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In the current transmission systems, the transmission capacity is still not enough. The information bandwidth of the optical fiber communication system is limited by the optical amplifier bandwidth, and more efficient use of the bandwidth is a very important issue. Therefore, the amplitude and phase shift keying (APSK) is one attractive method of multi-bit per symbol modulation scheme to improve the spectral efficiency, and it can effectively increase the transmission capacity. To improve the capacity and the spectral efficiency, the advanced modulation format is effective, and the coherent detection scheme is also effective. However, an optical phase-locked loop (PLL) to lock the local oscillator (LO) phase and the signal phase required for the homodyne detection is still difficult to realize and it makes the receiver circuit complicated. Using the digital coherent receiver, the optical carrier phase information can be recovered by means of the digital signal processing (DSP), and this scheme enables to eliminate the optical PLL circuit by the phase estimation algorithm through the DSP. The stored data can be offline processed by using the MATLAB program. This master thesis is focusing on studying the transmission performance of the APSK format using the DSP in the digital coherent receiver. 497km transmission experiment has been conducted. Subsequently, the stored data are offline processed by the algorithms of the DSP. Then, the APSK performances between back-to-back and 497km transmission are compared.

Amplitude and Phase Shift Keying (APSK) format is one of the most attractive advanced modulation formats because of its good spectral efficiency. As the information bandwidth of the current optical fiber communication system is limited by the optical amplifier bandwidth, it is important to utilize the limited bandwidth effectively. This master thesis focuses on to study the transmission performance of the APSK format both theoretically and experimentally. At first, a theoretical study was conducted using a numerical simulation. As the Extinction Ratio (ER) of the Amplitude Shift Keying (ASK) signal affects the performances of both the ASK and the Phase Shift Keying (PSK) signals, the effect of the ER upon the transmission performance of the APSK format was studied. A clear trade-off between the performance of the ASK signal and the PSK signal due to the change of the ER was observed. Then, in order to improve the performance of the APSK format, a method to improve the transmission performance was proposed. This method was named as ¡§zero-nulling method¡¨, and it solved the trade-off issue caused by the ER. The effectiveness of this method was confirmed through the numerical simulation. Next, an experimental study was conducted. An experimental setup including 330km optical fiber transmission line was prepared, and it was used to confirm the results of the theoretical simulation. The performance trade-off between the ASK and the PSK signals due to the ER was confirmed experimentally. Finally, another experimental study was conducted. An experimental setup of 500km transmission line was used for this study. By adopting the recirculating loop experimental setup, the transmission length could be extended to a few thousand kilometers. The applicability of the ¡§zero-nulling method¡¨ was confirmed using this experimental setup.

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The two-antenna problem in aeronautical mobile telemetry is created by the reception of two copies of the same RF waveform with different phases and time delays. Alamouti and Alamouti-like space time block codes can solve the two-antenna problem, but the decoder/detector needs to account for the different time delays between the signals received from the two transmit antennas. In this thesis, a comparison is made between the performance of Alamouti space-time block codes and time-reversed space-time block codes with 16-APSK to solve the two-antenna problem. The maximum likelihood decoder/detector for Alamouti-encoded 16-APSK is a sequence detector operating on a trellis with a large number of states. A practical state-reduction technique is presented. The results produce a trellis with 256 states and a small loss in bit error rate performance as long as the delay difference is not too big. The decoder/detector for the time-reversed space time block requires only waveform manipulations and channel matched filtering in the case where the two channels are simple delays. For the more general case of multipath propagation between the two transmit antennas and the receiver, the decoder/detector requires an equalizer; simulation results using a channel pair measured at a test range show that the decoder/detector is capable of achieving near AWGN performance with a modest equalizer.

Orientador: Jaime Portugheis / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-06T20:11:55Z (GMT). No. of bitstreams: 1 Cunha_DanielCarvalhoda_D.pdf: 2995961 bytes, checksum: 3bbce0e569994999c363151f6510cef1 (MD5) Previous issue date: 2006 / Resumo: Em varios sistemas de transmissão passa-faixa, uma recepção coerente satisfatória é dificil de ser alcancada. Para alguns destes sistemas, é comum supor que a rotaçãoo de fase introduzida pelo canal é constante durante um bloco de L simbolos e que ela varia de maneira independente de bloco a bloco. Este canal é denominado canal não-coerente de bloco. Investigamos a capacidade de um canal não-coerente de bloco utilizando a modulação M-APSK (do inglês, M-ary Amplitude Phase Shift Keying). Apresentamos a caracterização da distribuição de entrada que atinge a capacidade e obtivemos limitantes superiores e inferiores para a mesma. Adicionalmente, desenvolvemos um algoritmo que simultaneamente fornece a distribuição de entrada e os parametros da modulação M-APSK que maximizam a informação mutua com recepção coerente. A investigação da capacidade mostrou que o aumento de L faz a capacidade não-coerente convergir para a coerente. Alem disso, o uso de codificação diferencial torna a convergência mais rapida. Motivados por este comportamento, apresentamos um esquema de codificação eficiente em faixa. Este esquema é formado pela concatenação serial de um codigo LDPC (do ingles, Low-Density Parity Check ), um entrela¸cador e um codificador diferencial. Para o esquema apresentado, o receptor iterativo é descrito por um grafo-fator. Os desempenhos do esquema com diferentes tamanhos de codigos LDPC são comparados / Abstract: Coherent reception is not possible for many bandpass transmission systems. In some of these systems, it is commonly assumed that the unknown carrier phase rotation is constant over a block of L symbols and it is independent from block to block. This channel is denominated blockwise noncoherent channel. The blockwise noncoherent channel capacity using M-ary Amplitude and Phase Shift Keying (M-APSK) modulation is investigated. The characterization of the input distribution achieving capacity is presented. Upper and lower bounds to this capacity are derived. In addition, an algorithm for simultaneously computing the input distribution and the M-APSK constellation parameters which maximizes the mutual information with coherent reception is developed. The investigation of the capacity showed that as L increases, the noncoherent capacity converges to the coherent one. Besides that, the use of differential encoding makes this convergence faster. Motivated by this fact, a bandwidth efficient coding scheme is presented. This scheme is composed of a serial concatenation of a Low-Density Parity Check (LDPC) code, an interleaver, and a differential encoder. For this scheme, the iterative receiver is described by a factor graph. The scheme performances for different lengths of LDPC codes are compared. / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

Aeronautical telemetry systems have historically been implemented with constant envelope modulations like CPM. Shifts in system constraints including reduced available bandwidth and increased throughput demands have caused many in the field to reevaluate traditional methods and design practices. This work examines the costs and benefits of using APSK for aeronautical telemetry instead of CPM. Variable rate turbo codes are used to improve the power efficiency of 16- and 32-APSK. Spectral regrowth in nonlinear power amplifiers when driven by non-constant envelope modulation is also considered. Simulation results show the improved spectral efficiency of this modulation scheme over those currently defined in telemetry standards. Additionally, the impact of transitioning from continuous transmission to burst-mode is considered. Synchronization loops are ineffective in burst-mode communication. Data-aided feed forward algorithms can be used to estimate offsets in carrier phase, frequency, and symbol timing between the transmitter and the receiver. If a data-aided algorithm is used, a portion of the transmitted signal is devoted to a known sequence of pilot symbols. Optimum pilot sequences for the three synchronization parameters are obtained analytically and numerically for different system constraints. The alternating sequence is shown to be optimal given a peak power constraint. Alternatively, synchronization can be accomplished using blind algorithms that do not rely on a priori knowledge of a pilot sequence. If blind algorithms are used, the observation interval can be longer than for data-aided algorithms. There are combinations of pilot sequence length and packet length where data-aided algorithms perform better than blind algorithms and vice versa. The conclusion is that a sequential arrangement of blind algorithms operating over an entire burst performs better than a CRB-achieving data-aided algorithm operating over a short pilot sequence.