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<p>In this thesis, noncoherent cooperative amplify-and-forward (AF) half-duplex relay systems and wireless communication systems equipped with a single transmitter antenna and multiple receiver antennas (SIMO) are considered, in which perfect channel information is unavailable at the destination end. For the AF half-duplex relay systems, the use of the least square error (LSE) receiver is proposed for detection. By using perturbation theory on the eigenvalues, an asymptotic formula of pairwise error probability for the LSE detector is derived. The result shows that the full diversity gain function mimics coherent cooperative AF half-duplex relay systems, whereas the coding gain function mimics noncoherent multi-inputs multi-outputs (MIMO) systems.</p> <p>In order to design full diversity noncoherent signals for both systems, a novel concept called a uniquely factorable constellation (UFC) is proposed in this thesis. It is proved that such a UFC design guarantees the unique blind identification of channel coefficients and transmitted signals in a noise-free case for the SIMO channel by only processing two received signals, as well as full diversity with the noncoherent maximum likelihood (ML) receiver in a noisy case. By using the Lagrange's four-square theorem, an algorithm is developed to efficiently and effectively design various sizes of energy-efficient unitary UFCs to optimize the coding gain. In addition, a closed-form optimal energy scale is found to maximize the coding gain for the unitary training scheme based on the commonly-used quadrature amplitude modulation (QAM) constellations.</p> / Master of Applied Science (MASc)

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / This paper presents noncoherent limiter-discriminator detection and differential detection of FQPSK (Feher quadrature phase-shift-keying) with maximum-likelihood sequence estimation (MLSE) techniques. Noncoherent FQPSK systems are suitable for fast fading and cochannel interference channels and channels with strong phase noise, and they can offer faster synchronization and reduce outage events compared with conventional coherent systems. In this paper, both differential detection and limiter-discriminator detection of FQPSK are discussed. We use MLSE with lookup tables to exploit the memory in noncoherently detected FQPSK signals and thus significantly improve the bit error rate (BER) performance in an additive white Gaussian noise (AWGN) channel.

We introduced nested search methods to design (n, k) block codes for arbitrary channels by optimizing an appropriate metric spectrum in each iteration. For a given k, the methods start with a good high rate code, say k/(k + 1), and successively design lower rate codes up to rate k/2^k corresponding to a Hadamard code. Using a full search for small binary codes we found that optimal or near-optimal codes of increasing length can be obtained in a nested manner by utilizing Hadamard matrix columns. The codes can be linear if the Hadamard matrix is linear and non-linear otherwise. The design methodology was extended to the generic complex codes by utilizing columns of newly derived or existing unitary codes. The inherent nested nature of the codes make them ideal for progressive transmission. Extensive comparisons to metric bounds and to previously designed codes show the optimality or near-optimality of the new codes, designed for the fading and the additive white Gaussian noise channel (AWGN). It was also shown that linear codes can be optimal or at least meeting the metric bounds; one example is the systematic pilot-based code of rate k/(k + 1) which was proved to meet the lower bound on the maximum cross-correlation. Further, the method was generalized such that good codes for arbitrary channels can be designed given the corresponding metric or the pairwise error probability. In synchronous multiple-access schemes it is common to use unitary block codes to transmit the multiple users’ information, especially in the downlink. In this work we suggest the use of newly designed non-unitary block codes, resulting in increased throughput e&#64259;ciency, while the performance is shown not to be substantially sacri&#64257;ced. The non-unitary codes are again developed through suitable nested searches. In addition, new multiple-access codes are introduced that optimize certain criteria, such as the sum-rate capacity. Finally, the introduction of the asymptotically optimum convolutional codes for a given constraint length, reduces dramatically the search size for good convolutional codes of a certain asymptotic performance, and the consequences to coded code-division multiple access (CDMA) system design are highlighted.

UWB communication is an attractive technology that has the potential to provide low-power, low-complexity, and high-speed communications in short range links. One of the main challenges of the UWB communications is the highly frequency-selective channel, which induces hundreds of overlapped copies of the transmitted pulse with different delays and amplitudes. To collect the energy of these multipath components, coherent Rake receivers are proposed, but suffer from high implementation and computational costs on channel estimation. To avoid the stringent channel estimation, several noncoherent receivers, including energy detector (ED) and transmitted reference (TR), are proposed at the cost of degraded performance. In addition, when taking into account practical issues of UWB communications, e.g., non-Gaussian impulsive noise, non-ideal antennas, and limited, significant performance degradation may be introduced by noncoherent receivers. In this dissertation, we will present low-complexity, high-performance, noncoherent receiver designs for UWB communications that i) avoid the stringent channel estimation; ii) lower the computational complexity of the existing receivers with the aid of advanced digital signal processing techniques; and iii) improve the error performance of the noncoherent receivers by accommodating practical imperfections. First, we propose three multi-symbol detectors (MSDs) for multi-symbol different detection (MSDD), which has recently caught attention in UWB communications because of its high performance without requiring explicit channel estimation. To alleviate the non-deterministic polynomial hardness (NP-hard) of MSDD, we analyze the statistical model of MSDD and propose an iterative MSD and two MSDs based on relaxation technique with near-optimal performance and low complexity. Moreover, the error performance of MSDs is further enhanced by exploiting joint soft-input soft-output MSDD and forward error correction codes. Next, we consider the non-Gaussian noise in the presence of multi-access interference, which is impulsive when the number of active users is small. To mitigate the impulsive noise effect, in this dissertation, we propose new differential UWB receivers based on the generalized Gaussian distribution and Laplace distribution and achieve better error performance. Another main issue of UWB communications is the limited radio coverage. To extend the coverage and improve the performance of UWB systems, we focus on a novel differentially encoded decode-and-forward (DF) non-cooperative relaying scheme. Putting emphasis on the general case of multi-hop relaying, we illustrate a novel algorithm for the joint power allocation and path selection (JPAPS), minimizing an approximate of the overall bit error rate (BER). A simplified scheme is also presented, which reduces the complexity to O(N²) and achieves a negligible performance loss. Finally, we concentrate on code-multiplexing (CM) systems, which have recently drawn attention mainly because they enable noncoherent detection without requiring either a delay component, as in TR, or an analog carrier, as in frequency-shifted reference. In this dissertation, we propose a generalized code-multiplexing (GCM) system based on the formulation of a constrained mixed-integer optimization problem. The GCM extends the concept of existing CM while retaining their simple receiver structure, even offering better BER performance and a higher data rate in the sense that more data symbols can be embedded in each transmitted block. Moreover, the impacts of non-ideal antennas on the GCM systems are investigated given some practical antenna measurement data and IEEE 802.15.4a channel environments.

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

<p>This thesis is concerned with detection of transient signal families and detectors in nonlinear static sensor systems. The detection problems are treated within the framework of likelihood ratio based binary hypothesis testing.</p><p>An analytical solution to the noncoherent detection problem is derived, which in contrast to the classical noncoherent detector, is optimal for wideband signals. An optimal detector for multiple transient signals with unknown arrival times is also derived and shown to yield higher detection performance compared to the classical approach based on the generalized likelihood ratio test.</p><p>An application that is treated in some detail is that of ultrasonic nondestructive testing, particularly pulse-echo detection of defects in elastic solids. The defect detection problem is cast as a composite hypothesis test and a methodology, based on physical models, for designing statistically optimal detectors for cracks in elastic solids is presented. Detectors for defects with low computational complexity are also formulated based on a simple phenomenological model of the defect echoes. The performance of these detectors are compared with the physical model-based optimal detector and is shown to yield moderate performance degradation.</p><p>Various aspects of optimal detection in static nonlinear sensor systems are also treated, in particular the stochastic resonance (SR) phenomenon which, in this context, implies noise enhanced detectability. Traditionally, SR has been quantified by means of the signal-to-noise ratio (SNR) and interpreted as an increase of a system's information processing capability. Instead of the SNR, rigorous information theoretic distance measures, which truly can support the claim of noise enhanced information processing capability, are proposed as quantifiers for SR. Optimal detectors are formulated for two static nonlinear sensor systems and shown to exhibit noise enhanced detectability.</p>

This thesis is concerned with detection of transient signal families and detectors in nonlinear static sensor systems. The detection problems are treated within the framework of likelihood ratio based binary hypothesis testing. An analytical solution to the noncoherent detection problem is derived, which in contrast to the classical noncoherent detector, is optimal for wideband signals. An optimal detector for multiple transient signals with unknown arrival times is also derived and shown to yield higher detection performance compared to the classical approach based on the generalized likelihood ratio test. An application that is treated in some detail is that of ultrasonic nondestructive testing, particularly pulse-echo detection of defects in elastic solids. The defect detection problem is cast as a composite hypothesis test and a methodology, based on physical models, for designing statistically optimal detectors for cracks in elastic solids is presented. Detectors for defects with low computational complexity are also formulated based on a simple phenomenological model of the defect echoes. The performance of these detectors are compared with the physical model-based optimal detector and is shown to yield moderate performance degradation. Various aspects of optimal detection in static nonlinear sensor systems are also treated, in particular the stochastic resonance (SR) phenomenon which, in this context, implies noise enhanced detectability. Traditionally, SR has been quantified by means of the signal-to-noise ratio (SNR) and interpreted as an increase of a system's information processing capability. Instead of the SNR, rigorous information theoretic distance measures, which truly can support the claim of noise enhanced information processing capability, are proposed as quantifiers for SR. Optimal detectors are formulated for two static nonlinear sensor systems and shown to exhibit noise enhanced detectability.

The objective of this research work is to develop reliable and power-efficient synchronization algorithms for continuous phase modulation (CPM). CPM is a bandwidth and power efficient signaling scheme suitable for wireless and mobile communications. Binary CPM schemes have been widely used in many commercial and military systems. CPM with multilevel symbol inputs, i.e., M-ary CPM, can achieve a higher data rate than binary CPM. However, the use of M-ary CPM has been limited due to receiver complexity and synchronization problems. In the last decade, serially concatenated CPM (SCCPM) has drawn more attention since this turbo-like coded scheme can achieve near Shannon-limit performance by performing iterative demodulation/decoding. Note that SCCPM typically operates at a low signal-to-noise ratio, which makes reliable and power-efficient synchronization more challenging. In this thesis, we propose a novel timing and phase recovery technique for CPM. Compared to existing maximum-likelihood estimators, the proposed data-aided synchronizer can achieve a better acquisition performance when a preamble is short or channel model errors are present. We also propose a novel adaptive soft-input soft-output (A-SISO) module for iterative detection with parameter uncertainty. In contrast to the existing A-SISO algorithms using linear prediction, the parameter estimation in the proposed structure is performed in a more general least-squares sense. Based on this scheme, a family of fixed-interval A-SISO algorithms are utilized to implement blind iterative phase synchronization for SCCPM. Moreover, the convergence characteristics of iterative phase synchronization and detection are analyzed by means of density evolution. Particularly, an oscillatory convergence behavior is observed when cycle slips occur during phase tracking. In order to reduce performance degradation due to this convergence fluctuation, design issues, including delay depth of the proposed algorithms, iteration-stopping criteria and interleaver size, are also discussed. Finally, for completeness of the study on phase synchronization, we investigate the error probability performance of noncoherently detected full-response CPM, which does not require channel (or phase) estimation.

PN code tracking plays a very important role in CDMA communication systems. In literature, the influences of multipath fading and of multiuser interference on PN code tracking are studied separately. The multipath fading influence is mitigated by combining a rake receiver and a channel estimator in the Delay-Locked Loop (DLL). The multiuser interference is overcome by incorporating a data estimator into the DLL. In the downlink, PN code tracking may suffer from the multipath fading influence. However, the multipath fading and the multiuser interference influences exist in the uplink. Unfortunately, sole use of the aforementioned methods cannot solve out both influences simultaneously. In this thesis, two new Coherent Decision-Directed Delay-Locked Loop (CDD-DLL) PN-Code tracking schemes are developed and either can overcome both influences. First, a channel and a data estimators are incorporated into the DLL inherent with a rake receiver. This new scheme works properly in an environment with multipath fading and multiuser interference. Second, the original CDD-DLL is combined with a multipath interference canceller (MPI) to reduce both influences. Analytical results are derived for the two schemes proposed and are validated with numerical simulations. Simulation results show that the conventional DLLs working in a multipath fading and multiuser interference environment can be significantly improved using the new schemes. Moreover, the latter outperforms the former because the multipath interference is cancelled completely.