To see the other types of publications on this topic, follow the link: Multi-user Communication.
Dissertations / Theses on the topic 'Multi-user Communication'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Multi-user Communication.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hijazi, Samer L. "Multi-user detection for multi-carrier communication systems." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/147.
Full text
2
Gheitanchi, Shahin. "Collaborative multi-Carrier communication techniques for multi-user systems." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499569.
Full textAbstract:
Developing robust techniques for fast growing multi-user networks in pervasive environments is an important challenge. Multi-carrier communication is an established technique for achieving superior performance in multi-path frequency selective fading channels. In this thesis, new multi-carrier multiple access techniques using collaborative and cooperative approaches are proposed for multi-user systems in fading environments.
3
Price, Jennifer Elizabeth. "Resource allocation in multi-user communication systems." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3266771.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed August 7, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 134-140).
4
Sin, Chun Yin. "Performance analysis of multi-user wireless network /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ECED%202006%20SIN.
Full text
5
Girnyk, Maksym. "Cooperative communication for multi-user cognitive radio networks." Licentiate thesis, KTH, Kommunikationsteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96794.
Full textAbstract:
In recent years, the main trend in wireless communications has been shifted from voice transmission to data-centric communication. This shift has caused an increase in the data rate requirements for future wireless communication systems. These requirements result in need for large bandwidth. Being a limited and thus expensive resource, wireless spectrum needs to be used efficiently. For higher spectral efficiency, new transmission techniques as well as new dynamic spectrum-allocationpolicies are needed. Cognitive radio is a promising approach for increasing spectral efficiency of wireless systems. By exploiting advanced signal processing techniques and sophisticated transmission schemes, cognitive radio devices allow to serve new wireless users within the existing crowded spectrum. Typically, a cognitive radio network is installed in parallel to an existing primary network, a legacy owner of the spectrum. The cognitive radio network adapts to its electro-magnetic environment in order to limit or even avoid the disturbance to the primary network. This thesis focuses on the underlay cognitive radio paradigm, which assumes that both the primary network and the ad hoc cognitive radio network operate within the same time and frequency band, as well as at the same geographic location. The cognitive network is able to estimate the interference caused to the primary network by means of channel training and possible feedback. This knowledge is then used to adjust the cognitive network’s transmissions in such a way that the disturbance to the primary network is below some acceptable threshold. In the first part of the thesis, we discuss the multi-hop line cognitive networks, in which the information content before reaching its destination passes through several hops from node to node within the cognitive network. In this way, transmission power at the source terminal may be decreased, thus producing less interference to the primary network. Moreover, the powers at each terminal within the cognitive network may be optimally allocated so that the interference constraint at the primary network is satisfied. This power allocation can be realized in both centralized and decentralized ways, depending on the available information about the channel state. We discuss both of these allocations subject to different interference constraints employed at the primary network. In the second part of the thesis, we discuss the reliability of transmission within the line cognitive ad hoc networks in terms of outage probability and diversity. We also illustrate the benefit of network coding for such networks and provide a heuristic algorithm for optimal scheduling. In the final part of the thesis, we study the uplink relay-assisted cellular cognitive radio scenario. Both, the cognitive network and the primary network, contain a set of multi-antenna users that communicate with a corresponding base station. The users create mutual interference and hence limit each other’s performance. Using certain mathematical tools originally developed within the field of statistical physics, we are able derive a closed-form expression for the ergodic mutual information for arbitrary channels inputs, which enables characterization of the achievable rate region of such scenario.QC 20120612
6
Chen, Chiang-Yu. "Optimized resource allocation for MIMO multi-carrier multi-user communication systems /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
7
Jagannathan, Sumanth. "Interference and outage optimization in multi-user multi-carrier communication systems /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
8
Seong, Kibeom. "Cross-layer resource allocation for multi-user communication systems /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
9
Nguyen, Hung. "Network coding for cooperative multi-user wireless communication systems." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/353262/.
Full textAbstract:
In the first chapter, Space Time Trellis Codes (STTCs), Space Time Block Codes (STBCs)and Sphere-Packing-Space-Time Block Codes (SP-STBC) are reviewed. These schemes belong to the specific family of Multi-Input Multi-Output (MIMO) systems designed for achieving a diversity gain. The performance of the SP-STBC scheme is compared to other coded conventional modulation systems, namely to that of STBC-Phase Shift Keying or Quadrature Amplitude Modulation (STBC-PSK/QAM) and to that of STTC-Phase Shift Keying or Quadrature Amplitude Modulation (STTC-PSK/QAM). The rest of this chapter reviews other preliminaries pertaining to the context of cooperative communications and network coding. In Chapter 2, an in-depth study of the capacity and outage probability of the Continuous-input Continuous-output Memoryless Channel (CCMC), Discrete-input Continuous-output Memoryless Channel (DCMC) and of Differential Discrete-input Continuous-output Memoryless Channel (DDCMC) is presented. The study also considers various propagation phenomena, namely the smallscale fading and the large-scale fading. The frame-length is also taken into consideration when calculating the achievable throughput and outage probability, which serve as useful benchmarks for our near-capacity coding schemes. Extrinsic Information Transfer (EXIT) charts are used for designing Irregular Convolutional Coded Unity Rate Coded M-ary Phase Shift Keying (IrCC-URCMPSK), Irregular Convolutional Coded Unity Rate Coded Differential M-ary Shift Keying (IrCCURC-DMPSK) and Irregular Convolutional Coded Unity Rate Coded Space Time Trellis Coded M-ary Phase Shift Keying (IrCC-URC-STTC-MPSK) schemes. In Chapter 3, a novel Distributed Concatenated IrCC-URC-STTC (DC-IrCC-URC-STTC) scheme is proposed for cooperative single-user systems relying on single-antenna aided relays, based on the studies conducted in Chapter 1 and Chapter 2. In this contribution, each coding arrangement of the entire DC-IrCC-URC-STTC scheme is designed for achieving decoding convergence to a vanishingly low Bit Error Ratio (BER) by employing non-binary EXIT-charts. Additionally, the EXIT charts are employed for calculating the most appropriate positions of the relays by ensuring that decoding convergence to a vanishingly low BER occurs at a similar Signal-to-Noise Ratio (SNR) both at the relays and at the destination. In Chapter 4, Multi-User Cooperative Communications is designed for supporting M users with the aid of near-capacity network coding. We first derive the upper and lower Frame Error Ratio (FER) performance bounds of cooperative multi-user communications systems using network coding. Then, we investigate Near-Capacity Multi-user Network-coding (NCMN) based systems using the IrCC-URC-MPSK scheme of Chapter 2. In parallel to the investigation of coherent NCMN systems, we also explored Near-capacity Non-coherent Cooperative Network-coding aided Multi-user (NNCNM) based systems using the IrCC-URC-DMPSK, which do not require channel estimation at the receiver’s side. This reduces the complexity imposed, albeit this is achieved at a 3 dB SNR-loss. Moreover, a new technique referred to as the Pragmatic Algebraic Linear Equation Method (PALEM) was proposed for exactly determining the number of information sources that may be recovered from the composite NCMN stream, which results in a more accurate evaluation of the attainable FER performance of the NCMN and NNCNM based systems. The design principles presented in this contribution can be extended to a vast range of NCMN and NNCNM based systems using arbitrary channel coding schemes. In Chapter 5, the NCMN and NNCNM based systems of Chapter 4 are generalised for introducing the Generalised NCMN (GNCMN) system, which has a multi-layer architecture and it is capable of operating in multiple modes. More specifically, the GNCMN system may operate upon employing either individually or in a combined fashion using a single Channel Coding (CC) layer plus two network coding layers, namely Network Coding 1 (NC1) and Network Coding 2 (NC2). Additionally, the GNCMN system is capable of simultaneously exploiting the advantages of all the modes available in each layer of the system as well as appropriately combining the advantageous modes across all the three layers. Finally, in Chapter 6, the summary of our findings are presented in order to facilitate our discussions on future research.
10
Sharma, Vimal. "Multi-user spatial diversity techniques for wireless communication systems." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/34905.
Full textAbstract:
Multiple antennas at the transmitter and receiver, formally known as multiple-input multiple-output (MIMO) systems have the potential to either increase the data rates through spatial multiplexing or enhance the quality of services through exploitation of diversity. In this thesis, the problem of downlink spatial multiplexing, where a base station (BS) serves multiple users simultaneously in the same frequency band is addressed. Spatial multiplexing techniques have the potential to make huge saving in the bandwidth utilization. We propose spatial diversity techniques with and without the assumption of perfect channel state information (CSI) at the transmitter. We start with proposing improvement to signal-to-leakage ratio (SLR) maximization based spatial multiplexing techniques for both fiat fading and frequency selective channels.
11
Ng, Wing Kwan. "Performance analysis of the multi-user system /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20NGW.
Full text
12
Maier, Henning [Verfasser]. "Cyclic Interference Alignment in Multi-User Communication Networks / Henning Maier." Aachen : Shaker, 2015. http://d-nb.info/1074088190/34.
Full text
13
Jiang, Meilong. "Robust cross-layer scheduling design in multi-user multi-antenna wireless systems." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38346758.
Full text
14
Jiang, Meilong, and 江美龍. "Robust cross-layer scheduling design in multi-user multi-antenna wireless systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38346758.
Full text
15
Pan, Zhengang, and 潘振崗. "Generalized beamforming for downlink of multi-user MIMO systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29636139.
Full text
16
Choi, Lai U. "Multi-user MISO and MIMO transmit signal processing for wireless communication /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20CHOI.
Full textAbstract:
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 167-170). Also available in electronic version. Access restricted to campus users.
17
Agarwal, Mukul Ph D. Massachusetts Institute of Technology. "A universal, operational theory of multi-user communication with fidelity criteria." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70785.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 237-239).
This thesis has two flavors: 1. A theory of universal multi-user communication with fidelity criteria: We prove the optimality of digital communication for universal multi-user communication with fidelity criteria, both in the point-to-point setting and in the multi-user setting. In other words, we prove a universal source-channel separation theorem for communication with a distortion criterion, both in the point-to-point setting and the multi-user setting. In the multi-user setting, the setting is unicast, that is, the sources which various users want to communicate to each other are independent of each other. The universality is over the medium of communication: we assume that the medium might belong to a family. Both in the point-to-point setting, we assume that codes can be random: the encoder might come from a family of deterministic codes and the decoder has access to the particular realization of the deterministic code, and finally, an average is taken over all these deterministic codes. In Shannon's theory, random-coding is a proof technique. However, in our setting, random codes are essential: universal source-channel separation does not hold if codes are not allowed to be random. This happens because we are asking the universal question. We also show the partial applicability of our results to the traditional wireless telephony problem. 2. An operational theory of communication with a fidelity criterion: We prove the source-channel separation theorem operationally: we rely only on definitions of channel capacity as the maximum rate of reliable communication and the rate-distortion function as the minimum rate needed to compress a source to within a certain distortion level. We do not rely on functional simplifications, for example, mutual information expressions for the proofs. By operational, we do not mean that what we are doing is "practically operational". The view that we have can also be viewed as a layered black-box view: if there is a black-box that is capable of one form of communication, then the black-box can be layered in order to accomplish another form of communication.
by Mukul Agarwal.
Ph.D.
18
Zarakovitis, Charilaos C. "Convex optimization-based resource scheduling for multi-user wireless systems." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/11068.
Full text
19
Abedi, Saied. "Genetic multi-user detection for code division multiple access systems." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843016/.
Full textAbstract:
The origins of spread spectrum are in navigation and military systems. Techniques originally developed to reduce the effects of the intentional jamming also proved suitable for communications through dispersive channels in cellular applications. In 1949 the first time hoping spread spectrum multiple access system has been introduced by John Pierce. A direct-sequence spread spectrum system has been proposed by De Rosa-Rogoff later in 1950. He has also introduced the concept of processing gain. However the commercialisation of cellular direct-sequence code division multiple access (DS-CDMA) systems became possible only during the 1980's and 1990's. In 2000 and beyond we will be witness to the standardisation and commercialisation of wide band CDMA system with a bandwidth of 5 MHz or more. While CDMA presents a number of advantages for cellular mobile communications, it has its own drawbacks. Good air interface designs provide efficient solutions for the terrestrial cellular system. We first take a look at the problem of narrow-band and partial band interference suppression in a CDMA system. By using Poor's model for partial-band interference, some interference suppression techniques are analysed. Then the concept of hybrid genetic prediction is introduced which outperforms the nonlinear techniques in terms of SNR improvements. The performance of a CDMA system can be degraded by Multiple Access Interference (MAI) due to the presence of many users in the same bandwidth. After analysing the structure and performance of existing multi user detection techniques, a low complexity bit level detector is proposed to reduce MAI in synchronous CDMA (S-CDMA) system for an AWGN channel. It is shown how it is possible to reach almost the single user bound by combining detection theory and the fundamentals laws of evolution found in nature. Nonlinear mappings are added to the proposed detector to increase detector's performance by reducing the misleading effect of noise on the detection process. Then for Asynchronous CDMA (A-CDMA), a novel packet level genetic detector is proposed. The near-far resistance feature of the proposed detector is studied. The effect of different parameters of genetic engine i.e. chromosome length, gene's value or mutation and crossover probabilities on its performance are characterised. Different initialisation methods are introduced. For high bit rate CDMA system in multimedia applications in a dispersive CDMA channel, Inter Symbol Interference (ISI) becomes another highly important factor that degrades system performance. It is shown how it is possible to use a signal sub-space based detector as a core detector for a hybrid genetic Multi user detector.
20
Darweesh, Turki H. "Capacity and performance analysis of a multi-user, mixed traffic GSM network." Ottawa, 1999.
Find full text
21
Schepker, Henning F. [Verfasser]. "Compressive Sensing Multi-User Detection Approaches for Sporadic Communication / Henning F. Schepker." Aachen : Shaker, 2015. http://d-nb.info/1081885270/34.
Full text
22
Hsu, Kai-Chieh Frank. "High-performance vector processing for multi-user detection in spread-spectrum communication." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/MQ52998.pdf.
Full text
23
Catrein, Daniel. "Performance analysis and control of wireless communication networks with multi-user receivers /." Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016488053&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Full text
24
Spencer, Quentin H. "Transmission Strategies for Wireless Multi-user, Multiple-Input, Multiple-Output Communication Channels." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd378.pdf.
Full text
25
Mani, GaneshKumar. "Heterogeneous Residential Gateway Design Using OSGi : With multi-user and multi-service capabilities." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208327.
Full textAbstract:
As a result of developments, domestic usage of smart appliances by homeowners is increasing drastically. Clustering these appliances together and making them function as an efficient system defines a new place to live or new way of living called a “smart home”. While a smart home provides comfort to homeowners, realizing a smart home involves many technical and business oriented hurdles to be crossed. The primary goal of this thesis work is to design and evaluate the design of a residential gateway. This gateway should be designed as a standardized, secure, open source, hardware independent, and interoperable Residential Gateway. A service-oriented architecture is proposed using the OSGi framework to design the residential gateway and its individual components. These components include an access control component for homeowner authorization, a resource management component for managing connected devices, an automation component to realize an automation service, and finally a context component to provide context aware services to the homeowner. The final design proposed tries to solve the issues faced by some automation systems that are available in market. The evaluation of the design includes whether the design satisfies the basic requirements for a home gateway. This is followed by a comparison with existing systems with an emphasis on the improved features. The components proposed in the design could be used to construct a residential gateway that supports multiple services and multiple users. The proposed design will be taken into consideration during the design of Acreo’s home automation system.Som en följd av utvecklingen inom vetenskap och teknik så har användningen av smarta lösningar i hushållen ökat drastiskt. Att samla dessa apparater och få dem att fungera tillsammans som ett effektivt system, skapar ett nytt hem och ett nytt sätt att leva: ett smart hem. Å ena sidan så ger smartare lösningar ett bekvämare boende, men å andra sidan innebär det också många tekniska och affärsinriktade hinder att ta sig över. Det primära målet med denna avhandling är att utforma en bostadsgateway som är att utforma en standardiserad, säker, open source, maskinvaruoberoende, interoperabel Residential Gateway. En serviceorienterad arkitektur föreslås med hjälp av OSGi-ramverket för utformning av bostadsgateway-komponenter. Komponenterna innefattar behörighetskontroll för husägare för tillgångskontroll, resurshanteringskomponenter för hantering av anslutna enheter, automationskomponent för att inkludera automationstjänst och slutligen kontextkomponent för att tillhandahålla kontextbevakad tjänster till husägaren. Den slutliga designen som föreslås försöker lösa de problem som vissa automationssystem som finns på marknaden står inför. Utvärderingen av konstruktionen med grundläggande krav för att bygga hemgateways och med befintliga system ger information om de improviserade funktionerna. De komponenter som föreslås i konstruktionen kan användas för att bygga en bostadsgateway som stöder flera tjänster och flera användare. Den föreslagna konstruktionen kommer att beaktas vid utformningen av Acreos hemautomatiseringssystem.
26
Seo, Kyoungnam. "Multi-user interference reduction and throughput enhancement in OFDM-based multicarrier communication systems." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024948.
Full text
27
Kazem, Ihab. "Visibility-based zonal communication in massively multi-user online games and distributed simulations." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27862.
Full textAbstract:
Massively multi-user online games and distributed simulations aim at supporting a large number of users while keeping the communication among the parties synchronous and highly interactive. To achieve collaboration, the virtual world is divided into multiple adjacent hexagonal zones in order to properly organize the entities and efficiently manage their liaison. The data distribution structure is Peer-to-Peer (P2P)-based, to support home users, and is managed by a topology-aware protocol at the application layer rather than the network layer. However, such zoning restricts cross-zonal interactions and exposes the division of the world to the parties. Problems such as crowding one zone among others defeats the very purpose of interest management and makes geographic partitioning alone inefficient for modeling interactions. The objective of the thesis is to introduce the design, implementation, and performance study of an area of interest management approach to manage massively multi-user simulations and online games by shirting messaging from a purely zone-based approach to a visibility-driven one. This makes the partitioning transparent to users. Also, a novel idea is presented for dynamic load balancing to handle transient crowding that can be achieved in real-time without modifying the communication architecture. Implementation and performance measurements are also presented.
28
Maier, Henning Verfasser], Rudolf [Akademischer Betreuer] [Mathar, and Aydin [Akademischer Betreuer] Sezgin. "Cyclic Interference Alignment in Multi-User Communication Networks / Henning Maier ; Rudolf Mathar, Aydin Sezgin." Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1126271608/34.
Full text
29
Baharoon, Walid A. M. "Architect-user communication process through the use of computers in multi-unit housing design." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59621.
Full textAbstract:
It is commonly believed that by involving the user in the design process of his dwelling unit, a higher level of satisfaction could be achieved. Attempts have been made in several countries to include users in the design process of their units using different communication media including computers. However, today computers have been implemented primarily for the use of architects. This study aims at narrowing the architect-user communication gap by using computers in multi-unit housing design. The author reviews past work in user involvement in the design process through the use of computers and the possibility of introducing computers into the North American homebuilding Industry. Through an algorithm the author will demonstrate how the communication process can take place. Two simulations were conducted in order to test the proposed system in a realistic situation. The results of the study suggest that the user is able to make his own decisions, control his budget and satisfy his needs independently within a reasonable amount of time. These results could have further positive impact on the architect, user, building industry and the built environment.
30
Catrein, Daniel [Verfasser]. "Performance Analysis and Control of Wireless Communication Networks with Multi-User Receivers / Daniel Catrein." Aachen : Shaker, 2007. http://d-nb.info/1166512975/34.
Full text
31
Maier, Henning [Verfasser], Rudolf [Akademischer Betreuer] Mathar, and Aydin [Akademischer Betreuer] Sezgin. "Cyclic Interference Alignment in Multi-User Communication Networks / Henning Maier ; Rudolf Mathar, Aydin Sezgin." Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2015-036725.
Full text
32
LI, XIANGTAO. "PERFORMANCE ANALYSIS OF DECORRELATING DETECTORS FOR DUAL-RATE SYNCHRONOUS DS/CDMA SYSTEMS OVER FREQUENCY-SELECTIVE RAYLEIGH FADING CHANNELS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1028644891.
Full text
33
Parnes, Peter. "An IP-multicast based framework for designing synchronous distributed multi-user applications on the Internet." Doctoral thesis, Luleå tekniska universitet, Datavetenskap, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25971.
Full textAbstract:
This thesis examines the problems of how to design scalable, robust, and distributed real-time media applications for the Internet. An agent based framework for solving this problem is presented. The framework promotes several important design requirements such as modularity and reusability of software modules, remote management of applications, adaptiveness, robustness, accessibility, symmetry and the most important scalability. The issue of scalability is examined on several levels including data-distribution, different end-user platforms, scalability of real-time media flows, bandwidth adaption and scalability of sessions. The design of the framework is based on the important concept of IP-multicast, which allows for scalable distribution of data on the Internet. How this decision has influenced the design of the framework is examined in the thesis. The design of the framework have been verified by building a reference implementation in Java and building a number of high-level end-user applications for real-time e-meetings, e-learning (net-based learning) and social awareness via the e-corridor.Godkänd; 1999; 20061004 (ysko)
34
Cao, Huiyuan. "Design of a turn-taking control system based on tactile in multi-user, synchronous remote communication." Thesis, Compiègne, 2013. http://www.theses.fr/2013COMP2109/document.
Full textAbstract:
L'objectif principal de cette thèse est de concevoir un système impliquant un feedback tactile facilitant l’organisation du tour de parole dans le contexte de la communication verbale à distance et à plusieurs. Ces situations impliquant des technologies numériques sont actuellement décrites comme étant des "conferences call". Elles relèvent également du Computer Supported Collaborative Work (CSCW) lorsqu'elles impliquent une tâche collaborative. Curieusement, ces situations n'ont été l'objet que de très peu d'études en dépit des problèmes qu'elles suscitent et l'évolution de ces technologies s'est faite au profit d'un enrichissement par la vidéo. Cette thèse propose une autre forme d'enrichissement par un retour tactile permettant de dépasser l'une des principales difficultés de la communication verbale à distance à savoir le contrôle du tour de parole. Deux modalités de cet enrichissement ont été étudiés : la redondance et la substitution. Comme redondance avec le feedback visuel, nous avons fait l'hypothèse que la modalité tactile favorise l'alternance du tour de parole et augmente l'expression d'intentions non verbales à l'image des situations de face à face. Comme substitution au visuel, l'hypothèse a été de poser que le tactile produit un avantage en cela qu'il fluidifie le tour de parole. Le système conçu dans cette recherche montre, au moyen de trois expériences, que l'échange verbal à distance et sa distribution dans le cadre d'une tâche de prise de décision collective peut être efficient avec un enrichissement tactile et donner lieu à une auto-régulation du tour de paroleOur thesis aim was to design a system based on tactile modality to organize a synchronous, multi-user remote verbal communication to facilitate better turn-taking. The remote communication we studied is actually called the ‘conference call’, and relies on computer technology. A conference call is a form of CSCW, and it is thus a collaborative task. As conference calls have rarely been studied in previous research, a system designed to optimize this kind of work is of great value. Tactile modality is the basic element of the design and its impact is also studied in our thesis. As a modality of redundancy, tactile feedback accelerates the alternation of turn-taking. Moreover, it augments the intention of non-verbal exchanges, which accounts for most of the communication in face-to-face situations. As a modality of substitution, tactile modality shows a distinct advantage in making the turn-taking transfer smoother compared to visual modality. Finally, a conference call for a decision-making task under a simple turn-taking allocation system based on tactile modality provides evidence that this designed system’s controlled conference call has good efficiency and good distribution of the talking length of turn-taking
35
McCarthy, Stephen J. "Investigation of Power Reduction Methods for Multi-User MIMO WLAN Applications." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1416778581.
Full text
36
Awal, Mohammad abdul. "Efficient cqi feedback resource utilisation for multi-user multi-carrier wireless systems." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112223/document.
Full textAbstract:
La technologie OFDMA (Orthogonal frequency division multiple access) a été adoptée par les systèmes de télécommunications de 4ème génération (4G) comme technique de transmission et d'accès multiple pour ses performances supérieures en termes d'efficacité spectrale. Dans ce type de systèmes, l'adaptation dynamique du débit en fonction de la qualité du canal CQI (Channel Quality Indicator) constitue une problématique de recherche d'actualité qui attire l'attention de plusieurs acteurs académiques et industriels. Ce problème d'adaptation dynamique est encore plus complexe à gérer dans des environnements multi-utilisateurs hétérogènes et à ressources limitées tels que les systèmes OFDMA comme WiMAX Mobile et Long-term Evolution (LTE). Dans cette thèse, nous nous intéressons au problème d'allocation de ressources de l'information de feedback relative au CQI dans le cadre de systèmes OFDMA multi-porteuses multi-utilisateurs. Dans le but de réduire la charge (overhead) du feedback, nous proposons une méthode de prédiction du CQI basée sur l'exploitation de la corrélation temporelle de ce dernier et d'une solution inter-couches. L'objectif est de trouver des schémas d'allocation de ressources adaptatifs respectant les contraintes de qualité de service (QoS) applicatives.Nous proposons en premier lieu un algorithme de réduction de feedback PBF (Prediction Based Feedack) qui permet à la station de base (BS) à prédire certaines occurrences du CQI en se basant sur l'algorithme des moindres carrés récursif RLS (Recursive least-square). Les résultats de simulation montrent que l'outil de prédiction du CQI réduit sensiblement l'overhead du feedback et améliore par conséquent le débit de la liaison montante. Nous proposons, par la suite, une version opportuniste de PBF pour atténuer les éventuels effets de sur et sous estimations liées à l'algorithme de prédiction. Dans ce mécanisme, nous exploitons les informations inter-couches pour améliorer les performances des mécanismes de feedbacks périodiques dont PBF fait partie. L'approche opportuniste améliore sensiblement les performances du système pour les cas de mobilité élevée comparés aux cas de faible mobilité.Dans un second temps, nous proposons une plateforme (FEREP : feedback resource allocation and prediction) basée sur une approche inter-couches. Implémentée au niveau de la station BS, FEREP intègre les fonctionnalités de prédiction, d'adaptation dynamique du CQI et d'ordonnancement des demandes de feedback. Elle comporte trois modules. Le module FWA (feedback window adaptation) gère dynamiquement la fenêtre de feedbacks de chaque station mobile (MS) en se basant sur les messages ARQ (Automatic Repeat Request) reçus qui reflètent l'état actuel des canaux respectifs. Le module PBFS (priority-based feedback scheduling) effectue ensuite l'ordonnancement des feedbacks en tenant compte de la taille de la fenêtre de feedback, du profil de l'utilisateur sous la contrainte de la limitation des ressources globales du systèmes réservées au feedback. Afin de choisir les paramètres de transmission MCS (modulation and coding schemes), le module PBF (prediction based feedback) est utilisé pour les utilisateurs dont le feedabck n'a pas pu être ordonnancé dans la trame courante. Les résultats de simulation ont montré un gain significatif des performances de FREREP en comparaison à un mécanisme de référence, en particulier, sous de fortes contraintes de limitation des ressources du feedback.Le protocole ARQ génère un accusé de réception uniquement si l'utilisateur est sélectionné par l'ordonnanceur pour envoyer des données sur la liaison descendante. Dans le cas où la fréquence d'ordonnancement des utilisateurs sur le lien descendant est réduite, les messages ARQ s'en trouvent également réduits, dégradant par conséquent les performances de la plateforme FEREP proposée ci-dessus. En effet, dans ce cas la signalisation ARQ devient insuffisante pour adapter efficacement la fenêtre de feedback de chaque utilisateur. Pour pallier à ce problème, nous proposons l'algorithme DCRA (dynamic CQI resource allocation) qui utilise deux modes d'estimation de la fenêtre de feedback. Le premier est un mode hors-ligne basé sur des études empiriques permettant d'estimer la fenêtre moyenne optimale de feedback en utilisant les profils applicatif et de mobilité de l'utilisateur. Notre analyse de performance par simulation montre que la fenêtre de feedback peut être estimée en fonction de la classe de service des utilisateurs et de leurs profils de mobilité pour un environnement cellulaire donné. Le second mode de fonctionnement de DCRA effectue une adaptation dynamique de la fenêtre en temps réel dans le cas où la signalisation ARQ est suffisante. Une étude comparative avec les mécanismes DFS (deterministic feedback scheduling) et OFS (opportunistic feedback scheduling), a montré que DCRA arrive à réaliser un meilleur gain en ressources montantes grâce à la réduction de l'overhead des feedbacks, sans pour autant trop dégrader le débit descendant des utilisateurs. Du point de vue des utilisateurs, DCRA améliore les contraintes de QoS tels que le taux de perte de paquets et réduit la consommation énergétique des terminaux grâce à la réduction de feedbackOrthogonal frequency division multiple access (OFDMA) technology has been adopted by 4th generation (a.k.a. 4G) telecommunication systems to achieve high system spectral efficiency. A crucial research issue is how to design adaptive channel quality indicator (CQI) feedback mechanisms so that the base station can use adaptive modulation and coding (AMC) techniques to adjust its data rate based on the channel condition. This problem is even more challenging in resource-limited and heterogeneous multiuser environments such as Mobile WiMAX, Long-term Evolution (LTE) networks. In this thesis, we consider CQI feedback resource allocation issue for multiuser multicarrier OFDMA systems. We exploit time-domain correlation for CQI prediction and cross-layer information to reduce feedback overhead for OFDMA systems. Our aim is find resource allocation schemes respecting the users QoS constraints.Our study begins with proposing prediction based feedback (PBF) which allows the base station to predict the CQI feedbacks based on recursive least-square (RLS) algorithm. We showed that it is useful to use channel prediction as a tool to reduce the feedback overhead and improve the uplink throughput. Then, we propose an opportunistic periodic feedback mechanism to mitigate the possible under and over estimation effects of CQI prediction. In this mechanism, we exploited the cross-layer information to enhance the performance of periodic feedback mechanisms. The opportunistic mechanism improves the system performance for high mobility cases compared to low mobility cases.For OFDMA systems with limited feedback resource, we propose an integrated cross-layer framework of feedback resource allocation and prediction (FEREP). The proposed framework, implemented at the BS side, is composed of three modules. The feedback window adaptation (FWA) module dynamically tunes the feedback window size for each mobile station based on the received ARQ (Automatic Repeat Request) messages that reflect the current channel condition. The priority-based feedback scheduling (PBFS) module then performs feedback allocation by taking into account the feedback window size, the user profile and the total system feedback budget. To choose adapted modulation and coding schemes (MCS), the prediction based feedback (PBF) module performs channel prediction by using recursive least square (RLS) algorithm for the user whose channel feedback has not been granted for schedule in current frame. Through extensive simulations, the proposed framework shows significant performance gain especially under stringent feedback budget constraint.ARQ protocol receives users acknowledgement only if the user is scheduled in the downlink. The reduction in users scheduling frequency also reduces the rate of ARQ hints and degrades the performance of above contributions. In this case, it is difficult to exploit the ARQ signal to adapt the feedback window for that user. To address this issue, we propose a cross-layer dynamic CQI resource allocation (DCRA) algorithm for multiuser multicarrier OFDMA systems. DCRA uses two modes for feedback window estimation. The first one is an off-line mode based on empirical studies to derive optimal average feedback window based on user application and mobility profile. Our experimental analysis shows that the feedback window can be averaged according to users service class and their mobility profile for a given cell environment. DCRA performs a realtime dynamic window adaptation if sufficient cross-layer hints are available from ARQ signaling. DCRA increases uplink resource by reducing feedback overhead without degrading downlink throughout significantly compared to deterministic feedback scheduling (DFS) and opportunistic feedback scheduling (OFS). From the users perspective, DCRA improves QoS constraints like packet loss rate and saves users power due to feedback reduction
37
Ng, Ka Wai. "Generalized bit and power allocation for single and multi-user OFDM MIMO system in frequency selective fading channel /." View abstract or full-text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20NG.
Full text
38
Aziz, Hatem M. "Reducing Client-Server Communication for Efficient Real-Time Web Applications: The Use of Adaptive Polling as A Case Study for Multi-User Web Applications." Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/17341.
Full textAbstract:
A key challenge of current multi-user web applications is to provide users with interesting events and information in real-time. This research reviews the most common real-time web techniques to identify drawbacks while exploring solutions to improve simplicity, efficiency, and compatibility within a client-server environment. Two solutions are proposed for enhancing the efficiency of real-time web techniques by reducing client-server communication. First, a model of browser monitoring control observes the browser activity and decides if to postpone client-server communication in the case of inactive tabs. This model was implemented and tested with results demonstrating that a significant number of client-server connections can be avoided in the browser background. These results suggest the solution can be optimised for any real-time technique as it benefits from being a developer side technique that works consistently on all browsers. Second, ‘Adaptive Polling’ is a pull-based real-time web technique to overcome bandwidth issues of the reverse AJAX method of ‘Polling’ by controlling the frequency of requesting updates from the server based on the last server response. This approach is implemented and tested with results showing how a significant number of redundant connections can be avoided while the server does not return updates. This solution is a good alternative to other real-time web techniques as it features low latency, the simplicity of implementation, and compatibility with all browsers and servers.
39
Chitti, Krishna [Verfasser], and Brink Stephan [Akademischer Betreuer] Ten. "Analysis and optimization of wireless cellular multi-user multiple-input multiple-output communication systems / Krishna Chitti ; Betreuer: Stephan Ten Brink." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/1118507568/34.
Full text
40
Erpek, Tugba. "Multi-layer Optimization Aspects of Deep Learning and MIMO-based Communication Systems." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/102705.
Full textAbstract:
This dissertation addresses multi-layer optimization aspects of multiple input multiple output (MIMO) and deep learning-based communication systems. The initial focus is on the rate optimization for multi-user MIMO (MU-MIMO) configurations; specifically, multiple access channel (MAC) and interference channel (IC). First, the ergodic sum rates of MIMO MAC and IC configurations are determined by jointly integrating the error and overhead effects due to channel estimation (training) and feedback into the rate optimization.
Then, we investigated methods that will increase the achievable rate for parallel Gaussian IC (PGIC) which is a special case of MIMO IC where there is no interference between multiple antenna elements. We derive a generalized iterative waterfilling algorithm for power allocation that maximizes the ergodic achievable rate. We verified the sum rate improvement with our proposed scheme through extensive simulation tests.
Next, we introduce a novel physical layer scheme for single user MIMO spatial multiplexing systems based on unsupervised deep learning using an autoencoder. Both transmitter and receiver are designed as feedforward neural networks (FNN) and constellation diagrams are optimized to minimize the symbol error rate (SER) based on the channel characteristics. We first evaluate the SER in the presence of a constant Rayleigh-fading channel as a performance upper bound.
Then, we quantize the Gaussian distribution and train the autoencoder with multiple quantized channel matrices. The channel is provided as an input to both the transmitter and the receiver. The performance exceeds that of conventional communication systems both when the autoencoder is trained and tested with single and multiple channels and the performance gain is sustained after accounting for the channel estimation error.
Moreover, we evaluate the performance with increasing number of quantization points and when there is a difference between training and test channels. We show that the performance loss is minimal when training is performed with sufficiently large number of quantization points and number of channels.
Finally, we develop a distributed and decentralized MU-MIMO link selection and activation protocol that enables MU-MIMO operation in wireless networks. We verified the performance gains with the proposed protocol in terms of average network throughput.Doctor of Philosophy
41
Liu, Lingjia. "On delay-sensitive communication over wireless systems." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2725.
Full text
42
Smith, Jeffrey S. "Cyber-Synchronicity: The Concurrence of the Virtual and the Material via Text-Based Virtual Reality." Ohio : Ohio University, 2010. http://www.ohiolink.edu/etd/view.cgi?ohiou1260214092.
Full text
43
Gunyan, Scott Nathan. "An Examination into the Statistics of the Singular Vectors for the Multi-User MIMO Wireless Channel." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd539.pdf.
Full text
44
Salber, Daniel. "De l'interaction homme-machine individuelle aux systèmes multi-utilisateurs : l'exemple de la communication homme-homme mediatisée." Grenoble 1, 1995. http://tel.archives-ouvertes.fr/tel-00005060.
Full textAbstract:
Cette thèse s'inscrit dans le domaine de l'ingénierie des systèmes multi-utilisateurs. Dans notre modèle conceptuel, un système multi-utilisateur repose sur la combinaison de trois espaces fonctionnels : l'espace de production, l'espace de coordination et l'espace de communication. Ce dernier espace, la communication entre individus, fait l'objet de notre étude et définit la communication homme-homme médiatisée. L'approche adoptée s'articule en trois niveaux : les principes, issus des sciences non-informatiques (psychologie, sociologie, éthique, etc. ), les propriétés issues des principes et destinées à guider la conception et évaluer la réalisation, et enfin les techniques de mise en oeuvre informatique. Les principes traduisent les contributions de sciences non-informatiques comme les sciences sociales ou la psychologie cognitive à notre domaine d'étude. L'expérimentation psychologique Garden Movie, qui étudie l'influence de la disposition des caméras et de la surface de travail dans une tâche collecticielle, illustre l'utilisation des principes. Les propriétés sont des caractéristiques objectives et vérifiables d'un système informatique dont le choix est guidé par les principes. Nous proposons des propriétés pour les systèmes multi-utilisateurs et les systèmes de communication homme-homme médiatisée. Les propriétés permettent de guider la conception ainsi que l'étude de l'utilisabilité d'un système. Nous présentons la plate-forme d'observation du comportement des utilisateurs et Magicien d'Oz NEIMO pour l'étude expérimentale de l'utilisabilité. Nous illustrons son utilisation pour les systèmes de communication homme-homme médiatisée avec l'expérience Supratel. Les techniques comprennent deux volets : les modèles d'architecture logicielle guident la réalisation et les outils permettent la réalisation effective. Le choix des techniques est guide par les propriétés que le système doit vérifier. Nous présentons une grille d'analyse des modèles d'architecture logicielle pour les systèmes multi-utilisateurs que nous utilisons pour évaluer les modèles proposés dans la littérature. Constatant qu'aucun n'intègre harmonieusement les trois espaces de notre modèle conceptuel et l'insuffisance des modèles pour la communication homme-homme médiatisée, nous présentons CoPAC, un modèle d'architecture logicielle pour les systèmes multi-utilisateurs et la communication médiatisée. Nous illustrons sa mise en oeuvre avec la réalisation de notre médiaspace VideoPort. En ce qui concerne les outils, nous décrivons la réalisation de la bibliothèque UserLink pour la communication de médias continus. Nous proposons aussi la taxonomie IMPACT pour l'analyse des outils de communication homme-homme médiatisée
45
Ma, Hang. "Using chaos to enhance multi-user time-of-arrival estimation : application to UWB ranging systems." Thesis, Toulouse, INSA, 2014. http://www.theses.fr/2014ISAT0008/document.
Full textAbstract:
Dans les décennies à venir, la connaissance d’informations très précises concernant la position d’un objet permettra de créer des applications révolutionnaires dans les domaines sociaux, médicaux, commerciaux et militaires. La technologie Ultra-Wideband (UWB) est considérée comme un bon candidat permettant de fournir des capacités de localisation précise grâce à la mesure de l’estimation du temps d'arrivée (TOA). Dans cette thèse, des algorithmes de mesure de distance dans le cas multi-utilisateurs pour des systèmes UWB sont étudiés afin d'atteindre une bonne précision pour une faible complexité, avec de la robustesse aux interférences multi-utilisateur et dans le cas d’un grand nombre d'utilisateurs. Au cours de la dernière décennie, les signaux chaotiques ont reçu une attention significative en raison d'un certain nombre de caractéristiques intéressantes. Les signaux chaotiques sont des signaux non périodiques, déterministes ou considérés comme pseudo-aléatoires provenant de systèmes dynamiques non linéaires. Leur bonne autocorrélation et leurs faibles propriétés d’inter corrélation les rendent particulièrement résistants aux évanouissements par trajets multiples et capables d'atténuer les interférences multi-utilisateur (MUI). En raison de leur grande sensibilité aux conditions initiales, il est possible de générer un grand nombre de signaux chaotiques pour accroître la capacité globale du système. Dans cette thèse, deux nouveaux algorithmes d'estimation de TOA sont proposés dans un cadre multi-utilisateur avec une faible complexité et une bonne robustesse. Le nombre d'utilisateurs pris en charge par ces deux algorithmes est beaucoup plus grand que dans le cas des estimateurs de TOA actuels. Cependant, l'utilisation de séquences d'étalement classique et d’impulsion limite l'amélioration des performances et la capacité du système. Afin d’apporter des améliorations, des signaux chaotiques sélectionnés sont utilisés comme séquences d'étalement ou impulsion dans les algorithmes proposés. Grâce à l'utilisation de signaux chaotiques, notre algorithme est non seulement amélioré, mais permet également l’utilisation d’un plus grand nombre d'utilisateurs par comparaison avec l’algorithme utilisant des signaux classiquesIn the coming decades, highly accurate position information has the potential to create revolutionary applications in the social, medical, commercial and military areas. Ultra-Wideband (UWB) technology is considered as a potential candidate for enabling accurate localization capabilities through Time-of-Arrival (TOA) based ranging techniques. Over the past decade, chaotic signals have received significant attention due to a number of attractive features. Chaotic signals are aperiodic, deterministic, and random-like signals derived from nonlinear dynamical systems whose good autocorrelation, low cross-correlation and sensitivity to the initial conditions make them particularly suitable to ranging systems. In this thesis, two new multiuser TOA estimation algorithms are proposed with low complexity and robustness to MUI, the number of users supported by which is much larger than current multiuser TOA estimators. While, the use of classic spreading sequences and ranging pulse constrain the further improvement of ranging performance and system capacity. For breaking through the limit brought by the classic signals, the selected chaotic signals are employed as the spreading sequences or ranging pulse in our proposed algorithms. With the use of chaotic signals, our proposed algorithm not only obtains the additional improvement, but also with capability to support larger number of users comparing with its counterpart using classic signals
46
Nguyen, Anh-Minh Ngoc. "High-Quality Detection in Heavy-Traffic Avionic Communication System Using Interference Cancellation Techniques." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29069.
Full textAbstract:
This dissertation focuses on quantifying the effects of multi-user co-channel interference for an avionic communication system operating in a heavy-traffic aeronautical mobile environment and proposes advanced interference cancellation techniques to mitigate the interference.
The dissertation consists of two parts. The first part of the work investigates the use of a visualization method to quantify and characterize the multi-user co-channel interference (multiple access interference) effects impinging on an avionic communication system. The interference is caused by complex interactions of thousands of RF signals transmitted from thousands of aircraft; each attempts to access a common communication channel, which is governed by a specific channel contention access protocol. The visualization method transforms the co-channel interference, which is specified in terms of signal-overlaps (signal collisions), from a visual representation to a matrix representation for further statistical analysis. It is found that the statistical Poisson and its cumulative distribution provide the best estimates of multi-user co-channel interference. It is shown, using Monte Carlo simulation, that the co-channel interference of a victim aircraft operating in the heavy-traffic environment could result in as high as eight signal-overlaps. This constitutes to approximately 83.4% of success rate in signal detection for the entire three thousand aircraft environment using conventional FSK receiver. One key finding shows that high-quality communications, up to 98.5% success rate, is achievable if only three overlapping signals can be decoded successfully. The interference results found in the first part set the stage for interference cancellation research in the second part.
The second part of the work proposes the use of advanced interference cancellation techniques, namely sequential interference cancellation (SIC) and parallel interference cancellation (PIC), as potential solutions to mitigating the interference effects. These techniques can be implemented in radio receivers to perform multi-signal decoding functionality to remove the required interferers (three overlapping signals) so that high-quality communication, as described in the first part, can be achieved. Various performance graphs are shown for B-FSK and B-PSK for both SIC and PIC techniques. One key finding is that the system performance can be improved substantially to an additional 15% in signal reception success rate by using SIC or PIC. This means that critical information transmitted from 450 aircraft (out of approximately three thousand aircraft in the environment) is preserved and successfully decoded. Multi-signal decoding using these interference cancellation receivers comes at a small penalty of 2 - 4.5 dBs in Eb/No when sufficient signal-to-interference (SIR) ratio (7-12 dB) is provided.Ph. D.
47
Vulgari, Sofia Kiriaki. "Hand Gesture based Telemedicine enabled by Mobile VR." Thesis, Linnéuniversitetet, Institutionen för datavetenskap och medieteknik (DM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-88810.
Full textAbstract:
Virtual Reality (VR) is a highly evolving domain and is used in anincreasing number of areas in today's society. Among the technologiesassociated with VR and especially mobile VR, is hand tracking and handgesture recognition. Telemedicine is one of the elds where VR is startingto thrive, and so the concept of adding the use of hand gestures came to bein order to explore the possibilities that can come from it. This researchis conducted with the development of a prototype application that usessome of the most emerging technologies. Manomotion's hand trackingand hand gesture recognition algorithms, and Photon's servers and developerkit, which makes multi-user applications achievable, allowed theconceptual idea of the prototype to become reality. In order to test itsusability and how potential users perceive it, a user study with 24 participantswas made, 8 of which were either studying or working in themedical eld. Additional expert meetings and observations from the userstudy also contributed to ndings that helped show how hand gesturescan aect a doctor consultation in Telemedicine. Findings showed thatthe participants thought of the proposed system as a less costly and timesaving solution, and that they felt immersed in the VR. The hand gestureswere accepted and understood. The participants did not have dicultieson learning or executing them, and had control of the prototype environment.In addition, the data showed that participants considered it to beusable in the medical eld in the future.
48
Stanković, Veljko. "Multi-user MIMO wireless communications." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985258039.
Full text
49
Mohammedi, Merah Mounir. "Conception et réalisation d’un lien Light-Fidelity multi-utilisateur en intérieur." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV061/document.
Full textAbstract:
De nos jours, le nombre d'appareils connectés nécessitant un accès aux données mobiles est en augmentation constante. L'arrivée d'encore plus d'ojects multimédias connectés et la demande croissante d'informations par appareil ont mis en évidence les limites de la quatrième génération de réseaux cellulaires (4G). Cela a poussé au développement de nouvelles méthodes, dont la 5G. L'objectif est d'être en mesure de prendre en charge la croissance des systèmes portables, des capteurs ou des sysèmes associés à l'internet des objets (IoT). La vision derrière la 5G est de permettre une société entièrement mobile et connectée avec une expérience consistente.Les petites cellules sont la base des normes de communication avancées telles que 4G et maintenant 5G. Ils résultent de l’utilisation de bandes de fréquences plus élevées pour l’accès radiofréquences (RF) afin de supporter de nouvelles normes et exigences croissantes en bande passante. La 5G utilise des ondes millimétriques et nécessite un déploiement dans un environnement urbain intérieur et urbain dense, ce qui peut s'avérer être un défi. C’est là que la 5G devra inclure des solutions de réseau hybrides et pouvoir coexister avec d’autres technologies d’accès sans fil. La communication par lumière visible (VLC) s’inscrit dans ce moule puisque la lumière visible correspond à la bande comprise entre 400 et 800 THz. Le spectre disponible est des milliers de fois plus large que le spectre RF et il n’interfère pas avec celui-ci. Le principe se base sur la combinaison de l'éclairage avec un lien de communication pouvant atteindre des dizaines de gigabits par seconde. Le potentiel est d’offrir un complément à la 5G dans un réseau hybride, offrant une vitesse élevée, aucune interférence et une sécurité accrue au prix d’une couverture limitée et d’une faible maturité technologique.L’objectif de cette thèse est donc de proposer et d’évaluer une implémentation expérimentale d’un système VLC en intérieur et multi-utilisateurs afin de répondre aux objectifs de la configuration light-fidelity (Li-Fi) dans le contexte d’une petite cellule. La première étape de cette étude est un état de l'art détaillé sur le principe de VLC dans la communication sans fil en intérieur et de l’accès multi-utilisateur. Cela permet de mieux expliquer le concept de notre désign et de comparer notre approche aux travaux existants. La deuxième étape consiste en une analyse des principes et des hypothèses pour le système VLC multi-utilisateurs en intérieur portant à la fois sur la technique de modulation et sur les schémas d’accès multi-utilisateurs. Les conclusions tirées des analyses théoriques et numériques servent de base pour la suite du travail. La troisième étape consiste en plusieurs analyses expérimentales sur l'optimisation des performances de diffusion pour un utilisateur unique, puis sur les performances multi-utilisateurs du système à l'aide de divers schémas d'accès. Le débit total avec une LED blanche commerciale atteint 163 Mb/s avec un taux d'erreur réduit d'un facteur de 3,55 grâce au processus d'optimisation des performances. Cette technique a l'avantage d'augmenter la flexibilité pour un scénario avec plusieurs utilisateurs sans augmenter la complexité car seuls les paramètres des filtres de modulation sont altérés. La taille de la cellule obtenue est de 4.56 m² à une distance de 2,15 mètres du transmetteur. Le capacité peut atteindre jusqu'à 40 utilisateurs, ou 40.62 Mb/s dans un scénario à 4 utilisateurs. Il est donc démontré que le système proposé pourrait fonctionner comme une cellule à une distance réaliste, avec un débit de données élevé et la capacité de répondre aux besoins d’un grand nombre d’utilisateurs tout en limitant les coûts de mise en œuvreNowadays, the number of connected devices requiring access to mobile data is considerably increasing. The arrival of even more connected multimedia objects and the growing demand for more information per device highlighted the limits of the fourth generation of broadband cellular networks (4G). This pushed for the development of new methods, one of which is 5G. The goal is to be able to support the growth of wearable, sensors, or related internet-of-object (IoT) systems. The vision behind 5G is to enable a fully mobile and connected society with a consistent experience. In consequence, there is a fundamental need to achieve a seamless and consistent user experience across time and space.Small cells are the basis of advanced communications standards such as 4G and now, 5G. They exist as a result of using higher frequency bands for RF access in order to support new standards and the increasing demands in bandwidth. 5G use millimeter waves and requires a deployment across indoor and dense urban environment which may prove to be a challenge. This is where 5G will need to include hybrid networking solutions and be able to coexist with other wireless access technologies. Visible light communication (VLC) fits into that mold since visible light corresponds to the band between 400 and 800 THz. The available spectrum is multiple thousand times the size of the RF spectrum and it does not interfere with it. The technique combines illumination with communication at possibly tens of gigabits per second. It has the potential to offer a synergistic pairing with 5G in a hybrid network, offering high speed, no interferences, and more security at the cost of limited coverage and low technological maturity.The goal of this thesis is thus to propose and evaluate an experimental implementation of an indoor multi-user VLC system in order to answer the objectives of Li-Fi setup in the context of a small cell. The first step of this study is a detailed state-of-the-art on VLC in indoor wireless communication and multi-user access. It allows the design of our work to be better explained and to compare our approach with existing works. The second step is an analysis of the principles and hypothesis supporting the indoor multi-user VLC system in the study both on the modulation technique and the multi-user access schemes. The conclusions drawn from theoretical and numerical analysis are used as a basis for the rest of the work. The third step is the experimental setup investigations on the single-user broadcast performances optimization and then on the multi-user performances of the system using various schemes. The total throughput using an off-the-shelf white LED reaches 163 Mb/s with a bit-error rate decreased by a factor of 3.55 thanks to the performance optimization process. This technique has the advantage of increasing the flexibility for a multi-access scenario while not augmenting the complexity as it only optimizes the modulation filter parameters. The multi-user access is obtained for a cell size of 4.56 m² at a distance of 2.15 meter away from the transmitter. The user capacity can reach up to 40 users, or 40.62 Mb/s in a 4-user scenario. It is thus demonstrated that the proposed system could function as a cell at a realistic range, with high data rate and the ability to provide for a large amount of users while limiting the cost of implementation
50
Mapoka, Trust Tshepo. "Location based authenticated multi-services group key management for cyber security in high speed broadband wireless multicast communications : multi-service group key management scheme with location based handover authentication for multi-handoffs participating in multi-group service subscriptions, its performance evaluation and security correctness in high speed broadband wireless multicast communications." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14468.
Full textAbstract:
Secure information exchanges over cyberspace is on the increase due to the convergence of wireless and mobile access technologies in all businesses. Accordingly, with the proliferation of diverse multicast group service subscriptions that are possible to co-exist within a single broadband network, there is also huge demand by the mobile subscribers to ubiquitously access these services over high speed broadband using their portable devices. Likewise, the Network Providers (NPs) invest hugely in infrastructure deployment to disseminate these services efficiently and concomitantly. Therefore, cyber security in any business is obligatory to restrict access of disseminated services to only authorised personnel. This becomes a vital requirement for a successful commercialisation of exchanged group services. The standard way to achieve cyber security in a wireless mobile multicast communication environment is through confidentiality using Group Key Management (GKM).The existing GKM schemes for secure wireless multicast from literature only target single group service confidentiality; however, the adoption of multiple group service confidentiality in them involve inefficient management of keys that induce huge performance overheads unbearable for real time computing. Therefore, a novel authenticated GKM scheme for multiple multicast group subscriptions known as slot based multiple group key management (SMGKM) is proposed. In the SMGKM, the handovers move across diverse decentralised clusters of homogeneous or heterogeneous wireless access network technologies while participating in multiple group service subscriptions. Unlike the conventional art, the SMGKM advances its security by integrating location based authentication and GKM functions. Both functions are securely offloaded from the Domain Key Distributor (DKD) to the intermediate cluster controllers, Area Key Distributors (AKDs), in a distributed fashion, using the proposed location based authenticated membership list (SKDL). A significant upgrade of fast handoff performance with reduced performance overheads of the SMGKM scheme is achieved. The developed numerical analysis and the simulation results display significant resource economy in terms of reduced rekeying transmission, communication bandwidth and storage overheads while providing enhanced security. The performance of the SMGKM in a high speed environment is also evaluated and has demonstrated that SMGKM outperforms the previous work. Finally, the SMGKM correctness against various attacks is verified using BAN logic, the eminent tool for analysing the widely deployed security protocols. The security analysis demonstrates that SMGKM can counteract the security flaws and redundancies identified in the chosen related art.