Abstract
In this paper, we present a novel code-timing estimator for asynchronous direct-sequence (DS) code-division multiple-access (CDMA) systems utilizing bandlimited chip waveforms. We start from a maximum likelihood (ML) approach that models the inter-symbol interference (ISI) and multiple-access interference (MAI) as a colored Gaussian process with unknown covariance matrix in the frequency domain. The exact ML estimator is highly nonlinear and requires iterative searches over multidimensional parameter space that is impractical to implement. To deal with this difficulty, we invoke asymptotic (large-sample) approximations of the ML criterion and reparameterization techniques, which lead to an asymptotic ML estimator that yields codetiming and channel estimates via efficient non-iterative quadratic optimizations. To benchmark the proposed estimator, we provide Cramér-Rao bound (CRB) analysis for the code-timing estimation problem. Numerical simulation results are presented to illustrate the performance of the proposed code-timing estimator for bandlimited CDMA in multipath fading channels.
Original language | English |
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Pages (from-to) | 2440-2444 |
Number of pages | 5 |
Journal | Conference Record - International Conference on Communications |
Volume | 4 |
State | Published - 2003 |
Event | 2003 International Conference on Communications (ICC 2003) - Anchorage, AK, United States Duration: 11 May 2003 → 15 May 2003 |