Method and device for trilateration using LOS link prediction and pre-measurement LOS path filtering
A method for trilateration may include receiving a signal via each of a plurality of LOS paths and predicting performance of each LOS path. The method may also include filtering out signals received via LOS paths with performance below a predetermined threshold value. The method may further include performing trilateration using unfiltered signals to substantially determine a location of a device.
1. A method for trilateration, comprising:
receiving a signal via each of a plurality of LOS paths;
predicting a link margin of each LOS path;
filtering out signals received via LOS paths with predicted link margins below a predetermined threshold value by rejecting any signal with an associated predicted link margin less than a predetermined threshold link margin as an insufficiently detectable LOS path signal and to not use the signal for a time of arrival measurement; and
performing trilateration using signals via only LOS paths that remain after filtering out signals received via LOS paths with predicted link margins below the predetermined threshold value to substantially determine a location of a device.
2. The method of claim 1 , further comprising measuring a time of arrival for each signal.
3. The method of claim 2 , wherein filtering out signals received via LOS paths with predicted link margins below the predetermined threshold value is performed before measuring a time of arrival of each signal.
4. The method of claim 1 , further comprising filtering out signals received via a NLOS path.
5. The method of claim 1 , further comprising:
measuring a time of arrival for each signal, wherein filtering out signals received via LOS paths with predicted link margins below a predetermined threshold value is performed before measuring a time of arrival of each signal; and
filtering out any other signals after performing time of arrival measurement.
6. The method of claim 5 , further comprising providing predicted path performance for use in filtering out any other signals after performing time of arrival measurements.
7. The method of claim 1 , further comprising:
determining any intersections between each LOS path and any attenuating objects;
determining a RF signal power attenuation for each attenuating object for use in
predicting the link margin for each LOS path.
8. The method of claim 1 , further comprising estimating a receive antenna location and attitude.
9. The method of claim 1 , further comprising estimating a transmit antenna location and attitude.
10. The method of claim 1 , further comprising estimating a group of characteristics of any signal attenuating objects in an operating environment of the device, wherein the group of characteristics comprise a location in the operating environment, physical dimensions, and electromagnetic attenuative properties.
11. The method of claim 1 , further comprising accepting any signals received via a LOS path as being useable for performing trilateration in response to the predicted link margin of the LOS path being greater than or equal to a predetermined link margin threshold value.
12. A method for trilateration, comprising:
predicting a radio link margin for each LOS radio link between a receiver and each of a plurality of transmitters;
selecting only LOS radio links for range measurements that have a better predicted link margin relative to other radio links by rejecting any radio links with a link margin below a predetermined threshold link margin, wherein the predicted link margin is a ratio between a predicted receive power of a signal via the LOS radio link and a minimum detectable signal power and includes taking into account any attenuating objects in the LOS radio link between the receiver and each of the plurality of transmitters; and
determining the receiver's location using the selected radio links for range measurements.
13. The method of claim 12 , further comprising determining a probability of detecting signals for each LOS radio link.
14. The method of claim 12 , further comprising providing information on any marginal signals or radio links for use in filtering signals to reduce a probability of NLOS errors.
15. The method of claim 12 , further comprising filtering any LOS radio links with the predicted link margin being below a predetermined link margin threshold value.
16. The method of claim 12 , wherein taking into account any attenuating objects comprises:
determining any intersections between each LOS radio link and any attenuating objects; and
determining a signal power attenuation for each attenuating object.
17. The method of claim 12 , further comprising ensuring that a minimum of three detectable signal sources are selectable for location determination.
18. The method of claim 12 , further comprising performing pre-measurement and post-measurement filtering.
19. A device for trilateration, comprising:
a receiver to receive a signal from each of a plurality of transmitters over a respective LOS radio path;
a module to predict a link margin of each LOS radio path;
a filtering device to filter out signals received via LOS radio paths with a corresponding predicted link margin below a predetermined threshold link margin value by rejecting any signal with the corresponding predicted link margin less than the predetermined threshold link margin value as an insufficiently detectable LOS path signal and to not use the signal for a time of arrival measurement;
a module to determine a location of the receiver using signals that remain after filtering out signals received via LOS radio paths with a corresponding predicted link margin below the predetermined threshold link margin value; and
an output device to present the location of the receiver or a device associated with the receiver.
20. The device of claim 19 , further comprising a device to sense an attitude and location of the device or receiver.
21. The device of claim 19 , further comprising at least one device to sense, detect and map any attenuating objects in the respective radio paths.
22. The device of claim 19 , further comprising a memory, wherein the memory comprises at least one of antenna properties for an antenna associated with the receiver, antenna-to-receiver transmission line properties, a receivable bandwidth parameter, a minimum detectable signal power parameter, and properties associated with any attenuating objects in the respective radio paths.
23. The device of claim 19 , the filter device filters out signals before performing any measurements for determining the location of the receiver.
24. A device for trilateration, comprising:
means for predicting a radio link performance for each LOS radio link between a receiver and each of a plurality of transmitters;
means for selecting LOS radio links for range measurements that have a higher predicted link margin relative to other radio links by rejecting any radio links with an associated predicted link margin below a predetermined threshold link margin, wherein the predicted link margin is a ratio between a calculated receive power of a signal via the LOS radio link and a minimum detectable signal power; and
means for determining the receiver's location using the selected LOS radio links for range measurements.
25. The device of claim 24 , further comprising a pre-filter to filter any LOS radio links having the associated predicted link margin below the predetermined threshold link margin before any measurements for determining the receiver's location.
26. The device of claim 24 , further comprising a post-filter to reduce NLOS errors after any measurements for determining the receiver's location.
27. The device of claim 26 , further comprising means for providing radio link performance information to the post-filter.
28. The device of claim 24 , wherein the device is used in association with a vehicle to find a location of the vehicle.
29. A computer program product for trilateration, the computer program product comprising:
a computer usable medium having computer usable program code embodied therein, the computer usable medium comprising:
computer usable program code configured to predict a radio link margin for each LOS radio link between a receiver and each of a plurality of transmitters;
computer usable program code configured to select LOS radio links for range measurements that have the best predicted link margin relative to other LOS radio links by rejecting any LOS radio links with an associated predicted link margin below a predetermined threshold link margin, wherein the predicted link margin is a ratio between a calculated receive power of a signal via the LOS radio link and a minimum detectable signal power; and
computer usable program code configured to determine the receiver's location using the selected LOS radio links for range measurements.
30. The computer program product of claim 29 , further comprising computer usable program code configured to filter any LOS radio links with the associated predicted link margin below the predetermined threshold link margin.
31. The computer program product of claim 29 , further comprising computer usable program code configured to perform pre-measurement and post-measurement filtering.
32. A vehicle, comprising:
a device for locating the vehicle, wherein the device includes:
means for predicting a radio link margin for each LOS radio link between a receiver and each of a plurality of transmitters;
means for selecting LOS radio links for range measurements that have the best predicted radio link margin relative to other LOS radio links by rejecting any LOS radio links with an associated predicted link margin below a predetermined threshold link margin, wherein the predicted link margin is a ratio between a calculated receive power of a signal via the LOS radio link and a minimum detectable signal power; and
means for determining the vehicle's location using the selected LOS radio links for range measurements.
33. The vehicle of claim 32 , further comprising a pre-filter to filter any LOS radio links having the associated predicted link margin below the predetermined threshold link margin before any measurements for determining the receiver's location.
34. The vehicle of claim 32 , further comprising a post-filter to reduce NLOS errors after any measurements for determining the receiver's location.