State reduction of MLSE receivers for optical communications

Orientador: Renato da Rocha LopesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Sistemas ópticos são afetados pelas dispersões cromática e de modo de polarização que causam interferência intersimbólica. Para mitigar essas dispersões é utilizado um receptor de sequência de máxima verossimilhança, com uma métrica subótima adequada para esse sistema. Nesta dissertação uma técnica de redução de estados da treliça do algoritmo de Viterbi é descrita e adaptada para um sistema óptico de modulação por intensidade e detecção direta. A métrica é adaptada para compensar o efeito da redução de estados pela técnica de delayed-decision feedback sequence estimation. Resultados são apresentados em sistemas com dispersão cromática e de modo de polarizaçãoAbstract: Optical systems are affected by chromatic and polarization mode dispersion causing intersymbol interference. To mitigate these dispersions a maximumlikelihood sequence estimation receiver is used, with an appropriate suboptimal metric for this system. In this thesis a technique for reducing the number of states of the trellis of the Viterbi algorithm is described and adapted to an optical intensity modulation and direct detection. The metric is adapted to compensate for the effect of reducing the number of states by the technique of delayed-decision feedback sequence estimation. Results are presented for a system with chromatic and polarization mode dispersionsMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric

Low Complexity Decoding for Higher Order Punctured Trellis-Coded Modulation Over Intersymbol Interference Channels

Trellis-coded modulation (TCM) is a power and bandwidth efficient digital transmission scheme which offers very low structural delay of the data stream. Classical TCM uses a signal constellation of twice the cardinality compared to an uncoded transmission with one bit of redundancy per PAM symbol, i.e., application of codes with rates $\frac{n-1}{n}$ when $2^{n}$ denotes the cardinality of the signal constellation. Recently published work allows rate adjustment for TCM by means of puncturing the convolutional code (CC) on which a TCM scheme is based on. In this paper it is shown how punctured TCM-signals transmitted over intersymbol interference (ISI) channels can favorably be decoded. Significant complexity reductions at only minor performance loss can be achieved by means of reduced state sequence estimation.Comment: 4 pages, 5 figures, 3 algorithms, accepted and published at 6th International Symposium on Communications, Control, and Signal Processing (ISCCSP 2014

Low Complexity Decoding for Punctured Trellis-Coded Modulation Over Intersymbol Interference Channels

Classical trellis-coded modulation (TCM) as introduced by Ungerboeck in 1976/1983 uses a signal constellation of twice the cardinality compared to an uncoded transmission with one bit of redundancy per PAM symbol, i.e., application of codes with rates $\frac{n-1}{n}$ when $2^{n}$ denotes the cardinality of the signal constellation. The original approach therefore only comprises integer transmission rates, i.e., $R=\left\{ 2,\,3,\,4\,\ldots \right\}$, additionally, when transmitting over an intersymbol interference (ISI) channel an optimum decoding scheme would perform equalization and decoding of the channel code jointly. In this paper, we allow rate adjustment for TCM by means of puncturing the convolutional code (CC) on which a TCM scheme is based on. In this case a nontrivial mapping of the output symbols of the CC to signal points results in a time-variant trellis. We propose an efficient technique to integrate an ISI-channel into this trellis and show that the computational complexity can be significantly reduced by means of a reduced state sequence estimation (RSSE) algorithm for time-variant trellises.Comment: 4 pages, 7 pictured, accepted for 2014 International Zurich Seminar on Communication

Bibliographic Review on Distributed Kalman Filtering

In recent years, a compelling need has arisen to understand the effects of distributed information structures on estimation and filtering. In this paper, a bibliographical review on distributed Kalman filtering (DKF) is provided.\ud The paper contains a classification of different approaches and methods involved to DKF. The applications of DKF are also discussed and explained separately. A comparison of different approaches is briefly carried out. Focuses on the contemporary research are also addressed with emphasis on the practical applications of the techniques. An exhaustive list of publications, linked directly or indirectly to DKF in the open literature, is compiled to provide an overall picture of different developing aspects of this area

Beamforming in MISO Systems: Empirical Results and EVM-based Analysis

We present an analytical, simulation, and experimental-based study of beamforming Multiple Input Single Output (MISO) systems. We analyze the performance of beamforming MISO systems taking into account implementation complexity and effects of imperfect channel estimate, delayed feedback, real Radio Frequency (RF) hardware, and imperfect timing synchronization. Our results show that efficient implementation of codebook-based beamforming MISO systems with good performance is feasible in the presence of channel and implementation-induced imperfections. As part of our study we develop a framework for Average Error Vector Magnitude Squared (AEVMS)-based analysis of beamforming MISO systems which facilitates comparison of analytical, simulation, and experimental results on the same scale. In addition, AEVMS allows fair comparison of experimental results obtained from different wireless testbeds. We derive novel expressions for the AEVMS of beamforming MISO systems and show how the AEVMS relates to important system characteristics like the diversity gain, coding gain, and error floor.Comment: Submitted to IEEE Transactions on Wireless Communications, November 200

A 3.52 Gb/s mmWave Baseband with Delayed Decision Feedback Sequence Estimation in 40 nm

We present a digital baseband ASIC for 60 GHz single-carrier (SC) transmission that is optimized for communication scenarios in which most of the energy is concentrated in the first few channel taps. Such scenarios occur for example in office environments with strong reflections. Our circuit targets close-to-optimum maximum-likelihood performance under such conditions. To this end, we show for the first time how a reduced-state-sequence-estimation algorithm can be realized for the 1760 MHz bandwidth of the IEEE 802.11ad standard. The equalizer is complemented in the frontend by a synchronization unit for frequency offset compensation as well as a Golay-sequence based channel estimator and in the backend by an low density parity check (LDPC) decoder. In 40nm CMOS we achieve a measured data rate of up to 3.52 Gb/s using QPSK modulation