Dissertations / Theses on the topic 'Bit interleaved coded modulation'

Bit-interleaved coded modulation (BICM) is a pragmatic yet powerful approach for spectrally efficient coded transmission. BICM was originally designed as a superior alternative to the conventional trellis coded modulation in fading channels. However, its flexibility and ease of implementation also make BICM an attractive scheme for transmission over unfaded channels. In fact, a noticeable advantage of BICM is its simplicity and flexibility. Notably, most of today’s communication systems that achieve high spectral efficiency such as ADSL, Wireless LANs, and WiMax feature BICM. Perceptibly, the design of efficient BICM-based transmission strategies relies on the existence of a general analytical framework for evaluating its performance. Therefore, alongside its vast popularity and deployment, performance evaluation of BICM has attracted considerable attention. Developing such a performance evaluation framework is one of the main contributions of this thesis. In addition to conventional additive white Gaussian noise model, the practically important case of transmission over fading channels impaired by Gaussian mixture noise has also been studied. Different from previously proposed methods, our scheme results in closed-form expressions and is valid for arbitrary mapping rules and fading distributions. Furthermore, making use of the newly developed framework, we propose two novel transmission strategies. First, we consider the problem of optimal power allocation for a BICM system employing orthogonal frequency division multiplexing. In particular, we show that this problem translates into a linear program in the high signal-to-noise ratio regime. This reformulation extends the applicability and delivers considerable complexity reduction in comparison to existing algorithms. Finally, we propose novel detector architectures for a BICM system employing iterative decoding using hard-decision feedback at the receiver. We show that, taking the feedback error into account results in considerable performance improvement while retains decoding complexity.

Space-time block codes are a recently discovered, attractive modulation scheme for multiple antenna wireless channels. They are capable of providing full diversity over fading channels, at the same time requiring only low computational costs. Over the last few years, several distinct approaches to designing space-time codes have been proposed in the literature, including the layeredarchitecture, trellis codes, turbo codes and the orthogonal designs. Most work on space-time coding has focused on the problem of designing codes to perform well under quasi-static fading conditions. In practice, it is not unusual for a cellular handset to experience conditions which range from fast fading to nearly static within seconds (e.g., a vehicle suddenly braking). It is therefore of interest to design codes that are robust in the sense, that they perform well under a wide variety of channel fading conditions. A robust coding architecture called Bit-Interleaved Space-Time Coded Modulation is proposed for channels with multiple transmit and receive antennas. It is designed to perform well under a wide variety of channel fading conditions and which (when differentially encoded) does not require accurate channel estimates at the receiver. The architecture combines serial concatenation of short, full-diversity space-time block codes (inner code) with bit-interleaved coded modulation.This thesis examines the capacity aspects of this architecture namely, the ergodic capacity, the outage capacity and the ergodic and outage cut-off rates in Rayleigh flat-fading channels. It is shown that, if the inner block codes are chosen properly, not only is the capacity close to the information-theoretic limits, but also a better tradeoff between performance and coding complexity can be obtained.

In recent years, the invention of Turbo codes has spurred much interest in the coding community. Turbo codes are capable of approaching channel capacity closely at a decoding complexity much lower than previously thought possible. Although decoding complexity is relatively low, Turbo codes are still too complex to implement for many practical systems. This work is focused on low complexity channel coding schemes with Turbo-like performance. The issue of complexity is tackled by using single parity check (SPC) codes, arguably the simplest codes known. The SPC codes are used as component codes in multiple parallel and multiple serial concatenated structures to achieve high performance. An elegant technique for improving error performance by increasing the dimensionality of the code without changing the block length and code rate is presented. For high bandwidth efficiency applications, concatenated SPC codes are combined with 16-QAM Bit Interleaved Coded Modulation (BICM) to achieve excellent performance. Analytical and simulation results show that concatenated SPC codes are capable of achieving Turbo-like performances at a complexity which is approximately 10 times less than that of a 16-state Turbo code. A simple yet accurate generalised bounding method is derived for BICM systems employing large signal constellations. This bound works well over a wide range of SNRs for common signal constellations in the independent Rayleigh fading channel. Moreover, the bounding method is independent of the type and code rate of channel coding scheme. In addition to the primary aim of the research, an improved decoder structure for serially concatenated codes has been designed, and a sub-optimal, soft-in-soft-out iterative technique for decoding systematic binary algebraic block codes has been developed.

In this thesis, we propose a novel architecture for hybrid radio frequency (RF)/free–space optics (FSO) wireless systems. Hybrid RF/FSO systems are attractive since the RF and FSO sub–systems are affected differently by weather and fading phenomena. We give a thorough introduction to the RF and FSO technology, respectively. The state of the art of hybrid RF/FSO systems is reviewed. We show that a hybrid system robust to different weather conditions is obtained by joint bit–interleaved coded modulation (BICM) of the bit streams transmitted over the RF and FSO sub–channels. An asymptotic performance analysis reveals that a properly designed convolutional code can exploit the diversity offered by the independent sub–channels. Furthermore, we develop code design and power assignment criteria and provide an efficient code search procedure. The cut–off rate of the proposed hybrid system is also derived and compared to that of hybrid systems with perfect channel state information at the transmitter. Simulation results show that hybrid RF/FSO systems with BICM outperform previously proposed hybrid systems employing a simple repetition code and selection diversity.

A comparative study of various codeq. modulation schemes is carried out in terms of their different block length, number of iterations and complexity, quantified by the number of trellis states as well as the EXtrinsic Information Transfer (EXIT) charts are used for analysing their decoding convergence and Bit Error Ratio (BER). A threeDimensional (3-D) EXIT chart is introduced for MultiLevel Coding (MLC) invoking MultiStage Decoding (MSD). Based on this 3-D EXIT chart, we design a precodedMLC scheme employing both MSD and Parallel Independent Decoding (PID). In order to provide space diversity, we study the new arrangement of Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) and MLC combined with Space Time Block Codes (STBC) invoking a novel Sphere Packing (SP) modulation scheme. An equivalent-capacIty-based design of MLCs based on this SP modulation is proposed. We use the Binary Switching Algorithm (BSA) to optimise our cost function for the sake of obtaining appropriate bit-to-SP-symbol mapping schemes. A hybrid mapping scheme is introduced for achieving unequal error protection. Furthermore, bit-to-SP-symbol mapping to 256 constellation points is designed for a serially concatenated BICM-ID aided twin-antenna STBC arrangement for creating a system, which is capable of outperforming an identical-throughput 16-level Quadrature Amplitude Modulation (16QAM) scheme. Furthermore, the benefits of MLC PID designs employing Generalised Low Density Parity Check (GLDPC) codes are investigated, which results in a low-delay scheme useful for multimedia transmission. A stopping criterion is designed for this scheme for the sake of terminating the iterative decoding process, once the target BER is attained. We then contrive coding schemes for the wireless Internet by introducing a BICM-ID scheme combined with Luby Transform (LT) coding constructed for the AWGN-contaminated Binary Erasure Channel (BEC). An improved robust LT packetdegree distribution is introduced for determining the specific number of LT source packets combined with modulo-2 additions in order to create an LT-encoded packet. Furthermore, a Log-Likelihood Ratio (LLR) based reliability estimation scheme is invoked in order to achieve a performance improvement based on this amalgamated design. Finally, a near-capacity Irregular Bit-Interleaved Coded Modulation with Iterative Decoding (Ir-BICM-ID) scheme was designed with the aid of an EXIT chart. An Irregular Convolution Code (IrCC) is proposed for the sake of introducing a diverse range of outer code EXIT functions. By contrast, the inner code is based on the serially concatenated components constituted by an Irregular Unity-Rate Code (IrURC) and an Irregular Mapper (IrMapper). An EXIT chart matching algorithm is invoked for constructing an Ir-BICM-ID scheme, which exhibits a narrow but still open EXIT tunnel and hence approaches the theoretical capacity limit.

This dissertation examines the design of a bit-interleaved coded-modulation with iterative decoding (BICM-ID) system for transmission over a quasi-static fading (QSF) channel. We illustrate the design process for mismatching the extrinsic information transfer (EXIT) chart curves for 16-QAM mapping schemes and memory-two recursive systematic convolutional (RSC) codes. This design process is extremely complex and we define two classification metrics that enable us to reduce the number of mapper and encoder combinations. We use the probability of a decoding erasure to separate all 22 memory-two RSC codes into five groups. We conjecture that the codes in each group will have the same FER performance when coupled with the same mapping scheme. Similarly, we conjecture that all mapping schemes with the same distance spectrum will have identical FER performance curves when coupled with the same encoding scheme. We provide evidence to support the validity of these conjunctures, which allow us to make the set of 16-QAM mapping schemes practically searchable when attempting to find the best match for a particular encoder. Finally, this dissertation demonstrates the practical methodology for finding the best FER performance that can be achieved by a BICM-ID scheme using a memory-two RSC code matched to a 16-QAM mapping scheme for transmission over a QSF channel with various levels of antenna diversity. For example, by using our design framework, we observed that we are able to achieve a gain of 0.2dB at an FER of 2 x 10^-2 and a gain of 0.4dB at an FER of 4 x 10^-4 in the low and the high antenna diversity scenarios respectively over the RSC memory-two code (1, 5/7)₈ coupled with the best mapping schemes found in the literature.

Bit-interleaved coded modulation (BICM) is a very popular approach for spectrally efficient coded transmission. In BICM, the channel encoder is separated from the modulator by a bit level interleaver. The presence of a random interleaver in BICM allows the designer a flexibility to independently choose the code rate and the modulation order. This allows an easy adaptation of the transmission rate to the channel conditions. BICM maximizes the code diversity, and therefore, is a superior alternative to the conventional trellis coded modulation (TCM) in fading channels. In additive white Gaussian noise (AWGN) channels, BICM is suboptimal because it reduces the minimum Euclidean distance. However, its flexibility and ease of implementation makes it an attractive scheme even for transmission over non-fading channels. The objective of this thesis is to investigate and optimize new BICM designs in order to further improve the BICM-based transceivers. First, we develop an analytical framework for performance evaluation of a new generalized BICM (referred to as BICM-T) transmission over AWGN channels that can be used to predict and optimize the error rate performance of such systems. Second, we investigate the performance of BICM in non-Gaussian channels due to its practical relevance. Moreover, because of its various advantages in designing a wireless transceiver, we realize that a BICM-based transceiver will be the natural choice for cooperative communication systems. Therefore, we present an innovative BICM design for cooperative communication where various BICM modules can be optimized jointly considering the average signal to noise ratios of the direct and the two-hop Rayleigh fading channels. The results presented in this thesis show that by optimizing different system modules of our proposed BICM designs, significant gains in the bit error rate (BER) performance can be achieved.

At a time where almost 1.75 billion people around the world use the Internet on a regular basis, optical communication over optical fibers that is used in long distance and high demand applications has to be capable of providing higher communication speed and re-liability. In recent years, strong demand is driving the dense wavelength division multip-lexing network upgrade from 10 Gb/s per channel to more spectrally-efficient 40 Gb/s or 100 Gb/s per wavelength channel, and beyond. The 100 Gb/s Ethernet is currently under standardization, and in a couple of years 1 Tb/s Ethernet is going to be standardized as well for different applications, such as the local area networks (LANs) and the wide area networks (WANs). The major concern about such high data rates is the degradation in the signal quality due to linear and non-linear impairments, in particular polarization mode dispersion (PMD) and intrachannel nonlinearities. Moreover, the higher speed transceivers are expensive, so the alternative approaches of achieving the required rates is preferably done using commercially available components operating at lower speeds.In this dissertation, different LDPC-coded modulation techniques are presented to offer a higher spectral efficiency and/or power efficiency, in addition to offering aggregate rates that can go up to 1Tb/s per wavelength. These modulation formats are based on the bit-interleaved coded modulation (BICM) and include: (i) three-dimensional LDPC-coded modulation using hybrid direct and coherent detection, (ii) multidimensional LDPC-coded modulation, (iii) subcarrier-multiplexed four-dimensional LDPC-coded modulation, (iv) hybrid subcarrier/amplitude/phase/polarization LDPC-coded modulation, and (v) iterative polar quantization based LDPC-coded modulation.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada
A novel type-II hybrid automatic repeat request (HARQ) algorithm using adaptive modulations and bit-interleaved coded modulation (BICM) is presented. The algorithm uses different optimized puncturing patterns for different transmissions of the same data packet. The proposed approach exploits mapping diversity through BICM with iterative decoding. The modulation order is changed in each transmission to keep the number of symbols transmitted constant. We present new bit error rate and frame error rate analytical results for the proposed technique showing good agreement with simulation results. We compare the throughput performance of our proposed HARQ technique with a reference HARQ technique that uses different mapping arrangements but keeps the modulation order fixed. By using optimized puncturing patterns and adaptive modulations, our method provides significantly better throughput performance over the reference HARQ method in the whole signalto- noise ratio (SNR) range, and achieves a gain of 12 dB in the medium SNR region.

Diversity is a powerful technique to improve the reliability of digital communications systems over wireless channels. In this thesis, the error performance and precoder design of a bandwidth-efficient bit-interleaved coded modulation with iterative decoding (BICM-ID) system over a non-orthogonal amplify-and-forward (NAF) half-duplex single-relay channel is investigated to effectively combine cooperative, time and modulation diversities. At first, a tight union bound on the asymptotic bit error probability (BEP) of the NAF-BICM-ID system employing signal space diversity (SSD) via a precoder is derived for an arbitrary cooperative block length of 2N. This bound provides a useful tool to predict the error performance without the need of time-consuming simulations. A design criterion that characterizes the effect of the precoder to the performance is then developed, which gives an insight on how to obtain a good precoder to fully exploit diversity. Attention is then paid to the NAF-BICM-ID system using a 2x2 precoder, where a closed-form expression of the bound is obtained. Based on this expression, the optimal class of 2x2 precoders is developed. Different from the optimal precoders designed for uncoded systems, the derived precoder indicates that the source terminal only needs to send the superposition of the first symbol and the rotated version of the second one in the first time slot, while being silent in the remaining slot to achieve the best asymptotic performance. For a good convergence property, it is further shown that a rotation angle that maximizes the minimum Euclidean distance of the superposition constellation should be used. Optimal rotation angles are then analytically determined for various modulation schemes. The usefulness of the proposed precoder is verified by both the error bound and simulation results. Finally, based on extrinsic information transfer (EXIT) charts, both the convergence property and the asymptotic performance of the system
La diversité est une puissante technique qui permet d'améliorer la fiabilité des systèmes de communications numériques sans fil. Dans cette thèse, la performance en terme d'erreurs et de la conception de précodeurs est enquêtée pour un système à grande efficacité spectrale, utilisant la modulation codée avec entrelacement par bit avec décodage itératif (BICM-ID), à travers un canal semi-duplex non-orthogonal d'amplification-et-retransmission (NAF) afin de combiner efficacement les diversités de modulation, coopérative et temporelle. Premièrement, une borne serrée sur l'asymptote de la probabilité d'erreur par bit (BEP) du système NAF-BICM-ID avec diversité spatiale du signal (SSD), obtenue grâce au précodage, est développée pour une durée coopérative arbitraire de 2N. Cette borne devient un outil important pour prédire la performance en terme d'erreurs sans avoir recours à de longues simulations. Un critère de conception, qui caractérise l'effet du précodage sur la performance, est ensuite dérivé, ce qui donne une idée comment obtenir un bon précodeur pour exploiter la diversité à son maximum. L'attention se porte ensuite sur le système NAF-BICM-ID avec un précodeur 2x2, pour développer une expression analytique de la borne. Celle-ci est utilisée pour établir la série de précodeurs 2x2 optimale. Contrairement aux précodeurs 2x2 des systèmes sans codage, ceux-ci indiquent que le terminal source n'a besoin de transmettre qu'une superposition du premier symbole et une rotation du deuxième lors du premier créneaux, tout en restant silencieux durant le deuxième, pour atteindre asymptotiquement la meilleure performance. De plus, pour améliorer les propriétés de convergence, il est démontré que l'angle de rotation qui maximise la distance Euclidienne minimale de la constellation superposée est celui qui devrait être utilisé. Les angles optimaux pour différentes modulations à plusieurs niveaux sont ensuite$

Nowadays, the digital terrestrial television (DTT) market is characterized by the high capacity needed for high definition TV services. There is a need for an efficient use of the broadcast spectrum, which requires new technologies to guarantee increased capacities. Non-Uniform Constellations (NUC) arise as one of the most innovative techniques to approach those requirements. NUCs reduce the gap between uniform Gray-labelled Quadrature Amplitude Modulation (QAM) constellations and the theoretical unconstrained Shannon limit. With these constellations, symbols are optimized in both in-phase (I) and quadrature (Q) components by means of signal geometrical shaping, considering a certain signal-to-noise ratio (SNR) and channel model. There are two types of NUC, one-dimensional and two-dimensional NUCs (1D-NUC and 2D-NUC, respectively). 1D-NUCs maintain the squared shape from QAM, but relaxing the distribution between constellation symbols in a single component, with non-uniform distance between them. These constellations provide better SNR performance than QAM, without any demapping complexity increase. 2D-NUCs also relax the square shape constraint, allowing to optimize the symbol positions in both dimensions, thus achieving higher capacity gains and lower SNR requirements. However, the use of 2D-NUCs implies a higher demapping complexity, since a 2D-demapper is needed, i.e. I and Q components cannot be separated. In this dissertation, NUCs are analyzed from both transmit and receive point of views, using either single-input single-output (SISO) or multiple-input multiple-output (MIMO) antenna configurations. In SISO transmissions, 1D-NUCs and 2D-NUCs are optimized for a wide range of SNRs and different constellation orders. The optimization of rotated 2D-NUCs is also investigated. Even though the demapping complexity is not increased, the SNR gain of these constellations is not significant. The highest rotation gain is obtained for low-order constellations and high SNRs. However, with multi-RF techniques, the SNR gain is drastically increased, since I and Q components are transmitted in different RF channels. In this thesis, multi-RF gains of NUCs with and without rotation are provided for some representative scenarios. At the receiver, two different implementation bottlenecks are explored. First, the demapping complexity of all considered constellations is analyzed. Afterwards, two complexity reduction algorithms for 2D-NUCs are proposed. Both algorithms drastically reduce the number of distances to compute. Moreover, both are finally combined in a single demapper. Quantization of NUCs is also explored in this dissertation, since LLR values and I/Q components are modified when using these constellations, compared to traditional QAM constellations. A new algorithm that is based on the optimization of the quantizer levels for a particular constellation is proposed. The use of NUCs in multi-antenna communications is also investigated. It includes the optimization in one or two antennas, the use of power imbalance, the cross-polar discrimination (XPD) between receive antennas, or the use of different demappers. Assuming different values for the parameters evaluated, new Multi-Antenna Non-Uniform Constellations (MA-NUC) are obtained by means of a particularized re-optimization process, specific for MIMO. At the receiver, an extended demapping complexity analysis is performed, where it is shown that the use of 2D-NUCs in MIMO extremely increases the demapping complexity. As an alternative, an efficient solution for 2D-NUCs and MIMO systems based on Soft-Fixed Sphere Decoding (SFSD) is proposed. The main drawback is that SFSD demappers do not work with 2D-NUCs, since they perform a Successive Interference Cancellation (SIC) step that needs to be performed in separated I and Q components. The proposed method quantifies the closest symbol using Voronoi regions and allows SFSD demappers to work.
Hoy en día, el mercado de la televisión digital terrestre (TDT) está caracterizado por la alta capacidad requerida para transmitir servicios de televisión de alta definición y el espectro disponible. Es necesario por tanto un uso eficiente del espectro radioeléctrico, el cual requiere nuevas tecnologías para garantizar mayores capacidades. Las constelaciones no-uniformes (NUC) emergen como una de las técnicas más innovadoras para abordar tales requerimientos. Las NUC reducen el espacio existente entre las constelaciones uniformes QAM y el límite teórico de Shannon. Con estas constelaciones, los símbolos se optimizan en ambas componentes fase (I) y cuadratura (Q) mediante técnicas geométricas de modelado de la señal, considerando un nivel señal a ruido (SNR) concreto y un modelo de canal específico. Hay dos tipos de NUC, unidimensionales y bidimensionales (1D-NUC y 2D-NUC, respectivamente). Las 1D-NUC mantienen la forma cuadrada de las QAM, pero permiten cambiar la distribución entre los símbolos en una componente concreta, teniendo una distancia no uniforme entre ellos. Estas constelaciones proporcionan un mejor rendimiento SNR que QAM, sin ningún incremento en la complejidad en el demapper. Las 2D-NUC también permiten cambiar la forma cuadrada de la constelación, permitiendo optimizar los símbolos en ambas dimensiones y por tanto obteniendo mayores ganancias en capacidad y menores requerimientos en SNR. Sin embargo, el uso de 2D-NUCs implica una mayor complejidad en el receptor. En esta tesis se analizan las NUC desde el punto de vista tanto de transmisión como de recepción, utilizando bien configuraciones con una antena (SISO) o con múltiples antenas (MIMO). En transmisiones SISO, se han optimizado 1D-NUCs para un rango amplio de distintas SNR y varios órdenes de constelación. También se ha investigado la optimización de 2D-NUCs rotadas. Aunque la complejidad no aumenta, la ganancia SNR de estas constelaciones no es significativa. La mayor ganancia por rotación se obtiene para bajos órdenes de constelación y altas SNR. Sin embargo, utilizando técnicas multi-RF, la ganancia aumenta drásticamente puesto que las componentes I y Q se transmiten en distintos canales RF. En esta tesis, se han estudiado varias ganancias multi-RF representativas de las NUC, con o sin rotación. En el receptor, se han identificado dos cuellos de botella diferentes en la implementación. Primero, se ha analizado la complejidad en el receptor para todas las constelaciones consideradas y, posteriormente, se proponen dos algoritmos para reducir la complejidad con 2D-NUCs. Además, los dos pueden combinarse en un único demapper. También se ha explorado la cuantización de estas constelaciones, ya que tanto los valores LLR como las componentes I/Q se ven modificados, comparando con constelaciones QAM tradicionales. Además, se ha propuesto un algoritmo que se basa en la optimización para diferentes niveles de cuantización, para una NUC concreta. Igualmente, se ha investigado en detalle el uso de NUCs en MIMO. Se ha incluido la optimización en una sola o en dos antenas, el uso de un desbalance de potencia, factores de discriminación entre antenas receptoras (XPD), o el uso de distintos demappers. Asumiendo distintos valores, se han obtenido nuevas constelaciones multi-antena (MA-NUC) gracias a un nuevo proceso de re-optimización específico para MIMO. En el receptor, se ha extendido el análisis de complejidad en el demapper, la cual se incrementa enormemente con el uso de 2D-NUCs y sistemas MIMO. Como alternativa, se propone una solución basada en el algoritmo Soft-Fixed Sphere Decoding (SFSD). El principal problema es que estos demappers no funcionan con 2D-NUCs, puesto que necesitan de un paso adicional en el que las componentes I y Q necesitan separarse. El método propuesto cuantifica el símbolo más cercano utilizando las regiones de Voronoi, permitiendo el uso de este tipo de receptor.
Actualment, el mercat de la televisió digital terrestre (TDT) està caracteritzat per l'alta capacitat requerida per a transmetre servicis de televisió d'alta definició i l'espectre disponible. És necessari per tant un ús eficient de l'espectre radioelèctric, el qual requereix noves tecnologies per a garantir majors capacitats i millors servicis. Les constel·lacions no-uniformes (NUC) emergeixen com una de les tècniques més innovadores en els sistemes de televisió de següent generació per a abordar tals requeriments. Les NUC redueixen l'espai existent entre les constel·lacions uniformes QAM i el límit teòric de Shannon. Amb estes constel·lacions, els símbols s'optimitzen en ambdós components fase (I) i quadratura (Q) per mitjà de tècniques geomètriques de modelatge del senyal, considerant un nivell senyal a soroll (SNR) concret i un model de canal específic. Hi ha dos tipus de NUC, unidimensionals i bidimensionals (1D-NUC i 2D-NUC, respectivament). 1D-NUCs mantenen la forma quadrada de les QAM, però permet canviar la distribució entre els símbols en una component concreta, tenint una distància no uniforme entre ells. Estes constel·lacions proporcionen un millor rendiment SNR que QAM, sense cap increment en la complexitat al demapper. 2D-NUC també canvien la forma quadrada de la constel·lació, permetent optimitzar els símbols en ambdós dimensions i per tant obtenint majors guanys en capacitat i menors requeriments en SNR. No obstant això, l'ús de 2D-NUCs implica una major complexitat en el receptor, ja que es necessita un demapper 2D, on les components I i Q no poden ser separades. En esta tesi s'analitzen les NUC des del punt de vista tant de transmissió com de recepció, utilitzant bé configuracions amb una antena (SISO) o amb múltiples antenes (MIMO). En transmissions SISO, s'han optimitzat 1D-NUCs, per a un rang ampli de distintes SNR i diferents ordes de constel·lació. També s'ha investigat l'optimització de 2D-NUCs rotades. Encara que la complexitat no augmenta, el guany SNR d'estes constel·lacions no és significativa. El major guany per rotació s'obté per a baixos ordes de constel·lació i altes SNR. No obstant això, utilitzant tècniques multi-RF, el guany augmenta dràsticament ja que les components I i Q es transmeten en distints canals RF. En esta tesi, s'ha estudiat el guany multi-RF de les NUC, amb o sense rotació. En el receptor, s'han identificat dos colls de botella diferents en la implementació. Primer, s'ha analitzat la complexitat en el receptor per a totes les constel·lacions considerades i, posteriorment, es proposen dos algoritmes per a reduir la complexitat amb 2D-NUCs. Ambdós algoritmes redueixen dràsticament el nombre de distàncies. A més, els dos poden combinar-se en un únic demapper. També s'ha explorat la quantització d'estes constel·lacions, ja que tant els valors LLR com les components I/Q es veuen modificats, comparant amb constel·lacions QAM tradicionals. A més, s'ha proposat un algoritme que es basa en l'optimització per a diferents nivells de quantització, per a una NUC concreta. Igualment, s'ha investigat en detall l'ús de NUCs en MIMO. S'ha inclòs l'optimització en una sola o en dos antenes, l'ús d'un desbalanç de potència, factors de discriminació entre antenes receptores (XPD), o l'ús de distints demappers. Assumint distints valors, s'han obtingut noves constel·lacions multi-antena (MA-NUC) gràcies a un nou procés de re-optimització específic per a MIMO. En el receptor, s'ha modificat l'anàlisi de complexitat al demapper, la qual s'incrementa enormement amb l'ús de 2D-NUCs i sistemes MIMO. Com a alternativa, es proposa una solució basada en l'algoritme Soft-Fixed Sphere Decoding (SFSD) . El principal problema és que estos demappers no funcionen amb 2D-NUCs, ja que necessiten d'un pas addicional en què les components I i Q necessiten separar-se. El mètode proposat quantifica el símbol més pròxim utilitzan
Fuentes Muela, M. (2017). Non-Uniform Constellations for Next-Generation Digital Terrestrial Broadcast Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84743
TESIS

Optimising the throughput performance for wireless networks is one of the challenging tasks in the objectives of communication engineering, since wireless channels are prone to errors due to path losses, random noise, and fading phenomena. The transmission errors will be worse in a multihop scenario due to its accumulative effects. Network Coding (NC) is an elegant technique to improve the throughput performance of a communication network. There is the fact that the bit error rates over one modulation symbol of 16- and higher order- Quadrature Amplitude Modulation (QAM) scheme follow a certain pattern. The Scattered Random Network Coding (SRNC) system was proposed in the literature to exploit the error pattern of 16-QAM by using bit-scattering to improve the throughput of multihop network to which is being applied the Random Linear Network Coding (RLNC). This thesis aims to improve further the SRNC system by using Forward Error Correction (FEC) code; the proposed system is called Joint RLNC and FEC with interleaving. The first proposed system (System-I) uses Convolutional Code (CC) FEC. The performances analysis of System-I with various CC rates of 1/2, 1/3, 1/4, 1/6, and 1/8 was carried out using the developed simulation tools in MATLAB and compared to two benchmark systems: SRNC system (System-II) and RLNC system (System- III). The second proposed system (System-IV) uses Reed-Solomon (RS) FEC code. Performance evaluation of System IV was carried out and compared to three systems; System-I with 1/2 CC rate, System-II, and System-III. All simulations were carried out over three possible channel environments: 1) AWGN channel, 2) a Rayleigh fading channel, and 3) a Rician fading channel, where both fading channels are in series with the AWGN channel. The simulation results show that the proposed system improves the SRNC system. How much improvement gain can be achieved depends on the FEC type used and the channel environment.

[EN] Multiple-Input Multiple-Output (MIMO) technology in Digital Terrestrial Television (DTT) networks has the potential to increase the spectral efficiency and improve network coverage to cope with the competition of limited spectrum use (e.g., assignment of digital dividend and spectrum demands of mobile broadband), the appearance of new high data rate services (e.g., ultra-high definition TV - UHDTV), and the ubiquity of the content (e.g., fixed, portable, and mobile). It is widely recognised that MIMO can provide multiple benefits such as additional receive power due to array gain, higher resilience against signal outages due to spatial diversity, and higher data rates due to the spatial multiplexing gain of the MIMO channel. These benefits can be achieved without additional transmit power nor additional bandwidth, but normally come at the expense of a higher system complexity at the transmitter and receiver ends. The final system performance gains due to the use of MIMO directly depend on physical characteristics of the propagation environment such as spatial correlation, antenna orientation, and/or power imbalances experienced at the transmit aerials. Additionally, due to complexity constraints and finite-precision arithmetic at the receivers, it is crucial for the overall system performance to carefully design specific signal processing algorithms. This dissertation focuses on transmit and received signal processing for DTT systems using MIMO-BICM (Bit-Interleaved Coded Modulation) without feedback channel to the transmitter from the receiver terminals. At the transmitter side, this thesis presents investigations on MIMO precoding in DTT systems to overcome system degradations due to different channel conditions. At the receiver side, the focus is given on design and evaluation of practical MIMO-BICM receivers based on quantized information and its impact in both the in-chip memory size and system performance. These investigations are carried within the standardization process of DVB-NGH (Digital Video Broadcasting - Next Generation Handheld) the handheld evolution of DVB-T2 (Terrestrial - Second Generation), and ATSC 3.0 (Advanced Television Systems Committee - Third Generation), which incorporate MIMO-BICM as key technology to overcome the Shannon limit of single antenna communications. Nonetheless, this dissertation employs a generic approach in the design, analysis and evaluations, hence, the results and ideas can be applied to other wireless broadcast communication systems using MIMO-BICM.
[ES] La tecnología de múltiples entradas y múltiples salidas (MIMO) en redes de Televisión Digital Terrestre (TDT) tiene el potencial de incrementar la eficiencia espectral y mejorar la cobertura de red para afrontar las demandas de uso del escaso espectro electromagnético (e.g., designación del dividendo digital y la demanda de espectro por parte de las redes de comunicaciones móviles), la aparición de nuevos contenidos de alta tasa de datos (e.g., ultra-high definition TV - UHDTV) y la ubicuidad del contenido (e.g., fijo, portable y móvil). Es ampliamente reconocido que MIMO puede proporcionar múltiples beneficios como: potencia recibida adicional gracias a las ganancias de array, mayor robustez contra desvanecimientos de la señal gracias a la diversidad espacial y mayores tasas de transmisión gracias a la ganancia por multiplexado del canal MIMO. Estos beneficios se pueden conseguir sin incrementar la potencia transmitida ni el ancho de banda, pero normalmente se obtienen a expensas de una mayor complejidad del sistema tanto en el transmisor como en el receptor. Las ganancias de rendimiento finales debido al uso de MIMO dependen directamente de las características físicas del entorno de propagación como: la correlación entre los canales espaciales, la orientación de las antenas y/o los desbalances de potencia sufridos en las antenas transmisoras. Adicionalmente, debido a restricciones en la complejidad y aritmética de precisión finita en los receptores, es fundamental para el rendimiento global del sistema un diseño cuidadoso de algoritmos específicos de procesado de señal. Esta tesis doctoral se centra en el procesado de señal, tanto en el transmisor como en el receptor, para sistemas TDT que implementan MIMO-BICM (Bit-Interleaved Coded Modulation) sin canal de retorno hacia el transmisor desde los receptores. En el transmisor esta tesis presenta investigaciones en precoding MIMO en sistemas TDT para superar las degradaciones del sistema debidas a diferentes condiciones del canal. En el receptor se presta especial atención al diseño y evaluación de receptores prácticos MIMO-BICM basados en información cuantificada y a su impacto tanto en la memoria del chip como en el rendimiento del sistema. Estas investigaciones se llevan a cabo en el contexto de estandarización de DVB-NGH (Digital Video Broadcasting - Next Generation Handheld), la evolución portátil de DVB-T2 (Second Generation Terrestrial), y ATSC 3.0 (Advanced Television Systems Commitee - Third Generation) que incorporan MIMO-BICM como clave tecnológica para superar el límite de Shannon para comunicaciones con una única antena. No obstante, esta tesis doctoral emplea un método genérico tanto para el diseño, análisis y evaluación, por lo que los resultados e ideas pueden ser aplicados a otros sistemas de comunicación inalámbricos que empleen MIMO-BICM.
[CAT] La tecnologia de múltiples entrades i múltiples eixides (MIMO) en xarxes de Televisió Digital Terrestre (TDT) té el potencial d'incrementar l'eficiència espectral i millorar la cobertura de xarxa per a afrontar les demandes d'ús de l'escàs espectre electromagnètic (e.g., designació del dividend digital i la demanda d'espectre per part de les xarxes de comunicacions mòbils), l'aparició de nous continguts d'alta taxa de dades (e.g., ultra-high deffinition TV - UHDTV) i la ubiqüitat del contingut (e.g., fix, portàtil i mòbil). És àmpliament reconegut que MIMO pot proporcionar múltiples beneficis com: potència rebuda addicional gràcies als guanys de array, major robustesa contra esvaïments del senyal gràcies a la diversitat espacial i majors taxes de transmissió gràcies al guany per multiplexat del canal MIMO. Aquests beneficis es poden aconseguir sense incrementar la potència transmesa ni l'ample de banda, però normalment s'obtenen a costa d'una major complexitat del sistema tant en el transmissor com en el receptor. Els guanys de rendiment finals a causa de l'ús de MIMO depenen directament de les característiques físiques de l'entorn de propagació com: la correlació entre els canals espacials, l'orientació de les antenes, i/o els desequilibris de potència patits en les antenes transmissores. Addicionalment, a causa de restriccions en la complexitat i aritmètica de precisió finita en els receptors, és fonamental per al rendiment global del sistema un disseny acurat d'algorismes específics de processament de senyal. Aquesta tesi doctoral se centra en el processament de senyal tant en el transmissor com en el receptor per a sistemes TDT que implementen MIMO-BICM (Bit-Interleaved Coded Modulation) sense canal de tornada cap al transmissor des dels receptors. En el transmissor aquesta tesi presenta recerques en precoding MIMO en sistemes TDT per a superar les degradacions del sistema degudes a diferents condicions del canal. En el receptor es presta especial atenció al disseny i avaluació de receptors pràctics MIMO-BICM basats en informació quantificada i al seu impacte tant en la memòria del xip com en el rendiment del sistema. Aquestes recerques es duen a terme en el context d'estandardització de DVB-NGH (Digital Video Broadcasting - Next Generation Handheld), l'evolució portàtil de DVB-T2 (Second Generation Terrestrial), i ATSC 3.0 (Advanced Television Systems Commitee - Third Generation) que incorporen MIMO-BICM com a clau tecnològica per a superar el límit de Shannon per a comunicacions amb una única antena. No obstant açò, aquesta tesi doctoral empra un mètode genèric tant per al disseny, anàlisi i avaluació, per la qual cosa els resultats i idees poden ser aplicats a altres sistemes de comunicació sense fils que empren MIMO-BICM.
Vargas Paredero, DE. (2016). Transmit and Receive Signal Processing for MIMO Terrestrial Broadcast Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/66081
TESIS
Premiado

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California
Bit error rate (BER) and bandwidth efficiency of several variations of enhanced Feher patented quadrature phase shift keying (FQPSK) [1] are described. An enhanced FQPSK increases the channel packing density of that of the IRIG 106-00 standardized FQPSK-B by approximately 50% in adjacent channel interference (ACI) environment. As the bandwidth efficiency of FQPSK-B DOUBLES (2×) that of pulse code modulation/Frequency modulation (PCM/FM) [5], the enhanced FQPSK, with a simpler transceiver than FQPSK-B, has a channel packing density of TRIPLE (3×) that of PCM/FM. One of the other enhanced FQPSK prototypes has an end to end system loss of only 0.4 dB at BER=1x10^(-3) and 0.5 dB at BER=1x10^(-4) from ideal linearly amplified QPSK theory. The enhanced FQPSK has a simple architecture, thus is inexpensive and has small size, for ultra high bit rate implementation. With low redundancy forward error correction (FEC) coding which expands the spectrum by approximately 10%, further improvement of about 3-4.5dB E N b o is attained with NLA FQPSK-B and enhanced FQPSK at BER=1x10^(-5) .

Approved for public release; distribution is unlimited.
Trellis-Coded Modulation (TCM) is employed with quadrature amplitude modulation (QAM) to provide error correction coding with no expense in bandwidth. There are two common implementations of TCM, namely pragmatic TCM and Ungerboeck TCM. Both schemes employ Viterbi algorithms for decoding but have different code construction. This thesis investigates and compares the performance of pragmatic TCM and Ungerboeck TCM by implementing the Viterbi decoding algorithm for both schemes with 16-QAM and 64-QAM. Both pragmatic and Ungerboeck TCM with six memory elements are considered. Simulations were carried out for both pragmatic and Ungerboeck TCM to evaluate their respective performance. The simulations were done using Matlab software, and an additive white Gaussian noise channel was assumed. The objective was to ascertain that pragmatic TCM, with its reduced-complexity decoding, is more suitable to adaptive modulation than Ungerboeck TCM.
Civilian

In this thesis, bandwidth-efficient transmission with bit-interleaved coded modulation (BICM) over fading channels is considered. The main focus of this work is on the design and analysis of iterative decoding schemes employing hard-decision feedback. Although suboptimum by nature, hard-decision feedback allows for low-complexity iterative decoders, which renders this approach advantageous for practical implementations. Two particular 16-ary modulation schemes with their corresponding decoders are considered for bandwidth-efficient transmission. The first scheme is 16-ary quadrature amplitude modulation (16QAM) with coherent iterative decoding (ID), so-called BICM-ID, which relies on (possibly imperfect) channel estimation. We analyze the reliability of the output of the demodulator, which is the inner component decoder in the iterative decoding scheme, and we propose the application of a metric truncation technique to improve the quality of the decision variable and thus the performance of hard-decision feedback iterative decoding. Simulation results for different variants of this metric truncation show notable gains in power efficiency, while decoding complexity is not increased. The second scheme we consider is so-called twisted absolute amplitude and differential phase-shift keying (TADPSK), which allows for iterative decoding without the need for channel estimation. We extend previous work on iterative decision-feedback decoding for TADPSK, so-called iterative decision-feedback differential demodulation (DFDM), and propose a sliding-window DFDM (SWDFDM) module as inner component decoder. Similar to the case of 16QAM, the application of metric truncation yields significant performance improvements also for TADPSK transmission. Finally, we compare 16QAM and TADPSK transmission by means of simulations. Depending on the quality of channel estimation, TADPSK with low-complexity iterative DFDM is shown to outperform 16QAM BICM-ID in some cases.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

碩士
國立清華大學
電機工程學系
102
In this thesis, we investigate bit-interleaved coded dierential amplitude/ phase (APM) schemes for correlated fading channels. For uncoded APM schemes, the design criteria and optimization procedures for table construction and bit labeling search are investigated. For convolutional-coded APM schemes, the design criteria, which aim at improving the performance of error oor region, are proposed for the use of two kinds of interleavers, respectively. On the other hand, low-density parity-check (LDPC)-coded APM schemes are then designed by applying EXIT (extrinsic information transfer )-chart-based code search algorithms. The water-fall region performance of the LDPC-coded scheme can be improved, when comparing to that of the convolutional-coded schemes.

碩士
國立交通大學
電信工程系所
92
Bit-interleaved coded modulation (BICM) is a bandwidth-efficient scheme with a diversity order higher than the Ungerboeck’s trellis-coded modulation over fading channels. In this thesis, we investigate the performance of punctured BICM with soft and hard decoding over additive white Gaussian and Rayleigh fading channels. Tight BER upper bounds are derived for QAM constellation with gray labeling, which is known to have the best performance and constitutes a large portion of the practical applications of BICM systems. Both BICM with random (BICM-RLP) and fixed label position (BICM-FLP) mapping are analyzed. For BICM-RLP with soft decoding, the new upper bound is tighter than the well-known BICM Union and the Expurgated Bound proposed in [4]. The tight upper bounds for hard decision and for BICM-FLP with soft decision are newly derived results.

碩士
國立交通大學
電信工程系所
95
In this thesis, constellation labeling is jointly designed with the outer code by using an EXIT-chart based analysis to improve the performance of bit-interleaved coded modulation with iterative decoding (BICM-ID). A systematic design method is proposed to obtain a set of labelings with good EXIT-chart characteristics for the regular one-dimensional (complex) modulation. Given an outer code, the best matched labeling can be employed to improve the BER performance. Furthermore, the method is extended to the multi-dimensional modulation case, where a group of bits are mapped to a vector of one-dimensional complex symbols. This general mapping strategy allows for more flexibility and potential performance improvements. Verified by the simulation results, our design provides a significant SNR gain over the conventional ones.

In 2008, the European Digital Video Broadcasting (DVB) standardization committee issued the second generation of Digital Video Broadcasting-Terrestrial (DVB-T2) standard in order to enable the wide broadcasting of high definition and 3D TV programmes. DVB-T2 has adopted several new technologies to provide more robust reception compared to the first genaration standard. One important technology is the bit interleaved coded modulation (BICM) with doubled signal space diversity plus the usage of low-density parity check (LDPC) codes. Both techniques can be combined at the receiver side through an iterative process between the decoder and demapper in order to further increase the system performance. The object of my study was to design and prototype a DVB-T2 receiver which supports iterative process. The two main contributions to the demapper design are the proposal of a linear approximation of Euclidean distance computation and the derivation of a sub-region detection algorithm for the two-dimensional demapper. Both contributions allows the computational complexity of the demapper to be reduced for its hardware implementation. In order to enable iterative processing between the demapper and the decoder, we investigated the use of vertical shuffled Min-Sum LDPC decoding algorithm. A novel vertical shuffled iterative structure aiming at reducing the latency of iterative processing and the corresponding architecture of the decoder were proposed. The proposed demapper and decoder have been integrated in a real DVB-T2 demodulator and tested in order to validate the efficiency of the proposed architecture. The prototype of a simplified DVB-T2 transceiver has been implemented, in which the receiver supports both non-iterative process and iterative process. We published the first paper related to a DVB-T2 iterative receiver.

碩士
國立中央大學
通訊工程學系
101
Bit-Interleaved Coded Modulation (BICM) is a suitable channel coding in continuous fading channel. BICM with iterative decoding (BICM-ID) can provide better performance than BICM. But using pilot symbols will cause rate loss, so we add a differential encoder at the transmitter, and try different noncoherent receivers. We use computers to simulate the BICM (or BICM-ID) systems. In this thesis, we try three different metrics which can achieve better error performance than the system which uses pilot symbols. We further adopt iterative decoding at the receiver, and we observe that BICM-ID have better performance than BICM by simulation.

碩士
國立中央大學
通訊工程學系
101
Bit-interleaved coded modulation is a channel code that is suitable for continuous fading channel.To obtain channel state information,the transmitter periodically inserts pilot symbols to offer the receiver the ability to estimate channel amplitude and phase reference.When channel varies faster,the frequency of inserts pilot symbols should be higher,then it causes the rate loss.In this paper,we combine bit-interleaved coded modulation with differential encoding by a look-up table and use 16QAM modulation.At the receiver,we use noncoherent detector to avoid the rate loss.Simulation results show that combined bit-interleaved coded modulation and iterative decoding with differential encoding by a look-up table has better error performance than inserted pilot symbols with coherent detector.

碩士
國立中央大學
通訊工程學系
102
Bit-Interleaved Coded Modulation(BICM)and BICM with iterative decodingare suitable for continuous channel fading channels.BICM using differential encoding in transmitter and noncoherent receiver can avoid the rate loss due to pilot symbol. In this paper, we investigatedifferential encoding for bit interleaved coded of 16APSK. Design new differential encoding and corresponding table to simplify the complexity of differential encoding.Simulation results show that the new encoding has better performance. Try to find a better convolutional code for code rate of 3/4.

碩士
國立中央大學
通訊工程研究所
97
The main goal of the next generation wireless communication systems provides high data rates and high mobile service for the Internet and multimedia applications. Space-time coding was one of the most effective techniques to combat fading and to provide high reliable transmission. A noncoherent space-time code named unitary space-time modulation(USTM) in which the transmit and the receive antennas do not know the channel state information; trellis coded USTM for the noncoherent block fading channel can obtain signigicant coding gains; the reviewed scheme proposed a training-based trellis coded noncoherent space-time modulation scheme by properly interleaving space-time signals for the block fading channels. This scheme can enlarge temporal diversity at the price of increased complexity and delay thus can have good performance at high SNR. In this thesis, we propose a scheme of training-based trellis coded noncoherent space-time modulation which has larger diversity gains by training-basing and symbol-interleaving for the block fading channels. We utilize computers to search the best generator matrix which let the proposed scheme have the best BER. Simulation results confirm that our scheme has larger diversity thus has better BER at high SNR than the reviewed scheme.

碩士
國立交通大學
電信工程系所
93
This thesis proposes a coding scheme based on delay processor interleaved multilevel coded modulation (DPI-MCM). Conventional DPI-MCM requires the insertion of redundant pilot bits (usually “0” bits are used) whence decreases the net data throughput. Our scheme gives a better data throughput for it can do without pilot bits. We use a tail-biting-like structure so that the “tail” part of the decoded output obtained in the initial decoding iteration can be used as the pilot bits in the second iteration in a decision-feedback manner. As DPI-MCM can be regarded as a special case of bit-interleaved coded modulation (BICM), we also compare the performance with compatible interleaving depth.