Propagation delay estimation in asynchronous direct-sequence code-division multiple access systems

In an asynchronous direct-sequence code-division multiple access (DS-CDMA) communication system, the parameter estimation problem, i.e., estimating the propagation delay, attenuation and phase shift of each user's transmitted signal, may be complicated by the so-called near-far problem. The near-far problem occurs when the amplitudes of the users received signals are very dissimilar, as the case might be in many important applications. In particular, the standard method for estimating the propagation delays will fail in a near-far situation. Several new estimators, the maximum likelihood, an approximative maximum likelihood and a subspace-based estimator, are therefore proposed and are shown to be robust against the near-far problem. No knowledge of the transmitted bits is assumed, and the proposed estimators can thus be used for both acquisition and tracking. In addition, the Cramer-Rao bound is derived for the parameter estimation problem.

[1]  S. Rappaport,et al.  Spread-spectrum signal acquisition: Methods and technology , 1984, IEEE Communications Magazine.

[2]  Petre Stoica,et al.  MUSIC, maximum likelihood and Cramer-Rao bound , 1988, ICASSP-88., International Conference on Acoustics, Speech, and Signal Processing.

[3]  L. B. Milstein,et al.  Theory of Spread-Spectrum Communications - A Tutorial , 1982, IEEE Transactions on Communications.

[4]  Behnaam Aazhang,et al.  Multistage detection in asynchronous code-division multiple-access communications , 1990, IEEE Trans. Commun..

[5]  Craig K. Rushforth,et al.  Joint signal detection and parameter estimation in multiuser communications , 1993, IEEE Trans. Commun..

[6]  D. V. Sarwate,et al.  Noncoherent Parallel Acquisition of Pn Sequences in Direct-Sequence Spread-Spectrum Systems , 1992, IEEE Second International Symposium on Spread Spectrum Techniques and Applications.

[7]  Thomas L. Marzetta,et al.  Detection, Estimation, and Modulation Theory , 1976 .

[8]  Craig K. Rushforth,et al.  A Family of Suboptimum Detectors for Coherent Multiuser Communications , 1990, IEEE J. Sel. Areas Commun..

[9]  Petre Stoica,et al.  MUSIC, maximum likelihood, and Cramer-Rao bound , 1989, IEEE Transactions on Acoustics, Speech, and Signal Processing.

[10]  M.B. Pursley,et al.  Crosscorrelation properties of pseudorandom and related sequences , 1980, Proceedings of the IEEE.

[11]  E.G. Strom,et al.  Propagation delay estimation of DS-CDMA signals in a fading environment , 1994, 1994 IEEE GLOBECOM. Communications: Communications Theory Mini-Conference Record,.

[12]  Ralph Otto Schmidt,et al.  A signal subspace approach to multiple emitter location and spectral estimation , 1981 .

[13]  Bjorn Ottersten,et al.  Exact and Large Sample ML Techniques for Parameter Estimation and Detection in Array Processing , 1993 .

[14]  Ronald A. Iltis.  A digital receiver for demodulation of CDMA waveforms with a-priori unknown delays and amplitudes , 1991, MILCOM 91 - Conference record.

[15]  R. Lupas.  Near-Far Resistant Linear Multiuser Detection , 1989 .

[16]  H. Vincent Poor.  On parameter estimation in DS/SSMA formats , 1989 .

[17]  Todd K. Moon,et al.  Average acquisition time for SSMA channels , 1991, MILCOM 91 - Conference record.

[18]  Sergio Verdú,et al.  Minimum probability of error for asynchronous Gaussian multiple-access channels , 1986, IEEE Trans. Inf. Theory.

[19]  Todd K. Moon,et al.  A RASE approach to acquisition in SSMA systems , 1991, MILCOM 91 - Conference record.

[20]  Dilip V. Sarwate,et al.  Parallel acquisition of PN sequences in DS/SS systems , 1994, IEEE Trans. Commun..

[21]  Edward J. Wegman,et al.  Statistical Signal Processing , 1985 .

[22]  A. Gualtierotti.  H. L. Van Trees, Detection, Estimation, and Modulation Theory, , 1976 .

[23]  Stefan Parkvall,et al.  Near-Far Resistant Propagation Delay Estimators for Asynchronous Direct-Sequence Code Division Multiple Access Systems , 1994, Mobile Communications.