TY - JOUR
T1 - Decorrelating multiuser code-timing estimation for long-code CDMA with bandlimited chip waveforms
AU - Wang, Rensheng
AU - Li, Hongbin
PY - 2005/7
Y1 - 2005/7
N2 - This paper addresses the problem of multiuser code-timing estimation for asynchronous uplink code-division multiple-access (CDMA) systems with aperiodic spreading codes and bandlimited chip waveforms. Two decorrelating code-timing estimation schemes, namely the frequency-domain least-squares (FLS) and frequency-domain weighted least-squares (FWLS) estimators, are developed. The two proposed estimators offer different tradeoffs between complexity and estimation accuracy. A critical step for decorrelating-based estimation is to decompose the received signal into subsignals of shorter duration. We discuss how to perform the decomposition to ensure improved identifiability and statistical stability of the proposed schemes. Due to a unique signal structure in the frequency domain, both the FLS and FWLS estimators admit efficient implementations that result in significant complexity reductions. The Cramér-Rao bound for the estimation problem under study is derived and used as an assessment tool for the proposed estimators. Numerical results show that both of the proposed estimators can support overloaded systems (with more users than the processing gain) in multipath fading environments and significantly outperform a conventional technique based on matched-filter processing.
AB - This paper addresses the problem of multiuser code-timing estimation for asynchronous uplink code-division multiple-access (CDMA) systems with aperiodic spreading codes and bandlimited chip waveforms. Two decorrelating code-timing estimation schemes, namely the frequency-domain least-squares (FLS) and frequency-domain weighted least-squares (FWLS) estimators, are developed. The two proposed estimators offer different tradeoffs between complexity and estimation accuracy. A critical step for decorrelating-based estimation is to decompose the received signal into subsignals of shorter duration. We discuss how to perform the decomposition to ensure improved identifiability and statistical stability of the proposed schemes. Due to a unique signal structure in the frequency domain, both the FLS and FWLS estimators admit efficient implementations that result in significant complexity reductions. The Cramér-Rao bound for the estimation problem under study is derived and used as an assessment tool for the proposed estimators. Numerical results show that both of the proposed estimators can support overloaded systems (with more users than the processing gain) in multipath fading environments and significantly outperform a conventional technique based on matched-filter processing.
KW - Aperiodic/long spreading codes
KW - Bandlimited chip waveforms
KW - Code-division multiple access (CDMA)
KW - Parameter estimation
KW - Synchronization
UR - http://www.scopus.com/inward/record.url?scp=23844500025&partnerID=8YFLogxK
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U2 - 10.1109/TSP.2005.849177
DO - 10.1109/TSP.2005.849177
M3 - Article
AN - SCOPUS:23844500025
SN - 1053-587X
VL - 53
SP - 2369
EP - 2381
JO - IEEE Transactions on Signal Processing
JF - IEEE Transactions on Signal Processing
IS - 7
ER -