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Etude Dimplantation De Detecteurs Multi Utilisateurs Cdma
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Book Synopsis Étude d'implantation de détecteurs multi-utilisateurs CDMA by : Makram Touzri
Download or read book Étude d'implantation de détecteurs multi-utilisateurs CDMA written by Makram Touzri and published by . This book was released on 2007 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Des études récentes ont mis en évidence l’avantage de la détection multi-utilisateurs qui prend en compte l’observation de tous les utilisateurs lors de la détection. A l’origine et pour des raisons de complexité, les récepteurs opèrent la détection et le décodage de manière disjointe. Cependant les détecteurs optimaux sont très complexes. Il devenait intéressant de considérer des techniques de détection et décodage conjoints qui peuvent présenter performances et complexité avantageuses en vue d’implantation circuit. En se basant sur des études préalables, nous avons retenu une configuration de détection à suppression d’interférence successive (SIC) suivi du décodage et une configuration de détection et décodage conjoints intégrant un turbo décodeur à l’intérieur des unités de suppression d’interférence du détecteur SIC. Nous avons commencé par estimer l’effet de la quantification des données en comparaison avec les résultats théoriques des études préalables, ce qui nous a permis de choisir le nombre de bits de quantification adéquat et en application à l’UMTS. Dans une deuxième partie, nous avons modélisé en VHDL les éléments de base du détecteur SIC. A partir de ces modélisations, des analyses temporelles et des bilans de complexité surface, nous avons choisi les architectures adéquates pour chacune des configurations à implanter compte-tenu des contraintes du système UMTS dans sa liaison montante. Cette étude nous a permis de donner l’avantage à l’implantation de la détection et du décodage conjoints qui est la plus adaptée au système d’application sur le plan des performances, de la surface, du temps de traitement et de la flexibilité de fonctionnement.
Book Synopsis Multiuser Detection in CDMA Mobile Terminals by : Piero Castoldi
Download or read book Multiuser Detection in CDMA Mobile Terminals written by Piero Castoldi and published by Artech House. This book was released on 2002 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here's an authoritative, cutting-edge resource that gives you a thorough understanding of CDMA transmission and detection. It offers practical guidance in designing interference-reducing multi-user receivers for mobile radio systems and multi-user adaptive modems for accessing satellite earth stations. The book provides in-depth descriptions of CDMA principles, and of linear and non-linear multi-user detection , and covers the fine details of the realization of a linear multi-user receiver.
Book Synopsis Détection multi-utilisateurs et estimation aveugle du canal pour les systèmes CDMA by : Serguei Burykh
Download or read book Détection multi-utilisateurs et estimation aveugle du canal pour les systèmes CDMA written by Serguei Burykh and published by . This book was released on 2003 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cette thèse est consacrée à la détection multi-utilisateurs et l'estimation aveugle du canal pour les systèmes DS/CDMA. La détection multi-utilisateurs représente un ensemble d'algorithmes de traitement du signal dont le but ets de combattre l'interférence de l'accès multiple et leseffets du canal de propagation. L'estimation du canal en aveugle a pour l'objectif d'identifier le canal de propagation à partir des signaux observés à la sortie du canal en faisant des hypothèses statistiques sur les signaux d'entrée. Dans ce travail, nous proposons un nombre des techniques pour les récepteurs des systèmes DS/CDMA qui peuvent être implémentés en liaison montante mais aussi en liaison descendante. Nos hypothèses de base sont la périodicité des codes d'étalement et la disponibilité du code de l'utilisateur désiré au récepteur. Le premier groupe des algorithmes considérés correspond à celui des détecteurs multi-utilisateurs linéaires. Dans ce groupe, nous nous intéressons aux filtres de Wiener à rang réduit et nous proposons un nouveau filtre de rang réduit CGRRF. Ensuite, nous considérons le détecteur multi-utilisateurs aveugle de Wang & Poor et nous proposons son implémentation adaptative efficace pour la suppression conjointe de MAi et ISI. La partie suivante de travaill est consacrée aux techniques non-linéaires sous-optimales de détection multi-utilisateurs. En particulier, nous proposons le suppresseur d'interférence aveugle (BIC) qui estime les codes et les énergies des interféreurs en aveugle et qui est donc implémentable au niveau du mobile. La dernière partie de la thèse est dédiée à l'estimation du canal en aveugle en présence des résidus de porteuse.
Book Synopsis Frequency-Domain Multiuser Detection for CDMA Systems by : Paulo Silva
Download or read book Frequency-Domain Multiuser Detection for CDMA Systems written by Paulo Silva and published by CRC Press. This book was released on 2022-09-01 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Future broadband wireless communication systems are expected to be able to offer new and powerful services enabling fast transmission rates of several tens of Mbit/s. This is an ambitious challenge especially for mobile communication systems since these systems should be able to cope with severely time dispersive channels, associated to the signal multipath propagation. Moreover, these systems should have high spectral and power efficiencies, as well as high capacity and flexibility. Spread spectrum techniques, particularly coded division multiple access (CDMA) techniques allow high capacity and flexibility, continuous transmission requiring low-peak power requirements for the amplifiers, as well as some robustness against fading and time-dispersion effects associated with the multipath propagation. When employed in prefix assisted (PA) block transmission schemes combined with frequency-domain receiver implementations they become especially interesting for broadband wireless systems. In Frequency-Domain Multiuser Detection for CDMA Systems the use of PA block transmission is considered in the context of both DS (Direct Sequence) and MC (Multicarrier) CDMA schemes. The main goal is the study of frequency-domain multiuser detection techniques with iterative signal detection/decoding techniques, also in combination with estimation and cancelation of nonlinear distortion effects. The receiver structures are suitable to scenarios with high interference levels and strongly time-dispersive channels.
Book Synopsis Détection multi-utilisateurs en mode CDMA by : Moussa Abdi (Ingénieur).)
Download or read book Détection multi-utilisateurs en mode CDMA written by Moussa Abdi (Ingénieur).) and published by . This book was released on 2002 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Multi User Detection of CDMA Signals by : Anja Klein
Download or read book Multi User Detection of CDMA Signals written by Anja Klein and published by . This book was released on 1996 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Multi-user Detection in CDMA Sysem Using Adaptive Arrays at the Base Station by : Olga Muñoz Medina
Download or read book Multi-user Detection in CDMA Sysem Using Adaptive Arrays at the Base Station written by Olga Muñoz Medina and published by . This book was released on 1995 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Multi-user Detection for Multi-rate DS/CDMA Systems by : Jinwen Ma
Download or read book Multi-user Detection for Multi-rate DS/CDMA Systems written by Jinwen Ma and published by . This book was released on 2000 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless cellular communication is witnessing a rapid growth in market, technology and range of services. Current and future demands for wireless communication services motivate the need for handling multi-media traffic types. In a multimedia communication system, users with different and even time-varying rates and quality of services (QoS) requirements, such as voice, image and data, must be accommodated. The use of Spread Spectrum modulation with Code Division Multiple Access (CDMA) technology is an attractive approach for economical spectrally efficient and high quality cellular and personal communication services. This dissertation explores the technologies of applying different interference cancellation techniques to multi-rate CDMA systems that serve users with different QoS. Multiple Access Interference (MAI) and multipath propagation are the major issues in wireless communication systems. It is also true for multi-rate CDMA systems. Multi-user detection has been shown to be effective in combating the near-far problem and providing superior performance over conventional detection method. In this dissertation, we combine both linear minimum mean squared error (LMMSE) detector, nonlinear decision feedback detector, with other signal processing techniques, such as array processing and multipath combining, to create effective near-far resistant detectors for multi-rate CDMA systems. Firstly, we propose MMSE receivers for synchronous multi-rate CDMA system and compare the performance with the corresponding multi-rate decorrelating detectors. The multi-rate decorrelating detector is optimally near-far resistant and easy to implement. The proposed linear MMSE multi-rate receiver can be adaptively implemented only with the knowledge of the desired user. Due to the fact that MMSE detector offers best trade-off between the MAI cancellation and noise variance enhancement, it is shown that multi-rate MMSE receiver can offer better performance than the multi-rate decorrelator when the interfering users' Signal to Noise Ratio (SNR) is relatively low comparing to the desired user's SNR. Secondly, the asynchronous multi-rate CDMA system, we propose multi-rate multi-shoot decorrelating detectors and multi-rate multi-shot MMSE detectors. The performance of multi-shot detectors can be improved monotonically with increasing the number of stacked bits, but a great computational complexity is going to be introduced in order to get better performance. A debiasing method is introduced to multi-rate multi-shot linear detectors. Debiasing method optimizes multi-rate detectors based on the multi-rate multi-shot model. Debiasing multi-shot MMSE detector for multi-rate signals can offer performance than the corresponding debiasing multi-shot decorrelating detector. Thirdly, we propose linear space-time receivers for multi-rate CDMA systems. The minimum mean-squared error criteria is used. We perform a comparative study on the multi-rate receiver which uses either multipath (temporal) processing or array (spatial) processing, and the one which uses both array and multipath (space-time) processing. The space-time receiver for the multi-rate CDMA signals give us the potential of improving the capacity of multi-rate systems. The space-time processing combined with multiuser detection have the advantages of combating multipath fading through temporal processing, reducing MAI through MMSE method and provide antenna or diversity gain through spatial processing and increasing the capacity of the multi-rate CDMA systems. Lastly, the group-wise interference cancellation methods are proposed for multi-rate CDMA signals. The non-linear decision feedback detection (DFD) schemes are used in the proposed receivers. The proposed interference cancellation schemes benefit from the nature of the unequal received amplitudes for multi-rate CDMA signals. Users with same data rate are grouped together. Users with the highest data-rate are detected first. Interference between the groups is cancelled in a successive order. The results show that the group-wise MMSE DFD yields better performance than multi-rate linear MMSE detector and multi-rate decorrelating detector, especially for highly loaded CDMA systems.
Book Synopsis Multi-user Detection of DS-CDMA Systems in Rayleigh Fading Environments by : Gürcü Öz
Download or read book Multi-user Detection of DS-CDMA Systems in Rayleigh Fading Environments written by Gürcü Öz and published by . This book was released on 1996 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Equalization and Multi-user Detection for OFDM-based CDMA Schemes by :
Download or read book Equalization and Multi-user Detection for OFDM-based CDMA Schemes written by and published by . This book was released on 2003 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advanced Multi-user Direct-sequence Code Division Multiple Access (DS-CDMA) Detection Techniques for Cellular Communications by : Yan Qing Bian
Download or read book Advanced Multi-user Direct-sequence Code Division Multiple Access (DS-CDMA) Detection Techniques for Cellular Communications written by Yan Qing Bian and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Multi-user Detection Algorithms for Future DS-CDMA Mobile Systems by : Dimitris Koulakiotis
Download or read book Multi-user Detection Algorithms for Future DS-CDMA Mobile Systems written by Dimitris Koulakiotis and published by . This book was released on 2000 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Linear Multi-user Detection in DS-CDMA Cellular Systems by : Steven John Baines
Download or read book Linear Multi-user Detection in DS-CDMA Cellular Systems written by Steven John Baines and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Multi-user Detection and Blind Channel Estimation for DS-CDMA Systems by : Sergeï Burykh
Download or read book Multi-user Detection and Blind Channel Estimation for DS-CDMA Systems written by Sergeï Burykh and published by . This book was released on 2003 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis DS-CDMA Multi-user Detection in Asynchronous Multi-path Fading Channels Using Iterative Cancellations by : Xiaoli Liu
Download or read book DS-CDMA Multi-user Detection in Asynchronous Multi-path Fading Channels Using Iterative Cancellations written by Xiaoli Liu and published by . This book was released on 2004 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Detection Strategies for Asynchronous CDMA in Multi-path Channel by : Maria Leticia Sasabo
Download or read book Detection Strategies for Asynchronous CDMA in Multi-path Channel written by Maria Leticia Sasabo and published by . This book was released on 1998 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: In mobile radio communication systems using code division multiple access (CDMA), received signals suffer the near-far problem and multi-path fading. The main solution for the reduction of the near-far problem is multi-user detection but suffers in multi-path channel environments from a dependency on the accuracy of estimation of channel parameters. This work proposes and investigates new CDN1A detection strategies that are tolerably simple and give acceptable performance in a multi-path channel environments. This work develops a robust multi-path linear decorrelating detector (MLDD) and proposes algorithms for the reduction of noise enhancement for MLDD, the multi-path noise whitening matched filter (MWMF) detector and multi-path feedback (MFB) detector. The detectors thus derived operate on a path by path basis using a bank of matched filter and post detection selection combining. A novel algorithm for calculating the signal to noise ratio gain of the selection combiner has been introduced. The analytical results reveal that the selection combiner trades off only a slight degradation in signal to noise ratio gain, in comparison to the maximal ratio combiner (MRC), but with the added benefit of reduced complexity. On the other hand, the MRC performance depends on channel parameters that are difficult to obtain in multi-path fading channels. Both the analysis and simulation findings indicate that the MLDD and MFB detector are near-far resistant and have relatively less complexity than the corresponding detectors using a MRC. The MLDD is robust, since it does not require knowledge of the channel characteristics for operation, and, provided the feedback data are accurate, the bit error rate performance of the MFB detector is better than that of the MLDD. However, propagation of feedback data errors gives improvements over the MLDD only when the diversity level is large or signal-to-background noise ratio is high. Since the MWMF detector is not near-far resistant and has limited capacity in a multi-path channel, the MLDD is considered to be the most appropriate. The results also show that increasing either, the number of paths, or the number of users, degrades the detector bit error rate performance, although the use of diversity improves the situation. Nevertheless, the equivalence of users and paths cannot be taken as valid in general.
Book Synopsis DETECTION MULTIUTILISATEUR A ANTENNES MULTIPLES by : Ammar Chkeif
Download or read book DETECTION MULTIUTILISATEUR A ANTENNES MULTIPLES written by Ammar Chkeif and published by . This book was released on 1999 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: CE TRAVAIL DE THESE EST ESSENTIELLEMENT CONSACRE A LA DETECTION MULTI-UTILISATEUR POUR LE SYSTEME CDMA (CODE-DIVISION MULTIPLE-ACCESS) A ANTENNES MULTIPLES. LE SYSTEME CDMA EST LIMITE PAR LE NOMBRE D'UTILISATEURS QUI PEUVENT SIMULTANEMENT COMMUNIQUER SUR LE CANAL. CECI EST DU A LA DOMINATION DE L'INTERFERENCE ENTRE UTILISATEURS SUR LE BRUIT DU CANAL. CETTE INTERFERENCE PEUT ETRE COMBATTUE PAR L'UTILISATION D'UN RESEAU D'ANTENNES DIRECTIVES PERMETTANT LA SEPARATION SPATIALE DES UTILISATEURS. CEPENDANT, DANS LE CAS OU LE NOMBRE D'ANTENNES SERAIT INFERIEUR AU NOMBRE D'UTILISATEURS UNE SEPARATION COMPLETE N'EST PLUS POSSIBLE. LA DETECTION CONJOINTE A PARTIR DE LA TOTALITE DE L'OBSERVATION FOURNIE PAR LES ANTENNES EST UNE DEMARCHE NATURELLE. DANS CETTE THESE, NOUS AVONS PROPOSE PLUSIEURS SCHEMAS ITERATIFS POUR LA DETECTION MULTI-UTILISATEUR OU POUR L'ESTIMATION DU CANAL. CES SCHEMAS SONT BASES SUR L'ALGORITHME EM (EXPECTATION-MAXIMIZATION) ET L'ALGORITHME SAGE (SPACE-ALTERNATING GENERALIZED EXPECTATION-MAXIMIZATION). DANS LE CONTEXTE D'UN SYSTEME CDMA AVEC UN RESEAU D'ANTENNES, NOUS AVONS PROPOSE DEUX DETECTEURS LINEAIRES. CES DETECTEURS, DD (DECORRELATING DETECTOR) ET MMSE (MINIMUM-MEAN-SQUARE-ERROR) DETECTEUR, SONT BASES SUR L'ESTIMATION SOUS-ESPACE ; ET ILS NECESSITENT SEULEMENT LA CONNAISSANCE DE LA SIGNATURE TEMPORELLE DE L'UTILISATEUR DESIRE. LA MISE EN PLACE ADAPTATIVE DE CES DETECTEURS EST EGALEMENT PROPOSEE. POUR CELA, NOUS AVONS DEVELOPPE ET UTILISE UN NOUVEL ALGORITHME D'ESTIMATION ET DE POURSUITE DE SOUS-ESPACE : L'ALGORITHME OPAST (ORTHOGONAL PROJECTION APPROXIMATION SUBSPACE TRACKING). ENFIN, NOUS AVONS COMBINE LE DETECTEUR MMSE ADAPTATIF AVEC L'ANNULATION D'INTERFERENCE SEQUENTIELLE ET PARALLELE. DANS CETTE APPROCHE NOUS REDUISONS LA DIMENSION DU SOUS-ESPACE SIGNAL CHAQUE FOIS QU'UN INTERFERANT EST SUPPRIME. L'EVALUATION ANALYTIQUE DES PERFORMANCES, AINSI QUE LES RESULTATS DE SIMULATION CONFIRMENT L'EFFICACITE DES DETECTEURS PROPOSES.
