Communications: directive radio wave systems and devices (e.g. – Directive – Position indicating
Reexamination Certificate
2006-04-18
2006-04-18
Phan, Dao (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Position indicating
C342S108000
Reexamination Certificate
active
07030814
ABSTRACT:
System and method to determine the location of a receiver in a multipath environment are provided. The received signal is correlated with the reference signals associated with the transmitting sources. Each correlation function is processed to derive various types of signal constraints, such as probability densities and uncertainty regions or intervals. In some embodiments, these constraints are for the code-phases and the Doppler frequencies. These signal constraints are transformed into constraints on the receiver variables and then fused together into a unified receiver constraint. A-priori constraints, such as constraints on the location of the receiver or the timestamp, may be incorporated into the unified receiver constraint. Some embodiments estimate a location based also on the estimated Doppler frequency. The constraints used by the invention are based on models of multipath effects and are geared towards mitigating these effects. In one of these models, a probability density for code-phase is obtained by convolving a gaussian distribution with an exponential distribution that describes the extra delay introduced by multipath. Another approach is based on identifying outliers in the set of code-phases. In other approaches, uncertainty region constraints and probability densities are combined. The present invention achieves faster and more sensitive signal acquisition and higher location accuracy in multipath environment, without compromising performance in other environments.
REFERENCES:
patent: 5488589 (1996-01-01), DeAngelis
patent: 5515062 (1996-05-01), Maine et al.
patent: 5537511 (1996-07-01), DeAngelis et al.
patent: 6092033 (2000-07-01), Uhlmann
Casadei Stefano
Mann Wallace
Roy Benjamin Van
Stone Jesse
Kwok Edward C.
MacPherson Kwok & Chen & Heid LLP
Phan Dao
SiRF Technology Inc.
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