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Erlangen, Nürnberg, Univ., Diss., 2003. / Erscheinungsjahr an der Haupttitelstelle: 2002. Computerdatei im Fernzugriff.

The most two important concern in CDMA code design, one is the properties of spreading codes correlation, and another one is the number of users. The correlation properties will influence BER (bit error rate) of the system directly, and the number of users will express the system capacity. In optical-CDMA system, optical spreading code is impossible to achieve idea correlation properties. Because of the optical sequence is consisted of ¡¨0¡¨¡B¡¨1¡¨. We prove it after. According to the result we can define the best properties of correlation of the optical complementary codes. The ideal of auto-correlation is 0( ) and the optimum cross-correlation is 1( ). According to the requirement of the optimum complementary codes we must first to decide the value of the best threshold and prove it. The properties of correlation are satisfied with optical prime-hopping complementary codes that we architecture. We analysis the performance of the prime-hopping complementary codes in optical CDMA. Because of the hits of MAI decrease we can support most number of users, so we can clearly find the system with the prime-hopping complementary codes has the better performance.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In this paper, a hybrid frequency division multiple access/code division multiple access (FDMA/CDMA) system in a Rician fading channel is described and analysis. The performance of the hybrid system is compared with a wideband CDMA system, which occupies the same total bandwidth. The results show that for DPSK modulation with a RIKE receiver, a hybrid system can have a greater capacity with a strong direct path component or a high signal to noise ratio (SNR). Otherwise, a wideband system remains optimal.

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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.