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Dissertations / Theses on the topic 'Modulation Schemes'
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Ng, Soon Xin. "Coded modulation schemes for wireless channels." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271574.
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Osborne, William P., and Sharmin Ara. "REVIEW OF BANDWIDTH EFFICIENT MODULATION SCHEMES." International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/608415.
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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThe national telemetry ranges are being pushed to provide higher data rate telemetry services by users with increasingly complex test procedure for increasingly complex weapon systems. At the same time they are having trouble obtaining more spectrum in which to provide these higher rates because of the demand for spectrum in SHF range from various mobile/cellular Personal Communications Services (PCS) as well as congress’s desire to auction spectrum and to transfer as much spectrum as possible to commercial uses. In light of these pressures the industry is in need of a modulation standard that will out perform the existing PCM/FM standard. The motivation for the present review and analysis of the performance of various coded/uncoded modulation schemes arises from this issue. Comparison of the performance of these schemes will be utilized in the following work to find a suitable solution to the existing problem.
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Harms, Oliver. "Modulation schemes in ambient backscatter communication." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-372148.
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This thesis presents a study of different modulation schemes in the context of backscatter communication. Backscatter communication is a way of wireless communication where no active signal is transmitted. Instead surrounding signals are modified to transmit data. The goal of this thesis is to explore in how far different modulation schemes in combination with off-the-shelf hardware can be used to tackle the current data rate and distance limitations of backscatter systems. This thesis compares the modulation schemes on-off keying (OOK) and frequency-shift keying (FSK) using a constant carrier signal as well as a digital television signal. For the use of a constant carrier signal it is shown that high ranges of up to 225 meters in a line-of-sight environment and up to 30 meters in a non line-of sight environment are reachable extending the current distance limitations by far and even the use of high data rates lead to a range of 175 meters. Moreover, this thesis shows the feasibility of replacing the constant carrier with a television signal and achieves ranges of over a meter in surroundings of television signals with a signal strength of not more than -70 dBm.
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Hof, Axel. "On concatenated coding schemes employing trellis coded modulation." Düsseldorf VDI-Verl, 2009. http://d-nb.info/994364539/04.
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Corden, Ian Robert. "Efficient transmultiplexer algorithms multiband quadrature modulation schemes." Thesis, Staffordshire University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280562.
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Wong, Dennis Mou Ling. "Automatic classification of digital communication modulation schemes." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400128.
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Pérez, Rodenas Ezequiel. "QAM and PSK Modulation Schemes under Impulsive Noise." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-11943.
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Nowadays most of the communications systems are designed considering only to work under AWGN (Additive White Gaussian Noise). But the implementation of wireless systems in industrial facilities brings different kind of interference from machines or any other kind of electronic devices. Some of them are sources of randomly and high power noise, which commonly is known as impulsive noise. The objective in this thesis is to study the impact of the impulsive noise on a communication using QAM (Quadrature Amplitude Modulation) and PSK (Phase-Shift Keying) schemes, by observing the BER (Bit Error Rate) and the APD (Amplitude Probability Distribution). For that, it is developed a measurement method that will be used in a real industrial environment in future work. The content of this thesis is divided in two parts. In the first part is made a program in MATLAB to simulate the communication through a noisy channel. Then is developed a measurement method which is tested in three different ways corresponding to 3 different outputs of an spectrum analyzer, namely, 20,4 MHz IF output, video output and IQ data output. The relation of impulsive noise is presented in the second part with different statistical properties in the BER and the APD, in the setup with the best performance. At the end of the thesis a concluding section summarizes the results obtained during the work and some lines of future work in a real industrial environment with the developed method.
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Zeng, Yu. "Adaptive modulation schemes for optical wireless communication systems." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/3837/.
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High-speed wireless optical communication links have become more popular for personal mobile applications. This is a consequence of the increasing demand from the personal information service boom. Compared to the radio frequency domain, optical wireless communication offers much higher speeds and bit rates per unit power consumption. As stated by the official infrared standard IrDA optical communication enjoys much lower power consumption than Bluetooth, with an inherent security feature while in Line of Sight (LOS) applications. There are also drawbacks such as the infrared radiation cannot penetrate walls as radio frequencies do and interference from the background contribute to the channel dispersions. Focus on the modulation aspects of the optical wireless communication, this thesis try to improve the channel immunity by utilising optimised modulation to the channel. Modulation schemes such as on off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM) and pulse position and amplitude modulation PAPM schemes have been validated. The combined power and bandwidth requirements suggest that the adaptive modulation schemes can provide reliability when deployed in a real time channel, resulting in improved system performance. As a result, an adaptive modulation technique is proposed. Extensive simulations of severe noise distraction have been carried out to validate the new scheme. The simulation results indicate that the new scheme can provide increased immunity against channel noise fluctuation at a relatively low complexity. The scheme obtained formed a basis to support reliable mobile optical wireless communication applications. The adaptive scheme also takes the real time channel conditions into account, which is different from existing schemes. Guaranteed system performance can be secured without compromising power and bandwidth efficiency. This is also a new approach to realise reliable optical wireless links. Fuzzy logic control module has been developed to match the adaptive pattern.
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XAVIER, GUILHERME BARRETO. "MODULATION SCHEMES FOR FREQUENCY CODED QUANTUM KEY DISTRIBUTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6483@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA criptografia quântica foi proposta como uma solução para o problema da distribuição de chaves criptográficas com segurança total garantida pelos princípios da mecânica quântica. Através dessa técnica é possível saber se um espião tentou interceptar a transmissão, o que é impossível utilizando técnicas de transmissão clássicas. Nesse trabalho foi feito um breve resumo da teoria de criptografia quântica, de suas técnicas de transmissão e dos problemas tecnológicos enfrentados. Foi analisada em detalhes a técnica de transmissão de qubits utilizando codificação de freqüência e feita uma comparação dos diferentes esquemas de modulação frente aos protocolos BB84 e B92. Foi demonstrado que os dois esquemas de modulação existentes (AM-AM e PM-PM) são na realidade equivalentes e foi proposto um novo esquema, o AM-PM o único que suporta o protocolo BB84 clássico. Medidas foram realizadas classicamente nos formatos AM-AM e AM-PM.
Quantum cryptography has been proposed as a solution to the cryptographic key distribution problem with absolute security guaranteed by the principles of quantum mechanics. Through this scheme it is possible to find out whether a spy tried to eavesdrop on the transmission, which was impossible to discover using classical transmission techniques. In this work a brief review of quantum cryptography theory, transmission techniques and technological problems involved were performed. It was analyzed in detail the transmission technique employing frequency coding, and a comparison was made between the different modulation schemes and the BB84 and B92 protocols. It was demonstrated that the two existing modulation formats (AM-AM and PM-PM) are in fact equivalent and a new format (AM-PM) was proposed, the only one able to accommodate classical BB84. Classical measurements were performed on the AM-AM and AMPM formats.
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Lunn, Timothy John. "Performance estimation and design of block coded modulation schemes." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385293.
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Fairbanks, John S. "Challenges of Optimizing Multiple Modulation Schemes in Transponder Design." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605305.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaIncreasing gate counts in FPGA’s create an option of offering multiple waveform demodulation and modulation within a single transponder transceiver. Differing data rates, channel schemes, and network protocols can be addressed with the flexibility of software-based demodulation and modulation. Increased satellite longevity and reliability are benefits of software-based transceiver design. Newer packaging technology offers additional capability in reducing form factor and weight of a transponder. A review of the challenges in combining each of the above to produce the next generation of transponders is the subject of this paper.
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Verdin, Dan. "Synchronisation in sampled receivers for narrowband digital modulation schemes." Thesis, University of York, 1995. http://etheses.whiterose.ac.uk/10839/.
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Fortune, P. M. "Multi-level modulation schemes for digital cellular mobile radio." Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/421471/.
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Geisinger, Nathan P. "Classification of digital modulation schemes using linear and nonlinear classifiers." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Mar/10Mar%5FGeisinger.pdf.
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Thesis (Electrical Engineer and M.S. in Electrical Engineering)--Naval Postgraduate School, March 2010.Thesis Advisor(s): Fargues, Monique P. ; Cristi, Roberto ; Robertson, Ralph C. "March 2010." Description based on title screen as viewed on .April 27, 2010. Author(s) subject terms: Blind Modulation Classification, Cumulants, Principal Component Analysis, Linear Discriminant Analysis, Kernel-based functions. Includes bibliographical references (p. 211-212). Also available in print.
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D'Amours, Claude. "Hybrid DS/FH-CDMA systems employing FSK based modulation schemes." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10366.
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This thesis examines a hybrid DS/FH-CDMA system employing FSK based modulation schemes. The proposed modulation schemes are: non-coherent MFSK, a combination of MFSK and DPSK (called MFSK-DPSK) and wideband multitone (MT) FSK. In each case, the signal to be transmitted is modulated by a high rate BPSK signal (the PN sequence) and then it is hopped at a rate higher than the symbol rate into different frequency bins that are sufficiently spaced so that the fading in each channel appears to be an independent process. The main difference between each system is that a DS/FH-CDMA system employing wideband MT-FSK must employ fewer frequency bins to have the same (or comparable) bandwidth as systems employing MFSK or MFSK-DPSK. However, the advantage gained by using MT-FSK is the inherent diversity of the modulation scheme. The bit error rate performance of each modulation scheme in a Rayleigh fading channel is found (in some cases, upper bounds are used). Both frequency-nonselective and frequency-selective fading are considered. A hybrid DS/FH-CDMA system is presented. The multiple access interference is modelled as additional white Gaussian noise. Spectral efficiency expressions are obtained for the system employing the different modulation and coding schemes considered. It is shown that the spectral efficiency of the system is inversely proportional to the bit energy to noise spectral density ratio required to achieve the maximum allowable bit error rate. Furthermore, it is shown that coded MFSK and coded MFSK-DPSK can guarantee lower bit energy to noise spectral density ratio required to achieve the maximum allowable bit error rate of 10$\sp{-3}$ than coded MT-FSK, and thus lower bounds on the spectral efficiency of DS/FH-CDMA systems employing coded MFSK or MFSK-DPSK are higher than DS/FH-CDMA systems employing coded MT-FSK.
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Nguyen, Tien M., Hung H. Nguyen, James Yoh, Dean J. Sklar, and Thomas Eng. "BANDWIDTH EFFICIENT MODULATION SCHEMES FOR FUTURE TT&C APPLICATIONS." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/607603.
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International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper presents initial results of an investigation on bandwidth efficient waveforms for telemetry, tracking and commands (TT&C). Included in the investigation are waveforms that are currently being considered by the International Consultative Committee for Space Data Systems (CCSDS) and American Institute of Aeronautics and Astronautics (AIAA) for standards, advanced waveforms and others that have the potential to become future standards. The goal of this investigation is to recommend a suite of bandwidth efficient modulation schemes for further investigation. This suite of modulation scheme should be suitable for various TT&C applications with data rates ranging from a few hundreds Bit Per Second (bps) to a few hundreds Mega bps (Mbps). First, the philosophy of waveform evaluation is described. The description includes a list of waveform attributes leading to quantitative and qualitative figures of merit for bandwidth efficient waveforms. Then quantitative results for the two most important waveform attributes (bandwidth efficiency and bit error rate performance) are presented. These results will be used by a follow-on study to significantly reduce the number of candidate waveforms, so that all attributes can be more thoroughly evaluated.
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Raorane, Pooja Prakash. "Sampling Based Turbo and Turbo Concatenated Coded Noncoherent Modulation Schemes." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279071861.
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Vital, Juan Carlos Serrato. "Single and joint iterative decoding for higher order modulation schemes." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/730/.
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The research project described in this thesis concentrates on the study, and application of specific channel coding techniques, in particular, low-density parity-check (LDPC) codes, iterative decoding on Tanner graphs, and their application on joint iterative receivers based on the turbo principle, previously proposed. The construction of random LDPC codes that fulfil certain desirable characteristics, such as large girth, specific p and -y values, and acceptable BER and FER performance for short code lengths, traditionally requires a high degree of processing power (i. e. CPU cycles) to run stochastic routines that firstly search within all the possible combinations for those ones that match the desired characteristics of the LDPC matrix, and secondly determines the bit-error rate (BER) and frame-error rate (FER) performance. The construction of well structured LDPC codes by means of algebraic methods has provided LDPC codes that achieve excellent performance, with desirable structure on their LDPC matrices. However, from the universe of LDPC matrices, those ones created through well structured procedures are a small group. Multiple procedures to modify their characteristics such as length and rate have assisted to increase the pool of LDPC codes based on well structured procedures. This thesis study the problem of constructing random LDPC codes with particular length, girth, and column weight as design parameters, with reduced processing power, while providing, at the same time, a desirable structure to allow efficient use of the memory and of the parallel processing capacity to reduce delay through efficient encoding and decoding. Based on previous studies that analysed the same problem, an algorithm is introduced to construct the Girth-Partition and Shift (GPS) LDPC codes, which are half-rate quasi-cyclic (QC) LDPC codes. Several GPS constructions are analysed over the AWGN channel and the flat-fading channel. The effect on the BER and FER performance from variations on their design parameters, is included in this study. This work also includes the BER and FER performance of the concatenation in parallel of different LDPC codes, some of which are based on well structured procedures, such as Euclidean Geometries (EG) and Projective Geomtries (PG), and Margulis constructions based on the Cayley graph, while the rest are based on random procedures, such as Graphical Models (GM) and GPS-LDPC codes. The aim of the analysis of this scheme, combined with the referred LDPC code constructions, include the improvement of the BER and FER performance for short code lengths and the reduction of the encoding complexity. The BER and FER performance achieved by the parallel concatenation of the previously mentioned LDPC codes, is further analysed in a joint demapping, parallel channel decoding and source decoding system. The impact of each component on the overall system performance is also examined.
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Raafat, Ahmed. "Spatial modulation schemes and modem architectures for millimeter wave radio systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669478.
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The rapid growth of wireless industry opens the door to several use cases such as internet of things and device-to-device communications, which require boosting the reliability and the spectral efficiency of the wireless access network, while reducing the energy consumption at the terminals. The vast spectrum available in millimeter-wave (mmWave) frequency band is one of the most promising candidates to achieve high-speed communications. However, the propagation of the radio signals at high carrier frequencies suffers from severe path-loss which reduces the coverage area. Fortunately, the small wavelengths of the mmWave signals allow packing a large number of antennas not only at the base station (BS) but also at the user terminal (UT). These massive antenna arrays can be exploited to attain high beamforming and combining gains and overcome the path-loss associated with the mmWave propagation. In conventional (fully digital) multiple-input-multiple-output (MIMO) transceivers, each antenna is connected to a specific radio-frequency (RF) chain and high resolution analog-to-digital-converter. Unfortunately, these devices are expensive and power hungry especially at mmWave frequency band and when operating in large bandwidths. Having this in mind, several MIMO transceiver architectures have been proposed with the purpose of reducing the hardware cost and the energy consumption.
Fully connected hybrid analog and digital precoding schemes were proposed in with the aim of replacing some of the conventional RF chains by energy efficient analog devices. These fully connected mapping requires many analog devices that leads to non-negligible energy consumption. Partially connected hybrid architectures have been proposed to improve the energy efficiency of the fully connected transceivers by reducing the number of analog devices. Simplifying the transceiver’s architecture to reduce the power consumption results in a degradation of the attained spectral efficiency.
In this PhD dissertation, we propose novel modulation schemes and massive MIMO transceiver design to combat the challenges at the mmWave cellular systems. The structure of the doctoral manuscript can be expressed as
In Chapter 1, we introduce the transceiver design challenges at mmWave cellular communications. Then, we illustrate several state of the art architectures and highlight their limitations. After that, we propose scheme that attains high-energy efficiency and spectrum efficiency.
In chapter 2, first, we mathematically describe the state of the art of the SM and highlight the main challenges with these schemes when applied at mmWave frequency band. In order to combat these challenges (for example, high cost and high power consumption), we propose novel SM schemes specifically designed for mmWave massive MIMO systems. After that, we explain how these schemes can be exploited in attaining energy efficient UT architecture. Finally, we present the channel model, systems assumptions and the transceiver devices power consumption models.
In chapter 3, we consider single user SM system. First, we propose downlink (DL) receive SM (RSM) scheme where the UT can be implemented with single or multiple radio-frequency chains and the BS can be fully digital or hybrid architecture. Moreover, we consider different precoders at the BS and propose low complexity and efficient antenna selection schemes for narrowband and wideband transmissions. After that, we propose joint uplink-downlink SM scheme where we consider RSM in the DL and transmit SM (TSM) in the UL based on energy efficient hybrid UT architecture.
In chapter 4, we extend the SM system to the multi-user case. Specifically, we develop joint multi-user power allocation, user selection and antenna selection algorithms for the broadcast and the multiple access channels.
Chapter 5 is presented for concluding the thesis and proposing future research directions.Considerando los altos requerimientos de los servicios de nueva generación, las infraestructuras de red actual se han visto obligadas a evolucionar en la forma de manejar los diferentes recursos de red y computación. Con este fin, nuevas tecnologías han surgido para soportar las funcionalidades necesarias para esta evolución, significando también un gran cambio de paradigma en el diseño de arquitecturas para la futura implementación de redes.En este sentido, este documento de tesis doctoral presenta un análisis sobre estas tecnologías, enfocado en el caso de redes inter/intra Data Centre. Por consiguiente, la introducción de tecnologías basadas en redes ópticas ha sido estudiada, con el fin de identificar problemas actuales que puedan llegar a ser solucionados mediante el diseño y aplicación de nuevas técnicas, asimismo como a través del desarrollo o la extensión de los componentes de arquitectura de red.Con este propósito, se han definido una serie de propuestas relacionadas con aspectos cruciales, así como el control de dispositivos ópticos por SDN para habilitar el manejo de redes híbridas, la necesidad de definir un mecanismo de descubrimiento de topologías ópticas capaz de exponer información precisa, y el analizar las brechas existentes para la definición de una arquitectura común en fin de soportar las comunicaciones 5G.Para validar estas propuestas, se han presentado una serie de validaciones experimentales por medio de escenarios de prueba específicos, demostrando los avances en control, orquestación, virtualización y manejo de recursos con el fin de optimizar su utilización. Los resultados expuestos, además de corroborar la correcta operación de los métodos y componentes propuestos, abre el camino hacia nuevas formas de adaptar los actuales despliegues de red respecto a los desafíos definidos en el inicio de una nueva era de las telecomunicaciones.
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Alamri, Osamah R. "Turbo detection of sphere packing modulation aided space-time coding schemes." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435719.
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Golby, John N. A. "Investigation into PRS-precoded, constant-envelope, continuous-phase digital modulation schemes." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/8345.
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Bibliography: leaves 78-79.Partial response signaling ( PRS) has been used successfully to improve the spectral properties of Pulse Amplitude Modulated (PAM) digital transmission systems. This thesis investigation studied the effect of PRS on frequency- and phase-modulated carrier systems, in particular on their spectral performance and their maintenance of constant envelope.
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Camargo, Alfonso. "Adaptive modulation, channel coding and MIMO schemes for practical OFDM systems." Aachen Shaker, 2009. http://d-nb.info/99482971X/04.
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Arabaci, Murat. "Nonbinary-LDPC-Coded Modulation Schemes for High-Speed Optical Communication Networks." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195826.
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IEEE has recently finished its ratification of the IEEE Standard 802.3ba in June 2010 which set the target Ethernet speed as 100 Gbps. The studies on the future trends of the ever-increasing demands for higher speed optical fiber communications show that there is no sign of decline in the demand. Constantly increasing internet traffic and the bandwidth-hungry multimedia services like HDTV, YouTube, voice-over-IP, etc. can be shown as the main driving forces. Indeed, the discussions over the future upgrades on the Ethernet speeds have already been initiated. It is predicted that the next upgrade will enable 400 Gbps Ethernet and the one after will be toward enabling the astounding 1 Tbps Ethernet.Although such high and ultra high transmission speeds are unprecedented over any transmission medium, the bottlenecks for achieving them over the optical fiber remains to be fundamental. At such high operating symbol rates, the signal impairments due to inter- and intra-channel fiber nonlinearities and polarization mode dispersion get exacerbated to the levels that cripple the high-fidelity communication over optical fibers. Therefore, efforts should be exerted to provide solutions that not only answer the need for high-speed transmission but also maintain low operating symbol rates.In this dissertation, we contribute to these efforts by proposing nonbinary-LDPC-coded modulation (NB-LDPC-CM) schemes as enabling technologies that can meet both the aforementioned goals. We show that our proposed NB-LDPC-CM schemes can outperform their prior-art, binary counterparts called bit-interleaved coded modulation (BI-LDPC-CM) schemes while attaining the same aggregate bit rates at a lower complexity and latency. We provide comprehensive analysis on the computational complexity of both schemes to justify our claims with solid evidence. We also compare the performances of both schemes by using amplified spontaneous emission (ASE) noise dominated optical fiber transmission and short to medium haul optical fiber transmission scenarios. Both applications show outstanding performances of NB-LDPC-CM schemes over the prior-art BI-LDPC-CM schemes with increasing gaps in coding gain as the transmission speeds increase. Furthermore, we present how a rate-adaptive NB-LDPC-CM can be employed to fully utilize the resources of a long haul optical transport network throughout its service time.
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TALESARA, ANKIT. "SIMULATION/ANALYSIS OF MODULATION SCHEMES FOR UWB IN PRESENCE OF MULTIPATH AND MUI." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059741940.
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Khan, Muhammad Gufran. "On Modulation and Detection Schemes for Low-Complexity Impulse Radio UWB Communications." Doctoral thesis, Karlskrona : Blekinge Institute of Technology, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00516.
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Due to wealth of advantages offered by short range ultra wideband (UWB) technology, such as capacity improvement, fading reduction and localization, it has gathered a considerable attention. Distinct UWB qualities also pose many system design challenges like difficulties in using digital processing, complex channel estimation and different propagation characteristics. The main objective of the thesis is to develop and evaluate efficient modulation and detection schemes for impulse radio (IR) UWB with a focus on wireless sensor networks characterized by low cost and low power consumption. The content of the thesis comprises of five parts. In Part I, a coherent RAKE and non-coherent energy detector (ED) and transmitted reference (TR) receivers are examined and their bit-error-rate (BER) performance is evaluated using channels measured in an industrial environment. In specific, selective RAKE (SRake) and partial RAKE (PRake) for both maximal ratio combining (MRC) and equal gain combining (EGC) are compared. Based on the analysis and simulation results, it is concluded the SRake with EGC is to be preferred, whereas the best complexity/performance trade-off is provided by the ED based receivers. Part II presents several signaling and detection schemes; the proposed schemes are recursive TR (R-TR), dual-doublet TR (DDTR), doublet-shift TR (DSTR) and binary pulse position modulation (BPPM)/DSTR. Analysis and simulations verify that the proposed schemes may be preferred over the conventional TR in terms of BER, energy efficiency and/or implementation complexity. Part III presents a non-coherent kurtosis detector (KD) and a fourth-order detector (FD), which can discriminate between Gaussian noise and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. Empirical evaluations and simulations using channel measurements conducted in a corridor, an office and a laboratory environment verify that performance of the proposed FD receiver is slightly better than the ED in the low SNR region and its performance improves as the SNR increases. Part IV presents a robust weighted ED (WED) in which the weighting coefficients are estimated adaptively based on the received stochastic data. Simulation results confirm that performance of the proposed weight estimation method is close to that of a data-aided (DA) scheme. Finally, Part V focuses on a multi-user scenario and develops a weighted code-multiplexed TR (WCM-TR) receiver employing the robust adaptive weight estimation scheme. Secondly, a BPPM/CM-TR UWB system is presented to mitigate inter-frame interference (IFI) and multi-user interference (MUI) from other asynchronous users. The BPPM/CM-TR system is 3 dB energy-efficient and improves the BER performance by mitigating MUI/IFI in the high SNR region, while for the low SNR case and single-user scenario, a dual-mode BPPM/CM-TR system is suggested
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Vincent, Patrick J. "Effects of fading and data modulation on noncoherent m-sequence acquisition schemes." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/25877.
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Approved for public release; distribution is unlimited.In direct-sequence spread-spectrum systems, successful communications require phase synchronization of the m-sequence in the incoming signal with a locally generated m-sequence at the receiver. Many acquisition schemes which extract the phase of an incoming m-sequence have been studied, but most of them assume coherent demodulation (which is usually not available during acquisition) and or independent samples (which introduce a loss in the effective signal to noise ratio (SNR)). This thesis investigates the performance of two m-sequence acquisition schemes in the presence of fading and data modulation. A fixed sample size test and a truncated sequential test are studied without the usual assumptions of coherent demodulation or independent samples. The effects of fading and data modulation on our schemes' probability of false alarm, probability of detection and test length are thoroughly explored. We find that channel fading in effect induces a loss of signal SNR, but the desired power of the tests can be restored by suitable adjustments in the decision processor. We find that the effects of data modulation are less severe, but more problematic to correct
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Li, Qiao. "Using Watson perceptual model to improve quantization index modulation based watermarking schemes." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1443976/.
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Quantization index modulation (QIM) is a popular watermarking scheme that has received considerable attention. Nevertheless, there are practical limitations of QIM. For example, traditional QIM uses a fixed quantization step size, which may lead to poor fidelity in some areas of the content. More serious problems of the original QIM algorithm include its extremely sensitivity to valumetric scaling (e.g., changes in amplitude) and re-quantization (e.g., JPEG compression). In this thesis, we first propose using Watson's perceptual model to adaptively select the quantization step size based on the calculated perceptual "slack". Experimental results on 1000 images indicate improvements in fidelity as well as improved robustness in high-noise regimes. Watson's perceptual model is then modified such that the slacks scale linearly with valumetric scaling, thereby providing a QIM algorithm that is theoretically invariant to valumetric scaling. In practice, the robustness against valumetric scaling is significantly improved, but scaling can still result in errors due to cropping and roundoff that are an indirect effect of scaling. Two new algorithms are proposed the first based on regular QIM and the second based on rational dither modulation. A comparison with other methods demonstrates improved performance over other recently proposed valumetric-invariant QIM algorithms, with only small degradations in fidelity. Spread transform dither modulation (STDM) is a form of QIM that is more robust to re-quantization. However, the robustness of STDM to JPEG compression is still poor and it remains very sensitive to valumetric scaling. We describe how a perceptual model can be incorporated into the STDM framework to (i) provide robustness to valumetric scaling, (ii) reduce the embedding-induced perceptual distortion and (iii) significantly improve the robustness to re-quantization.
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Singhal, Amit. "Performance of amplitude modulation schemes for molecular communication over a fluid medium." Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/7011.
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Prasad, V. Himamshu. "Analysis and Comparison of Space Vector Modulation Schemes for Three-Leg and Four-Leg Voltage Source Inverters." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36578.
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Several space vector modulation schemes have been analyzed for three-leg and four-leg voltage source inverters. The analysis is performed with respect to a) switching losses, b) total harmonic distortion, c) peak-to-peak ripple in the line current and d) the ease of digital implementation. The analysis is performed over the entire range of modulation index and for varying load power factors (leading and lagging) under both balanced and unbalanced load conditions. The analysis shows that the performance of four-leg inverters is similar to three-leg inverters for various space vector modulation schemes. The analysis also verifies the fact that a modulation scheme with good harmonic performance usually has high switching losses and vice-versa. The analysis is verified using simulation and experiments. A novel algorithm for the calculation of total harmonic distortion of PWM signals has been proposed.Master of Science
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Ghosna, Fadi Jawdat. "Pulse position modulation coding schemes for optical inter-satellite links in free space." Thesis, University of Huddersfield, 2010. http://eprints.hud.ac.uk/id/eprint/8766/.
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The rapid and significant development of communications links between satellites has made it possible to use various applications such as relay voice, video, multimedia, etc. As a result, a great deal of research has been done in this field during the last few years to reduce power consumption and increase transmission reliability. This thesis is concerned with an analysis of intersatellite links in free space, with optical links using laser sources being considered in particular. It includes a literature survey and a thorough theoretical investigation into designing the model of the link in free space. This thesis describes the novel technique of designing the optical receiver that consists of PIN photodiode as a photodetector, Semiconductor optical amplifier (SOA) and a 3rd order Butterworth filter with central decision detection. In addition, it discusses the use of several different coding schemes for use in such links: multiple pulse position modulation (MPPM); digital pulse position modulation (DPPM); Dicode pulse position modulation (Dicode PPM). This novel technique of an optical receiver is investigated and new work is presented in order to examine the noise performance of this optical receiver and hence determine its sensitivity and the number of photons received for a specified error rate. Further new work is carried out to compare these coding schemes in terms of error weightings and coding efficiency through showing how the PCM error rate is affected by false alarm and erasure errors for MPPM, DPPM and Dicode PPM coding 3, 4, 5 and 6 bits of PCM. An original maximum likelihood sequence detector (MLSD) is presented in this thesis in order to perform these comparisons. In addition, computer simulations models (using MCAD) are performed to compare these three coding schemes operating with 3, 4, 5 and 6 bits of PCM in terms of sensitivity and bandwidth efficiency. These comparisons show that MPPM coding 3, 4, 5 and 6 bits of PCM is the appropriate coding scheme to be used in optical inter-satellite links in free space and PCM data rates of 1 Gbit/s.
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Kahraman, Betulhan. "Performance evaluation of UHF fading satellite channel by simulation for different modulation schemes." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24003.
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Camargo, Alfonso [Verfasser]. "Adaptive Modulation, Channel Coding and MIMO Schemes for Practical OFDM Systems / Alfonso Camargo." Aachen : Shaker, 2009. http://d-nb.info/1156517877/34.
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Chow, Y. C. "Performance analysis of bandwidth-efficient modulation schemes for high capacity wireless networks 1." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337257.
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Achar, Vasant Harish. "Advanced modulation schemes for suppression of stimulated Brillouin scattering in optical fibre amplifiers." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/419064/.
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High power single-frequency lasers have attracted much attention lately due to their potential for application in phased-array lasers, coherent LIDAR, gravitational wave detection, coherent beam combining and many more. Optical fibre amplifiers operating in master-oscillator power-amplifier (MOPA) configuration are very well suited for power scaling of these lasers. A severe limitation on power scaling of these lasers is imposed by the stimulated Brillouin scattering (SBS) in optical fibre amplifiers. Since SBS has potentially the lowest threshold of all the nonlinearities in optical fibres, it is critical that it be addressed. The central idea of this thesis is to use advanced modulation schemes for suppressing SBS in optical fibre amplifiers. These modulation schemes are aimed at phase modulating either Brillouin Stokes wave using cross phase modulation from the intensity modulated pump or the laser wave through pure phase modulation by using an electro-optic modulator. In both cases the spectral linewidth of the respective lightwaves is broadened due to phase modulation. We explore optimized modulation formats for optical spectral control and suppression of SBS. In the former case, we experimentally achieve 5 dB SBS threshold enhancement in Raman and rare-earth doped optical fibre amplifier. In the latter, we use periodic optimized phase modulation formats to achieve SBS threshold enhancement, theoretically. It is also demonstrated that these periodic arbitrary wave-forms perform better compared to the random waveforms like white Gaussian noise. Furthermore, we investigate Brillouin gain efficiency in optical fibres for lengths that are generally employed in high power fibre amplifiers. The optical fibres show a lower- than-expected threshold at these lengths which is attributed to the wave mixing effects. Simulations based on the bidirectional waves are carried out to support these experimental results.
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Xu, Yanjun. "Modulation and detection schemes based on chaotic attractors properties : application to wideband transmissions." Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000278/.
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Au cours des vingt dernières années, les systèmes de communications basés sur le chaos ont été étudiés, avec pour objectif la possibilité de générer les signaux large-bande par des circuits électroniques simples, permettant une faible complexité des circuits émetteurs-récepteurs. Cette thèse concerne l’étude de systèmes de transmissions large-bande basés sur le chaos, en utilisant certaines propriétés des attracteurs chaotiques. Tout d’abord, un système dynamique a été choisi et étudié, permettant de générer des signaux chaotiques qui possèdent des composantes périodiques. L’analyse de ces attracteurs chaotiques cycliques (CCA) met en évidence des propriétés spécifiques en lien avec leur période. Ensuite, deux schémas de modulation basés sur les CCAs sont proposés. Les détections non-cohérentes associées sont réalisées par l’observation des propriétés spécifiques des signaux rec¸us. L’évaluation des performances des systèmes basés sur les CCAs dans le cas d’un canal de bruit additif Gaussien montre des performances meilleures que celles des systèmes dits ”differential chaos shift keying (DCSK)”, en bas débit de symboles. En outre, les performances dans le cas multi-trajet sont comparables dans la bande de 2,4 GHzIn the past twenty years, chaos-based communication systems have been studied, considering the possibility of generating wideband signals by simple electronic circuits, hence low complexity in transceiver. The aim of this thesis is to study the chaos-based wideband transmission systems relying on the properties of chaotic attractors. Firstly, a dynamical system is selected and studied, allowing to generate the chaotic signals with a periodic component. The analysis of such chaotic cyclic attractors (CCA) shows the specific properties. Then, two CCA-based modulation schemes are proposed, with the simple noncoherent detections realized by observing the specific properties of the received signals. The performance evaluation of CCA-based systems in the additive white Gaussian noise (AWGN) channel shows a better noise performance with long symbol duration, compared to the one of differentially chaos shift keying (DCSK). In addition, they have a comparable multipath performance in the 2. 4 GHz ISM environment
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Talesara, Ankit. "Simulation/analysis of modulation schemes for UWB in prescence of multipath and MUI." Cincinnati, Ohio : University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1059741940.
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Kodheli, Oltjon. "OFDM-based schemes for next generation wireless systems." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11790/.
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The purpose of this study is to investigate two candidate waveforms for next generation wireless systems, filtered Orthogonal Frequency Division Multiplexing (f-OFDM) and Unified Filtered Multi-Carrier (UFMC). The evaluation is done based on the power spectral density analysis of the signal and performance measurements in synchronous and asynchronous transmission.
In f-OFDM we implement a soft truncated filter with length 1/3 of OFDM symbol. In UFMC we use the Dolph-Chebyshev filter, limited to the length of zero padding (ZP). The simulation results demonstrates that both waveforms have a better spectral behaviour compared with conventional OFDM. However, the induced inter-symbol interference (ISI) caused by the filter in f-OFDM, and the inter-carrier interference (ICI) induced in UFMC due to cyclic prefix (CP) reduction , should be kept under control.
In addition, in a synchronous transmission case with ideal parameters, f-OFDM and UFMC appear to have similar performance with OFDM. When carrier frequency offset (CFO) is imposed in the transmission, UFMC outperforms OFDM and f-OFDM.
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Dudak, Celal. "Effects Of Solid State Power Amplifier Nonlinearity On Various Phase Shift Keying Modulation Schemes." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605860/index.pdf.
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This study concentrates on the performance evaluation of a specific modulation scheme under nonlinear operation. This modulation scheme is the phase shift keying (PSK) modulation, exemplified by the special cases of BPSK, QPSK, OQPSK, π
/4-QPSK. The specific nonlinear block is chosen to be the solid state power amplifier (SSPA) structure whose simulation model is the Rapp model. Varying transmitter filter characteristic and one of the power amplifier parameters constitute the main methodology of simulations. Bit error rate (BER), error vector magnitude (EVM), and Space Frequency Coordination Group (SFCG) spectral mask constraint are the evaluation parameters taken into account throughout this study. Simulation results support the initial literature survey, which reveals additional features showing how each modulation scheme is affected by various SSPA nonlinearity characteristics.
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Riche, Larry. "The performance of high-order quadrature amplitude modulation schemes for broadband wireless communication systems." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2012. http://digitalcommons.auctr.edu/dissertations/300.
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The limited amount frequency spectrum available to wireless comnmnication systemsmakes it difficult to satisfy the rapidly growing demand for wireless service. Spectral efficiency can be increased by using higher order modulation schemes. However this come at the cost of increased probability of error. In this paper we investigate through MATLAB simulation, the implementation of orders of Quadrature Amplitude Modulation (QAM) more commonly used in wired networks. The BER performance of 64, 128, 256, 512, 1024, 2048, 4096, and 8192 QAM signals in the presence of Rayleigh and Rician multipath channels with additive white Gaussian noise are simulated.
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Katsaros, Georgios. "The impact of optical modulation schemes on fibre non-linearities in D-WDM systems." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407854.
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Ohn, Sungjae. "Circuits and Modulation Schemes to Achieve High Power-Density in SiC Grid-connected Converters." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89550.
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The emergence of silicon-carbide (SiC) devices has been a 'game changer' in the field of power electronics. With desirable material properties such as low-loss characteristics, high blocking voltage, and high junction temperature operation, they are expected to drastically increase the power density of power electronics systems. Recent state-of-the-art designs show the power density over 17 ; however, certain factors limit the power density to increase beyond this limit. In this dissertation, three key factors are selected to increase the power density of SiC-based grid-connected three-phase converters. Throughout this dissertation, the techniques and strategies to increase the power density of SiC three-phase converters were investigated.
Firstly, a magnetic integration method was introduced for the coupled inductors in the interleaved three-phase converters. Due to limited current-capacity compared to the silicon insulated-gate bipolar transistors (Si-IGBTs), discrete SiC devices or SiC modules, operate in parallel to handle a large current. When three-phase inverters are paralleled, interleaving can be used, and coupled inductors are employed to limit the circulating current. In Chapter 2, the conventional integration method was extended to integrate three coupled inductors into two; one for differential-mode circulating current and the other for common-mode circulating current. By comparing with prior research work, a 20% reduction in size and weight is demonstrated.
From Chapter 3 to Chapter 5, a full-SiC uninterruptible power supply (UPS) was investigated. With the high switching frequency and fast switching dynamics of SiC devices, strategies on electromagnetic inference become more important, compared to Si-IGBT based inverters. Chapter 3 focuses on a common-mode equivalent circuit model for a topology and pulse width modulation (PWM) scheme selection, to set a noise mitigation strategy in the design phase. A three terminal common-mode electromagnetic interference (EMI) model is proposed, which predicts the impact of the dc-dc stage and a large battery-rack on the output CM noise. Based on the model, severe deterioration of noise by the dc-dc stage and battery-rack can be predicted. Special attention was paid on the selection of the dc-dc stage's topology and the PWM scheme to minimize the impact. With the mitigation strategy, a maximum 16 dB reduction on CM EMI can be achieved for a wide frequency range.
In Chapter 4, an active PWM scheme for a full-SiC three-level back-to-back converter was proposed. The PWM scheme targets the size reduction of two key components: dc-link capacitors and a common-mode EMI filter. The increase in switching frequency calls for a large common-mode EMI filter, and dc-link capacitors in the three-level topology may take a considerable portion in the total volume. To reduce the common-mode noise emission, different combinations of the voltage vectors are investigated to generate center-aligned single pulse common-mode voltage. By such an alignment of common-mode voltage with different vector combinations, noise cancellation between the rectifier and the inverter can be maximally utilized, while the balancing of neutral point voltage can be achieved by the transition between the combinations. Also, to reduce the size of the dc-link capacitor for the three-level back-to-back converter, a compensation algorithm for neutral point voltage unbalance was developed for both differential-mode voltage and the common-mode voltage of the ac-ac stage. The experimental results show a 4 dB reduction on CM EMI, which leads to a 30% reduction on the required CM inductance value. When a 10% variation of neutral point voltage can be handled, the dc-link capacitance can be reduced by 56%.
In Chapter 5, a 20 kW full-SiC UPS prototype was built to demonstrate a possible size-reduction with the proposed PWM scheme, as well as a selection of topologies and PWM schemes based on the model. The power density and efficiency are compared with the state-of-the-art Si-IGBT based UPSs.
Chapter 6 seeks to improve power density by a change in a modulation method. Triangular conduction mode (TCM) operation of the three-level full-SiC inverter was investigated. The switching loss of SiC devices is reported to be concentrated on the turn-on instant. With zero-voltage turn-on of all switches, the switching frequency of a three-level three-phase SiC inverter can be drastically increased, compared to the hard-switching operation. This contributes to the size-reduction of the filter inductors and EMI filters. Based on the design to achieve a 99% peak efficiency, a comparison was made with a full-SiC three-level inverter, operating in continuous conduction mode (CCM), to verify the benefit of the soft switching scheme on the power density. A design procedure for an LCL filter of paralleled TCM inverters was developed. With 3.5 times high switching frequency, the total weight of the filter stage of the TCM inverter can be reduced by 15%, compared to that of the CCM inverter.
Throughout this dissertation, techniques for size reduction of key components are introduced, including coupled inductors in parallel inverters, an EMI filter, dc-link capacitors, and the main boost inductor. From Chapter 2 to 5, the physical size or required value of these key components could be reduced by 20% to 56% by different schemes such as magnetic integration, EMI mitigation strategy through modeling, and an active PWM scheme. An optimization result for a full-SiC UPS showed a 40% decrease in the total volume, compared to the state-of-the-art Si-IGBT solution. Soft-switching modulation for SiC-based three-phase inverters can bring a significant increase in the switching frequency and has the potential to enhance power-density notably. A three-level three-phase full-SiC 40 kW PV inverter with TCM operation contributed to a 15% reduction on the filter weight.Doctor of Philosophy
The power density of a power electronics system is regarded as an indicator of technological advances. The higher the power density of the power supply, the more power it can generate with the given volume and weight. The size requirement on power electronics has been driven towards tighter limits, as the dependency on electric energy increases with the electrification of transportation and the emergence of grid-connected renewable energy sources. However, the efficiency of a power electronics system is an essential factor and is regarded as a trade-off with the power density. The size of power electronics systems is largely impacted by its magnetic components for filtering, as well as its cooling system, such as a heatsink. Once the switching frequency of power semiconductors is increased to lower the burden on filtering, more loss is generated from filters and semiconductors, thus enlarging the size of the cooling system. Therefore, considering the efficiency has to be maintained at a reasonable value, the power density of Si-based converters appears to be saturated. With the emergence of wide-bandgap devices such as silicon carbide (SiC) or gallium nitride (GaN), the switching frequency of power devices can be significantly increased. This is a result of superior material properties, compared to Si-based power semiconductors. For grid-connected applications, SiC devices are adopted, due to the limitations of voltage ratings in GaN devices. Before commercial SiC devices were available, the power density of SiC- based three-phase inverters was expected to go over 20 𝑘𝑊 𝑑𝑚3 ⁄ . However, the state-of-the art designs shows the power density around 3 ~ 4 𝑘𝑊 𝑑𝑚3 ⁄ , and at most 17 𝑘𝑊 𝑑𝑚3 ⁄ . The SiC devices could increase the power density, but they have not reached the level expected. The adoption of SiC devices with faster switching was not a panacea for power density improvement. This dissertation starts with an analysis of the factors that prevent power density improvement of SiC-based, grid-connected, three-phase inverters. Three factors were identified: a limited increase in the switching frequency, large high-frequency noise generation to be filtered, and smaller but still significant magnetic components. Using a generic design procedure for three-phase inverters, each chapter seeks to frame a strategy and develop techniques to enhance the power density. For smaller magnetic components, a magnetic integration scheme is proposed for paralleled ac-dc converters. To reduce the size of the noise filter, an accurate modeling approach was taken to predict the noise phenomena during the design phase. Also, a modulation scheme to minimize the noise generation of the ac-ac stage is proposed. The validity of the proposed technique was verified by a full-SiC three-phase uninterruptible power supply with optimized hardware design. Lastly, the benefit of soft-switching modulation, which leads to a significant increase in switching frequency, was analyzed. The hardware optimization procedure was developed and compared to hard-switched three-phase inverters.
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Sankar, Hari. "LDPC code-based bandwidth efficient coding schemes for wireless communications." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1780.
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Han, Jieying, Brett T. Walkenhorst, and Enkuang D. Wang. "Adaptive Modulation Schemes for OFDM and SOQPSK Using Error Vector Magnitude (EVM) and Godard Dispersion." International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/577472.
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ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CAIn this paper, we develop a new approach which enables adaptation across two modulation schemes in the iNET standard: orthogonal frequency-division multiplexing (OFDM) and shaped-offset quadrature phased-shift keying (SOQPSK). We present the error vector magnitude (EVM) for OFDM and second-order Godard dispersion (D(²)) for SOQPSK as our link metrics that measure the degradation due to thermal noise and channel effects and then derive the mathematical relationship between these two metrics. This relationship enables us to utilize a set of empirically-derived rules that incorporate both modulation schemes.
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Geng, Liang. "Transmission capacity improvement for high speed multimode waveguide links using advanced optical launch and multilevel modulation schemes." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/245192.
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This dissertation investigates the potential technologies in both optical and electrical domains for transmission capacity improvement in multimode waveguide links. The first half of the dissertation focuses on the multimode waveguide made from glass, the multimode glass fibre. A new optical launch scheme is developed, namely low-loss Hermite-Gaussian launch, to achieve single mode group excitation in the multimode glass fibre. Novel implementations using elliptical Gaussian beam and square-shaped launching profiles are developed, achieving a coupling loss at least 2.5 dB lower than the previously reported line launch scheme. Theoretical calculations show that these launches provide 50% bandwidth-distance product improvement over the dual launch scheme for a 99% yield of the entire OM1 fibre installed base. It is also found experimentally that the low-loss Hermite-Gaussian launches outperform dual launch for fibres favouring either centre launch or offset launch. Misalignment tolerance measurements reveal that the bandwidth improvements over a perfectly aligned centre launch using these launches are maintained within a radial offset range of ≤ 8 μm. Error free transmissions at 10 Gbit/s are demonstrated for different orders of low-loss Hermite-Gaussian launches over 250 m worst case OM1 fibre without the use of equalisation. The second half of the dissertation concentrates on another type of multimode waveguide which is made from plastic, namely step-index plastic optical fibre (SI-POF). Both baseband and passband multilevel modulation schemes are investigated to provide over gigabit/s transmissions using LEDs. For the first time, fractionally-spaced equalisers are thoroughly examined in multilevel modulation systems for LED-based SI-POF links. Based on the link budget analysis, it is found that PAM-8 and CAP-64 are the best baseband and passband solutions respectively. For 25 m links, calculations show that PAM-8 and CAP-64 can achieve data rate up to 3 Gbit/s with system margins of 2.2 dB and 1.3 dB. Meanwhile for 50 m links, they achieve data rate up to 1.5 Gbit/s with system margins of 1.9 dB and 1.2 dB respectively. A new FPGA system is developed to experimentally evaluate the PAM-8 and CAP-64 schemes. Error free transmissions are achieved at 3 Gbit/s using PAM-8 for 25 m SI-POF and 1.5 Gbit/s using CAP-64 for 50 m SI-POF. These results record the highest bit-rate-distance-product achieved in LED-based SI-POF links without the use of forward error correction.
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Quinteros, Milton I. "Trellis Coded Modulation Schemes Using A New Expanded 16-Dimensional Constant Envelope Quadrature-Quadrature Phase Shift Keying Constellation." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/924.
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In this thesis, the author presents and analyzes two 4-dimensional Constant Envelope Quadrature-Quadrature Phase Shift Keying constellations. Optimal demodulators for the two constellations are presented, and one of them was designed and implemented by the author. In addition, a novel expanded 16-dimensional CEQ2PSK constellation that doubles the number of points without decreasing the distance between points or increasing the peak energy is generated by concatenating the aforementioned constellations with a particular method and restrictions. This original 16-dimensional set of symbols is set-partitioned and used in a multidimensional Trellis-Coded Modulation scheme along with a convolutional encoder of rate 2/3. Effective gain of 2.67 dB over uncoded CEQ2PSK constellation with low complexity is achieved theoretically. A coding gain of 2.4 dB with 8 dB SNR is obtained by using Monte Carlo simulations. The TCM systems and demodulators were tested under an Additive White Gaussian Noise channel by using Matlab's Simulink block diagrams.
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Heatley, D. J. T. "Optical modulation and receiver sensitivity : a study of the receiver sensitivity of analogue and digital modulation schemes suited to single and multi-channel video transmission over optical fibres." Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233055.
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Ji, Hui. "Study and optimization of new differential space-time modulation schemes based on the Weyl group for the second generation of MIMO systems." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0021/document.
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Actuellement, l’étude des systèmes multi-antennaires MIMO (Multiple Input Multiple Output) est orientée dans beaucoup de cas vers l’augmentation considérable du nombre d’antennes de la station de base (« massive MIMO », « large-scale MIMO »), afin notamment d’augmenter la capacité de transmission, réduire l’énergie consommée par bit transmis, exploiter la dimension spatiale du canal de propagation, diminuer l’influence des évanouissements, etc. Pour les systèmes MIMO à bande étroite ou ceux utilisant la technique OFDM (Orthogonal Frequency Division Multiplex), le canal de propagation (ou les sous-canaux correspondants à chaque sous-porteuse d’un système OFDM) sont pratiquement plats (non-sélectifs en fréquence), ce qui revient à considérer la réponse fréquentielle de chaque canal SISO invariante par rapport à la fréquence mais variante dans le temps. Ainsi, le canal de propagation MIMO peut être caractérisé en bande de base par une matrice dont les coefficients sont des nombres complexes. Les systèmes MIMO cohérents nécessitent pour pouvoir démoduler le signal en réception de disposer de la connaissance de cette matrice de canal, donc le sondage périodique, en temps réel, du canal de propagation. L’augmentation du nombre d’antennes et la variation dans le temps, parfois assez rapide, du canal de propagation, rend ce sondage de canal difficile, voire impossible. Il est donc intéressant d’étudier des systèmes MIMO différentiels qui n’ont pas besoin de connaître la matrice de canal. Pour un bon fonctionnement de ces systèmes, la seule contrainte est que la matrice de canal varie peu pendant la transmission de deux matrices d’information successives. Le sujet de cette thèse concerne l’étude et l’analyse de nouveaux systèmes MIMO différentiels. On considère des systèmes à 2, 4 et 8 antennes d’émission, mais la méthode utilisée peut être étendue à des systèmes MIMO avec 2n antennes d’émission, le nombre d’antennes de réception étant quelconque. Pour les systèmes MIMO avec 2 antennes d’émission qui ont été étudiés dans le cadre de cette thèse, les matrices d’information sont des éléments du groupe de Weyl. Pour les systèmes avec 2n antennes d’émission, (n ≥ 2), les matrices utilisées sont obtenues en effectuant des produits de Kronecker des matrices unitaires du groupe de Weyl. Pour chaque nombre d’antennes d’émission on identifie d’abord le nombre de matrices disponibles et on détermine la valeur maximale de l’efficacité spectrale. Pour chaque valeur de l’efficacité spectrale on détermine les meilleurs sous-ensembles de matrices d’information à utiliser (selon le spectre des distances ou le critère du produit de diversité). On optimise ensuite la correspondance ou mapping entre les vecteurs binaires et les matrices d’information. Enfin, on détermine par simulation les performances des systèmes MIMO différentiels ainsi obtenus et on les compare avec celles des systèmes similaires existants. […]At present, the study of multi-antenna systems MIMO (Multiple Input Multiple Output) is developed in many cases to intensively increase the number of base station antennas («massive MIMO», «largescale MIMO»), particularly in order to increase the transmission capacity, reduce energy consumed per bit transmitted, exploit the spatial dimension of the propagation channel, reduce the influence of fading, etc. For MIMO systems with narrowband or those using OFDM technique (Orthogonal Frequency Division Multiplex), the propagation channel (or the sub-channels corresponding to each sub-carrier of an OFDM system) are substantially flat (frequency non-selective). In this case the frequency response of each SISO channel is invariant with respect to frequency, but variant in time. Furthermore, the MIMO propagation channel can be characterized in baseband by a matrix whose coefficients are complex numbers. Coherent MIMO systems need to have the knowledge of the channel matrix to be able to demodulate the received signal. Therefore, periodic pilot should be transmitted and received to estimate the channel matrix in real time. The increase of the number of antennas and the change of the propagation channel over time, sometimes quite fast, makes the channel estimation quite difficult or impossible. It is therefore interesting to study differential MIMO systems that do not need to know the channel matrix. For proper operation of these systems, the only constraint is that the channel matrix varies slightly during the transmission of two successive information matrices. The subject of this thesis is the study and analysis of new differential MIMO systems. We consider systems with 2, 4 and 8 transmit antennas, but the method can be extended to MIMO systems with 2n transmit antennas, the number of receive antennas can be any positive integer. For MIMO systems with two transmit antennas that were studied in this thesis, information matrices are elements of the Weyl group. For systems with 2n (n ≥ 2) transmit antennas, the matrices used are obtained by performing the Kronecker product of the unitary matrices in Weyl group. For each number of transmit antennas, we first identify the number of available matrices and the maximum value of the spectral efficiency. For each value of the spectral efficiency, we then determine the best subsets of information matrix to use (depending on the spectrum of the distances or the diversity product criterion). Then we optimize the correspondence or mapping between binary vectors and matrices of information. Finally, the performance of differential MIMO systems are obtained by simulation and compared with those of existing similar systems. […]
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Lee, Moonhyun. "Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99694.
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With the increasing demands on electronic loads (e.g. desktop, laptop, monitor, LED lighting and server) in modern technology-driven lives, performance of switched-mode power supply (SMPS) for electronics have been growing to prominence. As front-end converters in typical SMPS structure, ac-dc power-factor correction (PFC) circuits play a key role in regulations of input power factor, harmonics and dc output voltage, which has a decisive effect on entire power-supply performances. Universal ac-line and low-power system (90–264 Vrms, up to 300–400 W) is one of the most common power-supply specifications and boost-derived PFC topologies have been widely used for the purpose. In order to concurrently achieve high efficiency and low-cost system in the PFC stage, zero-current switching (ZCS) control schemes are highly employed in control principles. Representative schemes are discontinuous conduction mode (DCM) and critical conduction mode (CRM). Both modes can realize ZCS turn-on without diode reverse recovery so that low switching losses and low-cost diode utilizations are obtainable.
Among various boost-family PFC topologies, three-level boost (TLB) converter has generated considerable research interest in high-voltage high-power applications. It is mainly due to the fact that the topology can have halved component voltage stresses, improved waveform qualities and electromagnetic interference (EMI) from phase interleaved continuous conduction mode (CCM) operations, compared to other two-level boost PFC converters. On the other hand, in the field of universal-line low-power applications, TLB PFC has been thoroughly out of focus since doubled component counts and increased control complexity than two-level topologies are practical burden for the low-cost systems. However, recent researches on TLB PFC with ZCS control schemes have found that cost-competitiveness of the topology is actually comparable to two-level boost PFC converters because the halved component voltage stresses enable usage of low voltage-rating components of which unit prices are cheaper than higher-rating ones. Based on the justification, researches on ZCS control schemes for TLB PFC have been conducted to get enhanced waveform qualities and performance factors.
Following the research stream, a three-level current modulation scheme that can be adopted in both DCM and CRM is proposed in Chapter 2 of this dissertation. Main concept of the proposed current modulation is additional degree-of-freedom in current-slope shaping by differentiating on-times of two active switches, which cannot be found from any other single-phase boost-derived PFC topologies. Using the multilevel feature, proposed operations in one switching period consist of three steps: common-switch on-time, single-switch on-time and common-switch off-time. The single-switch on-time step is key design factor of the proposed modulation that can be utilized either in fixed or adjustable form depending on control purpose. Based on the basic modulation concept, three-level CRM control scheme, adjustable three-level DCM control scheme, and spread-spectrum frequency modulation (SSFM) with adjustable three-level DCM scheme are proposed in Chapter 3–5, respectively.
In each chapter, implemented control scheme aims to improve different performance factors. In Chapter 3, the proposed three-level CRM scheme uses increased single-switch on-time period to reduce peak inductor current and magnitude of variable switching frequency. It is generally accepted fact that CRM operations suffer from high switching losses and poor efficiency at light load due to considerable increment of switching frequency. Thus, efficiency improvement effect by the proposed CRM scheme becomes remarkable as load condition goes lighter. In experimental verifications, maximum improvement is measured by 1.2% at light load (20%) and overall efficiency is increased by at least 0.4% all over the load range. In Chapter 4, three-level DCM control scheme adopts adjustable single-switch on-time period in fixed switching-frequency framework. The purpose of adjustable control scheme is to widen the length of non-zero inductor current period as much as possible so that discontinued current period and high peak current of DCM operations can be minimized. Experiment results show that, compared to conventional two-level DCM control, full-load peak inductor currents are reduced by 20.2% and 17.1% at 110 and 220 Vrms input voltage conditions, respectively. Moreover, due to turn-off switching energy decrements by the turn-off current reductions, efficiency is also improved by at least 0.4% regardless of input voltage and load conditions. In Chapter 5, a downward SSFM technique is developed first for DCM operations of boosting PFC converters including two-level topologies. This chapter aims to achieve significant reduction of high differential-mode (DM) EMI amplitudes from DCM operations, which is major drawback of DCM control. By using the simple linearized frequency modulation, peak DM EMI noise at full load condition is reduced by 12.7 dBμV than conventional fixed-frequency DCM control. On top of the proposed SSFM, the adjustable three-level DCM control scheme in Chapter 4 is adopted to get further reductions of EMI noises. Experimental results prove that the collaborations of SSFM and adjustable DCM scheme reduce the EMI amplitudes further by 2.5 dBμV than the result of SSFM itself. The reduced EMI amplitudes are helpful to design input EMI filter with higher cut-off frequency and smaller size.
Different from two-level boosting PFC converters, TLB PFC topology has two output capacitors in series and inherently suffers from voltage unbalancing issue, which can be noted as topological trade-off. In Chapter 6, two simple but effective voltage balancing schemes are introduced. The balancing schemes can be easily built into the proposed ZCS control schemes in Chapter 3–5 and experimental results validate the effectiveness of the proposed balancing principles.
For all the proposed control schemes in this dissertation, detailed operation principles, derivation process of key equations, comparative analyses, implementation method with digital controller and experimental verifications with TLB PFC prototype are provided.Doctor of Philosophy
Electronic-based devices and loads have been essential parts of modern society founded on rapid advancements of information technologies. Along with the progress, power supplying and charging of electronic products become routinized in daily lives, but still remain critical requisites for reliable operations. In many power-electronics-based supplying systems, ac-dc power-factor correction (PFC) circuits are generally located at front-end to feed back-end loads from universal ac-line sources. Since PFC stages have a key role in regulating ac-side current quality and dc-side voltage control, the importance of PFC performances cannot be emphasized enough from entire system point of view. Thus, advanced control schemes for PFC converters have been developed in quantity to achieve efficient operations and competent power qualities such as high power factor, low harmonic distortions and low electromagnetic interferences (EMI) noises. In this dissertation, a sort of PFC topologies named three-level boost (TLB) converter is chosen for target topology. Based on inherent three-level waveform capability of the topology, multiple zero-current switching (ZCS) control schemes are proposed. Compared to many conventional two-level PFC topologies, TLB PFC can provide additional degree-of-freedom to current modulation. The increased control flexibility can realize improvements of various waveform qualities including peak current stress, switching frequency range, harmonics and EMI amplitude. From the experimental results in this dissertation, improvements of waveform qualities in TLB PFC with the proposed schemes are verified with comparison to two-level current control schemes; in terms of efficiency, the results show that TLB PFC with the proposed schemes can have similar converter efficiency with conventional two-level boost converter in spite of increased component counts in the topology. Further, the proposed three-level control schemes can be utilized in adjustable forms to accomplish different control objectives depending on system characteristics and applications. In each chapter of this dissertation, a novel control scheme is proposed and explained with details of operation principle, key equations and digital implementation method. All the effectiveness of proposals and analyses are validated by a proper set of experimental results with a TLB PFC prototype.
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Susanto, Misfa. "Network Coding for Multihop Wireless Networks: Joint Random Linear Network Coding and Forward Error Correction with Interleaving for Multihop Wireless Networks." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14864.
Full textAbstract:
Optimising the throughput performance for wireless networks is one of the challenging tasks in the objectives of communication engineering, since wireless channels are prone to errors due to path losses, random noise, and fading phenomena. The transmission errors will be worse in a multihop scenario due to its accumulative effects. Network Coding (NC) is an elegant technique to improve the throughput performance of a communication network. There is the fact that the bit error rates over one modulation symbol of 16- and higher order- Quadrature Amplitude Modulation (QAM) scheme follow a certain pattern. The Scattered Random Network Coding (SRNC) system was proposed in the literature to exploit the error pattern of 16-QAM by using bit-scattering to improve the throughput of multihop network to which is being applied the Random Linear Network Coding (RLNC). This thesis aims to improve further the SRNC system by using Forward Error Correction (FEC) code; the proposed system is called Joint RLNC and FEC with interleaving. The first proposed system (System-I) uses Convolutional Code (CC) FEC. The performances analysis of System-I with various CC rates of 1/2, 1/3, 1/4, 1/6, and 1/8 was carried out using the developed simulation tools in MATLAB and compared to two benchmark systems: SRNC system (System-II) and RLNC system (System- III). The second proposed system (System-IV) uses Reed-Solomon (RS) FEC code. Performance evaluation of System IV was carried out and compared to three systems; System-I with 1/2 CC rate, System-II, and System-III. All simulations were carried out over three possible channel environments: 1) AWGN channel, 2) a Rayleigh fading channel, and 3) a Rician fading channel, where both fading channels are in series with the AWGN channel. The simulation results show that the proposed system improves the SRNC system. How much improvement gain can be achieved depends on the FEC type used and the channel environment.
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Demmer, David. "OFDM Precoding for Filter-Bank based Waveforms." Thesis, Paris, CNAM, 2019. http://www.theses.fr/2019CNAM1237/document.
Full textAbstract:
De nouveaux usages des systèmes de communications sans fils, tels que les réseaux de capteurs ou les voitures autonomes, ont émergé au cours des dernières années. Ces usages sont fondamentalement différents des applications haut-débit actuelles des réseaux cellulaires. La future technologie mobile, la 5G New Radio, introduit donc le concept de numérologie du signal afin de pouvoir satisfaire aux besoin hétérogènes des multiples applications supportées. En effet en supportant différentes numérologies de signaux, l'allocation temps/fréquence des signaux devient plus flexible et le signal transmis peut être adapté en conséquence. Cependant, supporte simultanément différentes numérologies génère de l'interférence et donc distord les signaux. Les filtrages spatiaux, comme la formation de faisceaux, est envisagée en 5G pour limiter l'interférence générée mais pour les communications au-dessus de 6 GHz. Il n'y a cependant pas de solutions proposées pour mes communications en-dessous de 6 GHz. Dans ce travail, des techniques d'atténuation des lobes secondaires sont étudiées pour faciliter le multiplexage des services pour les communications sous 6 GHz. L’interférence entre-utilisateurs est alors contrôlée mais la bande est également mieux utilisée. Une solution innovante, combinant bancs de filtres et orthogonalité complexe, est proposée. L'orthogonalité complexe est garanti grâce à un précodage OFDM qui remplace le précodage OQAM communément utilisé. De plus, le système développé, le Block-Filtered OFDM, utilise un récepteur 5G classique ce qui garantit la retro-compatibilité avec les techniques déjà déployée. Le modèle du BF-OFDM est entièrement décrit et adapté aux normes des réseaux mobiles. De plus, de multiples méthodes de conception des filtres prototypes sont proposées afin de mieux répondre aux besoins des systèmes. La forme d'onde étudiée est également comparée avec les autres solutions de l'état de l'art sur des scénarios d'étude classiques mais également adaptés aux nouveaux enjeux des technologies sans filsNew use cases for wireless communications recently emerged ranging from massive sensor networks to connected cars. These applications highly differ from typical signals supported by already deployed mobile technologies, which are mainly high data rate pipes. The forthcoming generation of mobile technology, 5G New Radio, introduces the concept of signal numerology so as to properly serve the requirements of the diverse applications it will support. Indeed by considering different numerologies, the time/frequency signal allocation is made more flexible which allows to shape the transmitted signal according to its needs. However, multiplexing signals with different numerologies generates interference and therefore signal distortion. Spatial filtering, such as beamforming, is envisioned for 5G above 6-GHz communications to limit inter-user interference. However, this issue still holds for sub-6 GHz systems where spatial filtering is not considered in 5G.In this work, we consider side lobe rejection techniques to ease service multiplexing in sub-6 GHz bands. Not only it provides inter-user interference mitigation but it also improves the bandwidth use efficiency in bands where frequency is a scarce resource. A novel solution, mixing filter-bank for confined spectrum and complex orthogonality for a straightforward re-use of known-how 4G/5G techniques, is proposed. The complex orthogonality is restored thanks to an OFDM precoding substituting the commonly used Offset-QAM signaling which limits the orthogonality to the real field. Moreover, the proposed solution, named Block-Filtered Orthogonal Frequency Division Multiplexing (BFOFDM), relies on a simple 5G receiver scheme which makes it backward compatible with already deployed technologies.The BF-OFDM system model is fully described and adapted to cellular standards. Besides, different prototype filter designs methods are proposed to either improve the intrinsic interference attenuation or to better confined the spectrum of the transmitted signal. Last but not least, the proposed waveform will be compared with state-of-the-art solutions for both typical and 5G oriented evaluation scenarios such as multi-service coexistence