Dans la première partie de la thèse, on considère des méthodes d'estimation des canaux utilisateurs dédiés en liaison descendante. Ces méthodes sont particulièrement avantageuses dans un contexte de transmission à formation de faisceaux. Elles ne supposent aucune connaissance a priori des retards des signaux reçus ainsi que les paramètres de formation des faisceaux; exploitent la totalité des séquences pilotes transmises ainsi que la dynamique structurée du canal.Dans la seconde partie, on commence par considérer un schéma d'égalisation au niveau chip et dite HDD-NLMS. Ce schéma utilise l'estimation de la précédente séquence chip comme réponse cible pour l'adaptation de l'égaliseur. Dans la suite propose les égalisateurs niveau symbole HSDPA N-Griffith et HDD-NLMS qui permettent une vitesse d'adaptation 16 fois plus élevée que dans le cas de l'utilisation des symboles PCPICH. Les solutions spécifiques HSDPA ont une complexité raisonnable et offrent des performances proches aux Max-SINR dans un environnement réel.Dans la dernière partie, nous évaluons l'avantage des égalisateurs au niveau chip par rapport au récepteur Rake conventionnel ainsi que l'avantage d'une décision hard par rapport à l'utilisation d'une contre réaction linéaire dans le contexte d'un récepteur avec élimination itérative parallèle des interférences. Cette contre réaction sera déduite d'un développement polynomial de l'inverse de la matrice de covariance en amont du premier étage d'égalisation. Etant donné que les égalisateurs à chaque étage sont différents, nous utilisons les résultats d'analyse des étages précédents afin de pouvoir estimer les paramètres de l'égalisateur à un étage donné.

This work presents the application of the theory and algorithms of Independent Component Analysis (ICA) to blind multiuser symbol estimation in downlink of Direct-Sequence Code Division Multiple Access (DS-CDMA) communication system. The main focus is on blind separation of convolved CDMA mixture and the improvement of the downlink symbol estimation. Term blind implies that the separation is performed based upon the observation only. Since the knowledge of system parameter is available only in the downlink environment, the blind multiuser detection algorithm is an attractive option in the downlink.<p>Firstly, the basic principles of ICA are introduced. The objective function and optimization algorithm of ICA are discussed. A typical ICA method, one of the benchmark methods for ICA, FastICA, is considered in details. Another typical ICA algorithm, InfoMAX, is introduced as well, followed by numerical experiment to evaluate two ICA algorithms.<p>Secondly, FastICA is proposed for blind multiuser symbol estimation as the statistical independence condition of the source signals is always met. The system model of simulation in downlink of DS-CDMA system is discussed and then an ICA based DS-CDMA downlink detector has been implemented with MATLAB. A comparison between the conventional Single User Detection (SUD) receiver and ICA detector has been made and the simulation results are analyzed as well. The results show that ICA detector is capable of blindly solving multiuser symbol estimation problem in downlink of DS-CDMA system.<p>The convergence of ICA algorithm is, then, discussed to obtain more stable simulation results. A joint detector, which combines ICA and SUD and where ICA is considered as an additional element attached to SUD detector, has been implemented. It was demonstrated that the joint detector gives the lowest error probability compared to conventional SUD receiver and pure ICA detector with training sequences.

This work presents the application of the theory and algorithms of Independent Component Analysis (ICA) to blind multiuser symbol estimation in downlink of Direct-Sequence Code Division Multiple Access (DS-CDMA) communication system. The main focus is on blind separation of convolved CDMA mixture and the improvement of the downlink symbol estimation. Term blind implies that the separation is performed based upon the observation only. Since the knowledge of system parameter is available only in the downlink environment, the blind multiuser detection algorithm is an attractive option in the downlink.<p>Firstly, the basic principles of ICA are introduced. The objective function and optimization algorithm of ICA are discussed. A typical ICA method, one of the benchmark methods for ICA, FastICA, is considered in details. Another typical ICA algorithm, InfoMAX, is introduced as well, followed by numerical experiment to evaluate two ICA algorithms.<p>Secondly, FastICA is proposed for blind multiuser symbol estimation as the statistical independence condition of the source signals is always met. The system model of simulation in downlink of DS-CDMA system is discussed and then an ICA based DS-CDMA downlink detector has been implemented with MATLAB. A comparison between the conventional Single User Detection (SUD) receiver and ICA detector has been made and the simulation results are analyzed as well. The results show that ICA detector is capable of blindly solving multiuser symbol estimation problem in downlink of DS-CDMA system.<p>The convergence of ICA algorithm is, then, discussed to obtain more stable simulation results. A joint detector, which combines ICA and SUD and where ICA is considered as an additional element attached to SUD detector, has been implemented. It was demonstrated that the joint detector gives the lowest error probability compared to conventional SUD receiver and pure ICA detector with training sequences.

In this thesis we propose and study a new CDMA architecture, namely parallel-transmission M-ary CDMA system. By using variable combination patterns of spreading codes, we can greatly improve the system bandwidth utilization. The more spreading codes used in each user, the higher bandwidth efficiency can achieve with more bits packed in each symbol. In addition, a user can adjust transmission data rate easily by changing the number of spreading codes used to fit varying system operational requirements. In this thesis, we should use maximum likelihood detection algorithms for signal detection to ensure an optimal performance in terms of bit error rate. The system performance of such a parallel-transmission M-ary CDMA system is analytically studied in both AWGN and Nakagami channels in the presence of multiple access interference and multi-path interference. The both theoretical analysis and computer simulations show that the scheme works pretty well under various channel condition.

This is a research on Performance Analysis of Random Complementary Code Based MIMO-CDMA System. In the first instance we discuss the produce method of random complementary codes by the basic matrix and pole matrix. Pole matrix is the produce method of Walsh Hadamard matrix. We discuss the properties of random complementary codes by the pole matrix and realize its auto-correlation and cross-correlation are perfect. Apply random complementary codes on Distributed Users and Antennas. Random complementary codes have the ideal auto-correlation and cross-correlation by way of direct-sequence spreading system, so it can solve multi-path interference and multi-access interference effectively. Apply Space-Time Block Codes on Distributed time and Antennas in the same user. Systems combine RCC with STBC. I design STBC RCC-CDMA System and two receivers. We discuss Signal Synthesis Receiver and Distributed Antennas Receiver with Rayleigh fading channel. In Chapter 2, we start to introduce random complete complementary codes and its property to resist interferences in different transmission. Chapter 3 is the introduction Performance Analysis of Random Complementary Code Based MIMO-CDMA System with full correlated Rayleigh fading channel. Chapter 4 is the introduction Performance Analysis of Random Complementary Code Based MIMO-CDMA System with multi-path Rayleigh fading channel. Chapter 5 is the introduce conclusion and to research a goal in the future.

In this thesis, the performance comparison of orthogonal frequency division multiple access (OFDMA) and complete complementary code based CDMA system is studied. The complete complementary code is composed of several sets of auto-complementary codes, any two of which are cross-complementary codes. The perfect correlation between code sets is the distinguishing feature of complete complementary code. OFDMA is used in the 4th. generation Mobile Communication systems. The OFDMA architecture can offer an MAI-free operation in both down-link (synchronous channel) and up-link (asynchronous channel) transmission under the AWGN channel.

PN code synchronization is a common and essential task at the receiver in CDMA communication systems. In most literatures, there usually exists assumption of synchronization between the received spreading sequence and a locally generated replica. Few practical and detail synchronization schemes are showed in literatures. Moreover, there are no sufficient knowledge about operation characteristics of loop elements and operation strategies. Hence, in this thesis we propose some schemes about PN code synchronization and then do some analysis to compare performance of those schemes in AWGN channel. Code synchronization at DSSS receivers is performed in two steps. One is code acquisition and the other is code tracking. In acquisition process, we propose so called some ¡§auxiliary decision criterions¡¨ in multiple-dwell detection strategies. Analytical results are validated with computer simulations. By use of auxiliary decision criterions, the acquisition process is outperforms the conventional multiple-dwell and single-dwell detection strategies in AWGN channel. In code tracking process, we use coherent DLL. Loop filter parameters are tuned by observing phase-plane trajectories to acquire stable lock points and convergence property. In addition, we proposed a coherent DLL chip implementation, and accomplish the design flow that includes verification, synthesis, place and route, and simulation.

Abstract For reducing the interference of multi-path and multi-user access, we propose to design a spreading code with ideal auto-correlation and cross-correlation. In this paper, we will introduce a code with ideal auto-correlation and cross-correlation. Recently, there has been great interest in applying zero correlation spreading codes to reduce interference of different users or their multi-path. The set of sequences having zero auto-correlation and cross-correlation plays an important part in typical DS-CDMA systems. A periodic sequence with zero out-of-phase auto-correlation is called a perfect or an orthogonal sequence, it can mitigate the multi-path interference. Similarly, a set of periodic sequences with zero cross-correlation values is called a set of uncorrelated sequences. However, it is impossible to be found in single sequence spreading code. In this paper, we propose a new code for ideal auto-correlation and cross-correlation, and the code set size is equal to the number of flock size.

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Universiẗat, Diss., 2001--Kaiserslautern.