Localization method and system using non-regenerative UWB relays

• US 9,311,798 B2
• Filed: 12/13/2012
• Issued: 04/12/2016
• Est. Priority Date: 12/15/2011
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation), Consorzio Nazi Interuniv Per Le Telecomunicazioni
• Original Assignee: Commissariat A L'Energie Atomique et AUX Energies Alternatives, Consorzio Nazi Interuniv Per Le Telecomunicazioni
• Inventors: Conti, Andrea, Dardari, Davide, Sibille, Alain, Derrico, Raffaele
• Primary Examiner(s): Lee, Benjamin C
• Assistant Examiner(s): DARAMOLA, ISRAEL O
• Application Number:
  US13/713,950
• Publication Number:
  US 20130154836A1
• Time in Patent Office: 1,216 Days
• Field of Search: 340/539.11, 340/572.1, 370/246, 375/138, 455/11.1
• US Class Current: 1/1
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00

Abstract

The present invention relates to a method and a system for determining the position of an object which can be a passive or an active tag (140). The system comprises a plurality of anchor nodes (111,112) and a plurality of non-regenerative relays (121,122,123) of known positions. In case of an active tag, a UWB pulse signal is emitted by the tag and received by the anchor nodes either directly or via a relay. In case of a passive tag, UWB pulse signals are sent by the anchors nodes and reflected back, either way being either a LOS path or a relayed path. A processing node (130) collects the signals received by the anchor nodes (111,112) to estimate the position of the tag.

Claims

1. A method, implemented by a processing node, for determining the position of an active tag with a radio locating system comprising a plurality of anchor nodes in known positions, and a plurality of non-regenerative relays in known positions, each of said relays being configured to relay a UWB (ultra-wide band) pulse signal emitted by said tag to one of the anchor nodes, the method comprising:

collecting UWB pulse signals received by said anchor nodes, the UWB pulse signals being received by the anchor nodes either directly from said tag through a LOS (line of sight) path or relayed by a relay through a relayed path; and

processing the thus collected signals to estimate the position of the tag together with a time of emission of originally emitted UWB pulse signal from the tag by maximizing a log maximum likelihood function over possible combinations of the position of the tag and the time of emission of originally emitted UWB pulse signal from the tag depending upon the collected signals, the maximum likelihood function taking into account a contribution of the UWB pulse signals being received by the anchor nodes directly from said tag through a LOS path and a contribution of the UWB signals being received by the anchor nodes relayed by a relay through a relayed path.

2. A method according to claim 1, wherein the non-regenerative relays are passive.

3. A method according to claim 1, wherein the non-regenerative relays are active.

4. A method according to claim 1, wherein the processing node further estimates a time of emission of the originally emitted UWB pulse signal from the tag by maximizing the log maximum likelihood function depending upon the collected signals.

5. A method according to claim 1, wherein the log maximum likelihood function is calculated as:

6. A method according to claim 1, wherein the UWB pulse signal is modulated with a time-hopping code and/or a bipolar code.

16. A method according to claim 1, wherein the maximum likelihood function is calculated based on a channel gain and a propagation delay between the tag and each relay in the system, a channel gain and a propagation delay between the tag and each anchor node in the system, and a channel gain and a propagation delay between each relay and each anchor node in the system.

7. A method, implemented by a processing node, for determining the position of a passive tag with a radio locating system comprising a plurality of anchor nodes of known positions, and a plurality of non-regenerative relays of known positions, each of said relays being configured to relay an interrogating UWB (ultra-wide band) pulse signal emitted from an anchor node to said passive tag and a UWB pulse signal reflected by said passive tag back to said anchor node, the method comprising:

collecting the UWB pulse signals received by said anchor nodes after reflection on said passive tag, the UWB pulse signals being received by the anchor nodes either through a LOS (line of sight) path or relayed by a relay through a relayed path; and

processing the thus collected signals to estimate the position of the passive tag by maximizing a log maximum likelihood function over possible combinations of the position of the passive tag and the time of emission of originally emitted UWB pulse signal from the passive tag depending upon the collected signals, the maximum likelihood function taking into account a contribution of the UWB pulse signals being received by the anchor nodes directly from said passive tag through a LOS path and a contribution of the UWB signals being received by the anchor nodes relayed by a relay through a relayed path.

8. A method according to claim 7, wherein the passive tag is adapted to backscatter an incoming signal according to code of binary symbols, a first binary state corresponding to a reflection of the incoming signal as it is and a second binary state corresponding to a reflection of the incoming signal with a reverse polarity.

9. A method according to claim 7, wherein the non-regenerative relays are passive.

10. A method according to claim 7, wherein the non-regenerative relays are active.

11. A method according to claim 7, wherein the log maximum likelihood function is calculated as:

12. A method according to claim 7, wherein each anchor node emits a UWB pulse signal which is modulated according to a unique time-hopping and/or bipolar code.

13. A radio locating system for estimating the position of an active tag, said radio locating system comprising:

a plurality of anchor nodes of known positions;

a plurality of non-regenerative relays of known positions, each of said relays being adapted to relay a UWB (ultra-wide band) pulse signal emitted by said tag to an anchor node;

a processing node configured to collect UWB pulse signals received by said anchor nodes, the UWB pulse signals being received by the anchor nodes either directly from said tag through a LOS (line of sight) path or relayed by a relay through a relayed path, and process the thus collected signals to estimate the position of the tag by maximizing a log maximum likelihood function over possible combinations of the position of the tag and the time of emission of originally emitted UWB pulse signal from the tag depending upon the collected signals, the maximum likelihood function taking into account a contribution of the UWB pulse signals being received by the anchor nodes directly from said tag through a LOS path and a contribution of the UWB signals being received by the anchor nodes relayed by a relay through a relayed path.

15. A radio locating system according to claim 13, wherein each non-regenerative relay comprises a first antenna and a second antenna, a first switch connected to said first antenna and being adapted to switch between the input of a first amplifier and the output of a second amplifier, a second switch connected to said second antenna and being adapted to switch between the input of the second amplifier and the output of the first amplifier, the first switch and second switch being either simultaneously switched to the respective input and output of the first amplifier, or simultaneously switched to the respective output and input of the second amplifier.

14. A radio locating system for estimating the position of an active tag, said radio locating system comprising:

a plurality of anchor nodes of known positions, each anchor node being configured to emit an interrogating UWB pulse signal;

a plurality of non-regenerative relays of known positions, each of said relays being adapted to relay an interrogating UWB (ultra-wide band) pulse signal emitted from an anchor node to said active tag and a UWB pulse signal reflected by said active tag back to said anchor node;

a processing node configured to collect the signals received by said anchor nodes after reflection on said active tag, either through a LOS (line of sight) path or relayed by a relay through a relayed path, and process the thus collected signals to estimate the position of the active tag by maximizing a log maximum likelihood function over possible combinations of the position of the active tag and the time of emission of originally emitted UWB pulse signal from the active tag depending upon the collected signals, the maximum likelihood function taking into account a contribution of the UWB pulse signals being received by the anchor nodes directly from said tag through a LOS path and a contribution of the UWB signals being received by the anchor nodes relayed by a relay through a relayed path.