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Abstract:
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This paper addresses the estimation of the code-phase(pseudorange) and the carrier-phase of the direct signal received from a direct-sequence spread-spectrum satellite transmitter. The
signal is received by an antenna array in a scenario with interference
and multipath propagation. These two effects are generally
the limiting error sources in most high-precision positioning applications.
A new estimator of the code- and carrier-phases is derived
by using a simplified signal model and the maximum likelihood
(ML) principle. The simplified model consists essentially of
gathering all signals, except for the direct one, in a component with
unknown spatial correlation. The estimator exploits the knowledge
of the direction-of-arrival of the direct signal and is much simpler
than other estimators derived under more detailed signal models.
Moreover, we present an iterative algorithm, that is adequate for a
practical implementation and explores an interesting link between
the ML estimator and a hybrid beamformer. The mean squared
error and bias of the new estimator are computed for a number
of scenarios and compared with those of other methods. The presented
estimator and the hybrid beamforming outperform the existing
techniques of comparable complexity and attains, in many
situations, the Cramér–Rao lower bound of the problem at hand. |
