Orthogonal Transform Multiplexing with Memoryless Nonlinearity: a Possible Alternative to Traditional Coded-Modulation Schemes

In this paper, we propose a novel joint coding-modulation technique based on serial concatenation of orthogonal linear transform, such as discrete Fourier transform (DFT) or Walsh-Hadamard transform (WHT), with memoryless nonlinearity. We demonstrate that such a simple signal construction may exhibit properties of a random code ensemble, as a result approaching channel capacity. Our computer simulations confirm that if the decoder relies on a modified approximate message passing algorithm, the proposed modulation technique exhibits performance on par with state-of-the-art coded modulation schemes that use capacity-approaching component codes. The proposed modulation scheme could be used directly or as a pre-coder for a conventional orthogonal frequency division multiplexing (OFDM) transmitter, resulting in a system possessing all benefits of OFDM along with reduced peak-to-average power ratio (PAPR)

Modulated Backscatter for Low-Power High-Bandwidth Communication

<p>This thesis re-examines the physical layer of a communication link in order to increase the energy efficiency of a remote device or sensor. Backscatter modulation allows a remote device to wirelessly telemeter information without operating a traditional transceiver. Instead, a backscatter device leverages a carrier transmitted by an access point or base station.</p><p>A low-power multi-state vector backscatter modulation technique is presented where quadrature amplitude modulation (QAM) signalling is generated without running a traditional transceiver. Backscatter QAM allows for significant power savings compared to traditional wireless communication schemes. For example, a device presented in this thesis that implements 16-QAM backscatter modulation is capable of streaming data at 96 Mbps with a radio communication efficiency of 15.5 pJ/bit. This is over 100x lower energy per bit than WiFi (IEEE 802.11).</p><p>This work could lead to a new class of high-bandwidth sensors or implantables with power consumption far lower than traditional radios.</p>Dissertatio

Receiver design for nonlinearly distorted OFDM : signals applications in radio-over-fiber systems

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 201

WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.

Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA

Photonic Modulation and Demodulation techniques for Multi-Gb/s Millimetre wave Wireless Links

Los sistemas de radio sobre fibra(Radio Over fibre ROF) ofrecen el ancho de banda y flexibilidad necesario para la generación y distribución de del señales inalámbricas del futuro en una arquitectura de red óptica, que reduce el coste de las redes centralizando el procesado y simplificando la ubicación de la antena (estación de base EB). El uso de sistemas de comunicaciones ópticas como una media de transporte de señales inalámbricas en enlaces RoF reduce el cuello de botella entre los estándares de acceso inalámbrico y cableado en un dominio convergente óptico. Las redes de acceso ópticas están evolucionando con capacidades de hasta 10 Gb/s con el estándard 10GEPON, dejando un cuello de botella entre tecnologías de acceso inalámbrico y óptico. . Eso ha motivado gran esfuerzo de investigación en la generación y distribución de señales inalámbricas de alta capacidad (> 10 Gb/s) basada en RoF. En esta tesis se ha investigado el uso de técnicas fotónicas para la generación , distribución y demodulación de señales inalámbricas moduladas vectorialmente. Esta tesis está principalmente dedicada a la generación de señales inalámbricas espectralmente eficientes como la modulación de fase en cuadratura (QPSK) o modulación de amplitud cuadratura de multinivel (M-QAM). El trabajo presentado en esta tesis está clasificado en dos partes: la primera de ellas trata de las técnicas fotónicas que utilizan señales eléctricas coherente para la generación y demodulación de señales inalámbricas, mientras la segunda parte trata de usar señales ópticas incoherentes. En la primera parte de la tesis, están presentadas diferentes arquitecturas de sistemas y están analizadas numéricamente, y demostradas experimentalmente. Un nuevo concepto denominado "modulación vectorial fotónica" (PVM) es propuesto para la generación de señales inalámbricas con una modulación M-QAM. Basado en esta técnica se presenta la generación de señales de capacidad 10Gb/s con una modulación de QPSK y 16-QAM.Sambaraju -, R. (2010). Photonic Modulation and Demodulation techniques for Multi-Gb/s Millimetre wave Wireless Links [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8857Palanci

Non-orthogonal Frequency Division Multiplexing with Index Modulation

Orthogonal Frequency Division Multiplexing (OFDM) is a well-established technique in wired and wireless communications due to its high spectral efficiency compared to other multicarrier transmission schemes. However, the explosion of Internet of Things (IoT) has demanded a more spectrally-efficient technique to utilize small bandwidths, on which numerous low-power low-rate devices operate. This thesis aims to provide solutions for this problem. First, the integration of index modulation to fast-OFDM, which is a special variant of OFDM, is investigated. The highest obtainable bit rate of this system is derived, which demonstrates enhancements compared to OFDM systems in the low-power low-rate regions. Furthermore, an improved one-dimension constellation is found to optimize the overall bit error rate (BER) of this system. Numerical results show that the proposed system exhibits enhancements in both bit rate and error performance, leading to higher spectral efficiency compared to OFDM in the low-power regions. The second part of the thesis is concerned with reducing the bandwidth consumed by multicarrier transmissions. This results in the mutual orthogonality among subchannels being relaxed, yielding a Non-orthogonal Frequency Division Multiplexing (NFDM) system. The main contribution in this part includes a novel and feasible design for NFDM systems, which is capable of eliminating inter-channel interference (ICI), which is the major limitation of the conventional NFDM system. Because ICI is completely eliminated, the BER performance of the proposed system is the same as that of an OFDM system over additive white Gaussian noise channels. The power spectrum density (PSD) of the proposed system is also investigated, leading to design guidelines and tradeoffs between the PSD shape and the system's bit rate. Finally, index modulation is incorporated in the proposed NFDM systems. Thanks to our ICI-free design of NFDM, this combined system (NFDM-IM) and fast-OFDM-IM share a similar simple two-stage signal detection mechanism. Improved QAM constellations are found for NFDM-IM systems to optimize their overall BER. Obtained results show that with low modulation orders such as 8-QAM (Quadrature Amplitude Modulation), NFDM-IM systems employing the improved constellation achieve BER performance close to that of NFDM in the low BER regions. With equivalent occupied bandwidth and error performance, an NFDM-IM system with optimal 8-QAM constellation produces better spectral efficiency than the one using the conventional hexagonal constellation

Doctor of Philosophy

dissertationThis dissertation deals with blind modulation identification of quadrature amplitude modulations (QAM) and phase-shift keying (PSK) signals in dual-polarized channels in digital communication systems. The problems addressed in this dissertation are as follows: First, blind modulation identification of QAM and PSK signals in single noisy channels and multipath channels are explored. Second, methods for blind separation of two information streams in a dual-polarized channel and identification of the modulation types of the two information streams are developed. A likelihood-based blind modulation identification for QAM and PSK signals in a single channel with additive white Gaussian noise (AWGN) is developed first. This algorithm selects the modulation type that maximizes a log-likelihood function based on the known probability distribution associated with the phase or amplitude of the received signals for the candidate modulation types. The approach of this paper does not need prior knowledge of carrier frequency or baud rate. Comparisons of theory and simulation demonstrate good agreement in the probability of successful modulation identification under different signal-to-noise ratios (SNRs). Simulation results show that for the signals in AWGN channels containing 10000 symbols and 20 samples per symbol, the system can identify BPSK, QPSK, 8PSK and QAMs of order 16, 32, 64, 128 and 256 with better than 99% accuracy at 4 dB SNR. Under the same condition, the simulation results indicate the two competing methods available in the literature can only reach at most 85% accuracy even at 20 dB SNR for all the modulation types. The simulation results also suggest that when the symbol length decreases, the system needs higher SNRs in order to get accurate identification results. Simulations using different noisy environments indicate that the algorithm is robust to variations of noise environments from the models assumed for derivation of the algorithm. In addition, the combination of a constant modulus amplitude (CMA) equalizer and the likelihood-based modulation identification algorithm is able to identify the QAM signals in multipath channels in a wide range of SNRs. When compared with the results for the signals in AWGN channels, the combination of the CMA equalizer and the likelihood-based modulation identification algorithm needs higher SNRs and longer signal lengths in order to obtain accurate identification results. The second contribution of this dissertation is a new method for blindly identifying PSK and QAM signals in dual-polarized channels. The system combines a likelihood-based adaptive blind source separation (BSS) method and the likelihood-based blind modulation identification method. The BSS algorithm is based on the likelihood functions of the amplitude of the transmitted signals. This system tracks the time-varying polarization coefficients and recovers the input signals to the two channels. The simulation results presented in this paper demonstrate that the likelihood-based adaptive BSS method is able to recover the source signals of different modulation types for a wide range of input SNRs. Comparisons with a natural gradient-based BSS algorithm indicate that the likelihood-based method results in smaller symbol error rates. When a modulation identification algorithm is applied to the separated signals, the overall system is able to identify different PSK and QAM signals with high accuracy at sufficiently high SNRs. For example, with 20,000 symbols, the system identified BPSK and 16-QAM signals with better than 99% accuracy when the input SNR was 8dB and the polarization coefficients rotated with a rate of 1.3 ms. Higher SNRs are needed to obtain similar levels of accuracy when the polarization changes faster or when the number of input symbols is shorter. When compared with the identification results for signals in AWGN channels, the system needs higher SNRs and longer signal length to obtain accurate results for signals in dual-polarized channels

Simulation of wireless communication system using OFDM principle

FDMA, TDMA and CDMA are the well known multiplexing techniques used in wireless communication systems. While working with the wireless systems using these techniques various problems encountered are (1) multi-path fading (2) time dispersion which lead to intersymbol interference (ISI) (3) lower bit rate capacity (4) requirement of larger transmit power for high bit rate and (5) less spectral efficiency. The use of orthogonal frequency division multiplexing (OFDM) technique provides better solution for the above mentioned problems. The benefits of OFDM are high spectral efficiency, resiliency of RF interference, and lower multi-path distortion. OFDM is a powerful modulation technique that is capable of high data rate and is able to eliminate ISI. The use of FFT technique to implement modulation and demodulation functions makes it computationally more efficient

Implementation and investigation of a real-time optical 16-QAM transmission system with FPGA-based coherent receiver

Diese Dissertation stellt die erste Echtzeitübertragung von 16-QAM mit FPGA-basierter DSPU vor. 2.5 Gb/s wurden dabei über 20 und 100 km übertragen und kohärent (heterodyn) in Echtzeit empfangen. Die Bitfehlerquote (BER) lag dabei unterhalb der Schwelle moderner Fehlervorwärtskorrekturverfahren mit 7% Overhead. Mit BPS (Blind Phase Search) und QPSK partitioning (QPSKP) wurden zwei unterschiedliche Techniken zur Phasenrückgewinnung implementiert und durch Echtzeitmessung verglichen. Der Einfluss der Auflösung der erforderlichen Analog-Digital-Umsetzer (ADC) wurde ebenfalls untersucht, welche ebenfalls eine Herausforderung für kohärente Echtzeitübertragung darstellt. Der Einfluss von Phasenrauschen wird hier auch gezeigt, welches vorwiegend von den verwendeten Lasern, optischen Verstärkern und nichtlinearen Effekten in den optischen Fasern abhängt. Darüber hinaus wurden verschiedene Arbeitspunkte des 16-QAM-Modulators in Echtzeit getestet und die optimalen Bedingungen für eine minimale Bitfehlerquote gefunden.In this dissertation the first published real-time implementation of a 16-QAM transmission system with FPGA-based DSP is presented. 2.5 Gb/s coherent 16-QAM data has been optically transmitted over 20 and 100 km and synchronously received by heterodyning in a real-time I&Q receiver, with BER below the threshold of a state-of-the-art FEC (7% overhead). Two techniques of feed-forward carrier phase recovery (Blind Phase Search (BPS) and QPSK partitioning (QPSKP)) were tested in a real-time transmission experiment and compared with each other. The influence of the required resolution of the analog-to-digital converter (ADC) has been investigated, which is a challenge of real-time coherent transmission systems. The influence of phase noise in 16-QAM, which is mainly contributed from laser sources, optical amplifiers, and nonlinear effects in optical fibers is also shown. Moreover, different operation points of a 16-QAM modulator were tested in real-time and an optimal condition is found which minimizes the BER.Tag der Verteidigung: 10.09.2013Paderborn, Univ., Diss., 201