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Antenna arrays in multi-user detection of spread spectrum signals

In a code division multiple access (CDMA) spread spectrum system, each user is assigned a unique scrambling code. If these codes are not mutually orthogonal, the resulting multiple access interference (MAI) causes frame error rates to be unacceptably high. A number of multi-user detection algorithms...

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Main Authors: Karim, M.R., Wei, S.
Format: Conference or Workshop Item
Language:English
Published: 2007
Subjects:
TA Engineering (General). Civil engineering (General)
Online Access:http://eprints.um.edu.my/8787/1/Antenna_arrays_in_multi-user_detection_of_spread_spectrum_signals.pdf
http://eprints.um.edu.my/8787/
http://www.scopus.com/inward/record.url?eid=2-s2.0-47949125568&partnerID=40&md5=e0a4e7a772382746b9087bed3683b3aa ieeexplore.ieee.org/xpls/absall.jsp?arnumber=4454747
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spelling my.um.eprints.87872014-01-03T02:39:41Z http://eprints.um.edu.my/8787/ Antenna arrays in multi-user detection of spread spectrum signals Karim, M.R. Wei, S. TA Engineering (General). Civil engineering (General) In a code division multiple access (CDMA) spread spectrum system, each user is assigned a unique scrambling code. If these codes are not mutually orthogonal, the resulting multiple access interference (MAI) causes frame error rates to be unacceptably high. A number of multi-user detection algorithms have been suggested by various authors. Optimal receivers based upon maximum likelihood sequence decoding are quite complex, their complexity increasing exponentially with the number of users in the system. Sub-optimal receivers such as linear detectors or adaptive cancellers are not as complex, but the error rates increase with the number of users. In this paper, we suggest a new multi-user detection procedure using an antenna array at the receiver. First, we provide an upper bound on the minimum mean-squared error due to MAI, and show how the frame error rate increases with the number of users. The transmitted symbols are estimated by inverting the transfer function of the channel, multiplying it with the outputs of matched filters, and then passing the result through a maximum likelihood decoder. Our analysis indicates that if the channel impulse response is known with sufficient accuracy, this procedure leads to an optimal design. In those cases where the impulse response is only approximately known, we estimate the transmitted symbols and compute the resulting baseband SNR. If this SNR is above a threshold, the baseband signal is acceptable and ready for maximum likelihood sequence decoding. Otherwise, the impulse response is adjusted in small steps until the SNR is above that threshold. 2007 Conference or Workshop Item PeerReviewed application/pdf en http://eprints.um.edu.my/8787/1/Antenna_arrays_in_multi-user_detection_of_spread_spectrum_signals.pdf Karim, M.R. and Wei, S. (2007) Antenna arrays in multi-user detection of spread spectrum signals. In: Department of Civil Engineering, Faculty of Engineering Building, University of Malaya, 50603 Kuala Lumpur, MALAYSIA, 2007, Orlando, FL. http://www.scopus.com/inward/record.url?eid=2-s2.0-47949125568&partnerID=40&md5=e0a4e7a772382746b9087bed3683b3aa ieeexplore.ieee.org/xpls/absall.jsp?arnumber=4454747
institution Universiti Malaya
building UM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Malaya
content_source UM Research Repository
url_provider http://eprints.um.edu.my/
language English
topic TA Engineering (General). Civil engineering (General)
spellingShingle TA Engineering (General). Civil engineering (General)
Karim, M.R.
Wei, S.
Antenna arrays in multi-user detection of spread spectrum signals
description In a code division multiple access (CDMA) spread spectrum system, each user is assigned a unique scrambling code. If these codes are not mutually orthogonal, the resulting multiple access interference (MAI) causes frame error rates to be unacceptably high. A number of multi-user detection algorithms have been suggested by various authors. Optimal receivers based upon maximum likelihood sequence decoding are quite complex, their complexity increasing exponentially with the number of users in the system. Sub-optimal receivers such as linear detectors or adaptive cancellers are not as complex, but the error rates increase with the number of users. In this paper, we suggest a new multi-user detection procedure using an antenna array at the receiver. First, we provide an upper bound on the minimum mean-squared error due to MAI, and show how the frame error rate increases with the number of users. The transmitted symbols are estimated by inverting the transfer function of the channel, multiplying it with the outputs of matched filters, and then passing the result through a maximum likelihood decoder. Our analysis indicates that if the channel impulse response is known with sufficient accuracy, this procedure leads to an optimal design. In those cases where the impulse response is only approximately known, we estimate the transmitted symbols and compute the resulting baseband SNR. If this SNR is above a threshold, the baseband signal is acceptable and ready for maximum likelihood sequence decoding. Otherwise, the impulse response is adjusted in small steps until the SNR is above that threshold.
format Conference or Workshop Item
author Karim, M.R.
Wei, S.
author_facet Karim, M.R.
Wei, S.
author_sort Karim, M.R.
title Antenna arrays in multi-user detection of spread spectrum signals
title_short Antenna arrays in multi-user detection of spread spectrum signals
title_full Antenna arrays in multi-user detection of spread spectrum signals
title_fullStr Antenna arrays in multi-user detection of spread spectrum signals
title_full_unstemmed Antenna arrays in multi-user detection of spread spectrum signals
title_sort antenna arrays in multi-user detection of spread spectrum signals
publishDate 2007
url http://eprints.um.edu.my/8787/1/Antenna_arrays_in_multi-user_detection_of_spread_spectrum_signals.pdf
http://eprints.um.edu.my/8787/
http://www.scopus.com/inward/record.url?eid=2-s2.0-47949125568&partnerID=40&md5=e0a4e7a772382746b9087bed3683b3aa ieeexplore.ieee.org/xpls/absall.jsp?arnumber=4454747
_version_ 1643688387878584320
score 13.211869

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