Network administration has become more difficult as the number of Internet users has grown and customer usage patterns have changed over time. Rapidly increasing subscriber bases, data intensive applications (such as streaming audio and video), heavy Web browsing, and large file downloads require significant resources and may tax existing network bandwidth. Reliability and quality of service are becoming serious issues for service providers across the country. Due to the dynamic nature of the information technology (IT) sector in general, it is difficult to predict future network usage patterns or what types of applications may be available, and how these applications may be used over time. This research presents a methodology to facilitate capacity planning and to improve the evaluation of network performance for connection-based networks using the Virginia Tech modem pool as a test bed. The abstract research question is can innovative business strategies be employed in lieu of, or in addition to, traditional management practices such as adding capacity in order to improve the performance of a dialup network? Examples of such strategies or business rules may include limiting the duration of an online session or limiting the number of times a given customer can dial into the pool in a specified time period. A complete network traffic characterization is conducted based on service time and interarrival time variables. A longitudinal analysis is performed to examine how traffic patterns have changed over time. Finally, a simulation model is utilized to examine how imposing different business rules during peak-periods of operation can reduce the blocking probability and improve the overall level-of-service. The potential contribution of this research appears to be significant based on the lack of existing literature. / Ph. D.

The purpose of this work is to assess and propose possible methods for increasing the transmission speed of the cable television distribution, concretely the UPC network in Brno. The first part of work collectively processes general knowledge and gives the reader into the issue. After that follows an analysis of TV cable networks UPC in Brno, especially view of data transmission. After familiarization with the physical aspect of the network is described data communications itself, including standard DOCSIS, respectively EuroDOCSIS. Particular attention is paid to factors that have effect on data transmission and speed. Benefit is the calculation of dividing ratio in different parts of the network and compared with the real load. As far as possible in the given work results of measurements with regard to the quality of the network. The last part is about how to increase speeds. Perspective solution is mainly a technology which is based on standard EuroDOCSIS 3.0, which introduces the concatenation of individual channels. Result of made tests of first cable modem EuroDOCSIS 3.0 confirms the very high speeds and currently preparedness for other major step in so long development of TV cable network.

This master's thesis deals with a narrowband power line communication technology (PLC) and focuses on the potential use in the sensor networks. This thesis addresses both the structure and basic properties of PLC standard and possible use of this application in practice. The main part of this work is implementation of the PLC networks with IC ST7570 of STMicroelectronics. As an example of practical use of PLC technology, this network is connected to the computer where the data from the sensor (meter) connected to a PLC modem, stored in a database using a PHP script as presented by the Internet. Problem solving in this thesis focuses primarily on the simplicity and universality of the resulting applications.

The advancements in wireless communications are the key-enablers of new applications with stringent requirements in low-latency, ultra-reliability, high data rate, high mobility, and massive connectivity. Diverse types of devices, ranging from tiny sensors to vehicles, with different capabilities need to be connected under various channel conditions. Thus, modern connectivity and network techniques at all layers are essential to overcome these challenges. In particular, the physical layer (PHY) transmission is required to achieve certain link reliability, data rate, and latency. In modern digital communications systems, the transmission is performed by means of a digital signal processing module that derives analog hardware. The performance of the analog part is influenced by the quality of the hardware and the baseband signal denoted as waveform. In most of the modern systems such as fifth generation (5G) and WiFi, orthogonal frequency division multiplexing (OFDM) is adopted as a favorite waveform due to its low-complexity advantages in terms of signal processing. However, OFDM requires strict requirements on hardware quality. Many devices are equipped with simplified analog hardware to reduce the cost. In this case, OFDM does not work properly as a result of its high peak-to-average power ratio (PAPR) and sensitivity to synchronization errors. To tackle these problems, many waveforms design have been recently proposed in the literature. Some of these designs are modified versions of OFDM or based on conventional single subcarrier. Moreover, multicarrier frameworks, such as generalized frequency division multiplexing (GFDM), have been proposed to realize varieties of conventional waveforms. Furthermore, recent studies show the potential of using non-conventional waveforms for increasing the link reliability with affordable complexity. Based on that, flexible waveforms and transmission techniques are necessary to adapt the system for different hardware and channel constraints in order to fulfill the applications requirements while optimizing the resources. The objective of this thesis is to provide a holistic view of waveforms and the related multiple access (MA) techniques to enable efficient study and evaluation of different approaches. First, the wireless communications system is reviewed with specific focus on the impact of hardware impairments and the wireless channel on the waveform design. Then, generalized model of waveforms and MA are presented highlighting various special cases. Finally, this work introduces low-complexity architectures for hardware implementation of flexible waveforms. Integrating such designs with software-defined radio (SDR) contributes to the development of practical real-time flexible PHY.:1 Introduction 1.1 Baseband transmission model 1.2 History of multicarrier systems 1.3 The state-of-the-art waveforms 1.4 Prior works related to GFDM 1.5 Objective and contributions 2 Fundamentals of Wireless Communications 2.1 Wireless communications system 2.2 RF transceiver 2.2.1 Digital-analogue conversion 2.2.2 QAM modulation 2.2.3 Effective channel 2.2.4 Hardware impairments 2.3 Waveform aspects 2.3.1 Single-carrier waveform 2.3.2 Multicarrier waveform 2.3.3 MIMO-Waveforms 2.3.4 Waveform performance metrics 2.4 Wireless Channel 2.4.1 Line-of-sight propagation 2.4.2 Multi path and fading process 2.4.3 General baseband statistical channel model 2.4.4 MIMO channel 2.5 Summary 3 Generic Block-based Waveforms 3.1 Block-based waveform formulation 3.1.1 Variable-rate multicarrier 3.1.2 General block-based multicarrier model 3.2 Waveform processing techniques 3.2.1 Linear and circular filtering 3.2.2 Windowing 3.3 Structured representation 3.3.1 Modulator 3.3.2 Demodulator 3.3.3 MIMO Waveform processing 3.4 Detection 3.4.1 Maximum-likelihood detection 3.4.2 Linear detection 3.4.3 Iterative Detection 3.4.4 Numerical example and insights 3.5 Summary 4 Generic Multiple Access Schemes 57 4.1 Basic multiple access and multiplexing schemes 4.1.1 Infrastructure network system model 4.1.2 Duplex schemes 4.1.3 Common multiplexing and multiple access schemes 4.2 General multicarrier-based multiple access 4.2.1 Design with fixed set of pulses 4.2.2 Computational model 4.2.3 Asynchronous multiple access 4.3 Summary 5 Time-Frequency Analyses of Multicarrier 5.1 General time-frequency representation 5.1.1 Block representation 5.1.2 Relation to Zak transform 5.2 Time-frequency spreading 5.3 Time-frequency block in LTV channel 5.3.1 Subcarrier and subsymbol numerology 5.3.2 Processing based on the time-domain signal 5.3.3 Processing based on the frequency-domain signal 5.3.4 Unified signal model 5.4 summary 6 Generalized waveforms based on time-frequency shifts 6.1 General time-frequency shift 6.1.1 Time-frequency shift design 6.1.2 Relation between the shifted pulses 6.2 Time-frequency shift in Gabor frame 6.2.1 Conventional GFDM 6.3 GFDM modulation 6.3.1 Filter bank representation 6.3.2 Block representation 6.3.3 GFDM matrix structure 6.3.4 GFDM demodulator 6.3.5 Alternative interpretation of GFDM 6.3.6 Orthogonal modulation and GFDM spreading 6.4 Summary 7 Modulation Framework: Architectures and Applications 7.1 Modem architectures 7.1.1 General modulation matrix structure 7.1.2 Run-time flexibility 7.1.3 Generic GFDM-based architecture 7.1.4 Flexible parallel multiplications architecture 7.1.5 MIMO waveform architecture 7.2 Extended GFDM framework 7.2.1 Architectures complexity and flexibility analysis 7.2.2 Number of multiplications 7.2.3 Hardware analysis 7.3 Applications of the extended GFDM framework 7.3.1 Generalized FDMA 7.3.2 Enchantment of OFDM system 7.4 Summary 7 Conclusions and Future works

High Frequency (3-30 MHz) (HF) Ionospheric Channel is used for military, civilian and amateur communications. By using Ionosphere, communication for distances beyond the line of sight is achieved. The main advantage of this type of communication is that it does not to require a satellite to communicate with a point beyond the line of sight. Actually the Ionosphere is used instead of a satellite. To use Ionosphere but not a satellite means independent communication for a country. The disadvantage of HF Ionospheric Communication is that the characteristics of the reflecting media (i.e. channel&rsquo / s transfer function) depends on many variables, e.g. sun spot number, hour of the day, season, solar cycles etc., so that mathematically modeling the channel is very difficult. Since military standards like STANAG 4538, STANAG 4285, STANAG 4415, MIL-STD-188-110A and MIL-STD-188-141A define the required performance of an HF modem in terms of Signal to Noise Ratio (SNR), Doppler Spread and Delay Spread according to desired conditions, a new approach to characterize the channel in terms of these three parameters is presented. In this thesis, HF Channel is considered as a system which involves various physical and chemical processes. A new method to characterize the HF channel to be used for modem performance evaluation is presented. In this study, it is aimed to relate modem/channel availability with the magnetic indices, which may be considered as the disturbances to the system. For this purpose the data taken from an HF communication experiment is used to model the channel to be used for modem availability calculations. The aim of the study is to asses the HF Channel Availability under Ionospheric Disturbances. This new technique will be a useful tool for HF Modem operators to select the optimum data rate or modulation method during HF Communication.

This master’s thesis deals with design and implementation of electric energy meter with support of automatic remote data collection. For the collecting of measured data is used narrowband PLC technology. The theoretical part describes the basic properties and standards of narrowband PLC technology, such as types of coupling circuits, modulations, frequency bands and interference problems. In the practical part, there is description of selected parts, such as control circuit power meter, modem, microcontroller and UART to USB converter. There are further described basic properties of narrowband PLC modem ST7570 by STMicroelectronics. The final chapter, implementation of the device, deals with designs of circuit PLC modem ST7570, power meter ADE7753 and converter USB to UART CP2102.

This thesis describes the design of a modem for a communication over residential power lines. First part is focused on the history, suitable frequency bands, modulation techniques and mainly on the selection of the optimal modem device. Second section contains the description of the hardware design of the modem itself and clarifies the implementation of the PLC module to be used as a communication interface for a full residential automation solution. Last chapters of this thesis introduce the communication protocol, design of the software for the ATmega32 MCU and present of the final field testing under real conditions.

Published Article / A company in South Africa is a three-phase induction motor protection relay manufacturer. The function of the protection relay is to capture running data, to provide protection against possible damage, to control an electric motor and to communicate this data to the System Control and Data Acquisition (SCADA) system in a control room. In the case of remote sites e.g. a pump station, the protection relays are used as standalone units. The protection relays are equipped with communication facilities to be used in an instrumentation environment. If a trip occurs or settings need to be changed a technician has to visit the remote site and address the problem. The ideal cost and time effective solution is to perform these tasks remotely via a reliable wireless network. A study was conducted to ascertain the viability of using the standard GSM cellular networks in South Africa to effectively control electric motors and to communicate with the Motor Protection Relays (MPRs) controlling the electric motors in order to determine the status of a motor, settings of the motor, trips that occurred and time of occurrence. It was shown that a node controller could be used to store all the data from various electric motors at a single location. It was also shown that the data from the different electric motors could be analysed at the node controller and that communication can then be initiated from the controller to a responsible person via the GSM network. It was further illustrated that, by making use of the GSM networks in South Africa together with the short message service (SMS), communication and control can be effectively established. SMSs proved to be a reliable means of communication between cellular phones, an embedded network and MPRs. It was shown that software protocols, although slower in communication speed, proved to be reliable and effective for the purpose of transferring information between the node controller and the motor protection relays connected to the electric motors.

Tese (Doutorado) - Naval Postgraduate Scholl, Monterey, CA, 2017. / Devido a falta de auxílios na navegação subaquática, um sistema capaz de ajudar um veículo submersível a manter a precisão da posição, permitindo que ele permaneça subaquático por períodos mais longos, é extremamente desejável. A precisão e confiabilidade / Made available in DSpace on 2018-02-14T17:42:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2017. Added 1 bitstream(s) on 2019-02-13T19:12:12Z : No. of bitstreams: 1 000015dd.pdf: 3906657 bytes, checksum: f7516e210feff674af44c4ed61eae57f (MD5)

Submitted by Samira Prince (prince@ufpa.br) on 2012-05-11T15:03:02Z No. of bitstreams: 1 Dissertacao_MetodoOtimizacaoNao-Linear.pdf: 913840 bytes, checksum: 617864f107ca5df3896d1e16920169c1 (MD5) / Approved for entry into archive by Samira Prince(prince@ufpa.br) on 2012-05-14T13:57:25Z (GMT) No. of bitstreams: 1 Dissertacao_MetodoOtimizacaoNao-Linear.pdf: 913840 bytes, checksum: 617864f107ca5df3896d1e16920169c1 (MD5) / Made available in DSpace on 2012-05-14T13:57:25Z (GMT). No. of bitstreams: 1 Dissertacao_MetodoOtimizacaoNao-Linear.pdf: 913840 bytes, checksum: 617864f107ca5df3896d1e16920169c1 (MD5) Previous issue date: 2011 / FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas / Este trabalho tem como objetivo apresentar um método para solucionar o problema de mapeamento entre as soluções teóricas de gerenciamento dinâmico de espectro (DSM) e os parâmetros de controle das densidades espectrais de potência (PSDs) de transmissão dos modems comerciais. O método utiliza algoritmos genéticos (AG) codificado em inteiros para solucionar o problema. O AG é responsável por achar os melhores parâmetros para representar uma PSD arbitrária, considerando as restrições impostas pelos equipamentos e padrões atuais DSL. O trabalho apresenta ainda um estudo comparativo do método proposto com um concorrente, além de estudo estatístico do método proposto, considerando média, desvio padrão e intervalo de confiança. Adicionalmente, são apresentados dois setups para uso em laboratório, sendo um para medição de PSDs e o outro para funções de transferência, os quais podem ser reaproveitados em outros trabalhos. / This work aims to present a method to solve the mapping problem between the theoretical dynamic spectrum management (DSM) solutions and the commercial DSL modems transmitting power spectrum densities (PSDs) parameters. The method uses an integer codi ed genetic algorithm (GA) to solve the problem. The GA is responsible for nding the ttest parameters that represents an arbitrary PSD, under the restrictions imposed by the actual DSL equipments and standards. This work shows a comparative study of the proposed method with another concurrent. A statistics study of the proposed method considering the average, standard deviation and con dence interval is done. Finally, two di erent laboratory setups are presented. One of them to PSD measurement and other to use in transfer function measurements. Both setups can be reused in other works.