicine. M2M is expected to become a significant portion of the Industrial Internet and, more broadly, the Internet of Things (IoT). The environments in which M2M systems are expected to operate may be challenging in terms of radio wave propagation due to their cluttered, multipath nature, which can cause deep signal fades and signal depolarization. Polarization diversity in two dimensions is a well-known technique to mitigate such fades. But in the presence of reflectors and retarders where multipath components arrive from any direction, we find the detrimental effects to be three-dimensional and thus consider herein mitigation approaches that are also 3D. The objectives of this dissertation are three. First, to provide a theoretical framework for depolarization in three dimensions. Second, to prepare a tripolar antenna design that meets cost, power consumption, and simplicity requirements of M2M applications and that can mitigate the expected channel effects. Finally, to develop new channel models in three dimensional space for wireless systems.
Accordingly, this dissertation presents a complete description of 3D electromagnetic fields, in terms of their polarization characteristics and confirms the advantage of employing tripolar antennas in multipath conditions. Furthermore, the experimental results illustrate that highly variable depolarization occurs across all three spatial dimensions and is dependent on small changes in frequency and space. Motivated by these empirical results, we worked with a collaborating institution to develop a three-dimensional tripolar antenna that can be integrated with a commercially available wireless sensor. This dissertation presents the testing results that show that this design significantly improves channels over traditional 2D approaches. The implications of tripolar antenna integration on M2M systems include reduction in energy use, longer wireless communication link distances, and/or greater link reliability. Similar results are shown for a planar antenna design that enables four different polarization configurations. Finally, the work presents a novel three-dimensional geometry-based stochastic channel model that builds the channel as a sum of shell-like sub-regions, where each sub-region consists of groups of multipath components. The model is validated with empirical data to show the approach may be used for system analyses in indoor environments.
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Munawar, Mohammad Ahmad. "Multi-interface Multi-channel wireless mesh networks." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/875.
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In this thesis we propose a multi-channel wireless network based on nodes that use multiple 802. 11 radio interfaces. The proposed system is singular, as it does not require new hardware or a new MAC, but instead leverages commodity 802. 11-based products. With this system, we target scenarios where the nodes are stationary and where their location can often be controlled. We evaluate the performance in this setup using an ad-hoc network approach whereby nodes generate as well as forward data. We also present and appraise a purely-wireless multi-channel infrastructure, which operates like the WLAN infrastructure-based networks in existence today, but without any fixed-line support. In such an infrastructure nodes dedicated for routing purposes provide wireless connectivity to users. We show that a multi-interface system provide significantly higher capacity in many scenarios. Our work puts forward various challenges, points to various anomalies in the operation of the 802. 11 MAC protocol, and shows the need to tackle unfairness issues. Our experiments demonstrate that the mere use of more dual-interface nodes does not necessarily create higher capacity. We also show that traffic differentiation significantly increases aggregate throughput in realistic scenarios. Finally, we provide an example of how simple channel-allocation algorithms in controlled random topologies can allow us to take advantage of a multi-interface system.
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Choi, Sangil. "Minimum interference channel assignment for multicast in multi-channel multi-radio wireless mesh networks." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468073.
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Meflah, L. "Multi-impairment and multi-channel optical performance monitoring." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/14226/.
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Next generation optical networks will evolve from static to dynamically reconfigurable architectures to meet the increasing bandwidth and service requirements. The benefits of dynamically reconfigurable networks (improved operations, reduced footprint and cost) have introduced new challenges, in particular the need for complex management which has put pressure on the engineering rules and transmission margins. This has provided the main drive to develop new techniques for optical performance monitoring (OPM) without using optical-to-electrical-to-optical conversions. When considering impairments due to chromatic dispersion in dynamic networks, each channel will traverse a unique path through the network thus the channels arriving at the monitoring point will, in general, exhibit different amounts of residual dispersion. Therefore, in a dynamic network it is necessary to monitor all channels individually to quantify the degradation, without the requirement of knowing the data path history. The monitoring feature can be used in conjunction with a dispersion compensation device which can either be optical or electrical or used to trigger real-time alarms for traffic re-routing. The proposed OPM technique is based on RF spectrum analysis and used for simultaneous and independent monitoring of power, chromatic dispersion (CD), polarisation mode dispersion (PMD) and optical signal-to-noise ratio (OSNR) in 40Gbit/s multi0channel systems. An analytical model is developed to describe the monitoring technique which allows the prediction of the measurement range. The experimental results are given for group velocity dispersion (GVD), differential group delay (DGD) and OSNR measurements. This technique is based on electro-optic down-conversion that simultaneously down-converts multiple channels, sharing the cost of the key components over multiple channels and making it cost effective for multi-channel operation. The measurement range achieved with this method is equal to 4742±100ps/nm for GVD, 200±4ps for DGD and 25±1dB for OSNR. To the knowledge of the author, these dispersion monitoring ranges are the largest reported to date for the bit-rate of 40Gbit/s with amplitude modulation formats.
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ALM, RAGNAR, and RUDY KYRÖNLAHTI. "Take time to make time : What to consider when managing multi-channel sales systems with the objective to increase sales efficiency." Thesis, KTH, Industriell Marknadsföring och Entreprenörskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199187.
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Traditional sales systems have been disrupted by technological developments. In order to adapt, companies are changing the way they interact with their customers in business-to-business markets. In the last three decades, multi-channel strategies have spurred the proliferation of different sales channels and new ways of managing sales systems. The purpose of this research was to investigate what should be considered when managing multi-channel sales systems with the objective of increasing sales efficiency. The study has investigated current utilisation of multi-channel sales systems in the context of a business-to-business setting in industrial companies that are involved in the Swedish automotive industry. Multi-channel sales systems can be utilised to achieve many different objectives. However, this research pays specific attention on how to improve sales efficiency by utilising multi-channel sales systems in the context of a business-to-business setting. The research employed an explorative case study, where semi-structured and structured interviews were conducted at a case company and at companies that are first or second tier suppliers in the Swedish automotive industry. The qualitative data were analysed using thematic analysis. The empirical findings indicate that the most prevalent measure for increasing sales efficiency is to prioritise and allocate customers based on economic attractiveness. Furthermore, the key issues that impede sales efficiency in multi-channels sales system are misaligned sales activities, deficient prioritisation procedures, insufficient promotion of customer value and inadequate focus on customers. The findings highlight key areas to address and may provide guidelines for the design and management of multi-channel sales systems with the specific purpose of obtaining sales efficiency. The implications of this research are mainly practical and are aimed at supporting sales managers, or individuals in similar positions engaged in multi-channel sales system design and management, in obtaining sales efficiency. Managers should focus on aligning sales activities across the whole sales system, allocate customers according to prioritisation and stay in line with market developments by understanding customer behaviours and perceptions.
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Lee, Su-Young. "Multi-channel scanning SQUID microscopy." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1490.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Caon, John. "Multi-channel radiometric data processing /." Title page, abstract and contents only, 1993. http://web4.library.adelaide.edu.au/theses/09SB/09sbc235.pdf.
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Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1994.Cover title: Advantages of multi-channel radiometric processing. Two maps have overlays. National map series reference Forbes, N.S.W. 1:250,000 S heet SI/55-7. Includes bibliographical references (leaf 38).
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Baker, R. J. "Multi-channel bulk queueing systems." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636016.
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This thesis deals with an area of queueing theory which, despite its obvious applicability to real-life, has received relatively little attention in the literature, the field of bulk-arrival, bulk-service, multi-channel queueing systems. In particular attention is focused on approximating the expected number in the queueing system in a steady state. The aim of this thesis is to provide the practitioner with a straightforward and reasonably accurate mans of calculating the expected number in the system. An introduction will be given to the subject area and the relevant literature will be reviewed. An approximation will be formulated to the mean number of a multi-channel simple queueing system based on the mean number in a single-channel simple queueing system. Multi-channel, bulk arrival systems are then considered. For systems with a fixed arrival batch size two methods are derived to approximate the mean number in the system, one simple straight line based method and one, more complicated, quadratic based approach. Probabilistic arrival batch size distributions are then considered, and a recursive approximation developed to the mean number in the system. The concept of bulk-service is introduced and formulae derived for the mean number in the system for fixed arrival batch sizes and probabilistic arrival batch sizes. Finally attention is given to how the methods derived could be extended to include all possible multi-channel, bulk-arrival and bulk-service queueing systems. Some suggestions for the future are given.
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Baek, Jongmin. "Multi-channel coded-aperture photography." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45814.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 87-89).
This thesis describes the multi-channel coded-aperture photography, a modified camera system that can extract an all-focus image of the scene along with a depth estimate over the scene. The modification consists of inserting a set of patterned color filters into the aperture of the camera lens. This work generalizes the previous research on a single-channel coded aperture, by deploying distinct filters in the three primary color channels, in order to cope better with the effect of a Bayer filter and to exploit the correlation among the channels. We derive the model and algorithms for the multi-channel coded aperture, comparing the simulated performance of the reconstruction algorithm against that of the original single-channel coded aperture. We also demonstrate a physical prototype, discussing the challenges arising from the use of multiple filters. We provide a comparison with the single-channel coded aperture in performance, and present results on several scenes of cluttered objects at various depths.
by Jongmin Baek.
M.Eng.
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González, Barrameda José Andrés. "Search Space Analysis and Efficient Channel Assignment Solutions for Multi-interface Multi-channel Wireless Networks." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20155.
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This thesis is concerned with the channel assignment (CA) problem in multi-channel
multi-interface wireless mesh networks (M2WNs). First, for M2WNs with general topologies,
we rigorously demonstrate using the combinatorial principle of inclusion/exclusion
that the CA solution space can be quantified, indicating that its cardinality is greatly
influenced by the number of radio interfaces installed on each router. Based on this analysis,
a novel scheme is developed to construct a new reduced search space, represented
by a lattice structure, that is searched more efficiently for a CA solution. The elements
in the reduced lattice-based space, labeled Solution Structures (SS), represent groupings
of feasible CA solutions satisfying the radio constraints at each node. Two algorithms
are presented for searching the lattice structure. The first is a greedy algorithm that
finds a good SS in polynomial time, while the second provides a user-controlled depthfirst
search for the optimal SS. The obtained SS is used to construct an unconstrained
weighted graph coloring problem which is then solved to satisfy the soft interference
constraints.
For the special class of full M2WNs (fM2WNs), we show that an optimal CA solution
can only be achieved with a certain number of channels; we denote this number as the
characteristic channel number and derive upper and lower bounds for that number as a
function of the number of radios per router. Furthermore, exact values for the required
channels for minimum interference are obtained when certain relations between the number
of routers and the radio interfaces in a given fM2WN are satisfied. These bounds are
then employed to develop closed-form expressions for the minimum channel interference
that achieves the maximum throughput for uniform traffic on all communication links.
Accordingly, a polynomial-time algorithm to find a near-optimal solution for the channel
assignment problem in fM2WN is developed.
Experimental results confirm the obtained theoretical results and demonstrate the
performance of the proposed schemes.
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Skalli, Habiba. "Channel assignment, routing and cross layer issues for multi-radio multi-channel wireless mesh netorks." Thesis, IMT Alti Studi Lucca, 2009. http://e-theses.imtlucca.it/16/1/Skalli_phdtheis.pdf.
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Next generation wireless mobile communications will be driven by converged networks that integrate disparate technologies and services. The Wireless Mesh Network (WMN) is envisaged to be one of the key components in the converged networks of the future, providing flexible, high-bandwidth wireless backhaul over large geographical
areas. While single radio mesh nodes, operating on a single channel suffer from capacity constraints, equipping mesh routers with multiple radios using multiple non-overlapping channels can significantly alleviate the capacity problem and increase the aggregate bandwidth available to the network. However, the assignment of channels to the radio interfaces poses significant challenges. The goal of channel
assignment algorithms in multi-radio mesh networks is to minimize interference while improving the aggregate network capacity and maintaining the connectivity of the network. In this thesis, we examine the unique constraints of channel assignment in wireless mesh networks and identify the key factors governing assignment schemes, with particular reference to interference, traffic patterns, and multipath connectivity. After presenting a taxonomy of existing channel assignment algorithms for WMNs, we describe a new channel assignment scheme, called MesTiC, which incorporates the mesh traffic pattern together with connectivity issues in order to minimize interference in multi-radio mesh networks. In a second part of this thesis, we consider that a paradigm shift from the classic routing schemes is needed. Usual approaches are not always
satisfactory since they often use shortest-path heuristic and tend to concentrate transmissions to certain nodes. To efficiently exploit the presence of multiple channels instead, a proper routing algorithm should avoid congested links and possibly make use of an estimation of the actual network traffic. Therefore, cross-layer information exchange
can be useful for an efficient functioning of the routing protocols. We analyze all these issues and propose and identify possible solutions.
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Legros, Benjamin. "Optimization of multi-channel and multi-skill call centers." Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00997410.
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Call centers have been introduced with great success by many service‐oriented companies. They become the main point of contact with the customer, and an integral part of the majority of corporations. The large‐scale emergence of call centers has created a fertile source of management issues. In this PhD thesis, we focus on various operations management issues of multi‐skill and multichannel call centers. The objective of our work is to derive, both qualitative and quantitative, results for practical management. In the first part, we focus on architectures with limited flexibility for multi‐skill call centers. The context is that of call centers with asymmetric parameters: unbalanced workload, different service requirements, a predominant customer type, unbalanced abandonments and high costs of crosstraining. The most knowing architectures with limited flexibility such as chaining fail against such asymmetry. We propose a new architecture referred to as single pooling with only two skills per agent and we demonstrate its efficiency under various situations of asymmetry. In the second part, we focus on routing problems in multi‐channel call centers. In the first study, we consider a blended call center with calls arriving over time and an infinitely backlogged queue of emails. The call service is characterized by three successive stages where the second one is a break. We focus on the optimization of the email routing to agents. The objective is to maximize the throughput of emails subject to a constraint on the call waiting time. Various guidelines to call center managers are provided. In particular, we prove for the optimal routing that all the time at least one of the two email routing parameters has an extreme value. In the second study, we examine a threshold policy on the reservation of agents for the inbound calls. We study a general non‐stationary model where the call arrival follows a non‐homogeneous Poisson process. The optimization problem consists on maximizing the throughput of outbound tasks under a constraint on the waiting time of inbound calls. We propose an efficient adaptive threshold policy easy to implement. This scheduling policy is evaluated through a comparison with the optimal performance measures found in the case of a constant stationary arrival rate, and also a comparison with other intuitive adaptive threshold policies in the general non‐stationary case. In the third study, we consider a call center model with a call back option, which allows to transform an inbound call into an outbound one. The optimization problem consists on minimizing the expected waiting time of the outbound calls while respecting a service level constraint on the inbound ones. We propose a routing policy with two thresholds, one on the reservation of the agents for inbound calls, and another on the number of waiting outbound calls. A curve relating the two thresholds is determined.
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Kaufmann, Silvan. "Multi Channel Management im Retailbanking : eine Analyse des Distributionsmanagements und des Kundenverhaltens im Multi Channel Banking /." Aachen : Shaker, 2004. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=010747513&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Carlqvist, Håkan. "Multiscale analysis of multi-channel signals." Doctoral thesis, KTH, Matematik (Avd.), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230.
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I: Amplitude and phase relationship between alpha and beta oscillations in the human EEG We have studied the relation between two oscillatory patterns within EEG signals (oscillations with main frequency 10 Hz and 20 Hz), with wavelet-based methods. For better comparison, a variant of the continuous wavelet transform, was derived. As a conclusion, the two patterns were closely related and 70-90 % of the activity in the 20 Hz pattern could be seen as a resonance phenomenon of the 10 Hz activity. II: A local discriminant basis algorithm using wavelet packets for discrimination between classes of multidimensional signals We have improved and extended the local discriminant basis algorithm for application on multidimensional signals appearing from multichannels. The improvements includes principal-component analysis and crossvalidation- leave-one out. The method is furthermore applied on two classes of EEG signals, one group of control subjects and one group of subjects with type I diabetes. There was a clear discrimination between the two groups. The discrimination follows known differences in the EEG between the two groups of subjects. III: Improved classification of multidimensional signals using orthogonality properties of a time-frequency library We further improve and refine the method in paper2 and apply it on 4 classes of EEG signals from subjects differing in age and/or sex, which are known factors of EEG alterations. As a method for deciding the best basis we derive an orthogonalbasis- pursuit-like algorithm which works statistically better (Tukey's test for simultaneous confidence intervals) than the basis selection method in the original local discriminant basis algorithm. Other methods included were Fisher's class separability, partial-least-squares and cross-validation-leave-one-subject out. The two groups of younger subjects were almost fully discriminated between each other and to the other groups, while the older subjects were harder to discriminate.QC 20101001
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Aagesen, Gustav. "Multi-channel Provisioning of Public Services." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for datateknikk og informasjonsvitenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-17149.
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Information technology facilitates a continuous change in how public services are organised and provided. Influenced by external and internal requirements, the changes are step-wise and non-linear, each step facilitating the next. Examples of requirements are related to supporting e-services, multi-channel provisioning, transparency, citizencentricity, mobility, and globalisation. Information infrastructures define the capabilities of a public agency for efficient service delivery, both internally and externally. Historically, information infrastructures have evolved over time and have drifted in use, leaving complex systems and use of systems at a national level. National government e-service infrastructures aim to support cross agency collaboration, provide access to shared components, and the reuse of previously defined functionality. Depending on its construction, an infrastructure as a platform for service provisioning can support or limit the development of an improved provisioning of services. There is a need for systems with mechanisms that support public services that evolve with the changing requirements of the environment. The objective of this PhD study is to contribute to the delivery of citizen-centric and demand driven services and to the establishment a hypothetical My Processes citizen’s portal. This portal will provide process-oriented multi-channel personalised interaction for all public services. Using a design science approach, this study is performed through the analysis of the existing knowledge base, the modelling of design artefacts, and case studies in the problem environment. The contributions of the study are: C1: A model describing the dynamics of e-government. C2: Future scenarios for citizen-centric and demand driven public services. C3: Requirements for an e-service infrastructure for public service provisioning. C4: A conceptual design for a national e-service infrastructure. C5: A conceptual e-service governance model. In addition to a general focus on process-oriented service provisioning throughout the research study, overviews of the current use of process models and the flexibility supported by process-aware information systems are also provided. The contributions are targeted towards system developers and researchers that are working with governance or development of e-government systems providing public services, and those that are working with holistic aspects of information infrastructure development.
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Hicks, C. M. "Modelling of multi-channel audio signals." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603997.
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This dissertation is concerned with the mathematical modelling of musical and audio signals. The emphasis is on multi-channel signals where either more than one copy of a single original is available for analysis, or where the signal comprises two or more parts. The most common example of this latter class is stereo signals which comprise a left and a right signal to create an auditory illusion of space. Two models are analysed in which we have multiple observations of a single signal. Both are based on the well-known auto-regressive (AR) model which has previously been successfully deployed in many audio applications. The first of these is the Multiply-Observed AR Model in which a single AR signal is contaminated by a number of independent interference signals to give multiple noisy observations of the original. It is shown that the statistics of the noise sources can be determined given certain broad assumptions. The model is applied to the problem of broadband noise reduction of a 78 r.p.m. record, of which a number of copies are available. The second model is the Ensemble-AR Model in which an ensemble of excitation sources drive identical AR filters to give multiple observed signals. Methods for estimation of the AR parameters from the observed data are derived. The model is applied to the detection of impulsive noise in audio signals, and interpolation of the missing data. The E-AR model is demonstrated to be superior to a similar single-channel approach in both of these areas. There is such a variety of stereo signals in existence that a very general model is needed to encompass their whole spectrum. The Coupled-ARMA Model put forward here is based on the ARMA model, but generates a pair of interdependent signals. Its structure allows efficient estimation of its parameters, and various methods for this are examined. Interpolators for Coupled-ARMA signals are derived. For much multi-channel audio work it is necessary to ensure that the observed signals are accurately aligned with each other. Where multiple copies of a disc or tape are under examination this is a difficult problem, since even minute time offsets and speed fluctuations lead to effects such as time-varying comb-filtering when the signals are summed. We examine this problem in detail, and develop a robust scheme for resynchronising signals in a Bayesian statistical framework. Quantisation of audio signals has received much recent research effort. The final part of the dissertation presents a flexible model-based quantisation algorithm. The algorithm is demonstrated in the quantisation of narrow-band signals, and as a powerful enhancement to a simple linear prediction coding system.
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Jones, Maximilian. "Disorder in multi-channel Luttinger liquids." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8147/.
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This thesis examines the effects of disorder upon a bundle of coupled one dimensional (ID) systems. Each 1D system is described as a Luttinger liquid, and the coupling between channels is weak enough such that this description remains valid. The coupling can be of either a density-density or current-current type. We consider continuous disorder in each channel, and derive renormalisation group (RG) equations governing the strength of the disorder. We analyse the effects of disorder in two specific examples: a lattice of identical channels, and two distinct channels. In both cases, close to the simultaneous metal-insulator transition, we arrive at coupled Berezinskii-Kosterlitz-Thouless (BKT) equations. Away from the simultaneous transition we analyse the RG equations numerically. Inter-channel interactions are found to shift the metal-insulator boundary, and destroy the mixed insulator-conductor phase close to the simultaneous transition.
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Zhang, Yan. "Secure and Spectrally-Efficient Channel Access in Multi-Channel Wireless Networks." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/577214.
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Wireless services have become an indispensable part of our social, economic, and everyday activities. They have facilitated and continue to facilitate rapid access to information and have created a highly-interconnected web of users who are untethered to particular locations. In fact, it is expected that in the very near future, the number of users that access the Internet through their mobile devices will surpass those access the Internet from the fixed infrastructure. Aside from mobile Internet access, wireless technologies enable many critical applications such as emergency response, healthcare and implantable medical devices, industrial automation, tactical communications, transportation networks, smart grids, smart homes, navigation, and weather services. The proliferation and wealth of wireless applications has created a soaring demand for ubiquitous broadband wireless access. This demand is further fueled by the richness of the information accessed by users. Low-bit rate voice communications and text have been replaced with graphics, high-definition video, multi-player gaming, and social networking. Meeting the growing traffic demand poses many challenges due to the spectrum scarcity, the cost of deploying additional infrastructure, and the coexistence of several competing technologies. These challenges can be addressed by developing novel wireless technologies, which can efficiently and securely manage multi-user access to the wireless medium. The multi-user access problem deals with the sharing of the wireless resource among contending users in an efficient, secure, and scalable manner. To alleviate contention and interference among the multiple users, contemporary wireless technologies divide the available spectrum to orthogonal frequency bands (channels). The availability of multiple channels has been demonstrated to substantially improve the performance and reliability of wireless networks by alleviating contention and interference. Multi-channel networks, whether cellular, sensor, mesh, cognitive radio, or heterogeneous ones, can potentially achieve higher throughput and lower delay compared to single-channel networks. However, the gains from the existence of orthogonal channels are contingent upon the efficient and secure coordination of channel access. Typically, this coordination is implemented at the medium access control (MAC) layer using a multi-channel MAC (MMAC) protocol. MMAC protocols are significantly more sophisticated than their single-channel counterparts, due to the additional operations of destination discovery, contention management across channels, and load balancing. A significant body of research has been devoted to designing MMAC protocols. The majority of solutions negotiate channel assignment every few packet transmissions on a default control channel. This design has several critical limitations. First, it incurs significant overhead due to the use of in-band or out-of-band control channels. Second, from a security standpoint, operating over a default control channel constitutes a single point of failure. A DoS attack on the control channel(s) would render all channels inoperable. Moreover, MMAC protocols are vulnerable to misbehavior from malicious users who aim at monopolizing the network resources, or degrading the overall network performance. In this dissertation, we improve the security and spectral efficiency of channel access mechanisms in multi-channel wireless networks. In particular, we are concerned with MAC-layer misbehavior in multi-channel wireless networks. We show that selfish users can manipulate MAC-layer protocol parameters to gain an unfair share of network resources, while remaining undetected. We identify possible misbehavior at the MAC-layer, evaluate their impact on network performance, and develop corresponding detection and mitigation schemes that practically eliminate the misbehavior gains. We extend our misbehavior analysis to MAC protocols specifically designed for opportunistic access in cognitive radio networks. Such protocols implement additional tasks such as cooperative spectrum sensing and spectrum management. We then discuss corresponding countermeasures for detecting and mitigating these misbehavior. We further design a low-overhead multi-channel access protocol that enables the distributed coordination of channel access over orthogonal channels for devices using a single transceiver. Compared with prior art, our protocol eliminates inband and out-of-band control signaling, increases spatial channel reuse, and thus achieves significant higher throughput and lowers delay. Furthermore, we investigate DoS attacks launched against the channel access mechanism. We focus on reactive jamming attacks and show that most MMAC protocols are vulnerable to low-effort jamming due to the utilization of a default control channel. We extend our proposed MMAC protocol to combat jamming by implementing cryptographic interleaving at the PHY-layer, random channel switching, and switching according to cryptographically protected channel priority lists. Our results demonstrate that under high load conditions, the new protocol maintains communications despite the jammer's effort. Extensive simulations and experiments are conducted to evaluate the impact of the considered misbehaviors on network performance, and verify the validity of the proposed mechanisms.
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Prax, Patrick. "Do MMORPGs enhance MMMCCL : Multi-Media Multi-Channel Communication Literacy." Thesis, Uppsala University, Media and Communication, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-106854.
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Purpose/Aim: The aim of the paper is to find out if there is a correlation between playing MMORPGs and having better skills in using multi-channel communication.
Material/Method: A media-skill test was conducted in the internet testing the participants’ ability to respond to targets in three different channels and media at the same time. The results of the study where used for statistical comparisons of the different groups of participants sorted according to their media use.
Main results: People who use the internet more and who play computer games, especially MMORPGs, have a better Multi-Media Multi-Channel Communication Literacy. There is fast learning visible for people with a use of the respective medium of up to five hours a week. Playing makes you better, not playing a lot.
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Wang, Kehao. "Multi-channel opportunistic access : a restless multi-armed bandit perspective." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00832569.
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In the thesis, we address the fundamental problem of opportunistic spectrum access in a multi-channel communication system. Specifically, we consider a communication system in which a user has access to multiple channels, but is limited to sensing and transmitting only on one at a given time. We explore how the smart user should exploit past observations and the knowledge of the stochastic properties of these channels to maximize its transmission rate by switching channels opportunistically. Formally, we provide a generic analysis on the opportunistic spectrum access problem by casting the problem into the restless multi-armed bandit (RMAB) problem, one of the most well-known generalizations of the classic multi-armed bandit (MAB) problem, which is of fundamental importance in stochastic decision theory. Despite the significant research efforts in the field, the RMAB problem in its generic form still remains open. Until today, very little result is reported on the structure of the optimal policy. Obtaining the optimal policy for a general RMAB problem is often intractable due to the exponential computation complexity. Hence, a natural alternative is to seek a simple myopic policy maximizing the short-term reward. Therefore, we develop three axioms characterizing a family of functions which we refer to as regular functions, which are generic and practically important. We then establish the optimality of the myopic policy when the reward function can be expressed as a regular function and the discount factor is bounded by a closed-form threshold determined by the reward function. We also illustrate how the derived results, generic in nature, are applied to analyze a class of RMAB problems arising from multi-channel opportunistic access. Next, we further investigate the more challenging problem where the user has to decide the number of channels to sense in each slot in order to maximize its utility (e.g., throughput). After showing the exponential complexity of the problem, we develop a heuristic v-step look-ahead strategy. In the developed strategy, the parameter v allows to achieve a desired tradeoff between social efficiency and computation complexity. We demonstrate the benefits of the proposed strategy via numerical experiments on several typical settings.
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Kaufmann, Silvan [Verfasser]. "Multi Channel Management im Retailbanking : Eine Analyse des Distributionsmanagements und des Kundenverhaltens im Multi Channel Banking / Silvan Kaufmann." Aachen : Shaker, 2004. http://d-nb.info/1172609861/34.
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Sardana, Divya. "Control-channel Reuse-based Multi-channel MAC Protocol for Ad Hoc Networks." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1249856000.
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Takeda, Kazuya. "Multi-Channel Multi-Modal Speech Corpus for In-Car Communication Research." INTELLIGENT MEDIA INTEGRATION NAGOYA UNIVERSITY / COE, 2004. http://hdl.handle.net/2237/10451.
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Amin, Shoaib. "Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers." Doctoral thesis, KTH, Signalbehandling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-197266.
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The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed. When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed. To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions. Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.QC 20161205
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Tervo, O. (Oskari). "Effective channel state acquisition in multi-cell multi-user MIMO system." Master's thesis, University of Oulu, 2013. http://urn.fi/URN:NBN:fi:oulu-201306011414.
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In a cellular network with small cells, where all the communication resources are shared, the inter-cell interference becomes a limiting factor of performance. The strategies for mitigating the inter-cell interference has been quite extensively studied lately. One of the promising candidates is coordinated beamforming/scheduling, where a certain number of cells is allowed to cooperate such that the transmission from each cell takes into account the interference it would cause to the users of other cells. In this thesis, the performances of different signaling strategies which perform the weighted sum rate maximization in time division duplex multi-cell multi-user MIMO downlink system are studied. The strategies consist of iterative decentralized algorithms, aiming at reduced pilot signaling overhead and faster convergence. The required control information between the cells is provided via uplink reference signals and a backhaul. Uplink reference signals include sounding reference signals and busy bursts. Based on the earlier work, the strategies have now been extended to a larger cellular system in which the frequency selectivity and the uncertainty of the channel information are also taken into account. The ability of the strategies to handle the large network can be seen from the simulation results. It is shown that even when there is strong inter-cell interference, the strategies utilizing parallel cell-specific iterations offer practical convergence speed. It is also noticed that the joint optimization over many frequency blocks brings a minor improvement on the sum rate performance, meaning that it could also be utilized with the same order of computational complexity compared to the frequency flat case. Finally, the robustness of the centralized strategy to the imperfect channel state information is shown and the trade-off between the CSI uncertainty and multi-user diversity is statedSolukkoverkossa, jossa solujen koot ovat pieniä ja kaikki käyttävät samoja taajuuksia, solujen välinen häiriö rajoittaa verkon suorituskykyä. Viime aikoina on laajasti tutkittu strategioita, joilla häiriötä saataisiin vähennettyä. Yksi lupaavista menetelmistä tähän tarkoitukseen on koordinoitu keilanmuodostus/skedulointi, jossa tietty ryhmä soluja voi koordinoida keskenään ja näin ottaa huomioon lähetyksestä aiheutuvan häiriön toisia soluja kohtaan. Tässä diplomityössä tutkitaan erilaisten painotetun summadatanopeuden maksimoivien signalointistrategioiden suorituskykyä aikajakodupleksoidussa usean solun ja käyttäjän moniantenniverkossa, jossa dataa lähetetään tukiasemasta käyttäjille. Strategiat perustuvat iteratiivisiin hajautettuihin algoritmeihin, joiden tarkoituksena on vähentää opetussignaloinnista aiheutuvaa kuormitusta ja nopeuttaa suppenemista. Kontrolli-informaation signaloimiseen verkossa käytetään käyttäjiltä tukiasemille lähetettäviä opetussignaaleja ja taustayhteyttä tukiasemien välillä. Työ perustuu aiemmin tehtyyn tutkimukseen, josta strategiat on nyt laajenettu suurempaan solukkojärjestelmään, ottaen huomioon myös taajuusselektiivisyyden ja kanavainformaation epävarmuuden vaikutukset. Simulointitulosten perusteella voidaan sanoa, että strategiat toimivat usean käyttäjän ja solun verkossa. Tuloksista nähdään, että rinnakaisia solukohtaisia iteraatioita hyödyntävillä strategioilla voidaan saavuttaa käytännöllinen suppenemisnopeus, vaikka solujen välinen häiriö on voimakasta. Taajuusselektiivisen kanavan tuloksista huomataan, että yhteisoptimointi usean taajuuslohkon yli parantaa vähän suorituskykyä verrattuna yhden taajuuden tapaukseen. Yhteisoptimointia voitaisiin siis myös hyödyntää, koska laskennallinen monimutkaisuus on samaa suuruusluokkaa verrattuna yhden taajuuden tilanteeseen. Epävarman kanavatiedon vaikutusta tutkitaan keskitetyllä optimointimenetelmällä, joka selvästi laskee suorituskykyä verrattuna täydellisen kanavan tapaukseen, mutta antaa kuitenkin selkeän parannuksen alkuperäiseen algoritmiin verrattuna. Koska opetussignaalien teho jaetaan käyttäjien kesken, tulokset näyttävät kompromissin kanavatiedon epävarmuuden ja monikäyttäjädiversiteetin välillä
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Determe, Jean-François. "Greedy algorithms for multi-channel sparse recovery." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/265808.
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During the last decade, research has shown compressive sensing (CS) to be a promising theoretical framework for reconstructing high-dimensional sparse signals. Leveraging a sparsity hypothesis, algorithms based on CS reconstruct signals on the basis of a limited set of (often random) measurements. Such algorithms require fewer measurements than conventional techniques to fully reconstruct a sparse signal, thereby saving time and hardware resources. This thesis addresses several challenges. The first is to theoretically understand how some parameters—such as noise variance—affect the performance of simultaneous orthogonal matching pursuit (SOMP), a greedy support recovery algorithm tailored to multiple measurement vector signal models. Chapters 4 and 5 detail novel improvements in understanding the performance of SOMP. Chapter 4 presents analyses of SOMP for noiseless measurements; using those analyses, Chapter 5 extensively studies the performance of SOMP in the noisy case. A second challenge consists in optimally weighting the impact of each measurement vector on the decisions of SOMP. If measurement vectors feature unequal signal-to-noise ratios, properly weighting their impact improves the performance of SOMP. Chapter 6 introduces a novel weighting strategy from which SOMP benefits. The chapter describes the novel weighting strategy, derives theoretically optimal weights for it, and presents both theoretical and numerical evidence that the strategy improves the performance of SOMP. Finally, Chapter 7 deals with the tendency for support recovery algorithms to pick support indices solely for mapping a particular noise realization. To ensure that such algorithms pick all the correct support indices, researchers often make the algorithms pick more support indices than the number strictly required. Chapter 7 presents a support reduction technique, that is, a technique removing from a support the supernumerary indices solely mapping noise. The advantage of the technique, which relies on cross-validation, is that it is universal, in that it makes no assumption regarding the support recovery algorithm generating the support. Theoretical results demonstrate that the technique is reliable. Furthermore, numerical evidence proves that the proposed technique performs similarly to orthogonal matching pursuit with cross-validation (OMP-CV), a state-of-the-art algorithm for support reduction.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Li, Zhou. "Multi-channel quantum dragons in rectangular nanotubes." Thesis, Mississippi State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1586984.
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Recently the theoretical discovery of single channel quantum dragons has been reported. Quantum dragons are a class of nanodevices that may have strong disorder but still permit energy-independent total quantum transmission of electrons. This thesis illustrates that multi-channel quantum dragons also exit in rectangular nanotubes and provide an approach to construct multi-channel quantum dragons in rectangular nanotubes. Rectangular nanotube multi-channel quantum dragons have been validated by matrix method based quantum transmission calculation. This work could pave the way for constructing multi-channel quantum dragons from more complex nanostructures such as single-walled zigzag carbon nanotubes and single-walled armchair carbon nanotubes.
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羅福隆 and Fook-loong Lo. "Performance of multi-channel random access networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31236029.
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Juillet, Daniel M. "Detonation diffraction in a multi-step channel." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5064.
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Approved for public release; distribution is unlimitedThis research investigated multiple detonation diffraction events in order to better understand the limits and benefits of diffraction strategies with respect to pulse detonation engine design. Hydrogen/air detonations were generated using swept ramp obstacles in a 1.27 m long channel with a cross section of 25.4 mm by 88.9 mm and were diffracted into various multiple-stepped openings. This allowed the detonation wave diffraction transmission limits to be determined for hydrogen/air mixtures and to better understand reinitiating mechanisms throughout the diffraction process. Tests were conducted for area ratios ranging from 2.00-2.60 with varying equivalence ratios from 0.5-1.5. Computational methods were used to better understand the diffraction phenomenon using a series of sensitivity studies for different chemistry sets, computational cell size and equivalence ratio. Experimental tests used combined optical shadowgraph and particle image velocimetry imaging systems to provide shock wave detail and velocity information. The images were observed through a newly designed explosive proof optical section and split flow detonation channel. It was found that area ratios of 2.0 could survive single and double diffraction events over a range an equivalence ratio range of 0.8 to 1.14 Area ratios of 2.3 survived the primary diffraction event for equivalence ratios near stoichiometric for the given step length. Detonation diffraction for area ratios of 2.6 did not survive the primary diffraction event for any equivalence ratio and were unable to transmit to a larger combustor.
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Power, Phillip David. "Non-linear multi-layer perceptron channel equalisation." Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343086.
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Kendall, Melanie J. "Speech perception with multi-channel cochlear implants." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267060.
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Kleist, Sofia, and Linnéa Lindstedt. "Brand image in multi-channel fashion companies." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-23786.
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Branding has become increasingly important in order to distinguish a brand from numerous competitors in the fashion industry. An effective way to differentiate the brand from others has shown to be through the brand image, which is why managers should work on sustaining a positive brand image. Managing brand image through different sales channels has become even more important due to the rise of multi-channels. The integration and effort of offline and online channels can result in both enhanced purchase intention and brand image. Previous literature has shown how purchase intention can be derived from the level of congruity between the consumer’s self-image and the brand’s image. Despite this, most previous research is conducted from a company perspective, why this research intends to provide theoretical contributions from a consumer perspective. This is particularly important for fashion brands, as for the ever-changing and highly competitive characteristics of the fashion market. Furthermore, an understanding of consumers’ perception of brand image in different sales channels has been missing in previous research. Therefore, the aim of this research is to investigate how consumers perceive brand image of multi-channel fashion companies for the purpose of providing insight into how brand image should be managed through different channels. Using a qualitative perspective, this explorative research conducts ten semi-structured interviews with women and men between the ages of 18 and 63, that are experienced within fashion consumption in online and offline channels. Analysis of the research findings indicates that there are 13 attributes that consumers consider as most prominent for brand image; six offline attributes and seven online attributes. For the offline image, it emerges that the surrounding environment, products and collections, price and value, store personnel and service, reputation are prominent attributes. For online, easy access and navigation, design and aesthetics, merchandise description, price and value, communication, services and reputation are prominent. It is also found that interviewees find it highly important that the image is consistent through different channels so that the brand conveys a holistic image.
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Huang, Wun-Yuan, and 黃文源. "Channel Assignment Study for Multi-Channel Multi-Radio Wireless Mesh Networks." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/03868574855987716539.
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碩士國立東華大學
資訊工程學系
97
With the popularity and development of networks in recent years, the wireless network has become an important research topic. Most research efforts on this area are to improve the performance of wireless network, particularly using multiple channels. While traditional wireless networks use single channel, there is no way to carry out many simultaneous transmission links at the same time, but multi-channel networks can solve the problem. However, there are some problems when using multi-channels. These problems are the interference and split problems. The split problems can be solved by using of multiple radios. The interference problem is a hot topic that lots of researchers try to solve. This paper focused on the architecture of the wireless mesh networks. The main research issue is how to improve network performance under multi-channel and multi-radio environments. We have to consider the interference problem for having good performance. There should be a good channel assignment mechanism to avoid interference. There are two types of methods on channel assignment: distributed channel assignment and centralized channel assignment. The difference between them is that when using the distributed channel assignment nodes decide which channel to use by themselves, but there is a controller in the centralized channel assignment. Our research focused on the centralized channel assignment. In this paper, three different centralized channel assignment algorithms were mentioned: 1. Load-aware channel assignment, 2. Coloring based load-aware channel assignment, and 3. Hybrid channel assignment. These three methods are compared in the multi-channel and multi-radio system under the architecture of the wireless mesh network. We use the NS2 network simulation tool to perform our experiments. We compare these three algorithms in terms of packet loss rate, end-to-end delay, and throughput.
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Xu, Wei. "Multi-channel edge detection /." 2005.
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Thesis (M.Sc.)--York University, 2005. Graduate Programme in Computer Science.Typescript. Includes bibliographical references (leaves 112-117). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11930
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Huang, Kuo-Wei, and 黃國瑋. "Channel Assignment Based on SIR in Multi-Channel Multi-Radio Wireless Mesh Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/06612801928335938813.
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碩士國立高雄大學
資訊工程學系碩士班
98
In IEEE 802.11s wireless mesh networks, overall throughput will be decreased by co-channel interference between links. To improve throughout and minimize interference, we should carefully assign channels to links in multi-radio and multi-channel wireless mesh networks. We have proposed a new channel assignment scheme in multi-radio and multi-channel wireless mesh networks that can help decrease co-channel interference. In the past, most researches assume protocol model where interference relation between links is binary. With this model, the problem of channel assignment can be transformed to classic node coloring problem in a graph. For a link to function, both ends of the link should have an interface operating on the same channel. However, this requirement may incur interference from neighboring nodes operating on the same channel and result in unusable links. We have proposed an algorithm of channel assignment based on signal-to-interference ratio (SIR). The order of channel assignments for links is based on the degree of interference each link experiences. For reserving connectedness, our algorithm restricts the number of available channels. Simulation results show that, the number of links assigned channels of the proposed approach is equal to the conventional approaches. The number of links in function is more in the proposed approach than in the counterparts. This confirms that the proposed channel assignment algorithm can degrease the number of non-functioning links due to co-channel interference.
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尹廣淳. "Channel-hopping Scheme and Channel-diverse Routing in Multi-radio Multi-hop Wireless Networks." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/39283070138850719865.
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碩士國立交通大學
電信工程研究所
99
In modern wireless networks with multiple orthogonal (non-overlapping) channels available, one essential performance topic is how to effectively exploit channel diversity to enable parallel communications. Generally, having a radio interface hop through all available channels produces better spectrum diversity than binding it permanently to one channel, at the cost of channel switching delays and potentially compromised network connectivity. Moreover, multi-hop communications become challenging due to the lack of a common rendezvous for discovering routes and the difficulty of relaying packets from hop to hop. In this thesis, we propose a multi-radio channel-hopping scheme (CHS) that preserves network connectivity. We prove that less than three radios are required by CHS in order to achieve good channel overlapping in widespread IEEE 802.11-based wireless systems. Corresponding channel-diverse routing (CDR) protocol is devised to realize efficient multi-hop communications. Simulation results demonstrate that the proposed CDR outperforms other strategies in an IEEE 802.11a multi-hop networking environment.
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Li, Xin-Ying, and 李欣盈. "Customer Satisfaction and Channel Loyalty of Multi-channel shopper." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/31835364686464997178.
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碩士國立臺北大學
企業管理學系
94
During the past 10 years, the discussions of channels have been focusing on channel patterns, channel structure, and channel membership. Some researches conducted through consumer’s point of view, discussing the difference between traditional channel and virtual channel or customer satisfaction and store loyalty of virtual channel. However, very few researches have been conducted on the context of which consumer purchase goods cross-channel employment. Thus, the purpose of this research is to examine multi-channel shopper existence, discuss the relation among multi-channel employment, customer satisfaction, and channel loyalty, and assess the impact of purchasing involvement on customer satisfaction and channel loyalty. The related literatures have been reviewed. Such as, channel service outputs, customer satisfaction, expectancy-disconfirmation model, customer loyalty, and purchasing involvement. The participants of this research are based in Taiwan, have purchased cosmetics or skin care product and must be older than 15 years old. Data was collected by questionnaires. The questionnaires were distributed through electrical form on the website and paper-printed form. We adopted Structural Equation Modeling (SEM) to analyze data, and examining the research hypothesis. Result of study show customer multi-channel employment positively influences the perceived level of the multi-channel portfolio of services output, an increase in the multi-channel portfolio of service outputs leads to increased positive disconfirmation of the customer’s expectations, disconfirmation positively influences satisfaction, customer satisfaction will positively influence customer attitude loyalty and behavior loyalty. The impact of purchasing involvement on customer satisfaction and channel loyalty is positive. The research findings are as following: (1)Multi-channel shopper is existence. (2)Customer multi-channel employment positively influences customer satisfaction, attitude loyalty and behavior loyalty. (3)The more involved customers were more likely to have customer satisfaction, attitude loyalty and behavior loyalty.
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Liu, An-Che, and 劉安哲. "Dynamic Channel Allocation Scheme in Multi-Channel CATV Network." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/78623724575791931859.
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碩士逢甲大學
資訊工程學系
89
Abstract With the development of Internet, the demand of bandwidth from user is more and more. To evaluate these resolving plans and the current environment of Taiwan, CATV network is a good resolving plan indeed. In recent standards of CATV, DOCSIS 1.1 is a generally acknowledge standard. There are many mechanisms of standard ensuring QoS (Quality of Service) and the idea of priority. We can promise that those higher priority users could get the higher transmitting performance through giving the different priority to different Cable Modem (CM), We can achieve some level of QoS to protect the base transmitting demand of QoS to users with different level. In this paper, we study the relationship between DOCSIS 1.1 and QoS, and proposed some advanced methods. And we proposed a method which adding a priority mechanism on the process of disposing CM channels. We used two mechanisms to ensure all the CMs have a best distributing situation in CATV network. First, we exploited a modified channel allocation scheme to ensure the CMs have the best distribution. And we use another channel balance scheme to balance the throughput and the number of CM for every channel.
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Chung, Yi-Fang, and 鍾依芳. "Distributed Channel Assignment in Multi-channel Wireless Mesh Network." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/78916500809284034399.
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碩士國立臺灣大學
資訊工程學研究所
99
In IEEE 802.11, channel resources are very limited and scarce. Thus channel assignment schemes which can effectively utilize available channels is one of the important issues in multi-channel wireless mesh networks. There are two approaches for channel assignment: centralized and distributed. We focus on distributed channel assignment, i.e., each node chooses its channel based on local information. The advantages of distributed approach are better flexibility and fault-tolerance. However, the problem of distributed channel assignment is channel oscillation which results that the channel assignment cannot converge for a long time and nodes change its channel repeatedly, and therefore the network throughput is throttled. In this thesis, we propose a new distributed channel assignment scheme to solve the channel oscillation problem, and to maximize the network throughput. Performance evaluation shows that our proposed algorithm improves the throughput and end-to-end delay in comparison to previously proposed distributed channel assignment schemes.
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Pentakota, Krishna Anand Santosh Spikanth. "Digitally Assisted Multi-Channel Receivers." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8398.
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This work presents a data estimation scheme for wide band multi-channel charge
sampling receivers with sinc filter banks together with a complete system calibration and
synchronization algorithm for the receiver. A unified model has been defined for the
receiver containing all first order mismatches, offsets and imperfections and a technique
based on least mean squares algorithm is employed to track these errors. The performance
of this technique under noisy channel conditions has been verified. The sinc filter bank is
compared with the conventional analog filter banks and it is shown that the sinc filter banks
have very low computational complexity in data estimation
Nextly, analytical tools for the design of clock-jitter tolerant multi-channel filterbank
receivers have been developed. Clock-jitter is one of the most fundamental obstacles
for the future generation of wideband receivers. Additionally all the trade-offs and
specifications of a design example for a multi-channel receiver that can process a 5 GHz
baseband signal with 40 dB of signal-to-noise-ratio (SNR) using sampling clocks that can
tolerate up to 5 ps of clock-jitter standard deviation are presented. A novel bandwidth
optimization technique has been presented. As a part of it the bandwidth of the filters present in each path is optimized thereby improving the performance of the receiver further
in the presence of sampling clock jitter. The amount of bandwidth reduction possible
depends on the order of the filter and the noise amplification provided by the reconstruction
matrix. It has been shown that 3rd order filters of bandwidth 1 GHz can be replaced with 1st
order filters of bandwidth 100 MHz without any depreciation in the output resolution,
implying huge power savings.
47
"Hierarchies and multi-channel queues." 2006. http://library.cuhk.edu.hk/record=b5892961.
Full textAbstract:
Cheung Ka Wo.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (leaves 61-63).
Abstracts in English and Chinese.
Chapter 1. --- Introduction --- p.1
Chapter 2. --- A review of Queueing theory --- p.7
Chapter 2.1 --- Introduction to Queueing theory --- p.7
Chapter 2.2 --- The M/M/l Queue --- p.13
Chapter 2.3 --- The M/M/c Queue --- p.15
Chapter 3. --- Model --- p.18
Chapter 3.1 --- Hierarchy --- p.18
Chapter 3.2 --- Random-assigning Model and M/M/l queues --- p.23
Chapter 3.3 --- Idle-assigning Model and M/M/c queues --- p.26
Chapter 3.4 --- Total Cost --- p.29
Chapter 4. --- Optimization --- p.36
Chapter 4.1 --- Minimum Total Cost --- p.36
Chapter 4.2 --- The Optimal Number of Workers --- p.42
Chapter 4.3 --- General Optimization --- p.45
Chapter 5. --- Routing --- p.52
Chapter 6. --- Conclusion --- p.56
Appendix --- p.58
Detail of computational results given in Section 4.2 --- p.58
Reference --- p.61
48
Shao, Kuei-Yu, and 邵桂裕. "Multi-Channel LED Driver Circuit." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/4mxxhr.
Full textAbstract:
碩士崑山科技大學
電子工程研究所
96
Displayer has become the inportant part of Electronical prudoct, and it also requires light source by Back light module. High brightness White Emitting Diode(LED) has become the important back light source. The profites of White light Led are cheep price、long life、and low power etc. The White light led is going to replace the traditional Sunlight bulb in the future. Therefore,driver IC will reveal its is important. In this paper, three LED drivers with uniform current adjustment mechanism were designed by the H-Spice tool. The first chip uses a high-gain OPA, an NMOS transistor and a resistor to implement a current source that can be controlled by an external voltage. It would drive sixteen high-brightness white-light LEDs through sixteen current mirrors. The second chip is trying to add a bandgap reference voltage circuit and to use a cascode mirror circuit construction. Because the chip will produce heat by itself, in order to promote the precision and yield of the whole circuit, we need a steady reference voltage. which will not change a lot when the input voltage and temperature change. The cascode mirror circuit construction is designed to reduce the effects of drain-source voltage drop on the mirrored current because the turn-on voltage of LED is process-dependent. The third chip is designed to improve the bandgap reference construction of the second chip in order to make LED driving current adjustable. These LED drivers use the full-custom-design methodology of the 0.35μm 2P4M CMOS technology provided by Taiwan Semiconductor Manufacturing Company (TSMC) as the design and simulation platform in this paper.
49
Hsieh, Chihwen, and 謝志文. "A Multi-Channel Communication Framework." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/33198951094136207964.
Full text
50
CHEN, CONG-MIN, and 陳聰敏. "VLSI multi-layer channel routing." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/01171891948013845965.
Full text