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Title of Thesis

New Schemes of MUD for Synchronous DS-CDMA and its Overloaded Systems

Author (s)
Muhammad Aamer Saleem
Institute/University/Department Details
Mohammad Ali Jinnah University, Karachi
Session
2007
Subject
Electronic Engineering
Number of Pages
125
Keywords (Extracted from title, table of contents and abstract of thesis)
 Multiple access interference, multiuser detection, practical swarm optimization

Abstract

The demand for better techniques in the field of multiuser detection for CDMA and WCDMA systems has grown especially in the last decade. This is due to the exponential growth in the number of subscribers and high data rate requirements due to multimedia and wireless internet services. However, there are many formidable limiting factors on the way to achieving this objective. One of the most challenging issue is the multiple access interference (MAI) in multiuser detection (MUD). Another issue is the computational complexity of the multiuser detector, which grows exponentially with the number of users for maximum likelihood detector (MLD). This will prohibit the use of MLD as multiuser detector unless its computational complexity is decreased substantially. These two major issues have been addressed in this dissertation. The problem of MAI has been tackled in a simple manner in this dissertation by using the concept of an additional redundant user, named as ‘Pseudo-user’, for DSCDMA systems. In this proposed scheme, the matched filters followed by minor linear processing have resulted in the removal of MAI completely. This scheme is theoretically independent of the number of users. However, this has been achieved at the expense of a minor percentage loss in bandwidth and noise enhancement. The percentage loss of bandwidth can be decreased by increasing the number of users. The complexity issue of MLD has been addressed by using particle swarm optimization (PSO) technique. Two soft versions of PSO have been proposed. The results achieved are almost optimal, but at a much lower computational complexity as compared to that of conventional approach for MLD. The above two schemes, i.e. the pseudo-user scheme and PSO scheme along with multicarrier modulation, have been applied to WCDMA overloaded systems in order to assert their practical applicability. The proposed schemes were tried on two types of channels  simple additive white Gaussian noise (AWGN) channel and slowly flat fading channel. The results have been compared with some standard techniques as well as recently reported techniques in the literature.

 

 

 


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S. No. Chapter Title of the Chapters Page Size (KB)
  0    
1 1 Introduction 1
  1.1 Multiple Access Techniques 1
  1.2 CDMA Systems 2
  1.3 Contributions of Dissertation 4
46 KB
  1.4 Organization of Dissertation 5
       
 
2 2 Multiuser Detection 6
  2.1 Introduction 6

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  2.2 Background 6
  2.3 CDMA Signal and Channel Model 11
  2.4 Multiuser Detectors 13
       
       
       
3 3 MUD using Pseudo-user Concept 28
  3.1 Introduction 28
  3.2 System Model 28


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  3.3 Proposed PU-PIC Detector for AWGN Channel 30
  3.4 Performance of PU-PIC Detector in AWGN Channel 33
  3.5 Proposed PU-PIC Detector for Multipath SFFR Channel 36
  3.6 Performance of PU-PIC Detector in SFFR Channel 38
4 4 PSO-Based Multiuser Detection 41
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  4.1 Introduction 41
  4.2 Introduction to PSO 42
  4.3 PSO-Based MUD for AWGN Channel 49
  4.4 PSO-Based MUD for Multipath SFFR Channel 58
       
       
5 5 MUD for Overloaded CDMA System 64
  5.1 Introduction 64
  5.2 Overloaded System with PU-PIC Detector in AWGN Channel 65
  5.3 Overloaded System in Multipath SFFR Channel 77
       
       
       
6 6 Conclusion and Future Work 85
  6.1 Conclusion 84
  6.2 Future Work 86
       
       

 

 

 

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7 7 Reference 88