Digital data transmission over mobile radio channels

The aim of this work is to study data transmission over a microwave digital mobile radio channel at 900 MHz, where the channel is subjected to multipath fading. Besides the fading, the other impairments assumed here are additive noise, co-channel interference and adjacent channel interference. Two modulation techniques are investigated in this work, namely Quadrature-Amplitude-Modulation (QAM) and Quadrature-Phase-Shift- Keying (QPSK). The channel is characterised digitally, assuming multipath Rayleigh fading in the presence of noise. The detection process studied here are near-maximum likelihood schemes: non-linear equalisation methods are also considered in detail. The thesis is also concerned with carrier synchronisation and channel estimation under conditions of Rayleigh fading. Since the carrier syncn,honisation is a most important requirement in mobile radio, a Digital Phase Locked Loop (DPLL) technique has been designed and investigated in the form of a feedback digital synchronisation system. Two types of channel estimation technique, namely feedforward and feedback estimators, are also investigated in this work. The feedback estimator is modified by the addition of a digital control system, in order to reduce its delay, and to cope with rapidly fading signals. Successful carrier synchronisation is demonstrated by the use of space diversity. The study was completed using models of the component parts of the system, and by the use of extensive computer simulations to analyse the system under various operating conditions

Study of continuous-phase four-state modulation for cordless telecommunications. Assessment by simulation of CP-QFSK as an alternative modulation scheme for TDMA digital cordless telecommunications systems operating in indoor applications

One of the major driving elements behind the explosive boom in wireless revolution is the advances in the field of modulation which plays a fundamental role in any communication system, and especially in cellular radio systems. Hence, the elaborate choice of an efficient modulation scheme is of paramount importance in the design and employment of any communications system. Work presented in this thesis is an investigation (study) of the feasibility of whether multilevel FSK modulation scheme would provide a viable alternative modem that can be employed in TDMA cordless communications systems. In the thesis the design and performance analysis of a non-coherent multi-level modem that offers a great deal of bandwidth efficiency and hardware simplicity is studied in detail. Simulation results demonstrate that 2RC pre-modulation filter pulse shaping with a modulation index of 0.3, and pre-detection filter normalized equivalent noise bandwidth of 1.5 are optimum system parameter values. Results reported in chapter 5 signify that an adjacent channel rejection factor of around 40 dB has been achieved at channel spacing of 1.5 times the symbol rate while the DECT system standards stipulated a much lower rejection limit criterion (25-30dB), implying that CP-QFSK modulation out-performs the conventional GMSK as it causes significantly less ACI, thus it is more spectrally efficient in a multi-channel system. However, measured system performance in terms of BER indicates that this system does not coexist well with other interferers as at delay spreads between 100ns to 200ns, which are commonly encountered in such indoor environment, a severe degradation in system performance apparently caused by multi-path fading has been noticed, and there exists a noise floor of about 40 dB, i.e. high irreducible error rate of less than 5.10-3. Implementing MRC diversity combiner and BCH codec has brought in a good gain.Higher Education Ministr

Recent Trends in Communication Networks

In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges

Real-time digital signal processing for new wavelength-to-the-user optical access networks

Nowadays, optical access networks provide high capacity to end users with growing availability of multimedia contents that can be streamed to fixed or mobile devices. In this regard, one of the most flexible and low-cost approaches is Passive Optical Network (PON) that is used in Fiber-to-the-Home (FTTH). Due to the growing of the bandwidth demands, Wavelength Division Multiplexing (WDM), and later on ultra-dense WDM (udWDM) PON, with a narrow channel spacing, to increase the number of users through a single fiber, has been deployed. The udWDM-PON with coherent technology is an attractive solution for the next generation optical access networks with advanced digital signal processing (DSP). Thanks to the higher sensitivity and improved channel selectivity in coherent detection with efficient DSP, optical networks support larger number of users in longer distances. Since the cost is the main concern in the optical access networks, this thesis presents DSP architectures in coherent receiver (Rx), based on low-cost direct phase modulated commercial DFB lasers. The proposals are completely in agreement with consept of wavelength-to-the-user, where each client in optical network is dedicated to an individual wavelength. Next, in a 6.25 GHz spaced udWDM grid with the optimized DSP techniques and phase-shift-keying (PSK) modulation format, the high sensitivity is achieved in real-time field-programmable-gate-array (FPGA) implementations. Moreover, this thesis reduces hardware complexity of optical carrier recovery (CR) with two various strategies. First, based on differential mth-power frequency estimator (FE) by using look-up-tables (LUTs) and second, LUT-free CR architecture, with optimizing the power consumption and hardware resources, as well as improving the channel selectivity in terms of speed and robustness. Furthermore, by designing very simple but efficient clock recovery, a symbol-rate DSP architecture, which process data using only one sample per symbol (1-sps), for polarization diversity (POD) structure, becomes possible. It makes the DSP independent from state-of-polarization (SOP), even in the case of low-cost optical front-end and low-speed analog-to-digital converters (ADCs), keeps the performance high as well as sensitivity in real-time implementations on FPGA.Avui en dia, les xarxes d'accés òptic proporcionen una alta capacitat als usuaris finals amb una creixent disponibilitat de continguts multimèdia que es poden transmetre a dispositius fixos o mòbils. En aquest sentit, un dels enfocaments més flexibles i de baix cost és la Xarxa Òptica Passiva (PON) que s'utilitza a Fibra-fins-la-Llar (FTTH). A causa del creixent requeriment de l'ample de banda, s'ha desplegat la multiplexació de divisió d'ona (WDM) i, posteriorment, el PON amb WDM d'alta densitat (udWDM), amb un espaiat estret de canals, per augmentar el nombre d'usuaris a través d'una sola fibra. L'udWDM-PON amb tecnologia coherent és una solució atractiva per a les xarxes d'accés òptic d'última generació amb processament avançat de senyal digital (DSP). Gràcies a la major sensibilitat i a la selectivitat millorada del canal en la detecció coherent amb DSP eficient, les xarxes òptiques suporten un nombre més gran d'usuaris a distàncies més llargues. Atès que el cost és la principal preocupació en les xarxes d'accés òptic, aquesta tesi presenta arquitectures DSP en receptor coherent (Rx), basades en làsers DFB comercials modulats en fase directa de baix cost. Les propostes estan d'acord amb la asignació de la longitud d'ona a l'usuari, on a cada client de la xarxa òptica se li dedica a una longitud d'ona individual. A continuació, en una graella udWDM espaciada de 6,25 GHz amb les tècniques de DSP optimitzades i el format de modulació de fase (PSK), s'aconsegueix l'alta sensibilitat en implementacions field-programable-gate-array (FPGA) en temps real. A més, aquesta tesi redueix la complexitat del maquinari de recuperació òptica de portadors (CR) amb dues estratègies diverses. Primer, basat en un estimador de freqüència de potència diferencial (FE) mitjançant l'ús de taules de cerca (LUTs) i, en segon lloc, l'arquitectura CR sense LUT, amb l'optimització del consum d'energia i els recursos de maquinari, a més de millorar la selectivitat del canal en termes de velocitat i robustesa. A més, al dissenyar una recuperació de rellotge molt simple, però eficaç, es fa possible una arquitectura DSP a la velocitat dels símbols, que processa dades utilitzant només una mostra per símbol (1-sps) per a l'estructura de la diversitat de polarització òptica (POD). Fa que el DSP sigui independent de l'estat de polarització (SOP), fins i tot en el cas dels analog-to-digital converters (ADC) de front-end òptics de baix cost, i manté el rendiment alt i la sensibilitat en les implementacions en temps real de FPGA

Real-time digital signal processing for new wavelength-to-the-user optical access networks

Nowadays, optical access networks provide high capacity to end users with growing availability of multimedia contents that can be streamed to fixed or mobile devices. In this regard, one of the most flexible and low-cost approaches is Passive Optical Network (PON) that is used in Fiber-to-the-Home (FTTH). Due to the growing of the bandwidth demands, Wavelength Division Multiplexing (WDM), and later on ultra-dense WDM (udWDM) PON, with a narrow channel spacing, to increase the number of users through a single fiber, has been deployed. The udWDM-PON with coherent technology is an attractive solution for the next generation optical access networks with advanced digital signal processing (DSP). Thanks to the higher sensitivity and improved channel selectivity in coherent detection with efficient DSP, optical networks support larger number of users in longer distances. Since the cost is the main concern in the optical access networks, this thesis presents DSP architectures in coherent receiver (Rx), based on low-cost direct phase modulated commercial DFB lasers. The proposals are completely in agreement with consept of wavelength-to-the-user, where each client in optical network is dedicated to an individual wavelength. Next, in a 6.25 GHz spaced udWDM grid with the optimized DSP techniques and phase-shift-keying (PSK) modulation format, the high sensitivity is achieved in real-time field-programmable-gate-array (FPGA) implementations. Moreover, this thesis reduces hardware complexity of optical carrier recovery (CR) with two various strategies. First, based on differential mth-power frequency estimator (FE) by using look-up-tables (LUTs) and second, LUT-free CR architecture, with optimizing the power consumption and hardware resources, as well as improving the channel selectivity in terms of speed and robustness. Furthermore, by designing very simple but efficient clock recovery, a symbol-rate DSP architecture, which process data using only one sample per symbol (1-sps), for polarization diversity (POD) structure, becomes possible. It makes the DSP independent from state-of-polarization (SOP), even in the case of low-cost optical front-end and low-speed analog-to-digital converters (ADCs), keeps the performance high as well as sensitivity in real-time implementations on FPGA.Avui en dia, les xarxes d'accés òptic proporcionen una alta capacitat als usuaris finals amb una creixent disponibilitat de continguts multimèdia que es poden transmetre a dispositius fixos o mòbils. En aquest sentit, un dels enfocaments més flexibles i de baix cost és la Xarxa Òptica Passiva (PON) que s'utilitza a Fibra-fins-la-Llar (FTTH). A causa del creixent requeriment de l'ample de banda, s'ha desplegat la multiplexació de divisió d'ona (WDM) i, posteriorment, el PON amb WDM d'alta densitat (udWDM), amb un espaiat estret de canals, per augmentar el nombre d'usuaris a través d'una sola fibra. L'udWDM-PON amb tecnologia coherent és una solució atractiva per a les xarxes d'accés òptic d'última generació amb processament avançat de senyal digital (DSP). Gràcies a la major sensibilitat i a la selectivitat millorada del canal en la detecció coherent amb DSP eficient, les xarxes òptiques suporten un nombre més gran d'usuaris a distàncies més llargues. Atès que el cost és la principal preocupació en les xarxes d'accés òptic, aquesta tesi presenta arquitectures DSP en receptor coherent (Rx), basades en làsers DFB comercials modulats en fase directa de baix cost. Les propostes estan d'acord amb la asignació de la longitud d'ona a l'usuari, on a cada client de la xarxa òptica se li dedica a una longitud d'ona individual. A continuació, en una graella udWDM espaciada de 6,25 GHz amb les tècniques de DSP optimitzades i el format de modulació de fase (PSK), s'aconsegueix l'alta sensibilitat en implementacions field-programable-gate-array (FPGA) en temps real. A més, aquesta tesi redueix la complexitat del maquinari de recuperació òptica de portadors (CR) amb dues estratègies diverses. Primer, basat en un estimador de freqüència de potència diferencial (FE) mitjançant l'ús de taules de cerca (LUTs) i, en segon lloc, l'arquitectura CR sense LUT, amb l'optimització del consum d'energia i els recursos de maquinari, a més de millorar la selectivitat del canal en termes de velocitat i robustesa. A més, al dissenyar una recuperació de rellotge molt simple, però eficaç, es fa possible una arquitectura DSP a la velocitat dels símbols, que processa dades utilitzant només una mostra per símbol (1-sps) per a l'estructura de la diversitat de polarització òptica (POD). Fa que el DSP sigui independent de l'estat de polarització (SOP), fins i tot en el cas dels analog-to-digital converters (ADC) de front-end òptics de baix cost, i manté el rendiment alt i la sensibilitat en les implementacions en temps real de FPGA.Postprint (published version

LOW-POWER IMPULSE-RADIO ULTRA-WIDEBAND TECHNIQUES FOR BIOMEDICAL APPLICATIONS.

Ph.DDOCTOR OF PHILOSOPH

Key Signal Processing Technologies for High-speed Passive Optical Networks

With emerging technologies such as high-definition video, virtual reality, and cloud computing, bandwidth demand in the access networks is ever-increasing. Passive optical network (PON) has become a promising architecture thanks to its low cost and easy management. IEEE and ITU-T standard organizations have been standardizing the next-generation PON, targeting on increasing the single-channel capacity from 10 Gb/s to 25, 50, and 100 Gb/s as the solution to address the dramatic increase of bandwidth demand. However, since the access network is extremely cost-sensitive, many research problems imposed in the physical layer of PON need to be addressed in a cost-efficient way, which is the primary focus of this thesis. Utilizing the low-cost 10G optics to build up high-speed PON systems is a promising approach, where signal processing techniques are key of importance. Two categories of signal processing techniques have been extensively investigated, namely optical signal processing (OSP) and digital signal processing (DSP). Dispersion-supported equalization (DSE) as a novel OSP scheme is proposed to achieve bit-rate enhancement from 10 Gb/s to 25 Gb/s based on 10G class of optics. Thanks to the bandwidth improved by DSE, the non-return-zero on-off keying which is the simplest modulation format is able to be adopted in the PON system without complex modulation or DSP. Meanwhile, OSP is also proposed to work together with DSP enabling 50G PON while simplifying the DSP complexity. Using both DSE and simple feed-forward equalizer is able to support 50 Gb/s PAM-4 transmission with 10G optics. For C-band 50 Gb/s transmission, injection locking techniques as another OSP approach is proposed to compress the directly modulated laser chirp and increase system bandwidth in the optical domain where a doubled capacity from 25 Gb/s to 50 Gb/s over 20 km fiber can be built on top of 10G optics. For DSP, we investigated the advantages of neural network (NN) on the mitigation of the time-varying nonlinear semiconductor optical amplifier pattern effect. In order to reduce the expense caused by the high computation complexity of NN, a pre- equalizer is introduced at the central office that allows cost sharing for all connected access users. In order to push the PON system line rate to 100 Gb/s, a joint nonlinear Tomlinson- Harashima precoding-Volterra algorithm is proposed to compensate for both linear and nonlinear distortions where 100 Gb/s PAM-4 transmission over 20 km fiber with 15 GHz system bandwidth can be achieved

Advanced Modulation and Coding Technology Conference

The objectives, approach, and status of all current LeRC-sponsored industry contracts and university grants are presented. The following topics are covered: (1) the LeRC Space Communications Program, and Advanced Modulation and Coding Projects; (2) the status of four contracts for development of proof-of-concept modems; (3) modulation and coding work done under three university grants, two small business innovation research contracts, and two demonstration model hardware development contracts; and (4) technology needs and opportunities for future missions