Systems and methods for positioning using multipath signals
AssigneeThe Charles Stark Draper Laboratory, Inc.
InventorsJohn M. Elwell, Jr., Donald E. Gustafson, John R. Dowdle
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Abstract
A signal processing technique for RF active, passive, or aided localization approaches that utilizes multipath signals as additional measurements with a filter or estimator, e.g., a nonlinear filter. The filter uses indirect and direct path measurements or any other available signals to build parametric models of observable indirect paths. If one or more direct path measurements are subsequently lost (e.g., due to obstruction), the filter maintains an estimate of the position of the person or object of interest using indirect path measurements.
Claims14
A method for positioning using a multipath wireless signal, the method comprising the steps of:
- receiving a plurality of wireless signals comprising multipath signals;
- processing the plurality of wireless signals to identify at least one indirect path;
- determining an initial estimate for {r}, wherein {r} is a position of a receiver;
- determining initial estimates of and {wn, τ0n} for the at least one indirect path based on a parametric model relating {r} to a length of the at least one indirect path, the parametric model assuming, without prior knowledge of a local infrastructure or propagation channels associated with the at least one indirect path, that at least one multipath signal has experienced at least one specular reflection off a planar surface along the at least one indirect path before reaching the receiver;
- receiving a subsequent plurality of wireless signals comprising multipath signals;
- and
- updating the initial estimates of {r} and {wn, τ0n} using a nonlinear filter and the subsequent plurality of wireless signals applied to that filter,
- wherein wn is a unit vector in a direction of the at least one indirect path from a reflecting surface closest to the receiver and τ0n is a scalar geometry-dependent offset associated by the parametric model to the length of the at least one indirect path.
An apparatus for positioning using a multipath wireless signal, the apparatus comprising:
- a receiver for receiving a plurality of wireless signals comprising multipath signals;
- and
- a processor configured to (i) process the plurality of wireless signals to identify at least one indirect path, (ii) determine an initial estimate of {r}, wherein {r} is a position of the receiver, (iii) determine initial estimates of {wn, τ0n} for the at least one indirect path based on a parametric model relating {r} to a length of the at least one indirect path, the parametric model assuming, without prior knowledge of a local infrastructure or propagation channels associated with the at least one indirect path, that at least one multipath signal has experienced at least one specular reflection off a planar surface along the at least one indirect path before reaching the receiver, and (iv) update the initial estimates of {r} and {wn, τ0n} using a nonlinear filter and subsequent wireless signals applied to that filter,
- wherein wn is a unit vector in a direction of the at least one indirect path from a reflecting surface closest to the receiver and τ0n is a scalar geometry-dependent offset associated by the parametric model to the length of the at least one indirect path.
Dependencies are inferred from the claim text.