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Dissertations / Theses on the topic 'Delay spread'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 July 2025

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1

Fofanah, Ibrahim, and Wannaw Assegu. "Delay Spread Characterization of the Aeronautical Channel." International Foundation for Telemetering, 2012. http://hdl.handle.net/10150/581653.

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ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California<br>Radio transmission channel influences greatly the quality of transmitted voice and data signal in terms of data rate and robustness. This degradation is as a result of many factors, notable amongst them are having multiple replica of the transmitted signal at the receiver (multipath), changes of frequency as a result of the movement of the aircraft (Doppler shift) and noise. Thi

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2

Emami, Seyed Majid. "Communication through high delay spread X bandwidth (HDB) channels /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Thayaparan, Subramaniam. "Delay-locked loop techniques in direct sequence spread-spectrum receivers." Thesis, Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21904108.

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4

Noronha, Joseph Ajay Neil. "Ultrawideband Channel Sounding Studies in Outdoor and Outdoor-Indoor Environments." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/10006.

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Ultrawideband (UWB) is one of the most promising communication technologies in recent times with the promise of high data rates and spectral reuse. This work analyses the outdoor and outdoor-to-indoor propagating characteristics of the UWB pulse, which can be of the order of a few gigahertz in bandwidth. The aim of the thesis is to provide the parameters needed in order to develop a channel model for such cases. The channel model would then play an important role in determining physical layer (PHY) solutions to optimally exploit these characteristics. The measurements carried out on the Virg

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GONCALVES, JULIANA VALIM OLIVER. "SIGNAL VARIABILITY, COHERENCE BANDWIDTH AND DELAY SPREAD ON MOBILE RADIO PROPAGATION ENVIRONMENT AT 3.5GHZ." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15393@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>Nesta dissertação, é apresentado estudo realizado sobre a variabilidade do sinal, da banda de coerência e do espalhamento de retardos em um ambiente de rádio propagação móvel, por meio de medição em campo de um sinal WiMAX propagado ao longo do canal rádio móvel. A análise da estatística do sinal capturado é comparada com valores teóricos. O sinal WiMAX utilizado possui a tecnologia OFDM-256, como base da sua camada física, e frequência central de 3,410 GHz. A partir dos dados

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Sanzhong, Li, Zhang Qishan, and L. L. Cheng. "DESIGN OF A PARALLEL MULTI-CHANNEL BPSK DIRECT-SEQUENCE SPREAD-SPECTRUM RECEIVER." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609680.

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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>A parallel multi-channel receiver for binary phase shift keyed (BPSK) direct-sequence (DS) spread-spectrum (SS) is introduced in this paper. It adopts a Costas carrier frequency-tracking loop which maintains frequency lock rather than phase lock, and the delay-lock error can be noncoherently obtained to track the PN code. For airborne applications, this method will extend effectively the receiver’s tracking dynamics range for the carrier Doppler shift. A erasable

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Kurri, Prasada Reddy. "Root Mean Square-Delay Spread Characteristics for Outdoor to Indoor Wireless Channels in the 5 GHz Band." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1305119898.

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8

Sakarai, Deesha S. "Wireless Channel Characterization for Large Indoor Environments at 5 GHz." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1338494030.

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9

Blakaj, Valon, and Gent Gashi. "Implementation of a 3D terrain-dependent Wave Propagation Model in WRAP." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-36774.

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The radio wave propagation prediction is one of the key elements for designing an efficient radio network system. WRAP International has developed a software for spectrum management and radio network planning.This software includes some wave propagation models which are used to predict path loss. Current propagation models in WRAP perform the calculation in a vertical 2D plane, the plane between the transmitter and the receiver. The goal of this thesis is to investigate and implement a 3D wave propagation model, in a way that reflections and diffractions from the sides are taken into account.T

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10

Zhao, Honglin, Xianming Zhao, and Tingxian Zhou. "Remote Control Multiple Mobile Target System with CDMA." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/611458.

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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California<br>At present, multiple mobile targets will be remote controlled in many remote control and telemetry system, in which multiple access technology will be applied. This paper proposes a communication scheme to remote control multiple mobile targets using Coded-Division Multiple Access(CDMA) technique. It's feasibility, advantage and shortcoming are analyzed. Moreover, the key techniques of Direct-Sequence Spread Spectrum(DS/SS) system, i.e. the correlatio

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Adegoke, Elijah. "Radio frequency channel characterization for energy harvesting in factory environments." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/33412.

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This thesis presents ambient energy data obtained from a measurement campaign carried out at an automobile plant. At the automobile plant, ambient light, ambient temperature and ambient radio frequency were measured during the day time over two days. The measurement results showed that ambient light generated the highest DC power. For plant and operation managers at the automobile plant, the measurement data can be used in system design considerations for future energy harvesting wireless sensor nodes at the plant. In addition, wideband measurements obtained from a machine workshop are present

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12

Katz, M. (Marcos). "Code acquisition in advanced CDMA networks." Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:9514268849.

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Abstract The present dissertation deals with initial synchronization in Code Division Multiple Access (CDMA) networks. In the first part of this thesis an extensive and up-to-date review of the literature is presented. The basic theory of code acquisition as well as different techniques and structures used to achieve the initial synchronization are discussed. A survey of the most common theoretical approaches allowing performance characterization of the acquisition process is included. The effect of noise, interference, carrier Doppler, multipath propagation, fading and data modulation on sys

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Hägglund, Erik. "Design of a DVB-T Receiver : For SFN on a DSP-Processor." Thesis, Linköpings universitet, Datorteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-86070.

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The goal of this thesis was to implement a DVB-T receiver on Coresonic’s DSP-processor and attempt to evaluate how to design a receiver that is robust against very strong echoes with a long delay. Long delayed echoes is very common in Single Frequency Networks (SFN) which is why focus was put on finding algorithms that work well in SFN.The thesis involved analyzing different algorithms involved in making a DVB-T receiver where the focus was to find a good channel estimation algorithm. The thesis also included programming the DSP-processor and making some smaller modifications to their hardware

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Khalifa, Nabil. "Approches d'acquisition et de poursuite de signaux à spectre étale : Application à la réception des signaux GPS." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/932f5c99-f8db-418d-8477-c674f7f6ba30.

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L'étalement de spectre permet d'atténuer les interférences, de résister aux brouillages, de combattre les trajets multiples et d'offrir une possibilité de communication à accès multiples l'acquisition peut être lente ou rapide selon la longueur du code et surtout selon le niveau du rapport signal à bruit (SNR) à l'entrée du récepteur si ce dernier a un niveau suffisant, on peut utiliser plusieurs techniques rapides et peu complexes, telle que l'estimation séquentielle dans le cas ou le SNR à l'entrée du récepteur est insuffisant, il est nécessaire d'effectuer une recherche sur la totalité du c

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Holzer, Justin T. "Wideband Channel Characterization for MIMO Scenario." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd481.pdf.

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Newhall, William George. "Wideband Propagation Measurement Results, Simulation Models, and Processing Techniques for a Sliding Correlator Measurement System." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35678.

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Radio wave propagation measurements provide a way to accurately and reliably characterize environments to assist in the development and optimization of wireless communication systems. As digital radio systems occupy wider bandwidths and use multipath signal combining to enhance quality of service, knowledge of time dispersion and the multipath structure of radio channels become increasingly important. The wideband measurement system presented herein provides a practical means to precisely measure the delays and strengths of individual multipath components which arrive at a radio receiver. <

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Valencia-Payán, Juan David. "In-home and low-voltage channel characterization of non-cooperative and cooperative power line communication." Universidade Federal de Juiz de Fora, 2014. https://repositorio.ufjf.br/jspui/handle/ufjf/700.

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Lai, Zhihua. "The development of an intelligent ray launching algorithm for wireless network planning." Thesis, University of Bedfordshire, 2010. http://hdl.handle.net/10547/134379.

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Current propogation models are no longer sufficient for wireless network planning. They are neither accurate (empirical) nor fast enough (deterministic) to be applicable in the applications of Automated Cell Planning. This thesis focuses on the development of a new method, namely Intelligent Ray Launching Algorithm (IRLA), which is based on a fast, accurate and robust algorithm that is especially suitable for wireless network planning. The infrastructure of IRLA is thoroughly analysed in this thesis and the results are presented. Foster's design methodology has been used to parallelise the new

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Strydom, Trudie. "Acoustic models of cochlear implants." Thesis, University of Pretoria, 2010. http://hdl.handle.net/2263/30721.

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Acoustic models are useful tools to increase understanding of cochlear implant perception. Two particular issues in modelling cochlear implant perception were considered in the present study, which aimed at improving acoustic models. The first included an electricallayer in the model, while the second manipulated synthesis signal parameters. Two parts of the study explored the effects of current decay, compression function and simultaneous stimulation, by including the electrical layer. The SPREAD model, which incorporated this layer, yielded the asymptote in speech intelligibility at seven ch

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Delay, Guillaume. "Analyse des écoulements transitoires dans les systèmes d'injection directe essence : effets sur l'entraînement d'air instationnaire du spray." Phd thesis, Toulouse, INPT, 2005. http://oatao.univ-toulouse.fr/7367/1/delay1.pdf.

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L'objectif de cette étude est de déterminer l'effet des fluctuations de débit liquide instantané d'un injecteur sur l'entraînement d'air instationnaire d'un spray conique creux de type injection directe essence. Pour ce faire, nous utilisons plusi eurs outils, expérimentaux et numériques. Une méthode de mesure de débit liquide instantané, basée sur la modélisation physique des écoulements pulsés est utilisée. La mesure de la vitesse (Anémométrie Laser Doppler) de l'écoulement à l'axe de la conduite alimentant l'injecteur suffit pour reconstruire l'écoulement avant l'injecteur. Un logiciel de m

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Minkara, Rania. "Locating wireless base stations within a dynamic indoor environment." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681053.

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The mobility that wireless communication offers to users, added to the ease of installation have increased the demand on such communication systems. However, the main drawback of wireless communication is the degradation of the signal as it travels through the channel due to the different propagation mechanisms the signal undergoes. To minimise the effect of the channel and get the best service, the base stations must be appropriately located within the environment. This requires proper knowledge of the channel characteristics. Ray tracing software is used throughout this work to generate the

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Arsalane, Nabil. "Channel Emulation for active characterization of MIMO communication systems." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0069/document.

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Cette thèse s’inscrit dans le domaine de la caractérisation des systèmes de communication sans fil utilisant la diversité des antennes. En effet, ces systèmes permettent de lutter contre les évanouissements des signaux, lorsque le terminal est placé dans un environnement riche en multi-trajets. L’objectif d'une telle recherche est : d’étudier l'association de plusieurs antennes à l'émission et / ou la réception pour améliorer le bilan de liaison, et la capacité des systèmes sans fil, (diminution de BER (Bit Error Rate), augmentation de débit ...). Cette thèse s’intéresse à l'aspect électromagn

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Engström, Jeanette. "Att dela och sprida information. En studie med fokus på litteraturforskare." Thesis, Högskolan i Borås, Institutionen Biblioteks- och informationsvetenskap / Bibliotekshögskolan, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-20210.

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The aim of this Bachelor’s thesis is to obtain understanding and knowledge about how literary scholars collaborate regarding information. Seven scholars have been studied in the aim to find out social and cultural elements which create particular prerequisites for their practice, with focus on information sharing. The method used has consisted of semi-structured interviews. The informants have been studied from a socio cultural and domain analysis starting point, which means that they are studied in the light of being members in their practice. The result of the study has shown that informatio

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Shang, Lei, and lei shang@ieee org. "Modelling of Mobile Fading Channels with Fading Mitigation Techniques." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061222.113303.

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This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated i

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Viera, Sotillo Juan Pablo. "Experimental study of the effect of nozzle geometry on the performance of direct-injection diesel sprays for three different fuels." Doctoral thesis, Universitat Politècnica de València, 2017. http://hdl.handle.net/10251/81857.

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This thesis studies the influence of internal nozzle flow characteristics over a large spectrum of experimental conditions and diagnostics. Experiments were carried out for two nozzle geometries---cylindrical and conical single hole nozzles---and three different fuels. Two of the fuels are pure components---n-heptane and n-dodecane---while the third fuel consists of a three-component surrogate to better represent the physical and chemical properties of diesel fuel. Measurements include a complete hydraulic characterization consisting of instantaneous injection rate and spray momentum flux meas

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Peraza, Ávila Jesús Enrique. "Experimental study of the diesel spray behavior during the jet-wall interaction at high pressure and high temperature conditions." Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/149389.

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[EN] The potential of diesel engines in terms of robustness, efficiency and energy density has made them widely used as power generators and propulsion systems. Specifically, fuel atomization, vaporization and air-fuel mixing, have a fundamental effect on the combustion process, and consequently, a direct impact on pollutant formation, fuel consumption and noise emission. Since the combustion chamber has a limited space respect to the spray penetration, wall impingement is considered to be a common event in direct injection diesel engines, having a relevant influence in the spray evolution and

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Gunn, Kpoti Mawutodzi. "Developing Strategies For Year-Round Spray Irrigation of Wastewater Effluent in Ohio." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1262207613.

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Tseng, Ya-Ting. "Three-Dimensional Model of Solid Ignition and Ignition Limit by a Non-Uniformly Distributed Radiant Heat Source." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1307551796.

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Nilaphai, Ob. "Vaporization and Combustion Processes of Alcohols and Acetone-Butanol-Ethanol (ABE) blended in n-Dodecane for High Pressure-High Temperature Conditions : Application to Compression Ignition Engine." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2020/document.

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La préoccupation de plus en plus importante ces dernières décennies, liée à l’épuisement des ressources pétrolières et au réchauffement climatique par les gaz à effet de serre a accentué l’intérêt du butanol comme carburant alternatif dans le secteur des transports grâce à ses propriétés adaptées pour le moteur à allumage par compression. Cependant, le faible rendement des procédés de production et de séparation empêche encore sa commercialisation en tant que carburant. C’est pourquoi le mélange de fermentation intermédiaire de la production de butanol, Acétone-Butanol-Ethanol(ABE), est de plu

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Moradinia, Pourya, and Imal Sakhi. "Mobile Opportunistic Services for Experience Sharing : Via a NetInf Android Application." Thesis, KTH, Radio Systems Laboratory (RS Lab), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104297.

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Information-Centric Networking (ICN) is a new research area concerning creating a new network architecture that would be more suitable for both current and the future's network. The MOSES (Mobile Opportunistic Services for Experience Sharing) project is part of this development. The project works with the development and demonstration of the Network of Information (NetInf) protocol, which is an implementation of the ICN concept. This Master’s thesis project is part of the MOSES project and aims to assist the MOSES project with the demonstration of a mobile opportunistic sharing concept based o

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Azad, Md Saiful. "Medium access control, error control and routing in underwater acoustic networks: a discussion on protocol design and implementation." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423364.

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The journey of underwater communication which began from Leonardo’s era took four and a half centuries to ﬁnd practical applications for military purposes during World War II. However, over the last three decades, underwater acoustic communications witnessed a massive development due to the advancements in the design of underwater communicating peripherals and their supporting protocols. Successively, doors are opened for a wide range of applications to employ in the underwater environment, such as oceanography, pollution monitoring, offshore exploration, disaster prevention, navigation assi

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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.

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The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of th

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Arunkumar, K. P. "Underwater Acoustic Communications: Algorithms for Delay-Scale Spread Wideband Channels." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5923.

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In wideband wireless communication systems, the relative motion of the transmitter, receiver, or scatterers in the medium causes the Doppler effect, which stretches or compresses the transmitted waveforms, resulting in inter-symbol interference and a consequent severe performance degradation. To counter this, specialized transmitter and receiver architectures are needed for energy- and spectrally-efficient communications in channels characterized by path-dependent delays and time-scales. In this thesis, we develop and evaluate improved receiver side signal processing algorithms for two existin

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Tseng, Chi-Hsiang, and 曾其祥. "Decision-Directed Coherent Delay-Lock Tracking Loop for BPPDS- Spread-Spectrum Signals." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/16285366484577280953.

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碩士<br>國立交通大學<br>電信研究所<br>82<br>In this thesis the coherent decision-directed delay-lock tracking loop(CDD-DLL) scheme is employed to develop a tracking loop for the binary pulse-position modulated direct sequence( BPPDS) CDMA system. It not only keeps the of BPPDS-CDMA system which has transmitting energy saving, a superior suppression of cross-correlation noise(CCN) and a significant spreading effect on white noise, but also has of components balance and hardware simplicity. In this propos

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Tasi, Chia-chun, and 蔡嘉峻. "A Study on Multi-Path Delay Spread Estimation for OFDM Wireless Communication Systems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/37621421604680371238.

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碩士<br>朝陽科技大學<br>網路與通訊研究所<br>95<br>In this thesis, we investigate the effect of multi-path wireless channels for the Orthogonal Frequency Division Multiplexing (OFDM) communication systems. In the European specification standard, the different modes by the number of sub-carriers, for example, 2K, 4K and 8K, etc., are used to combat the multi-path delay spread due the different transmission channels. We propose an estimation scheme to accurately estimate the multi-path delay spread and then the proper cyclic prefix can be added to reduce the inter-symbol interference (ISI).

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Salih, Murat. "Closed-loop joint code delay synchronization and carrier phase recovery for direct-sequence spread spectrum systems." 1996. https://scholarworks.umass.edu/dissertations/AAI9619432.

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We propose a closed-loop system for acquisition of the pseudo-noise (PN) signal in direct-sequence spread-spectrum (DS/SS) systems. We introduce a novel idea of using an auxiliary signal, as opposed to the PN signal itself, for correlation with the incoming signal. The correlation function of the auxiliary signal and the PN signal has a triangle shape that covers essentially the entire period of the PN signal. Consequently, their correlation provides the direction for the phase update of the local signal generator in the acquisition scheme. With coherent demodulation, mean and variance of the

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Chen, Po-Lin, and 陳柏霖. "Mobility for OFDM-based WLAN systems in time-varying multipath Rayleigh fading channel with long delay spread." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/46350187877269860315.

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碩士<br>國立中山大學<br>通訊工程研究所<br>93<br>OFDM-based WLAN systems are originally used for nearly static environment. But in the trend of user-convenience, if we want to support mobility, the most important issue is the Doppler effect caused by the object velocity. We investigate how the Doppler effect, signal-to-noise ratio (SNR) and imperfect estimation of channel impulse response (CIR) and the maximum Doppler shift fd influence the final bit error rate (BER) under the simulation environment, modified WLAN 802.11a specification. For these effects, we give some simulation results and conclusions. If CI

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Hwang, Yeu-Jyh, and 黃禹治. "Performance of Delay-locked Loops in Direct Sequence Spread Spectrum Systems over Slowly Time-varying multipath fading channels." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/23495938328999162413.

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Sinha, Saurabh. "A multi-dimensional spread spectrum transceiver." Thesis, 2008. http://hdl.handle.net/2263/28885.

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The research conducted for this thesis seeks to understand issues associated with integrating a direct spread spectrum system (DSSS) transceiver on to a single chip. Various types of sequences, such as Kasami sequences and Gold sequences, are available for use in typical spread spectrum systems. For this thesis, complex spreading sequences (CSS) are used for improved cross-correlation and autocorrelation properties that can be achieved by using such a sequence. While CSS and DSSS are well represented in the existing body of knowledge, and discrete bulky hardware solutions exist – an effort to

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Bartone, Chris G. "Measured noise performance of a direct-sequence spread-spectrum system and a comparison of single-vice dual-channel delay-lock loops." Thesis, 1987. http://hdl.handle.net/10945/22347.

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Dabin, Jason Anthony. "A statistical ultra wideband indoor channel model and the effects of antenna directivity on multipath delay spread and path loss in ultra wideband indoor channels." Thesis, 2004. http://library1.njit.edu/etd/fromwebvoyage.cfm?id=njit-etd2004-047.

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Wang, Chien-Chih, and 王建智. "Audio Watermark Algorithm based on Time-Spread Echo method with Exponential Decay." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/33496043360391591230.

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碩士<br>國立成功大學<br>電機工程學系碩博士班<br>94<br>Conventional watermarking techniques based on single echo hiding provide many benefits, but also have several disadvantages, for example, a lenient decoding process, weakness against multiple encoding attacks, etc. In this work, we propose an exponential decay time-spread echo as an alternative to the time-spread echo method in conventional echo hiding. Spreading an echo in the time domain is achieved by using pseudo-noise (PN) sequences with exponential decay. By exponential-decay spreading the echo, the amplitude of each echo can be reduced, i.e., the ener

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