• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 160
  • 32
  • 31
  • 30
  • 22
  • 15
  • 10
  • 7
  • 7
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • Tagged with
  • 390
  • 64
  • 55
  • 50
  • 46
  • 45
  • 44
  • 43
  • 43
  • 39
  • 37
  • 37
  • 36
  • 33
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Wavelet-based multi-carrier code division multiple access systems

Muayyadi, Ali January 2003 (has links)
No description available.
2

Multiuser detection and channel estimation for DS-CDMA systems

Lampe, Alexander. January 1900 (has links) (PDF)
Erlangen, Nürnberg, Univ., Diss., 2003. / Erscheinungsjahr an der Haupttitelstelle: 2002. Computerdatei im Fernzugriff.
3

Spread Codes Design and Performance Analysis for Optical CDMA Systems

Lo, Ho-tai 30 August 2006 (has links)
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.
4

ANALYSIS OF HYBRID FDMA/CDMA SYSTEMS IN RICIAN FADING

Haiou, Zheng, Naitong, Zhang 10 1900 (has links)
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.
5

Linear Prediction Approach for Blind Multiuser Detection in Multicarrier CDMA Systems

Qin, Qin 15 October 2002 (has links)
No description available.
6

SEMIBLIND MULTIUSER DETECTION FOR MC-CDMA

SHEN, HANHONG January 2005 (has links)
No description available.
7

An Unified Approach to Analyze a Generic M-ary CDMA System

Chao, Chien-yao 30 July 2004 (has links)
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.
8

Design of I/Q Column-wise Complementary Code

Chen, Hong-lun 07 August 2008 (has links)
none
9

An application of independent component analysis to DS-CDMA detection

Fang, Yue 30 October 2006
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.
10

An application of independent component analysis to DS-CDMA detection

Fang, Yue 30 October 2006 (has links)
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.

Page generated in 0.0269 seconds