Dissertations / Theses on the topic 'MIMO decoder'
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Krishnan, Praveen G. "Fast sphere decoder for MIMO systems." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/umrthes_09007dcc80318823.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 16, 2007) Includes bibliographical references (p. 38).
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Quesenberry, Joshua Daniel. "Communication Synthesis for MIMO Decoder Matrices." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/51149.
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The design in this work provides an easy and cost-efficient way of performing an FPGA implementation of a specific algorithm through use of a custom hardware design language and communication synthesis. The framework is designed to optimize performance with matrix-type mathematical operations. The largest matrices used in this process are 4x4 matrices. The primary example modeled in this work is MIMO decoding. Making this possible are 16 functional unit containers within the framework, with generalized interfaces, which can hold custom user hardware and IP cores.
This framework, which is controlled by a microsequencer, is centered on a matrix-based memory structure comprised of 64 individual dual-ported memory blocks. The microsequencer uses an instruction word that can control every element of the architecture during a single clock cycle. Routing to and from the memory structure uses an optimized form of a crossbar switch with predefined routing paths supporting any combination of input/output pairs needed by the algorithm.
A goal at the start of the design was to achieve a clock speed of over 100 MHz; a clock speed of 183 MHz has been achieved. This design is capable of performing a 4x4 matrix inversion within 335 clock cycles, or 1,829 ns. The power efficiency of the design is measured at 17.15 MFLOPS/W.
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Mohammed, Karim Ossama. "A MIMO decoder accelerator for next generation wireless communications." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1875366181&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Patel, Vipul Hiralal. "A system on programmable chip approach for MIMO lattice decoder." ScholarWorks@UNO, 2004. http://louisdl.louislibraries.org/u?/NOD,167.
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Thesis (M.S.)--University of New Orleans, 2004.Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Electrical Engineering."--Thesis t.p. Vita. Includes bibliographical references.
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Lim, Melvin Chi Hearn. "Linear Precoder and Decoder Design for the Multiuser MIMO Downlink." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509007.
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Kapfunde, Goodwell. "Near-capacity sphere decoder based detection schemes for MIMO wireless communication systems." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/11350.
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The search for the closest lattice point arises in many communication problems, and is known to be NP-hard. The Maximum Likelihood (ML) Detector is the optimal detector which yields an optimal solution to this problem, but at the expense of high computational complexity. Existing near-optimal methods used to solve the problem are based on the Sphere Decoder (SD), which searches for lattice points confined in a hyper-sphere around the received point. The SD has emerged as a powerful means of finding the solution to the ML detection problem for MIMO systems. However the bottleneck lies in the determination of the initial radius. This thesis is concerned with the detection of transmitted wireless signals in Multiple-Input Multiple-Output (MIMO) digital communication systems as efficiently and effectively as possible. The main objective of this thesis is to design efficient ML detection algorithms for MIMO systems based on the depth-first search (DFS) algorithms whilst taking into account complexity and bit error rate performance requirements for advanced digital communication systems. The increased capacity and improved link reliability of MIMO systems without sacrificing bandwidth efficiency and transmit power will serve as the key motivation behind the study of MIMO detection schemes. The fundamental principles behind MIMO systems are explored in Chapter 2. A generic framework for linear and non-linear tree search based detection schemes is then presented Chapter 3. This paves way for different methods of improving the achievable performance-complexity trade-off for all SD-based detection algorithms. The suboptimal detection schemes, in particular the Minimum Mean Squared Error-Successive Interference Cancellation (MMSE-SIC), will also serve as pre-processing as well as comparison techniques whilst channel capacity approaching Low Density Parity Check (LDPC) codes will be employed to evaluate the performance of the proposed SD. Numerical and simulation results show that non-linear detection schemes yield better performance compared to linear detection schemes, however, at the expense of a slight increase in complexity. The first contribution in this thesis is the design of a near ML-achieving SD algorithm for MIMO digital communication systems that reduces the number of search operations within the sphere-constrained search space at reduced detection complexity in Chapter 4. In this design, the distance between the ML estimate and the received signal is used to control the lower and upper bound radii of the proposed SD to prevent NP-complete problems. The detection method is based on the DFS algorithm and the Successive Interference Cancellation (SIC). The SIC ensures that the effects of dominant signals are effectively removed. Simulation results presented in this thesis show that by employing pre-processing detection schemes, the complexity of the proposed SD can be significantly reduced, though at marginal performance penalty. The second contribution is the determination of the initial sphere radius in Chapter 5. The new initial radius proposed in this thesis is based on the variable parameter α which is commonly based on experience and is chosen to ensure that at least a lattice point exists inside the sphere with high probability. Using the variable parameter α, a new noise covariance matrix which incorporates the number of transmit antennas, the energy of the transmitted symbols and the channel matrix is defined. The new covariance matrix is then incorporated into the EMMSE model to generate an improved EMMSE estimate. The EMMSE radius is finally found by computing the distance between the sphere centre and the improved EMMSE estimate. This distance can be fine-tuned by varying the variable parameter α. The beauty of the proposed method is that it reduces the complexity of the preprocessing step of the EMMSE to that of the Zero-Forcing (ZF) detector without significant performance degradation of the SD, particularly at low Signal-to-Noise Ratios (SNR). More specifically, it will be shown through simulation results that using the EMMSE preprocessing step will substantially improve performance whenever the complexity of the tree search is fixed or upper bounded. The final contribution is the design of the LRAD-MMSE-SIC based SD detection scheme which introduces a trade-off between performance and increased computational complexity in Chapter 6. The Lenstra-Lenstra-Lovasz (LLL) algorithm will be utilised to orthogonalise the channel matrix H to a new near orthogonal channel matrix H ̅.The increased computational complexity introduced by the LLL algorithm will be significantly decreased by employing sorted QR decomposition of the transformed channel H ̅ into a unitary matrix and an upper triangular matrix which retains the property of the channel matrix. The SIC algorithm will ensure that the interference due to dominant signals will be minimised while the LDPC will effectively stop the propagation of errors within the entire system. Through simulations, it will be demonstrated that the proposed detector still approaches the ML performance while requiring much lower complexity compared to the conventional SD.
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Singh, Arun Kumar. "Le compromis Débit-Fiabilité-Complexité dans les systèmes MMO multi-utilisateurs et coopératifs avec décodeurs ML et Lattice." Thesis, Paris, ENST, 2012. http://www.theses.fr/2012ENST0005/document.
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Dans les télécommunications, le débit-fiabilité et la complexité de l’encodage et du décodage (opération à virgule flottante-flops) sont largement reconnus comme représentant des facteurs limitant interdépendants. Pour cette raison, tout tentative de réduire la complexité peut venir au prix d’une dégradation substantielle du taux d’erreurs. Cette thèse traite de l’établissement d’un compromis limite fondamental entre la fiabilité et la complexité dans des systèmes de communications « outage »-limités à entrées et sorties multiples (MIMO), et ses scénarios point-à-point, utilisateurs multiple, bidirectionnels, et aidés de feedback. Nous explorons un large sous-ensemble de la famille des méthodes d’encodage linéaire Lattice, et nous considérons deux familles principales de décodeurs : les décodeurs à maximum de vraisemblance (ML) et les décodeurs Lattice. L‘analyse algorithmique est concentrée sur l’implémentation de ces décodeurs ayant comme limitation une recherche bornée, ce qui inclue une large famille de sphère-décodeurs. En particulier, le travail présenté fournit une analyse à haut rapport Signal-à-Bruit (SNR) de la complexité minimum (flops ou taille de puce électronique) qui permet d’atteindre a) une certaine performance vis-à-vis du compromis diversité-gain de multiplexage et b) une différence tendant vers zéro avec le non-interrompu (optimale) ML décodeur, ou une différence tendant vers zéro comparé à l’implémentation exacte du décodeur (régularisé) Lattice. L’exposant de complexité obtenu décrit la vitesse asymptotique d’accroissement de la complexité, qui est exponentielle en terme du nombre de bits encodésIn telecommunications, rate-reliability and encoding-decoding computational complexity (floating point operations - flops), are widely considered to be limiting and interrelated bottlenecks. For this reason, any attempt to significantly reduce complexity may be at the expense of a substantial degradation in error-performance. Establishing this intertwined relationship constitutes an important research topic of substantial practical interest. This dissertation deals with the question of establishing fundamental rate, reliability and complexity limits in general outage-limited multiple-input multiple-output (MIMO) communications, and its related point-to-point, multiuser, cooperative, two-directional, and feedback-aided scenarios. We explore a large subset of the family of linear lattice encoding methods, and we consider the two main families of decoders; maximum likelihood (ML) based and lattice-based decoding. Algorithmic analysis focuses on the efficient bounded-search implementations of these decoders, including a large family of sphere decoders. Specifically, the presented work provides high signal-to-noise (SNR) analysis of the minimum computational reserves (flops or chip size) that allow for a) a certain performance with respect to the diversity-multiplexing gain tradeoff (DMT) and for b) a vanishing gap to the uninterrupted (optimal) ML decoder or a vanishing gap to the exact implementation of (regularized) lattice decoding. The derived complexity exponent describes the asymptotic rate of exponential increase of complexity, exponential in the number of codeword bits
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Sevelimedu, Veeravalli Vinodh. "Study of MIMO, orthogonal codes and core operator architecture design for ML decoder." Thesis, Linköping University, Department of Electrical Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10155.
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In the high-end research process of wireless systems and in the race for the development of the new technologies, MIMO (Multiple Input, Multiple Output) is getting more attention now days. It has a high potential usage in the 3G and 4G communications and beyond. The MIMO based system has got the ability to increase the data throughput in spectrum-limited conditions. With the increase and complexity of wireless applications, the spectrum efficiency improvement in the physical layer will be saturated. MIMO is predicted to be one of the major features for the next generation wireless networking. This thesis work is a part of an ongoing project of the Generic MIMO decoder design carried out at the research laboratory, LESTER at Lorient, France. I was involved in the study of MIMO concepts, orthogonal and Space-time codes and later involved in the design and optimization of the architecture for the core operator for the ML decoder used in the reception of the MIMO system,which is presented in this report work.
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Correia, Tiago Miguel Pina. "FPGA implementation of Alamouti encoder/decoder for LTE." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12679.
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Mestrado em Engenharia Electrónica e TelecomunicaçõesMotivados por transmissões mais rápidas e mais fiáveis num canal sem fios, os sistemas da 4G devem proporcionar processamento de dados mais rápido a baixa complexidade, elevadas taxas de dados, assim como robustez na performance reduzindo também, a latência e os custos de operação. LTE apresenta, na sua camada física, tecnologias como OFDM e MIMO que prometem alcançar elevadas taxas de dados e aumentar a eficiência espectral. Especificamente a camada física do LTE emprega OFDMA para downlink e SC-FDMA para uplink. A tecnologia MIMO permite também melhorar significativamente o desempenho dos sistemas OFDM com as vantagens de multiplexação e diversidade espacial diminuindo o efeito de desvanecimento de multi-percurso no canal. Nesta dissertação são implementados um codificador e um descodificador com base no algoritimo de Alamouti num sistema MISO nomeadamente para serem incluídos num OFDM transceiver que segue as especificações da camada física do LTE. A codificação/descodificação de Alamouti realiza-se no espaço e frequência e os blocos foram projetados e simulados em Matlab através do ambiente Simulink com o auxílio dos blocos da Xilinx inseridos no seu software System Generator para DSP. Pode-se concluir que os blocos baseados no algoritmo de Alamouti foram implementados em hardware com sucesso.
Motivated by faster transmissions and more reliable wireless channel, future 4G systems should provide faster data processing at low complexity, high data rates, as well as robustness in performance while also reducing the latency and operating costs. LTE presents in its physical layer technologies such as OFDM and MIMO that promise to achieve high data rates and increase spectral efficiency. Specifically the physical layer of LTE employs OFDMA on the downlink and SC-FDMA for uplink. MIMO technology also allows to significantly improve the performance of OFDM systems with the advantages of multiplexing and spatial diversity by decreasing the effect of multipath fading in the channel. In this thesis we implemented an encoder and a decoder based on an Alamouti algorithm in a MISO system namely to be added to an OFDM transceiver that follows closely the LTE physical layer specifications. Alamouti coding/decoding is performed in frequency and space and the blocks were projected and simulated in Matlab using Simulink environment through the Xilink's blocks in the System Generator for DSP. One can conclude that the blocks based on Alamouti algorithm were well-implemented.
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El, chall Rida. "Récepteur itératif pour les systèmes MIMO-OFDM basé sur le décodage sphérique : convergence, performance et complexité." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0019/document.
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Pour permettre l’accroissement de débit et de robustesse dans les futurs systèmes de communication sans fil, les processus itératifs sont de plus considérés dans les récepteurs. Cependant, l’adoption d’un traitement itératif pose des défis importants dans la conception du récepteur. Dans cette thèse, un récepteur itératif combinant les techniques de détection multi-antennes avec le décodage de canal est étudié. Trois aspects sont considérés dans un contexte MIMOOFDM: la convergence, la performance et la complexité du récepteur. Dans un premier temps, nous étudions les différents algorithmes de détection MIMO à décision dure et souple basés sur l’égalisation, le décodage sphérique, le décodage K-Best et l’annulation d’interférence. Un décodeur K-best de faible complexité (LC-K-Best) est proposé pour réduire la complexité sans dégradation significative des performances. Nous analysons ensuite la convergence de la combinaison de ces algorithmes de détection avec différentes techniques de codage de canal, notamment le décodeur turbo et le décodeur LDPC en utilisant le diagramme EXIT. En se basant sur cette analyse, un nouvel ordonnancement des itérations internes et externes nécessaires est proposé. Les performances du récepteur ainsi proposé sont évaluées dans différents modèles de canal LTE, et comparées avec différentes techniques de détection MIMO. Ensuite, la complexité des récepteurs itératifs avec différentes techniques de codage de canal est étudiée et comparée pour différents modulations et rendement de code. Les résultats de simulation montrent que les approches proposées offrent un bon compromis entre performance et complexité. D’un point de vue implémentation, la représentation en virgule fixe est généralement utilisée afin de réduire les coûts en termes de surface, de consommation d’énergie et de temps d’exécution. Nous présentons ainsi une représentation en virgule fixe du récepteur itératif proposé basé sur le décodeur LC K-Best. En outre, nous étudions l’impact de l’estimation de canal sur la performance du système. Finalement, le récepteur MIMOOFDM itératif est testé sur la plateforme matérielle WARP, validant le schéma proposéRecently, iterative processing has been widely considered to achieve near-capacity performance and reliable high data rate transmission, for future wireless communication systems. However, such an iterative processing poses significant challenges for efficient receiver design. In this thesis, iterative receiver combining multiple-input multiple-output (MIMO) detection with channel decoding is investigated for high data rate transmission. The convergence, the performance and the computational complexity of the iterative receiver for MIMO-OFDM system are considered. First, we review the most relevant hard-output and soft-output MIMO detection algorithms based on sphere decoding, K-Best decoding, and interference cancellation. Consequently, a low-complexity K-best (LCK- Best) based decoder is proposed in order to substantially reduce the computational complexity without significant performance degradation. We then analyze the convergence behaviors of combining these detection algorithms with various forward error correction codes, namely LTE turbo decoder and LDPC decoder with the help of Extrinsic Information Transfer (EXIT) charts. Based on this analysis, a new scheduling order of the required inner and outer iterations is suggested. The performance of the proposed receiver is evaluated in various LTE channel environments, and compared with other MIMO detection schemes. Secondly, the computational complexity of the iterative receiver with different channel coding techniques is evaluated and compared for different modulation orders and coding rates. Simulation results show that our proposed approaches achieve near optimal performance but more importantly it can substantially reduce the computational complexity of the system. From a practical point of view, fixed-point representation is usually used in order to reduce the hardware costs in terms of area, power consumption and execution time. Therefore, we present efficient fixed point arithmetic of the proposed iterative receiver based on LC-KBest decoder. Additionally, the impact of the channel estimation on the system performance is studied. The proposed iterative receiver is tested in a real-time environment using the MIMO WARP platform
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Jaldén, Joakim. "Detection for multiple input multiple output channels : analysis of sphere decoding and semidefinite relaxation." Doctoral thesis, KTH, Signalbehandling, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4199.
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The problem of detecting a vector of symbols, drawn from a finite alphabet and transmitted over a multiple-input multiple-output (MIMO) channel with Gaussian noise, is of central importance in digital communications and is encountered in several different applications. Examples include, but are not limited to; detection of symbols spatially multiplexed over a multiple-antenna channel and the multiuser detection problem in a code division multiple access (CDMA) system. Two algorithms previously proposed in the literature are considered and analyzed. Both algorithms have their origin in other fields of science but have gained mainstream recognition as efficient algorithms for the detection problem considered herein. Specifically, we consider the sphere decoder and semidefinite relaxation detector. By incorporating assumptions applicable in the communications context the performance of the two algorithms is addressed. The first algorithm, the sphere decoder, offers optimal performance in terms of its error probability. Further, the algorithm has proved extremely efficient in terms of computational complexity for moderately sized problems at high signal to noise ratio (SNR). Although it is recognized that the algorithm has an exponential worst case complexity, there has been a widespread belief that the algorithm has a polynomial average complexity at high SNR. A contribution made herein is to show that this is incorrect and that the average complexity, as the worst case complexity, is exponential in the number of symbols detected. Instead, another explanation of the observed efficiency of the algorithm is offered by deriving the exponential rate of growth and showing that this rate, although strictly positive for finite SNR, is small in the high SNR regime. The second algorithm, the semidefinite relaxation (SDR) detector, offers polynomial complexity at the expense of suboptimal performance in terms of error probability. Nevertheless, previous numerical observations suggest that error probability of the SDR algorithm is close to that of the optimal detector. Herein, the near optimality is of the SDR algorithm is given a precise meaning by studying the diversity of the SDR algorithm when applied to the (real valued) i.i.d.~Rayleigh fading channel and it is shown that the SDR algorithm achieves the same diversity order as the optimal detector. Further, criteria under which the SDR estimates coincide with the optimal estimates are derived and discussed.Ett grundläggande problem som påträffats inom digital kommunikation är detektering av en symbolvektor, tillhörande ett ändligt symbolalfabet, som sänts över en MIMO (från engelskans multiple-input multiple-output) kanal med Gausiskt brus. Detta problem påträffas bland annat då symboler sänts över en trådlös kanal med flera antenner hos mottagaren och sändaren samt då flera användare i ett CDMA system simultant skall avkodas. In denna avhandling behandlas två mottagaralgoritmer konstruerade för detta ändamål. Algoritmerna har sin bakgrund i andra forskningsområden men kan i nuläget sägas vara mycket välkända inom kommunikationsområdet. De benämns vanligtvis som sfäravkodaren (eng. sphere decoder) samt den semidefinita relaxeringsdetektorn (eng. semidefinite relaxation detector). Algoritmerna analyseras i denna avhandling matematiskt genom att införa förenklande antaganden som är relevanta och applicerbara för de kommunikationsproblem som är av intesse. Den första algoritmen, sfäravkodaren, löser dessa detektionsproblem på ett optimalt sätt i betydelsen att den minimerar sannolikheten för att detektorn fattar ett felaktigt beslut rörande det sända meddelandet (symbolvektorn). Också vad gäller algoritmens komplexitet har simuleringar visat att den är oväntat låg, åtminstone vid höga signalbrusförhållanden (SNR). Trots att det är allmänt känt att algoritmen i sämsta fall har exponentiell komplexitet så har detta lett till den allmänt spridda uppfattningen att medelkomplexiteten (eller den förväntade komplexiteten) endast är polynomisk vid höga signalbrusförhållanden. Ett av huvudbidragen i denna avhandling är att visa att denna uppfattning är felaktig och att också medelkomplexiteten växer exponentiellt i antalet symboler som simultant detekteras. Ytterligare ett bidrag ligger i att ge en alternativ förklaring till den observerat låga medelkomplexiteten. Det visas att den exponentiella hastighet med vilken komplexiteten växer beror på signalbrusförhållande, och att den är låg för höga SNR. Den andra algoritmen, den semidefinita relaxeringsdetektorn, erbjuder polynomisk komplexitet vid en något högre felsannolikhet. Intressant nog har dock felsannolikheten tidigare, genom simuleringar, visat sig vara endast marginellt högre än felsannolikheten hos den optimala mottagaren. Bidraget som relaterar till den semidefinita relaxeringsmottagaren ligger i att både förklara och i att ge en specifik kvatifierbar mening åt uttalandet att felsannolikheten endast är marginellt högre. I syfte att åstadkomma detta studeras diversitetsordningen för detektorn, och det bevisas att diversitetsordningen för den semidefinita relaxeringsdetektorn är densamma som för den optimala mottagaren. Utöver detta karakteriseras också de krav som måste uppfyllas för att den detektorn skall finna den optimala lösningen.
QC 20100901
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Palanivelu, Arul Durai Murugan. "Tree search algorithms for joint detection and decoding." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1145039374.
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Barbero, Liñan Luis G. "Rapid prototyping of a fixed-complexity sphere decoder and its application to iterative decoding of turbo-MIMO systems." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/11903.
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This thesis concentrates on the analysis of the sphere decoder (SD) for MIMO detection. It provides optimal maximum likelihood (ML) performance with reduced complexity compared to the maximum likelihood detector (MLD). However, a field-programmable gate array (FPGA) implementation of the algorithm presents several disadvantages due to its variable complexity and the sequential nature of its tree search. This research proposes a fixed-complexity sphere decoder (FSD) to overcome the drawbacks of the SD. It provides a fixed complexity and achieves quasi-maximum likelihood (ML) performance, combining a search through a small subset of the transmitted constellation with a novel channel matrix ordering. This represents a novel approach compared to most optimizations of the SD in the literature, which concentrate on reducing the average complexity of the algorithm. As a result, an implementation of the FSD is shown to provide the same error performance using less FPGA resources and achieving a considerably higher (and constant) throughput compared to previous SD hardware implementations. The same FSD concept is applied to a large MIMO system with 4 antennas at both ends of the link and 64-quadrature amplitude modulation (QAM). A list extension of the FSD (LFSD) combines the same channel matrix ordering and an extended fixed search to generate a list of candidates for short-value calculation. Depending on the size of the extended search, different levels of performance and complexity can be achieved making the algorithm suitable for reconfigurable architectures. Its FPGA implementation shows how soft-value information can be obtained with a fully pipelined architecture. It provides a constant throughput which is considerably higher than previously presented soft-MIMO detector implementations.
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Younis, Abdelhamid. "Spatial modulation : theory to practice." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8990.
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Spatial modulation (SM) is a transmission technique proposed for multiple–input multiple– output (MIMO) systems, where only one transmit antenna is active at a time, offering an increase in the spectral efficiency equal to the base–two logarithm of the number of transmit antennas. The activation of only one antenna at each time instance enhances the average bit error ratio (ABER) as inter–channel interference (ICI) is avoided, and reduces hardware complexity, algorithmic complexity and power consumption. Thus, SM is an ideal candidate for large scale MIMO (tens and hundreds of antennas). The analytical ABER performance of SM is studied and different frameworks are proposed in other works. However, these frameworks have various limitations. Therefore, a closed–form analytical bound for the ABER performance of SM over correlated and uncorrelated, Rayleigh, Rician and Nakagami–m channels is proposed in this work. Furthermore, in spite of the low–complexity implementation of SM, there is still potential for further reductions, by limiting the number of possible combinations by exploiting the sphere decoder (SD) principle. However, existing SD algorithms do not consider the basic and fundamental principle of SM, that at any given time, only one antenna is active. Therefore, two modified SD algorithms tailored to SM are proposed. It is shown that the proposed sphere decoder algorithms offer an optimal performance, with a significant reduction of the computational complexity. Finally, the logarithmic increase in spectral efficiency offered by SM and the requirement that the number of antennas must be a power of two would require a large number of antennas. To overcome this limitation, two new MIMO modulation systems generalised spatial modulation (GNSM) and variable generalised spatial modulation (VGSM) are proposed, where the same symbol is transmitted simultaneously from more than one transmit antenna at a time. Transmitting the same data symbol from more than one antenna reduces the number of transmit antennas needed and retains the key advantages of SM. In initial development simple channel models can be used, however, as the system develops it should be tested on more realistic channels, which include the interactions between the environment and antennas. Therefore, a full analysis of the ABER performance of SM over urban channel measurements is carried out. The results using the urban measured channels confirm the theoretical work done in the field of SM. Finally, for the first time, the performance of SM is tested in a practical testbed, whereby the SM principle is validated.
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Aubert, Sébastien. "Advanced Techniques for Achieving Near Maximum-Likelihood Soft Detection in MIMO-OFDM Systems and Implementation Aspects for LTE/LTE-A." Phd thesis, INSA de Rennes, 2011. http://tel.archives-ouvertes.fr/tel-00730797.
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Cette thèse traite des systèmes MIMO à multiplexage spatial, associés à la modulation OFDM. L'étude s'attarde particulièrement sur les systèmes 4x4, inclus ou à l'étude dans les normes 3GPP LTE et 3GPP LTE-A. Ces dimensions particulières nécessitent une étude de conception poussée du récepteur. Il s'agit notamment de proposer des détecteurs qui affichent à la fois de bonnes performances, une faible latence et une complexité de calcul réalisable dans un système embarqué. Le défi consiste plus particulièrement à proposer un détecteur offrant des performances quasi-optimales, tout en ne nécessitant qu'une complexité de calcul polynomiale. Une attention particulière est prêtée aux problèmes d'implantation. Ainsi, avantage est donné aux algorithmes à complexité fixe et permettant la réalisation d'opérations en parallèle. En réponse aux problématiques rencontrées, l'architecture du détecteur requiert une attention particulière. Le choix stratégique adopté est de chercher à transférer au prétraitement - qui ne dépend pas des données - le plus possible de complexité de calcul. Au cours de ce travail et suite à l'introduction du contexte général et des principaux pré-requis, l'inventaire des grandes tendances dans la littérature en ce qui concerne les détecteurs à décision dure est fait. Ils constituent le coeur du sujet et un détecteur original est proposé, incluant notamment les aspects de réduction de réseau et de décodage sphérique. Son avantage par rapport aux techniques existantes est ainsi démontré, et les résultats prometteurs sont maintenus lors de son extension à la décision souple. Comme attendu, le choix de transférer au prétraitement la complexité de calcul s'avère gagnant. Notamment, la réduction de complexité de calcul qu'il permet est présentée dans cette thèse. Parmi les principaux résultats, ce travail a débouché sur la proposition d'un détecteur original, qui a démontré un compromis entre performance et complexité de calcul efficace. Notamment, il requiert une complexité de calcul presque constante - selon les tailles de constellation -, tout en offrant des performances proches du maximum de vraisemblance. Par conséquent, le détecteur à décision souple proposé se positionne par rapport à l'état de l'art comme une solution d'une grande efficacité dans les systèmes 4x4.
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XIAO, GUOPING. "VLSI architectures design for encoders of High Efficiency Video Coding (HEVC) standard." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2644058.
Full textAbstract:
The growing popularity of high resolution video and the continuously increasing demands for high quality video on mobile devices are producing stronger needs for more efficient video encoder. Concerning these desires, HEVC, a newest video coding standard, has been developed by a joint team formed by ISO/IEO MPEG and ITU/T VCEG. Its design goal is to achieve a 50% compression gain over its predecessor H.264 with an equal or even higher perceptual video quality. Motion Estimation (ME) being as one of the most critical module in video coding contributes almost 50%-70% of computational complexity in the video encoder. This high consumption of the computational resources puts a limit on the performance of encoders, especially for full HD or ultra HD videos, in terms of coding speed, bit-rate and video quality. Thus the major part of this work concentrates on the computational complexity reduction and improvement of timing performance of motion estimation algorithms for HEVC standard.
First, a new strategy to calculate the SAD (Sum of Absolute Difference) for motion estimation is designed based on the statistics on property of pixel data of video sequences. This statistics demonstrates the size relationship between the sum of two sets of pixels has a determined connection with the distribution of the size relationship between individual pixels from the two sets. Taking the advantage of this observation, only a small proportion of pixels is necessary to be involved in the SAD calculation. Simulations show that the amount of computations required in the full search algorithm is reduced by about 58% on average and up to 70% in the best case.
Secondly, from the scope of parallelization an enhanced TZ search for HEVC is proposed using novel schemes of multiple MVPs (motion vector predictor) and shared MVP. Specifically, resorting to multiple MVPs the initial search process is performed in parallel at multiple search centers, and the ME processing engine for PUs within one CU are parallelized based on the MVP sharing scheme on CU (coding unit) level. Moreover, the SAD module for ME engine is also parallelly implemented for PU size of 32×32. Experiments indicate it achieves an appreciable improvement on the throughput and coding efficiency of the HEVC video encoder.
In addition, the other part of this thesis is contributed to the VLSI architecture design for finding the first W maximum/minimum values targeting towards high speed and low hardware cost. The architecture based on the novel bit-wise AND scheme has only half of the area of the best reference solution and its critical path delay is comparable with other implementations. While the FPCG (full parallel comparison grid) architecture, which utilizes the optimized comparator-based structure, achieves 3.6 times faster on average on the speed and even 5.2 times faster at best comparing with the reference architectures. Finally the architecture using the partial sorting strategy reaches a good balance on the timing performance and area, which has a slightly lower or comparable speed with FPCG architecture and a acceptable hardware cost.
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HICKS, CHRISTOPHER D. "PERFORMANCE ANALYSIS OF MIMO LINEAR PRECODERS/DECODERS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154397576.
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Varadarajan, Badri. "The Design of Linear Space-Time Codes for Quasi-static Flat-fading Channels." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5030.
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The reliability and data rate of wireless communication have traditionally been limited by the presence of multipath fading in wireless channels. However, dramatic performance improvements can be obtained by the use of multiple transmit and receive antennas. Specifically, multiple antennas increase reliability by providing diversity gain, namely greater immunity to deep channel fades. They also increase data rates by providing multiplexing gain, i.e., the ability to multiplex multiple symbols in one signaling interval.
Harvesting the potential benefits of multiple antennas requires the use of specially designed space-time codes at the transmitter front-end. Space-time codes introduce redundancy in the transmitted signal across two dimensions, namely multiple transmit antennas and multiple signaling intervals. In this work, we focus on linear space-time codes, which linearly combine the real and imaginary parts of their complex inputs to obtain transmit vectors for multiple signaling intervals.
We aim to design optimum linear space-time codes. Optimality metrics and design principles for space-time codes are shown to depend strongly on the codes' function in the overall transmitter architecture. We consider two cases, depending on whether or not the space-time code is complemented by a powerful outer error-control code.
In the absence of an outer code, the multiplexing gain of a space-time code is measured by its rate, while its diversity gain is measured by its raw diversity order. To maximize multiplexing and diversity gains, the space-time code must have maximum possible rate and raw diversity order. We show that there is an infinite set of maximum-rate codes, almost all of which also have maximum raw diversity order. However, different codes in this set have different error rate for a given input alphabet and SNR. Therefore, we develop analytical and numerical optimization techniques to find the code in this set which has the minimum union bound on error rate. Simulation results indicate that optimized codes yield significantly lower error rates than unoptimized codes, at the same data rate and SNR.
In a concatenated architecture, a powerful outer code introduces redundancy in the space-time code inputs, obtaining additional diversity. Thus, the raw diversity order of the space-time inner code is only a lower limit to the total diversity order of the concatenated transmitter. On the other hand, we show that the rate of the space-time code places an upper limit on the multiplexing ability of the concatenated architecture. We conclude that space-time inner codes should have maximum possible rate but need not have high raw diversity order. In particular, the serial-to-parallel converter, which introduces no redundancy at all, is a near-optimum space-time inner code. This claim is supported by simulation results.
On the receiver side, we generalize the well known sphere decoder to develop new detection algorithms for stand-alone space-time codes. These new algorithms are extended to obtain efficient soft-output decoding algorithms for space-time inner codes.
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Liang, Ying, and 梁瑩. "A study on low complexity near-maximum likelihood spherical MIMO decoders." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43703987.
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Liang, Ying. "A study on low complexity near-maximum likelihood spherical MIMO decoders." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43703987.
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Liang, Cao. "Hardware/Software Co-Design Architecture and Implementations of MIMO Decoders on FPGA." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/416.
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During the last years, multiple-input multiple-output (MIMO) technology has attracted great attentions in the area of wireless communications. The hardware implementation of MIMO decoders becomes a challenging task as the complexity of the MIMO system increases. This thesis presents hardware/software co-design architecture and implementations of two typical lattice decoding algorithms, including Agrell and Vardy (AV) algorithm and Viterbo and Boutros (VB) algorithm. Three levels of parallelisms are analyzed for an efficient implementation with the preprocessing part on embedded MicroBlaze soft processor and the decoding part on customized hardware. The decoders for a 4 by 4 MIMO system with 16-QAM modulation scheme are prototyped on a Xilinx XC2VP30 FPGA device. The hardware implementations of the AV and VB decoders show that they support up to 81 Mbps and 37 Mbps data rate respectively. The performances in terms of resource utilizations and BER are also compared between these two decoders.
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Jin, Jie. "Low power design for high performance wireless digital baseband building blocks /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20JIN.
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Azarian, Yazdi Kambiz. "Outage limited cooperative channels protocols and analysis /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1154740723.
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Liao, Yen-Chin, and 廖彥欽. "Research on Sphere/LDPC Decoder for Coded-MIMO Systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/10789537397358749203.
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博士國立交通大學
電子工程系所
96
This dissertation presents algorithm designs for sphere decoders and low-density parity check (LDPC) code decoders in multi-input multi-output (MIMO) systems from implementation point of view. Based on statistical techniques, complexity reduction schemes are proposed. Sphere decoders of hard-decision outputs and LDPC decoding algorithms in AWGN channel are discussed first. Then the sphere decoders with soft-decision outputs for channel-coded MIMO systems are investigated. Sphere decoding algorithm is one realization of maximum likelihood signal detection for MIMO systems, and the computation can vary with channel due to the fading phenomena. Among several modified algorithms, K-best algorithm is suitable for hardware implementation for the constant computation and predictable hardware complexity. However, K-best algorithm has to be realized with the assumption of worst channel condition in order to maintain the system performance. For complexity reduction, an early pruning scheme combined with K-best algorithm is presented. According to the system model and channel statistics the expected complexity can be analyzed as well. Based on the complexity analysis, an early-pruned multi-K-best algorithm is proposed by which the lowest decoding speed can be further improved. The simulation results in 64-QAM 4 × 4 MIMO channel show that 90% complexity can be reduced with imperceptible degradation in both symbol error rate and bit error rate above 10−5. For decoding LDPC codes, min-sum algorithm is one common simplification of Log-BP algorithm, but there is a performance gap due to the approximation inaccuracy. Normalization schemes are investigated to compensate the approximation error. Moreover, the normalization factor can be described by a function of the decoder inputs, noise variance, and the decoding iteration number. The data-dependent correction terms can be analyzed and derived by order statistic and density evolution. Simulated in DVB-S2 system, the dynamic normalization schemes effectively mend the SNR loss from Log-BP algorithm to min-sum algorithm with few normalization overheads, and 1.0dB SNR improvement, which is about 95% of the SNR loss from Log-BP to min-sum algorithm, can be achieved. For channel coded MIMO systems, a sphere decoder is modified to a list sphere decoder that generates a candidate list for computing the soft inputs. Under iterative message passing decoding, the candidate list and the soft value generation impact the decoding convergence. Sufficiently large candidate list is required to avoid error floor. Thus, a path augmentation technique is proposed by which a larger and distinct list can be employed in computing the probabilistic information of each received bit. Compared with directly generating a larger list, path augmentation performs comparatively less operations. In our simulation based on a 64-QAM 4×4 MIMO system with LDPC codes defined in IEEE802.11n, the proposed augmented-list sphere decoder based on 64-best algorithm achieves the lowest error floor and saves about 50% computations, if compared to the standard list sphere decoder which is based on 128-best algorithm. Moreover, by the proposed early pruning scheme and multi-K-best algorithm, 94% reduction in sorting complexity can be achieved.
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Hu, Kai-Shiang, and 胡凱翔. "Design of STBC Decoder in MIMO systems for IEEE802.16 standard." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/04596239693248357243.
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碩士雲林科技大學
電機工程系碩士班
96
This thesis is focused on the investigation of the decoder structure of space-time block code (STBC) in a multiple input multiple output (MIMO) system. At the receiver, the received STBC encoded signals are respectively decoded by using two algorithms, namely, the maximum likelihood (ML) decoder and the least-square zero-forcing (LS-ZF) decoder. The decoding efficiency and hardware complexity for both algorithms are presented. We have found from the simulation results that the performance of an ML decoder is about 4 dB better than that of an LS-ZF decoder. To compare the hardware complexity of the two decoders, we first use Matlab to determine the optimum bit-lengths representing the fractional parts of received data. The results of fixed-point simulation show that the LS-ZF and the ML decoders need 8 bits and 5 bits, respectively. Subsequently, verilog HDL is used to perform the structural design of the circuit over a Modelsim platform. Simulation results demonstrate that the ML decoder outperforms the LS-ZF decoder by about 4 dB. The numbers of logic gates required to build the STBC decoders for the ML and the LS-ZF decoders are 11509 and 9801, respectively. That is, the complexity of an ML decoder is only about 1.17 times of that of an LS-ZF decoder.
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Cheng, Yong-Lin, and 鄭詠霖. "Efficient Design of Soft-Ouput Decoder for MIMO-OFDM Systems." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/61839920873329275460.
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碩士國立中興大學
電機工程學系所
103
As the development of communication technology, demands of high data rates of wireless communications grow rapidly. The multiple antenna system plays an important role. The reason is that channel capacity increases linearly with the minimum number of antennas. Therefore, it has the advantage over the single input single output (SISO) system in terms of high data transmission rates. However, interference between multiple antennas needs to be overcome. In addition, low density parity check (LDPC) codec is added because it can approach the Shannon Limit and helps reduce power consumption in transmission, as well as enhance error correction capability. In this thesis, integration and implementation of multiple input multiple output (MIMO) with LDPC codec systems are performed. They include several parts: theories of MIMO-OFDM and LDPC codec, algorithms of signal detection and circuit design, log-likelihood ratio (LLR) demodulator circuit design, additive white Gaussian noise (AWGN) generator circuit design, integration and design of MIMO-LDPC system. The signal detector was implemented by the K-Best algorithm, which combines the properties of both breadth-first and depth-first algorithms with constant throughput. In comparison with the conventional K-Best, this algorithm using enumeration circuit to obtain the estimated transmitted symbol results in less symbol numbers to expand the best K paths, while the performance is still excellent. For the LLR demodulator, instead of the conventional LLR calculation using partial Euclidean distance (PED), the linear approximated LLR algorithm is used in the LDPC decoder. The integration of MIMO detector with LDPC decoder achieves excellent bit error rate (BER) performance. The Matlab simulation shows the fixed point results very close to the floating point results. When EbN0 = 18 dB for 64-QAM modulation with 44 antennas, the BER can be as low as 10-7. Finally, this MIMO Detector was verified using Xilinx Virtex-7 FPGA board successfully.
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Chen, Hsin-Ta, and 陳信達. "A Low Complexity Look-Ahead Sphere Decoder for MIMO Detection." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/12663278057776005265.
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碩士國立中正大學
通訊工程研究所
99
Traditional depth-first sphere decoder is an algorithm which is capable of obtaining the optimal ML solution by using the idea of tree search. The algorithm has much lower complexity compared to the exhaustive search, but requires reverse searching operations, making the overall complexity varying for different channel realizations. For the ease of hardware implementation, K-best algorithm has been proposed. K-best algorithm finds K nodes of relative small cumulative PED(partial Euclidean distance) in each layer and then traverse down to the next layer. Since no reverse search is required, the K-best algorithm has fixed complexity. In this paper, we introduce a new algorithm based on a new lattice representation and make use of a look-ahead technique to reduce both time and computational complexity of the K-best algorithm. Two further improved algorithm, 4-Layer Early Pruned algorithm and 4-Layer Relaxed K-Best have been proposed to reduce the computational complexity. The complexity of the proposed algorithms has been compared both analytically and via computer simulations. Simulation results showed that the proposed algorithms achieve better error rate and also lower computational complexity compared to the K-best algorithm.
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Cheng-Ming, Chen. "A New Reduced-Complexity Sphere Decoder for MIMO Spatial Multiplexing System." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1607200623202900.
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Chen, Cheng-Ming, and 陳楨明. "A New Reduced-Complexity Sphere Decoder for MIMO Spatial Multiplexing System." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/34656840105342549856.
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碩士國立臺灣大學
電信工程學研究所
94
In this thesis we propose an algorithm which combines the Sphere Decoding algorithm (SDA) and the Ordered Successive Interference Cancellation algorithm (OSIC) to reduce the computation time of the SDA. We name it SD-OSIC algorithm. This algorithm has the near-ML (Maximum Likelihood) Performance and needs to search fewer lattice points inside the sphere radius, hence the searching problem are reduced to a lower dimension ones. We also derive the number of multiplication and addition operations of SD-OSIC and conventional SDA. Numerical simulation reveals our proposed algorithm requires less loop iterations than conventional SDA and in some scenario SD-OSIC requires less computation power than the SDA. With the supports of these two comparisons, we conclude our algorithm requires less computation time than the conventional SDA.
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Cheng-ChiehHuang and 黃政傑. "Low-Complexity MIMO Detector Based on the Fixed-Complexity Sphere Decoder." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/56496529955246061661.
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Wang, Chihjung, and 王致融. "Low Complexity Soft-Output Detector for MIMO System with Viterbi Decoder." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/25188115470753682658.
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碩士國立中正大學
通訊工程研究所
99
The multiple-input multiple-output system is able to provide high transmission data rate for wireless communication systems. The baseband MIMO detectors are divided into two categories, the hard-output and soft-output detectors, where the latter one is able to work together with an error control code (ECC) decoder to yield a lower coded BER performance. In the soft-output detector, the soft a posteriori probability (APP) is computed and is to be sent to the following ECC decoder. To provide complete APP information, all possible data must be calculated. This may cause formidable computational complexity. Two well-known low-complexity detectors to provide approximate APP information are the LISt-Sequential detector (LISS) and Layered Orthogonal Lattice Detector (LORD). We consider in this thesis that the following ECC decoder is a soft Viterbi decoder. The input signal to the Viterbi decoder is quantized with different number of bits. The results from computer simulations lead us to conclude that the LORD detector and the LISS detector with few candidates lead to very close coded BER, when QPSK and 16-QAM are used as the modulation and when the two detectors work with the same Viterbi decoder. However, the LORD detector is of fixed complexity and therefore is easier to realize in hardware.
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Wang, Hsiao-Chi, and 王曉淇. "A High Throughput Low Complexity Soft-output Sphere Decoder for MIMO Communications." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/82736348986678769250.
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碩士國立清華大學
電機工程學系
97
In this thesis, a high throughput fixed complexity soft-output sphere decoder supporting QPSK, 16-QAM, and 64-QAM modulation in the 4x4 MIMO system is proposed. For achieving soft-output, the proposed tree search algorithm is presented. Some simulation results help to modify the tree search algorithm of the original fixed-complexity sphere decoder (FSD) for soft-output detection. Compared with the optimal soft-output sphere decoder, the proposed soft-output FSD (SFSD) has a little frame error rate (FER) degradation (0.5dB), but the benefit is that SFSD has fixed complexity and can suit to a parallel or full pipeline hardware design. Moreover, a high throughput hardware architecture is proposed to implement the SFSD algorithm. A simplified enumeration method is proposed to reduce the hardware complexity. The parallel architecture is proposed to achieve high throughput. For the high clock frequency, many pipelines are inserted into the proposed architecture. In addition, the proposed SFSD is implemented by the 0.18um CMOS cell-library of HP laboratory. The area of proposed hardware implementation is about 100k equivalent gates corresponding to the two-input drive-one NAND gate. The maximum throughput can reach to 120Mbps with 16-QAM modulation. Finally, the FPGA emulation is made to verify the proposed design is able to work. Then a high performance high throughput soft-output MIMO detector has completely accomplished in the thesis.
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Wang, To-Ping, and 王拓評. "Design of a New Complex Sphere Decoder for Soft-Output MIMO Detection." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/81987854974940585916.
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碩士國立臺灣大學
電子工程學研究所
95
The services, such as on-line videos, high definition TV (HDTV), interactive games, provided by the next generation wireless communication systems produce the demand for much higher throughput and better Quality of Service (QoS) under the situation of limited bandwidth. Nowadays, OFDM is widely adopted to improve bandwidth utilization in many communication systems and has become the main modulation technique of many standards. In the future, MIMO will be the next widely accepted technique because of its provision for diversity and spectrum efficiency. MIMO system can easily satisfy the demand for high throughput by increasing the number of transmit and receive antennas. For the QoS concern, the detection complexity grows exponential with the antenna number in theory. Corresponding literatures propose sphere decoder to mitigate this problem and conserve the near ML performance. However, the arithmetic complexity is still much more than other detection schemes. In order to overcome this trade-off problem, the thesis combines modified tabular enumeration and best-first tree search algorithm and therefore proposes the new sphere decoding algorithm: modified best-first (MBF) algorithm. After mathematic induction and software simulation by the iterative MIMO detection & decoding system, we demonstrate that MBF can not only reduce the enumeration complexity, especially for high-order QAM, but also conserve high performance from the characteristic of the best-first algorithm. Besides, in order to avoid the performance attenuation of high dimension MIMO system, we integrate successive interference cancellation algorithm, early termination algorithm and MBF into proposed MBF-SIC algorithm. Finally, we give the hardware design to show that the proposed soft-output MIMO complex-plane sphere decoder composed of MBF-SIC is reasonable for hardware implementation.
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Lee, Tsung-Hsueh, and 李宗學. "Design and Implementation of a New Complex Sphere Decoder for MIMO Detection." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/84274405802171326659.
Full textAbstract:
碩士國立臺灣大學
電子工程學研究所
95
More and more services are provided in the next generation wireless communicaiton systems, including on-line videos, high definition TV (HDTV), interactive games and so on. The demand for throughput and QoS is getting higher. However, the bandwidth is limited. OFDM is widely adopted in many communication systems and has become a main modulation technique of many standards. MIMO will be the next widely accepted technique because of its provision for diversity and/or spectrum efficiency. To apply the MIMO techniques, the number of transmitting and receiving antennas needs be more than one. Among spatial multiplexing MIMO detection, sphere decoding algorithm is the first that was proposed to do maximum-likelihood equalization’detection with acceptable complexity. In the thesis, sphere decoder related literatures are surveyed and a new complex-plane sphere decoder is designed and implemented. Depth-first search with closest point first order is introduced directly on complex-valued signals. List-Enumeration algorithm is proposed to overcome the problem of enumeration in complex-plane sphere decoder. The list can be implemented by either an unified list and several individual lists. In addition, backward-Layer controlled algorithm and diminished dimensionality algorithm are proposed to further reduce the hardware complexity. Two architectures, parallel forward/backward search and single calculation unit, are proposed to implement the new algorithm. The tradeoffs of these two versions are between area, power, and throughput. The hardware can support different constellations and numbers of antennas. Simulation and implementation results indicate the proposed algorithm and architecture outperform other solutions and form a solid foundation for future wireless communication systems that adopt MIMO processing.
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Lin, Hsin-Lei, and 林心蕾. "Design of Synchronization and Decoder Circuits for MIMO-OFDM Wireless Communication Systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/33916429550633495617.
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博士國立中興大學
電機工程學系所
96
The designs of synchronization and MIMO decoder are proposed in this dissertation since the MIMO method and OFDM technique can be used for improving either the performance or the data rate of wireless communication. The synchronization is investigated since the frequency is more sensitive in OFDM system. A novel digital oscillator of synchronization combined with the CORDIC algorithm and Sinusoidal function is designed for the MIMO wireless communication. The synchronization was implemented using TSMC 0.18 μm 1P6M CMOS technology at 1.8V, and the core area was about 1.682 mm^2 of a 2-by-2 antenna system. A memory-based oscillator needs an accumulator and a sin/cos generator to perform frequency compensation, and the size of memory severely limits the precision. The proposed circuit reduces the memory by using sinusoidal. Furthermore, comparing to the iterative CORDIC computation, the proposed CSIO architecture operates the CORDIC only once. Moreover, a high throughput and low-cost JVBPSD algorithm using efficient candidate searching is proposed for SDM-MIMO wireless system. It can operate at a 166 MHz clock frequency, and the average throughput of the efficient candidate searching MIMO decoder is 95 Mbps with 64-QAM modulation at 30 dB SNR. The core area of the proposed MIMO decoder using a TSMC 90nm technology with different modulations in a 4-by-4 SDM-MIMO wireless system is about 0.675 mm^2.
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Chen, Chieh-Yu, and 陳婕妤. "Power-Aware Space-Time-Trellis-Coded MIMO Decoder with Embedded SNR Estimator." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46414151585951822334.
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碩士國立清華大學
電機工程學系
99
Space-time trellis code (STTC) has been widely applied to coded multiple-input multiple-output (MIMO) systems because of its gains in coding and diversity. However, its great decoding complexity makes it less promising in chip realization compared to the space-time block code (STBC). The complexity of STTC decoding lies in the branch metric calculation in the Viterbi algorithm. Compared with the Viterbi decoder for convolutional code, the STTC Viterbi decoder has a large amount of the complex-number multiplications to calculate the branch metrics. Besides, the amount of the branch metric calculations increases significantly in proportional with the number of antennas and the modulation order. The large amount of calculation and complexity design is a major result that STTC code is not applied to the specifications of wireless communication systems. In order to overcome the bottleneck, we propose an algorithm which reduce the complexity of the Viterbi decoder for STTC. The proposed Viterbi decoder for STTC apply the well-known algorithm, T-algorithm, to reduce the calculations of branch metric and reduce the complexity of the hardware design. Beside, the proposed Viterbi decoder uses the characteristics of the STTC code and hardware architecture to provide accuracy estimated SNR value. The proposed Viterbi decoder reduces the complexity and the power consumption in proportional to the SNR value. Based on the proposed Viterbi decoder, a reconfigurable MIMO STTC Viterbi decoder is designed and implemented using 0.18 um technology. The proposed decoder supports the QPSK, 8PSK and 16-QAM modulations with 4×1 and 4×4 MIMO system. The throughput of the proposed decoder achieves 59.2Mbps, 33.8Mbps, and 15.0Mbps for Q-PSK, 8-PSK, and 16-QAM modulations, respectively.
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Chen, Yan-Tong, and 陳彥同. "An Integrated Message-Passing Detector and Decoder for Polar-Coded Massive MIMO Systems." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/00784071685577586836.
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碩士國立交通大學
電子研究所
105
A 1.34mm2 40nm CMOS soft-output message-passing detector and bidirectional polar decoder are designed for a QPSK massive MIMO system. The proposed reliable symbol interference cancellation technique and adaptive variance detection reduce the complexity of message passing detector (MPD) by more than 90% and generate soft log likelihood ratio (LLR) information for an ECC decoder. Exploiting a folded memory configuration saves half memory elements. An interleaved bidirectional propagation double column polar decoder is proposed to reduce the total latency of the whole decoding procedure. This work presents the first integration of an MPD and a polar decoder, delivering a throughput of 7.61Gb/s for massive MIMO systems. A soft-output MPD, which is essential to maximize channel capacity, is proposed. Compared to previous solutions, the proposed MPD achieves a 6.9 higher throughput with 49% less energy, despite the soft outputs. The proposed bidirectional polar decoder achieves a 1.35 increase in throughput with comparable energy inputs.
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Sung, Chih-Sheng, and 宋志晟. "A Complex K-Best Sphere Decoder with Efficient Search Design for MIMO Systems." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/23930620613307534003.
Full textAbstract:
碩士國立交通大學
電信工程系所
97
In wireless communication systems, multiple-input and multiple-output (MIMO) technology offers significant increases in data rate and link range without additional bandwidth or transmit power. However, the design of high performance and low complexity receivers for MIMO systems is a challenging task. The maximum-likelihood (ML) detection is the optimal detection scheme but its complexity grows exponentially with the number of transmit antennas. The sphere decoding algorithm (SDA) achieves the ML performance with reduced complexity. Nevertheless, the throughput of the conventional SDA is not stable. The K-best SDA which keeps only K-best candidates at each layer for the search of next layer is guaranteed to have a stable throughput. However, to achieve a near-ML performance, the value of K should be sufficiently large. Besides, applying a sorting algorithm to find K-best candidates at each layer requires a large amount of memory access. In this thesis, we propose a complex K-best sphere decoder with an efficient search architecture. The proposed K-best sphere decoder significantly reduces the sorting complexity. We also provide the hardware architecture of the proposed complex candidate search method. It is demonstrated through analysis and simulations that the proposed K-best sphere decoder achieves a near-ML performance without requiring a large value of K.
39
Yeh, Che-hung, and 葉哲宏. "Joint LDPC Decoder and Channel Estimator for MIMO-OFDM Systems in Fast Fading Channel." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/77552901953575219516.
Full textAbstract:
碩士國立中正大學
通訊工程研究所
95
Multiple input multiple output- orthogonal frequency division multiplexing (MIMO-OFDM) that is a highly efficient data transmission system does not increase any transmission power or bandwidth to improve the channel capacity. For exploiting the space, time and frequency diversity, the low density parity-check (LDPC) is used as a channel coding with a built-in interleaver. We used suboptimal soft demapping algorithms, linear minimum mean square error- soft interference cancellation (LMMSE-SIC), to reduce computational complexity caused a large constellation size and a lot of transmission antennas in the receiver. In this thesis a jointed LDPC decoder and channel estimator algorithm was proposed. The algorithms applied soft bits information of LDPC to avoid estimate errors in low bits reliability during the demapping process. Finally, we used time domain channel correlation to enhance the accuracy of estimates. Computer simulations under fast fading conditions and normalized Doppler frequency 0.01 show that performance of the proposed channel estimation algorithms are 0.12 dB worse than perfect channel estimation algorithms as packet error rate is 0.01.
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Huang, Li-Wen, and 黃立文. "An Interference Alignment Approach to Joint Precoder and Decoder Designs over Multiuser MIMO Interference Channels." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/75405225315804070083.
Full textAbstract:
碩士國立中央大學
通訊工程研究所
100
In multiuser interference channels, each transmitter desires to communicate its data to the intended receiver, and the multiuser interference will cause severe performance degradation on the sum rate performance if the interference signals are not appropriately mitigated. Recently, the idea of interference alignment has been emerged to utilize the spatial dimension offered by multiple antennas to overcome the interference problem and achieve the maximum sum rate performance. Although there have been some interference alignment approaches for designing precoders and decoders in recent literatures, they do not consider the desired signal strength from one transmitter to the intended receiver and the noise effect. In some cases, users may have the extremely poor SINR performance even if users’ interference signals are all appropriately aligned. Toward this end, this thesis proposes a novel iterative interference alignment approach which jointly designs the precoder and the decoder by maximizing the worst signal-to-interference and noise ratio (SINR) among users with multiple antennas. In fact, the considered optimization problem is non-convex. Based on the Karush-Kuhn-Tucker (K.K.T.) conditions, we first derive the optimality condition for designing the decoder, and propose three methods, named as bisection approach, lower bound approximation approach and SINR approximation approach, to achieve the optimal solution. For the precoder designs, we resort to the semidefinite programming (SDP) and rank relaxation techniques to transform the optimization problem into a convex form to obtain the optimal solution. Numerical results reveal that our proposed algorithms perform much better than the two existing algorithms in [1] and [2] in the generalized multiuser multi-input multi-output (MIMO) interference channels.
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Botha, P. R. (Philippus Rudolph). "Iterative decoding of space-time-frequency block coded mimo concatenated with LDPH codes." Diss., 2013. http://hdl.handle.net/2263/33344.
Full textAbstract:
In this dissertation the aim was to investigate the usage of algorithms found in computer
science and apply suitable algorithms to the problem of decoding multiple-input multipleoutput
(MIMO) space-time-frequency block coded signals. It was found that the sphere
decoder is a specific implementation of the A* tree search algorithm that is well known in
computer science. Based on this knowledge, the sphere decoder was extended to include
a priori information in the maximum a posteriori probability (MAP) joint decoding of the
STFC block coded MIMO signals. The added complexity the addition of a priori information
has on the sphere decoder was investigated and compared to the sphere decoder without
a priori information. To mitigate the potential additional complexity several algorithms that
determine the order in which the symbols are decoded were investigated. Three new algorithms
incorporating a priori information were developed and compared with two existing
algorithms. The existing algorithms compared against are sorting based on the norms of the
channel matrix columns and the sorted QR decomposition.
Additionally, the zero forcing (ZF) and minimum mean squared error (MMSE) decoderswith and without decision feedback (DF) were also extended to include a priori information.
The developed method of incorporating a priori information was compared to an existing
algorithm based on receive vector translation (RVT). The limitation of RVT to quadrature
phase shift keying (QPSK) and binary shift keying (BPSK) constellations was also shown in
its derivation. The impact of the various symbol sorting algorithms initially developed for
the sphere decoder on these decoders was also investigated. The developed a priori decoders
operate in the log domain and as such accept a priori information in log-likelihood ratios
(LLRs). In order to output LLRs to the forward error correcting (FEC) code, use of the
max-log approximation, occasionally referred to as hard-to-soft decoding, was made.
In order to test the developed decoders, an iterative turbo decoder structure was used together
with an LDPC decoder to decode threaded algebraic space-time (TAST) codes in a Rayleigh
faded MIMO channel. Two variables that have the greatest impact on the performance of the
turbo decoder were identified: the hard limit value of the LLRs to the LDPC decoder and the
number of independently faded bits in the LDPC code.Dissertation (MEng)--University of Pretoria, 2013.
gm2014
Electrical, Electronic and Computer Engineering
unrestricted
42
Louw, Daniel Johannes. "Non-binary LDPC coded STF-MIMO-OFDM with an iterative joint receiver structure." Diss., 2010. http://hdl.handle.net/2263/28061.
Full textAbstract:
The aim of the dissertation was to design a realistic, low-complexity non-binary (NB) low density parity check (LDPC) coded space-time-frequency (STF) coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system with an iterative joint decoder and detector structure at the receiver. The goal of the first part of the dissertation was to compare the performance of different design procedures for NB-LDPC codes on an additive white Gaussian noise (AWGN) channel, taking into account the constraint on the code length. The effect of quantisation on the performance of the code was also analysed. Different methods for choosing the NB elements in the parity check matrix were compared. For the STF coding, a class of universal STF codes was used. These codes use linear pre-coding and a layering approach based on Diophantine numbers to achieve full diversity and a transmission rate (in symbols per channel use per frequency) equal to the number of transmitter antennas. The study of the system considers a comparative performance analysis of di erent ST, SF and STF codes. The simulations of the system were performed on a triply selective block fading channel. Thus, there was selectivity in the fading over time, space and frequency. The effect of quantisation at the receiver on the achievable diversity of linearly pre-coded systems (such as the STF codes used) was mathematically derived and verified with simulations. A sphere decoder (SD) was used as a MIMO detector. The standard method used to create a soft-input soft output (SISO) SD uses a hard-to-soft process and the max-log-map approximation. A new approach was developed which combines a Hopfield network with the SD. This SD-Hopfield detector was connected with the fast Fourier transform belief propagation (FFT-BP) algorithm in an iterative structure. This iterative system was able to achieve the same bit error rate (BER) performance as the original SISO-SD at a reduced complexity. The use of the iterative Hopfield-SD and FFT-BP decoder system also allows performance to be traded off for complexity by varying the number of decoding iterations. The complete system employs a NB-LDPC code concatenated with an STF code at the transmitter with a SISO-SD and FFT-BP decoder connected in an iterative structure at the receiver. The system was analysed in varying channel conditions taking into account the effect of correlation and quantisation. The performance of different SF and STF codes were compared and analysed in the system. An analysis comparing different numbers of FFT-BP and outer iterations was also done. AFRIKAANS : Die doel van die verhandeling was om ’n realistiese, lae-kompleksiteit nie-binˆere (NB) LDPC gekodeerde ruimte-tyd-frekwensie-gekodeerde MIMO-OFDM-sisteem met iteratiewe gesamentlike dekodeerder- en detektorstrukture by die ontvanger te ontwerp. Die eerstem deel van die verhandeling was om die werkverrigting van verskillende ontwerpprosedures vir NB-LDPC kodes op ’n gesommeerde wit Gausruiskanaal te vergelyk met inagneming van die beperking op die lengte van die kode. Verskillende metodes om die nie-bineêre elemente in die pariteitstoetsmatriks te kies, is gebruik. Vir die ruimte-tyd-frekwensiekodering is ’n klas universele ruimte-tyd-frekwensiekodes gebruik. Hierdie kodes gebruik lineêre pre-kodering en ’n laagbenadering gebaseer op Diofantiese syfers om volle diversiteit te bereik en ’n oordragtempo (in simbole per kanaalgebruik per frekwensie) gelyk aan die aantal senderantennes. Die studie van die sisteem oorweeg ’n vergelykende werkverrigtinganalisie van verskillende ruimte-tyd-, ruimte-freksensie- en ruimte-tyd-frekwensiekodes. Die simulasies van die sisteem is gedoen op ’n drievoudig selektiewe blokwegsterwingskanaal. Daar was dus selektiwiteit in die wegsterwing oor tyd, ruimte en frekwensie. Die effek van kwantisering by die ontvanger op die bereikbare diversiteit van lineêr pre-gekodeerde sisteme (soos die ruimte-tyd-frekwensiekodes wat gebruik is) is matematies afgelei en bevestig deur simulasies. ’n Sfeerdekodeerder (SD) is gebruik as ’n MIMO-detektor. Die standaardmetode wat gebuik is om ’n sagte-inset-sagte-uitset (SISO) SD te skep, gebruik ’n harde-na-sagte proses en die maksimum logaritmiese afbeelding-benadering. ’n Nuwe benadering wat ’n Hopfield-netwerk met die SD kombineer, is ontwikkel. Hierdie SD-Hopfield-detektor is verbind met die FFT-BP-algoritme in iteratiewe strukture. Hierdie iteratiewe sisteem was in staat om dieselfde bisfouttempo te bereik as die oorspronklike SISO-SD, met laer kompleksiteit. Die gebruik van die iteratiewe Hopfield-SD en FFT-BP-dekodeerdersisteem maak ook daarvoor voorsiening dat werkverrigting opgeweeg kan word teen kompleksiteit deur die aantal dekodering-iterasies te varieer. Die volledige sisteem maak gebruik van ’n QC-NB-LDPC-kode wat met ’n ruimte-tyd-frekwensiekode by die sender aaneengeskakel is met ’n SISO-SD en FFT-BP-dekodeerder wat in ’n iteratiewe struktuur by die ontvanger gekoppel is. Die sisteem is onder ’n verskeidenheid kanaalkondisies ge-analiseer met inagneming van die effek van korrelasie en kwantisering. Die werkverrigting van verskillende ruimte-frekwensie- en ruimte-tyd-frekwensiekodes is vergelyk en in die sisteem ge-analiseer. ’n Analise om ’n wisselende aantal FFT-BP en buite-iterasies te vergelyk, is ook gedoen. CopyrightDissertation (MEng)--University of Pretoria, 2010.
Electrical, Electronic and Computer Engineering
unrestricted
43
Al-Quwaiee, Hessa. "Bidirectional Fano Algorithm for Lattice Coded MIMO Channels." Thesis, 2013. http://hdl.handle.net/10754/292300.
Full textAbstract:
Recently, lattices - a mathematical representation of infinite discrete points in the Euclidean space, have become an effective way to describe and analyze communication systems especially system those that can be modeled as linear Gaussian vector channel model. Channel codes based on lattices are preferred due to three facts: lattice codes have simple structure, the code can achieve the limits of the channel, and they can be decoded efficiently using lattice decoders which can be considered as the Closest Lattice Point Search (CLPS).
Since the time lattice codes were introduced to Multiple Input Multiple Output (MIMO) channel, Sphere Decoder (SD) has been an efficient way to implement lattice decoders. Sphere decoder offers the optimal performance at the expense of high decoding complexity especially for low signal-to-noise ratios (SNR) and for high- dimensional systems. On the other hand, linear and non-linear receivers, Minimum Mean Square Error (MMSE), and MMSE Decision-Feedback Equalization (DFE), provide the lowest decoding complexity but unfortunately with poor performance. Several studies works have been conducted in the last years to address the problem of designing low complexity decoders for the MIMO channel that can achieve near optimal performance. It was found that sequential decoders using backward tree
search can bridge the gap between SD and MMSE. The sequential decoder provides
an interesting performance-complexity trade-off using a bias term. Yet, the sequential decoder still suffers from high complexity for mid-to-high SNR values.
In this work, we propose a new algorithm for Bidirectional Fano sequential Decoder (BFD) in order to reduce the mid-to-high SNR complexity. Our algorithm consists of first constructing a unidirectional Sequential Decoder based on forward search using the QL decomposition. After that, BFD incorporates two searches, forward and backward, to work simultaneously till they merge and find the closest lattice point to the received signal. We show via computer simulations that BFD can reduce the mid-to-high SNR complexity for the sequential decoder without changing the bias value.
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Ali, Konpal S. "On Lattice Sequential Decoding for Large MIMO Systems." Thesis, 2014. http://hdl.handle.net/10754/316732.
Full textAbstract:
Due to their ability to provide high data rates, Multiple-Input Multiple-Output (MIMO) wireless communication systems have become increasingly popular. Decoding of these systems with acceptable error performance is computationally very demanding.
In the case of large overdetermined MIMO systems, we employ the Sequential Decoder using the Fano Algorithm. A parameter called the bias is varied to attain different performance-complexity trade-offs. Low values of the bias result in excellent performance but at the expense of high complexity and vice versa for higher bias values. We attempt to bound the error by bounding the bias, using the minimum distance of a lattice. Also, a particular trend is observed with increasing SNR: a region of low complexity and high error, followed by a region of high complexity and error falling, and finally a region of low complexity and low error. For lower bias values, the stages of the trend are incurred at lower SNR than for higher bias values. This has the important implication that a low enough bias value, at low to moderate SNR, can result in low error and low complexity even for large MIMO systems. Our work is compared against Lattice Reduction (LR) aided Linear Decoders (LDs). Another impressive observation for low bias values that satisfy the error bound is that the Sequential Decoder's error is seen to fall with increasing system size, while it grows for the LR-aided LDs.
For the case of large underdetermined MIMO systems, Sequential Decoding with two preprocessing schemes is proposed – 1) Minimum Mean Square Error Generalized Decision Feedback Equalization (MMSE-GDFE) preprocessing 2) MMSE-GDFE preprocessing, followed by Lattice Reduction and Greedy Ordering. Our work is compared against previous work which employs Sphere Decoding preprocessed using MMSE-GDFE, Lattice Reduction and Greedy Ordering. For the case of large systems, this results in high complexity and difficulty in choosing the sphere radius. Our schemes, particularly 2), perform better in terms of complexity and are able to achieve almost the same error curves, depending on the bias used.
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Jenkal, Ravi S. "Architectures and design methodology for energy efficient MIMO decoders." 2008. http://www.lib.ncsu.edu/theses/available/etd-11062008-130200/unrestricted/etd.pdf.
Full text
46
Ben, Atitallah Ismail. "High-Dimensional Analysis of Convex Optimization-Based Massive MIMO Decoders." Thesis, 2017. http://hdl.handle.net/10754/623468.
Full textAbstract:
A wide range of modern large-scale systems relies on recovering a signal from noisy linear measurements. In many applications, the useful signal has inherent properties, such as sparsity, low-rankness, or boundedness, and making use of these properties
and structures allow a more efficient recovery. Hence, a significant amount of work has been dedicated to developing and analyzing algorithms that can take advantage of the signal structure. Especially, since the advent of Compressed Sensing (CS) there has been significant progress towards this direction. Generally speaking, the signal structure can be harnessed by solving an appropriate regularized or constrained M-estimator.
In modern Multi-input Multi-output (MIMO) communication systems, all transmitted signals are drawn from finite constellations and are thus bounded. Besides, most recent modulation schemes such as Generalized Space Shift Keying (GSSK) or Generalized Spatial Modulation (GSM) yield signals that are inherently sparse. In the recovery procedure, boundedness and sparsity can be promoted by using the ℓ1 norm regularization and by imposing an ℓ∞ norm constraint respectively.
In this thesis, we propose novel optimization algorithms to recover certain classes of structured signals with emphasis on MIMO communication systems. The exact analysis permits a clear characterization of how well these systems perform. Also, it allows an automatic tuning of the parameters. In each context, we define the appropriate performance metrics and we analyze them exactly in the High Dimentional Regime (HDR).
The framework we use for the analysis is based on Gaussian process inequalities; in particular, on a new strong and tight version of a classical comparison inequality (due to Gordon, 1988) in the presence of additional convexity assumptions. The new
framework that emerged from this inequality is coined as Convex Gaussian Min-max Theorem (CGMT).
47
Natarajan, Lakshmi Prasad. "Low-Complexity Decoding and Construction of Space-Time Block Codes." Thesis, 2013. http://etd.iisc.ernet.in/2005/3372.
Full textAbstract:
Space-Time Block Coding is an efficient communication technique used in multiple-input multiple-output wireless systems. The complexity with which a Space-Time Block Code (STBC) can be decoded is important from an implementation point of view since it directly affects the receiver complexity and speed. In this thesis, we address the problem of designing low complexity decoding techniques for STBCs, and constructing STBCs that achieve high rate and full-diversity with these decoders. This thesis is divided into two parts; the first is concerned with the optimal decoder, viz. the maximum-likelihood (ML) decoder, and the second with non-ML decoders.
An STBC is said to be multigroup ML decodable if the information symbols encoded by it can be partitioned into several groups such that each symbol group can be ML decoded independently of the others, and thereby admitting low complexity ML decoding. In this thesis, we first give a new framework for constructing low ML decoding complexity STBCs using codes over the Klein group, and show that almost all known low ML decoding complexity STBCs can be obtained by this method. Using this framework we then construct new full-diversity STBCs that have the least known ML decoding complexity for a large set of choices of number of transmit antennas and rate. We then introduce the notion of Asymptotically-Good (AG) multigroup ML decodable codes, which are families of multigroup ML decodable codes whose rate increases linearly with the number of transmit antennas. We give constructions for full-diversity AG multigroup ML decodable codes for each number of groups g > 1. For g > 2, these are the first instances of g-group ML decodable codes that are AG or have rate more than 1. For g = 2 and identical delay, the new codes match the known families of AG codes in terms of rate. In the final section of the first part we show that the upper triangular matrix R encountered during the sphere-decoding of STBCs can be rank-deficient, thus leading to higher sphere-decoding complexity, even when the rate is less than the minimum of the number of transmit antennas and the number receive antennas. We show that all known AG multigroup ML decodable codes suffer from such rank-deficiency, and we explicitly derive the sphere-decoding complexities of most known AG multigroup ML decodable codes.
In the second part of this thesis we first study a low complexity non-ML decoder introduced by Guo and Xia called Partial Interference Cancellation (PIC) decoder. We give a new full-diversity criterion for PIC decoding of STBCs which is equivalent to the criterion of Guo and Xia, and is easier to check. We then show that Distributed STBCs (DSTBCs) used in wireless relay networks can be full-diversity PIC decoded, and we give a full-diversity criterion for the same. We then construct full-diversity PIC decodable STBCs and DSTBCs which give higher rate and better error performance than known multigroup ML decodable codes for similar decoding complexity, and which include other known full-diversity PIC decodable codes as special cases. Finally, inspired by a low complexity essentially-ML decoder given by Sirianunpiboon et al. for the two and three antenna Perfect codes, we introduce a new non-ML decoder called Adaptive Conditional Zero-Forcing (ACZF) decoder which includes the technique of Sirianunpiboon et al. as a special case. We give a full-diversity criterion for ACZF decoding, and show that the Perfect codes for two, three and four antennas, the Threaded Algebraic Space-Time code, and the 4 antenna rate 2 code of Srinath and Rajan satisfy this criterion. Simulation results show that the proposed decoder performs identical to ML decoding for these five codes. These STBCs along with ACZF decoding have the best error performance with least complexity among all known STBCs for four or less transmit antennas.
48
Lin, Bo-Yan, and 林帛諺. "Implementation and Study of Sphere Decoders on DSP-Based MIMO Platform." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/bq53du.
Full textAbstract:
碩士國立交通大學
電子工程系所
96
The sphere decoding algorithm can achieve the BER performance of the brute-force decoding method with lower complexity. In this thesis, we implement a sphere decoder in a Digital Signal Processor (DSP) based Multi-Input Multi-Output (MIMO) platform. We analyze the fixed point effect, different QR decomposition algorithms, and propose a hardware structure which enables the Quixote DSP board achieve higher data rate. Finally, we derive the equations of different types of space-time-frequency codes in the MIMO-OFDM system and find that they can be decode by the sphere decoder.
49
Jithamithra, G. R. "Space-Time Block Codes With Low Sphere-Decoding Complexity." Thesis, 2013. http://etd.iisc.ernet.in/handle/2005/2612.
Full textAbstract:
One of the most popular ways to exploit the advantages of a multiple-input multiple-output (MIMO) system is using space time block coding. A space time block code (STBC) is a finite set of complex matrices whose entries consist of the information symbols to be transmitted. A linear STBC is one in which the information symbols are linearly combined to form a two-dimensional code matrix. A well known method of maximum-likelihood (ML) decoding of such STBCs is using the sphere decoder (SD).
In this thesis, new constructions of STBCs with low sphere decoding complexity are presented and various ways of characterizing and reducing the sphere decoding complexity of an STBC are addressed. The construction of low sphere decoding complexity STBCs is tackled using irreducible matrix representations of Clifford algebras, cyclic division algebras and crossed-product algebras. The complexity reduction algorithms for the STBCs constructed are explored using tree based search algorithms. Considering an STBC as a vector space over the set of weight matrices, the problem of characterizing the sphere decoding complexity is addressed using quadratic form representations. The main results are as follows.
A sub-class of fast decodable STBCs known as Block Orthogonal STBCs (BOSTBCs) are explored. A set of sufficient conditions to obtain BOSTBCs are explained. How the block orthogonal structure of these codes can be exploited to reduce the SD complexity of the STBC is then explained using a depth first tree search algorithm. Bounds on the SD complexity reduction and its relationship with the block orthogonal structure are then addressed. A set of constructions to obtain BOSTBCs are presented next using Clifford unitary weight designs (CUWDs), Coordinate-interleaved orthogonal designs (CIODs), cyclic division algebras and crossed product algebras which show that a lot of codes existing in literature exhibit the block orthogonal property.
Next, the dependency of the ordering of information symbols on the SD complexity is discussed following which a quadratic form representation known as the Hurwitz-Radon quadratic form (HRQF) of an STBC is presented which is solely dependent on the weight matrices of the STBC and their ordering. It is then shown that the SD complexity is only a function of the weight matrices defining the code and their ordering, and not of the channel realization (even though the equivalent channel when SD is used depends on the channel realization). It is also shown that the SD complexity is completely captured into a single matrix obtained from the HRQF.
Also, for a given set of weight matrices, an algorithm to obtain a best ordering of them leading to the least SD complexity is presented using the HRQF matrix.
50
Abediseid, Walid. "Efficient Lattice Decoders for the Linear Gaussian Vector Channel: Performance & Complexity Analysis." Thesis, 2011. http://hdl.handle.net/10012/6271.
Full textAbstract:
The theory of lattices --- a mathematical approach for representing infinite discrete points in Euclidean space, has become a powerful tool to analyze many point-to-point digital and wireless communication systems, particularly, communication systems that can be well-described by the linear Gaussian vector channel model. This is mainly due to the three facts about channel codes constructed using lattices: they have simple structure, their ability to achieve the fundamental limits (the capacity) of the channel, and most importantly, they can be decoded using efficient decoders called lattice decoders.
Since its introduction to multiple-input multiple-output (MIMO) wireless communication systems, sphere decoders has become an attractive efficient implementation of lattice decoders, especially for small signal dimensions and/or moderate to large signal-to-noise ratios (SNRs). In the first part of this dissertation, we consider sphere decoding algorithms that describe lattice decoding. The exact complexity analysis of the basic sphere decoder for general space-time codes applied to MIMO wireless channel is known to be difficult. Characterizing and understanding the complexity distribution is important, especially when the sphere decoder is used under practically relevant runtime constraints. In this work, we shed the light on the (average) computational complexity of sphere decoding for the quasi-static, LAttice Space-Time (LAST) coded MIMO channel.
Sphere decoders are only efficient in the high SNR regime and low signal dimensions, and exhibits exponential (average) complexity for low-to-moderate SNR and large signal dimensions. On the other extreme, linear and non-linear receivers such as minimum mean-square error (MMSE), and MMSE decision-feedback equalization (DFE) are considered attractive alternatives to sphere decoders in MIMO channels. Unfortunately, the very low decoding complexity advantage that these decoders can provide comes at the expense of poor performance, especially for large signal dimensions. The problem of designing low complexity receivers for the MIMO channel that achieve near-optimal performance is considered a challenging problem and has driven much research in the past years. The problem can solved through the use of lattice sequential decoding that is capable of bridging the gap between sphere decoders and low complexity linear decoders (e.g., MMSE-DFE decoder).
In the second part of this thesis, the asymptotic performance of the lattice sequential decoder for LAST coded MIMO channel is analyzed. We determine the rates achievable by lattice coding and sequential decoding applied to such a channel. The diversity-multiplexing tradeoff under such a decoder is derived as a function of its parameter--- the bias term. In this work, we analyze both the computational complexity distribution and the average complexity of such a decoder in the high SNR regime. We show that there exists a cut-off multiplexing gain for which the average computational complexity of the decoder remains bounded. Our analysis reveals that there exists a finite probability that the number of computations performed by the decoder may become excessive, even at high SNR, during high channel noise. This probability is usually referred to as the probability of a decoding failure. Such probability limits the performance of the lattice sequential decoder, especially for a one-way communication system. For a two-way communication system, such as in MIMO Automatic Repeat reQuest (ARQ) system, the feedback channel can be used to eliminate the decoding failure probability.
In this work, we modify the lattice sequential decoder for the MIMO ARQ channel, to predict in advance the occurrence of decoding failure to avoid wasting the time trying to decode the message. This would result in a huge saving in decoding complexity. In particular, we will study the throughput-performance-complexity tradeoffs in sequential decoding algorithms and the effect of preprocessing and termination strategies. We show, analytically and via simulation, that using the lattice sequential decoder that implements a simple yet efficient time-out algorithm for joint error detection and correction, the optimal tradeoff of the MIMO ARQ channel can be achieved with significant reduction in decoding complexity.