Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-05-30T12:08:23Z No. of bitstreams: 1 gléversonfabnercondelemos.pdf: 2102819 bytes, checksum: e934ec8e8bf0daaaa39a52749b708828 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-30T13:52:51Z (GMT) No. of bitstreams: 1 gléversonfabnercondelemos.pdf: 2102819 bytes, checksum: e934ec8e8bf0daaaa39a52749b708828 (MD5) / Made available in DSpace on 2017-05-30T13:52:51Z (GMT). No. of bitstreams: 1 gléversonfabnercondelemos.pdf: 2102819 bytes, checksum: e934ec8e8bf0daaaa39a52749b708828 (MD5) Previous issue date: 2011-09-12 / A presente dissertação versa sobre técnicas de baixo custo para detecção, modulação e demodulação de constelações M-QAM (quadrature amplitude modulation) de ordem elevada, ou seja, M = 2n, n = {2,3, · · · ,16}. Al´em disso, s˜ao propostas constelações alternativas para M-QAM, M = 22n, n = {1,2, · · · ,8}, que buscam minimizar a PAPR (peak to average power ratio) quando um sistema OFDM (orthogonal frequency division multiplexing) ´e utilizado para a transmissão de dados. Uma implementação, de baixo custo e em dispositivo FPGA (field programmable gate array), de um esquema de modulação constante e adaptativa para sistemas OFDM, quando a modulação é MQAM, M = 22n, n = {1,2, · · · ,8}, é descrita e analisada. O desempenho das técnicas de detecção propostas é avaliado através de simulações computacionais quando o ruído é AWGN (additive white Gaussian noise) e AIGN (additive impulsive Gaussian noise). Os resultados em termos de BER × Eb/N0 indicam que as perdas de desempenho geradas com as técnicas propostas não são significativas e, portanto, tais técnicas são candidatas adequadas para a implementação de um sistema OFDM com elevada eficiência espectral. Os resultados computacionais revelam ainda que as propostas alternativas para constelações M-QAM reduzem a PAPR, mas, em contrapartida, degradam consideravelmente a BER. Finalmente, a análise da complexidade computacional das técnicas de detecção e demodulação, as quais foram implementadas em dispositivo FPGA, indica que há uma redução do custo computacional, ou seja, redução do uso de recursos de hardware do dispositivo FPGA quando tais técnicas são implementadas para a demodulação e detecção de símbolos M-QAM de ordem elevada. / This dissertation deals with low-cost techniques for detection, modulation and demodulation of high order M-QAM (quadrature amplitude modulation) constellations, i.e., M = 2n, n = {2,3, · · · ,16}. In addition, alternative constellations are proposed to M-QAM, M = 22n, n = {1,2, · · · ,8}, which seek to minimize the PAPR (peak to average power ratio) when an OFDM (orthogonal frequency division multiplexing) system is used for data transmission. A low-cost implementation using a FPGA (field programmable gate array) device of a modulation scheme for constant and adaptive OFDM systems when the modulation is M-QAM, M = 22n, n = {1,2, · · · ,8}, is described and analyzed. The performance of the proposed detection techniques is evaluated through computer simulations when the noise is AWGN (additive white Gaussian noise) and AIGN (additive impulsive Gaussian noise). The results in terms of BER × Eb/N0 indicate that the performance losses generated by the proposed techniques are not significant and, therefore, such techniques are appropriate candidates for the implementation of an OFDM system with high spectral efficiency. The computational results reveal that the alternative proposals for M-QAM constellations reduce the PAPR, but, considerably degrade the BER. Finally, the analysis of computational complexity of detection and demodulation techniques, which were implemented in a FPGA device, indicates that there is a computational cost reduction, i.e., a reduction of resource usage of hardware device such as FPGA when these techniques are implemented for the demodulation and detection of high-order M-QAM symbols.

Emerging broadband wireless packet data networks are increasingly employing spectrally efficient modulation methods like Quadrature Amplitude Modulation (QAM) to increase the channel efficiency and maximize data throughput. Unfortunately, the performance of high level QAM modulations in the wireless channel is sensitive to channel imperfections and throughput is degraded significantly at low signal-to-noise ratios due to bit errors and packet retransmission. To obtain a more robust physical layer, broadband systems are employing multilevel QAM (M-QAM) to mitigate this reduction in throughput by adapting the QAM modulation level to maintain acceptable packet error rate (PER) performance in changing channel conditions. This thesis presents an adaptive M-QAM modem hardware architecture, suitable for use as a modem core for programmable software defined radios (SDRs) and broadband wireless applications. The modem operates in burst mode, and can reliably synchronize to different QAM constellations burst-by-burst. Two main improvements exploit commonality in the M-QAM constellations to minimize the redundant hardware required. First, the burst synchronization functions (carrier, clock, amplitude, and modulation level) operate reliably without prior knowledge of the QAM modulation level used in the burst. Second, a unique bit stuffing and shifting technique is employed which supports variable bit rate operation, while reducing the core signal processing functions to common hardware for all constellations. These features make this architecture especially attractive for implementation with Field Programmable Gate Arrays (FPGAs) and Application-Specific Integrated Circuits (ASICs); both of which are becoming popular for highly integrated, cost-effective wireless transceivers.

Emerging broadband wireless packet data networks are increasingly employing spectrally efficient modulation methods like Quadrature Amplitude Modulation (QAM) to increase the channel efficiency and maximize data throughput. Unfortunately, the performance of high level QAM modulations in the wireless channel is sensitive to channel imperfections and throughput is degraded significantly at low signal-to-noise ratios due to bit errors and packet retransmission. To obtain a more robust physical layer, broadband systems are employing multilevel QAM (M-QAM) to mitigate this reduction in throughput by adapting the QAM modulation level to maintain acceptable packet error rate (PER) performance in changing channel conditions. This thesis presents an adaptive M-QAM modem hardware architecture, suitable for use as a modem core for programmable software defined radios (SDRs) and broadband wireless applications. The modem operates in burst mode, and can reliably synchronize to different QAM constellations burst-by-burst. Two main improvements exploit commonality in the M-QAM constellations to minimize the redundant hardware required. First, the burst synchronization functions (carrier, clock, amplitude, and modulation level) operate reliably without prior knowledge of the QAM modulation level used in the burst. Second, a unique bit stuffing and shifting technique is employed which supports variable bit rate operation, while reducing the core signal processing functions to common hardware for all constellations. These features make this architecture especially attractive for implementation with Field Programmable Gate Arrays (FPGAs) and Application-Specific Integrated Circuits (ASICs); both of which are becoming popular for highly integrated, cost-effective wireless transceivers.

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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / Remote, high speed, high explosive wave front monitoring requires very high bandwidth telemetry to allow transmission of diagnostic data before the explosion destroys the sensor system itself. The main motivation for this study is that no known existing implementation of this sort has been applied to realistic weapons environments. These facts have prompted the research and gathering of data that can be used to extrapolate towards finding the best modulation method for this application. In addition to research of similar existing analysis and testing operations, data was recently captured from a Joint Test Assembly (JTA) Air Launched Cruise Missile (ALCM) flight.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / The main objectives of iNET (Integrated Network Enhanced Telemetry) are increased data rate and improved spectral efficiency [1]. In this paper we propose that transmission scheme for the physical layer is coded 16-QAM OFDM (Quadrature Amplitude Modulation-Orthogonal Frequency Division Multiplexing) which enables high data rate and spectrum efficiency. However in high mobility scenarios, where the channel is time-varying the receiver design is more challenging. Therefore in this paper pilot-assisted channel estimation is used at the receiver, with convolutional coding and error correction to enhance the performance; while the effect of inter symbol interference (ISI) is mitigated by cyclic prefix. The focus of this paper is to evaluate the performance of OFDM with 16-QAM over an aeronautical channel. The 16-QAM with OFDM enables 4 bits/symbol and provides a higher data rate than QPSK hence it is chosen in this paper. The implementation of OFDM is done using Inverse Fast Fourier Transform (IFFT) and the Fast Fourier Transform (FFT). In this paper we simulate how the performance of Coded 16-QAM OFDM is enhanced using equalization to compensate for inter symbol interference, convolutional coding is used for error correction, puncturing for improving data rate and the insertion of cyclic prefix (CP) to avoid inter carrier interference.

Digital resampling is a process that converts a digital signal from one sampling rate to another. This process is performed by means of interpolating between the input samples to produce output samples at an output sampling rate. The digital interpolation process is accomplished with an interpolation filter.<p> The problem of resampling digital signals at an output sampling rate that is incommensurate with the input sampling rate is the first topic of this thesis. This problem is often encountered in practice, for example in multiplexing video signals from different sources for the purpose of distribution. There are basically two approaches to resample the signals. Both approaches are thoroughly described and practical circuits for hardware implementation are provided. A comparison of the two circuits shows that one circuit requires a division to compute the new sampling times. This time scaling operation adds complexity to the implementation with no performance advantage over the other circuit, and makes the 'division free' circuit the preferred one for resampling.<p> The second topic of this thesis is performance analysis of interpolation filters for Quadrature Amplitude Modulation (QAM) signals in the context of timing recovery. The performance criterion of interest is Modulation Error Ratio (MER), which is considered to be a very useful indicator of the quality of modulated signals in QAM systems. The methodology of digital resampling in hardware is employed to describe timing recovery circuits and propose an approach to evaluate the performance of interpolation filters. A MER performance analysis circuit is then devised. The circuit is simulated with MATLAB/Simulink as well as implemented in Field Programmable Gate Array (FPGA). Excellent agreement between results obtained from simulation and hardware implementation proves the validity of the methodology and practical application of the research works.

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.

Digital resampling is a process that converts a digital signal from one sampling rate to another. This process is performed by means of interpolating between the input samples to produce output samples at an output sampling rate. The digital interpolation process is accomplished with an interpolation filter.<p> The problem of resampling digital signals at an output sampling rate that is incommensurate with the input sampling rate is the first topic of this thesis. This problem is often encountered in practice, for example in multiplexing video signals from different sources for the purpose of distribution. There are basically two approaches to resample the signals. Both approaches are thoroughly described and practical circuits for hardware implementation are provided. A comparison of the two circuits shows that one circuit requires a division to compute the new sampling times. This time scaling operation adds complexity to the implementation with no performance advantage over the other circuit, and makes the 'division free' circuit the preferred one for resampling.<p> The second topic of this thesis is performance analysis of interpolation filters for Quadrature Amplitude Modulation (QAM) signals in the context of timing recovery. The performance criterion of interest is Modulation Error Ratio (MER), which is considered to be a very useful indicator of the quality of modulated signals in QAM systems. The methodology of digital resampling in hardware is employed to describe timing recovery circuits and propose an approach to evaluate the performance of interpolation filters. A MER performance analysis circuit is then devised. The circuit is simulated with MATLAB/Simulink as well as implemented in Field Programmable Gate Array (FPGA). Excellent agreement between results obtained from simulation and hardware implementation proves the validity of the methodology and practical application of the research works.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / This paper shows the design and testing of a test bed at Morgan State University as part of the development of a Link Dependent Adaptive Radio (LDAR). It shows the integration of variable rate QAM/OFDM modulation and a variable rate Punctured Convolutional Coder. It also shows a dynamic aeronautical channel simulator developed to capture the dynamics of these channels. Performance results are show for combinations of modulation, coding and channel variations that provide motivation for the potential of the LDAR system.