THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS

Persistent Link:
http://hdl.handle.net/10150/194932
Title:
THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS
Author:
Tang, Zuqiang
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This dissertation provides a comprehensive analysis of the coding-spreading tradeoff problem in finite-sized synchronous DS-CDMA systems. In contrast to the large system which has a large number of users, the finite-sized system refers to a system with a small number of users. Much work has been performed in the past on the analysis of the spectral efficiency of synchronous DS-CDMA systems and the associated coding-spreading tradeoff problem. However, most of the analysis is based on the large-system assumptions. In this dissertation, we focused on finite-sized systems with the help of numerical methods and Monte-Carlo simulations.Binary-input achievable information rates for finite-sized synchronous DS-CDMA systems with different detection/decoding schemes on AWGN channel are numerically calculated for various coding/spreading apportionments. We use these results to determine the existence and value of an optimal code rate for a number of different multiuser receivers, where optimality is in the sense of minimizing the SNR required for reliable multiuser communication. Our results are consistent with the well-known fact that all coding (no spreading) is optimal for the maximum a posteriori receiver.Simulations of the LDPC-coded synchronous DS-CDMA systems with iterative multiuser detection/decoding and MMSE multiuser detection/single-user decoding are also presented to show that the binary-input capacities can be closely approached with practical schemes. The coding-spreading tradeoff is examined using these LDPC code simulation results, where agreement with the information-theoretic results is demonstrated.We extend our work to the DS-CDMA systems on two idealized Rayleigh flat-fading channels: the chip-level flat-fading (CLFF) and the (code) symbol-level flat-fading (SLFF). These models represent ideal fast fading and slow fading channels, respectively. Both information-theoretic results and LDPC code simulation results are presented to show the effects of channel fading on system performance and the coding-spreading tradeoff. It is shown that fast fading can be beneficial to system performance under the condition of perfect channel state information at receiver, but slow fading is very harmful. Slow fading also increases the importance of coding greatly, compared to the AWGN and fast fading.Finally, we present some comparisons with large-system results on AWGN and CLFF channels, which show both consistencies and discrepancies.
Type:
text; Electronic Dissertation
Keywords:
DS-CDMA; LDPC; Coding-Spreading Tradeoff
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Electrical & Computer Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Ryan, William E.
Committee Chair:
Ryan, William E.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleTHE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMSen_US
dc.creatorTang, Zuqiangen_US
dc.contributor.authorTang, Zuqiangen_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis dissertation provides a comprehensive analysis of the coding-spreading tradeoff problem in finite-sized synchronous DS-CDMA systems. In contrast to the large system which has a large number of users, the finite-sized system refers to a system with a small number of users. Much work has been performed in the past on the analysis of the spectral efficiency of synchronous DS-CDMA systems and the associated coding-spreading tradeoff problem. However, most of the analysis is based on the large-system assumptions. In this dissertation, we focused on finite-sized systems with the help of numerical methods and Monte-Carlo simulations.Binary-input achievable information rates for finite-sized synchronous DS-CDMA systems with different detection/decoding schemes on AWGN channel are numerically calculated for various coding/spreading apportionments. We use these results to determine the existence and value of an optimal code rate for a number of different multiuser receivers, where optimality is in the sense of minimizing the SNR required for reliable multiuser communication. Our results are consistent with the well-known fact that all coding (no spreading) is optimal for the maximum a posteriori receiver.Simulations of the LDPC-coded synchronous DS-CDMA systems with iterative multiuser detection/decoding and MMSE multiuser detection/single-user decoding are also presented to show that the binary-input capacities can be closely approached with practical schemes. The coding-spreading tradeoff is examined using these LDPC code simulation results, where agreement with the information-theoretic results is demonstrated.We extend our work to the DS-CDMA systems on two idealized Rayleigh flat-fading channels: the chip-level flat-fading (CLFF) and the (code) symbol-level flat-fading (SLFF). These models represent ideal fast fading and slow fading channels, respectively. Both information-theoretic results and LDPC code simulation results are presented to show the effects of channel fading on system performance and the coding-spreading tradeoff. It is shown that fast fading can be beneficial to system performance under the condition of perfect channel state information at receiver, but slow fading is very harmful. Slow fading also increases the importance of coding greatly, compared to the AWGN and fast fading.Finally, we present some comparisons with large-system results on AWGN and CLFF channels, which show both consistencies and discrepancies.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectDS-CDMAen_US
dc.subjectLDPCen_US
dc.subjectCoding-Spreading Tradeoffen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineElectrical & Computer Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRyan, William E.en_US
dc.contributor.chairRyan, William E.en_US
dc.contributor.committeememberRyan, William E.en_US
dc.contributor.committeememberMarcellin, Michael W.en_US
dc.contributor.committeememberGoodman, Nathanen_US
dc.contributor.committeememberLeonard, John L.en_US
dc.identifier.proquest1058en_US
dc.identifier.oclc137353738en_US
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