Multi-Gigabaud Solutions for Millimeter-wave Communication

With the growing number of mobile network and internet services subscriptions, faster communication will provide a better experience for users. In the next generation mobile network, the fifth generation (5G), communication data rate will achieve several Gigabits per second with ultra-low latency. The capacity enhancement of the mobile backhaul and fronthaul is a challenge. The transmission capacity can be enhanced by increasing the bandwidth, increasing the spectrum efficiency and increasing both the bandwidth and the spectrum efficiency at the same time. \ua0Millimeter-wave frequency bands have the bandwidth in the order of GHz which provide great opportunities to realize high data rate communications. In this case, millimeter-wave frontend modules and wideband modems are needed in communication systems. In this thesis, a 40 Gbps real-time differential quadrature phase shift keying (DQPSK) modem has been presented to support high-speed communications [A]. As a complete system, it aims to work together with the D-band frontend module published in [1] providing more than 40 GHz bandwidth. In this modem, the modulator is realized in a single field programmable gate array (FPGA) and the demodulator is based on analog components. Although millimeter-wave frequency bands could provide wide available bandwidth, it is challenging to generate high output power of the carrier signal. In addition, the transmitter needs to back off several dB in output power in order to avoid the non-linear distortion caused by power amplifiers. In this thesis, an outphasing power combining transmitter is proposed [B] to use the maximum output power of power amplifiers while maintaining the signal quality at the same time. This transmitter is demonstrated at E-band with commercially available components.Increasing the spectrum efficiency is an additional method to enhance the transmission capacity. High order modulation signals such as quadrature amplitude modulation (QAM) signals are commonly used for this purpose.\ua0 In this case, receivers usually require coherent detection in order to demodulate the signals. Limited by the sampling rate of the analog to digital converters (ADCs), the traditional digital carrier recovery methods can be only applied to a symbol rate lower than the sampling rate. A synchronous baseband receiver is proposed [C] with a carrier recovery subsystem which only requires a low-speed ADC with a sampling rate of 100 MSps

Carrier Recovery in burst-mode 16-QAM

Wireless communication systems such as multipoint communication systems (MCS) are becoming attractive as cost-effective means for providing network access in sparsely populated, rugged, or developing areas of the world. Since the radio spectrum is limited, it is desirable to use spectrally efficient modulation methods such as quadrature amplitude modulation (QAM) for high data rate channels. Many MCS employ time division multiple access (TDMA) and/or time division duplexing (TDD) techniques, in which transmissions operate in bursts. In many cases, a preamble of known symbols is appended to the beginning of each burst for carrier and symbol timing recovery (symbol timing is assumed known in this thesis). Preamble symbols consume bandwidth and power and are not used to convey information. In order for burst-mode communications to provide efficient data throughput, the synchronization time must be short compared to the user data portion of the burst. Traditional methods of communication system synchronization such as phase-locked loops (PLLs) have demonstrated reduced performance when operated in burst-mode systems. In this thesis, a feedforward (FF) digital carrier recovery technique to achieve rapid carrier synchronization is proposed. The estimation algorithms for determining carrier offsets in carrier acquisition and tracking in a linear channel environment corrupted by additive white Gaussian noise (AWGN) are described. The estimation algorithms are derived based on the theory of maximum likelihood (ML) parameter estimation. The estimations include data-aided (DA) carrier frequency and phase estimations in acquisition and non-data-aided (NDA) carrier phase estimation in tracking. The DA carrier frequency and phase estimation algorithms are based on oversampling of a known preamble. The NDA carrier phase estimation makes use of symbol timing knowledge and estimates are extracted from the random data portion of the burst. The algorithms have been simulated and tested using Matlab® to verify their functionalities. The performance of these estimators is also evaluated in the burst-mode operations for 16-QAM and compared in the presence of non-ideal conditions (frequency offset, phase offset, and AWGN). The simulation results show that the carrier recovery techniques presented in this thesis proved to be applicable to the modulation schemes of 16-QAM. The simulations demonstrate that the techniques provide a fast carrier acquisition using a short preamble (about 111 symbols) and are suitable for burst-mode communication systems

Robust multilevel coherent optical systems with linear processing at the receiver

This paper investigates optical coherent systems based on polarization multiplexing and high-order modulations such as phase-shift keying (PSK) signals and quadrature amplitude modulations (QAM). It is shown that a simple linear receiver processing is sufficient to perfectly demultiplex the two transmitted streams and to perfectly compensate for group velocity dispersion (GVD) and polarization mode dispersion (PMD). In addition, in the presence of a strong phase noise of the lasers at the transmitter and receiver, a symbol-by-symbol detector with decision feedback is able to considerably improve the receiver robustness with a limited complexity increase. We will also discuss the channel estimation and the receiver adaptivity to time-varying channel conditions as well as the problem of the frequency acquisition and tracking. Finally, a new two-dimensional (polarization/time) differential encoding rule is proposed to overcome a polarization-ambiguity problem. In the numerical results, the receiver performance will be assessed versus the receiver complexity

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

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

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

Optimization of digital signal processing routines for high speed coherent transmissions

Alcuni moduli di un ricevitore coerente per trasmissioni ottiche vengono analizzati e ottimizzati per ridurre il tempo di esecuzione e migliorare le perfomances.ope

Spectral characterization and performance evaluation for advanced digital optical modulation formats at 40 Gb/s

Orientadores: Helio Waldman, Darli Augusto de Arruda MelloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Comparamos o desempenho de quatro arquiteturas de recuperação de portadora tipo feedforward em receptores QPSK e 8-PSK coerentes com multiplexação de polarização e decodificação diferencial. Analisamos os cenários que apresentam desequilíbrio entre as SNRs nas duas polarizações, tal como ocorre em sistemas com PDL. Usando simulações de Monte Carlo, observamos que o método de estimação conjunta proposto apresenta penalidade em SNR de 1,1 dB de penalidade em SNR para uma razão largura de linha/ taxa de símbolo = 5 × 10-3, enquanto as outras três arquiteturas investigadas têm penalidade de 1,8 dB, 2,0 dB, e 3,9 dB para o formato de modulação QPSK. Para o formato 8-PSK, a arquitetura de recuperação conjunta apresenta 1,1 dB para uma razão largura de linha/ taxa de símbolo = 7, 5 × 10-4, enquanto as outras três arquiteturas têm penalidade 1,5 dB, 1,7 dB e 2,8 dB, para BER = 10-3 e um desequilíbrio em SNR de 3 dB.Abstract: This work compares the performance of four feedforward carrier recovery architectures in coherent QPSK and 8-PSK receivers, with polarization multiplexing and differential decoding. We focused on the scenarios showing an SNR imbalance between orthogonal polarizations, as in PDL impaired systems. Using Monte Carlo simulations, we observed that the proposed joint estimation method yields an SNR penalty of 1.1 dB, for a laser linewidth/ baudrate ratio of 5×10-3, while the other three investigated architectures 1.8 dB, 2.0 dB and 3.9 dB, for the QPSK modulation format. As for 8-PSK, the proposed joint feedforward carrier recovery architecture exhibits a 1.1 dB SNR penalty for a laser linewidth/ baudrate ratio of 7.5 × 10-4, while the other three architectures 1.5 dB, 1.7 dB and 2.8 dB, for a BER = 10-3 and 3 dB SNR imbalance. Keywords: optical communication, coherent receiver, phase modulation.MestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric