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Article: Downlink transmission of broadband OFCDM systems - Part IV: Soft decision

TitleDownlink transmission of broadband OFCDM systems - Part IV: Soft decision
Authors
KeywordsFading channel
Interference cancellation
Minimum mean-square error (MMSE) detection
Orthogonal frequency-division multiplexing (OFDM)
Packet-error rate (PER)
Soft-decision function
Two-dimensional (2-D) spreading
Issue Date2006
PublisherIEEE.
Citation
Ieee Journal On Selected Areas In Communications, 2006, v. 24 n. 6, p. 1208-1220 How to Cite?
AbstractIn this paper, the performance of turbo-coded orthogonal frequency and code-division multiplexing (OFCDM) systems is investigated with soft multicode interference (MCI) cancellation and minimum mean-square error (MMSE) detection for downlink transmission in future high-speed wireless communications. To regenerate the soft interference signal, the conventional turbo decoding algorithm must be modified to provide log-likelihood ratio (LLR) values for all coded bits. Based on the LLR outputs of turbo decoder, two soft-decision functions are proposed, called LLR-soft-decision and Gaussian-soft-decision functions. The Gaussian assumptions used for deriving these two soft functions are verified by simulation results, and simple methods are proposed to estimate parameters used in the soft functions in practical systems. By means of computer simulations, the performance of soft MCI cancellation is studied extensively and compared with that of hard ones. It is shown that in a highly frequency-selective channel, soft MCI cancellation and MMSE detection can significantly improve the performance of turbo-coded OFCDM systems. Two iterations in turbo decoding are sufficient for both hard and soft-decision functions. The proposed soft-decision functions outperform the hard-decison function with various channel conditions and system parameters, such as the channel correlation, the quality of channel estimation, the number of iterations in turbo decoding and the frequency-domain spreading factor (N F). Furthermore, the Gaussian-soft-decision function provides better performance than the LLR-soft-decision function. Finally, although frequency diversity gain is saturated for large channel correlation when N F is large as in [6], the gain increases further with increasing N F for small channel correlation even when N F is large. © 2006 IEEE.
Persistent Identifierhttp://hdl.handle.net/10722/44743
ISSN
2015 Impact Factor: 3.672
2015 SCImago Journal Rankings: 2.915
References

 

DC FieldValueLanguage
dc.contributor.authorZhou, Yen_HK
dc.contributor.authorWang, Jen_HK
dc.date.accessioned2007-10-30T06:09:13Z-
dc.date.available2007-10-30T06:09:13Z-
dc.date.issued2006en_HK
dc.identifier.citationIeee Journal On Selected Areas In Communications, 2006, v. 24 n. 6, p. 1208-1220en_HK
dc.identifier.issn0733-8716en_HK
dc.identifier.urihttp://hdl.handle.net/10722/44743-
dc.description.abstractIn this paper, the performance of turbo-coded orthogonal frequency and code-division multiplexing (OFCDM) systems is investigated with soft multicode interference (MCI) cancellation and minimum mean-square error (MMSE) detection for downlink transmission in future high-speed wireless communications. To regenerate the soft interference signal, the conventional turbo decoding algorithm must be modified to provide log-likelihood ratio (LLR) values for all coded bits. Based on the LLR outputs of turbo decoder, two soft-decision functions are proposed, called LLR-soft-decision and Gaussian-soft-decision functions. The Gaussian assumptions used for deriving these two soft functions are verified by simulation results, and simple methods are proposed to estimate parameters used in the soft functions in practical systems. By means of computer simulations, the performance of soft MCI cancellation is studied extensively and compared with that of hard ones. It is shown that in a highly frequency-selective channel, soft MCI cancellation and MMSE detection can significantly improve the performance of turbo-coded OFCDM systems. Two iterations in turbo decoding are sufficient for both hard and soft-decision functions. The proposed soft-decision functions outperform the hard-decison function with various channel conditions and system parameters, such as the channel correlation, the quality of channel estimation, the number of iterations in turbo decoding and the frequency-domain spreading factor (N F). Furthermore, the Gaussian-soft-decision function provides better performance than the LLR-soft-decision function. Finally, although frequency diversity gain is saturated for large channel correlation when N F is large as in [6], the gain increases further with increasing N F for small channel correlation even when N F is large. © 2006 IEEE.en_HK
dc.format.extent751002 bytes-
dc.format.extent2894 bytes-
dc.format.extent2319 bytes-
dc.format.mimetypeapplication/pdf-
dc.format.mimetypetext/plain-
dc.format.mimetypetext/plain-
dc.languageengen_HK
dc.publisherIEEE.en_HK
dc.relation.ispartofIEEE Journal on Selected Areas in Communicationsen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rights©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.en_HK
dc.subjectFading channelen_HK
dc.subjectInterference cancellationen_HK
dc.subjectMinimum mean-square error (MMSE) detectionen_HK
dc.subjectOrthogonal frequency-division multiplexing (OFDM)en_HK
dc.subjectPacket-error rate (PER)en_HK
dc.subjectSoft-decision functionen_HK
dc.subjectTwo-dimensional (2-D) spreadingen_HK
dc.titleDownlink transmission of broadband OFCDM systems - Part IV: Soft decisionen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0733-8716&volume=24&issue=6&spage=1208&epage=1220&date=2006&atitle=Downlink+transmission+of+broadband+OFCDM+systems-part+IV:+soft+decisionen_HK
dc.identifier.emailZhou, Y:yqzhou@eee.hku.hken_HK
dc.identifier.authorityZhou, Y=rp00214en_HK
dc.description.naturepublished_or_final_versionen_HK
dc.identifier.doi10.1109/JSAC.2005.864010en_HK
dc.identifier.scopuseid_2-s2.0-33746264959en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33746264959&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume24en_HK
dc.identifier.issue6en_HK
dc.identifier.spage1208en_HK
dc.identifier.epage1220en_HK
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridZhou, Y=7405367062en_HK
dc.identifier.scopusauthoridWang, J=11439898400en_HK

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