Location finding system and method

• US 6,657,549 B1
• Filed: 08/02/2000
• Issued: 12/02/2003
• Est. Priority Date: 08/05/1999
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Avery, David M.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): SHIMIZU, MATSUICHIRO
• Application Number:
  US09/631,361
• Time in Patent Office: 1,217 Days
• Field of Search: 340/825.49, 340/569, 342/457, 342/419
• US Class Current: 340/8.1
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A method of locating an article or person employs at least one transponding station (TS1) having its own radio identity carded by a person or article in the radio coverage area of a radio system. The system employs a plurality of clusters of spatially separate radio units (M1 to M7) having transceivers and received signal strength determining modules, each of the radio units having an individual identity. Each cluster is associated with a network interrogating station (NIU(1), NIU(2)) employing transceivers for communicating with at least the radio units in its cluster. A central station (10) has a transceiver for communicating with a plurality of the interrogating stations and storage for storing a database encompassing the locations of the radio units (M1 to M7).

Claims

1. A radio system, comprising:

a plurality of spatially separate radio units identifiable by a set of radio unit identifications, each radio unit including a first transceiver means and a received signal strength determining means;

an interrogating station including a second transceiver means for communicating with said radio units;

a central station including a third transceiver means for communicating with said interrogating station, said central station further including a storage means for storing a database including a location of each radio unit, and

a transponding station identifiable by a transponding station identification, said transponding station including a fourth transceiver means for communicating with said radio units and said interrogating station,

wherein, in response to an emergency request, said central station transmits an enquiry signal to said interrogating station, said enquiry signal including said transponding station identification,

wherein said interrogating station rebroadcasts the enquiry signal to said transponding station and transmits individual wake-up messages to said radio units, each wake-up message including a corresponding radio unit identification,

wherein, in response to receiving the wake-up messages, each radio unit is placed in a faster wake-up mode for determining a location of said transponder station than in a non-location determining mode,

wherein, in response to hearing the transponding station identity in the enquiry signal, said transponding station transmits a reply signal to said radio units, the reply signal including the transponding station identity,

wherein, in response to receiving the reply signal and being placed in the faster wake-up mode, each radio unit identifies said transponding station from the reply signal and determines a received signal strength of the reply signal,

wherein said radio units and said interrogating station relay the transponding station identification and the determines received signal strengths of the relay signal together with the set of radio unit identifications to said central station, and

wherein said central station computes the location of said transponding station relative to the location of each radio unit.

2. A method of operating a radio system including a plurality of spatially separate radio units, an interrogating station, a central station and a transponding station said method comprising:

transmitting an enquiry signal from the central station to the interrogating station in response to an emergency request, the enquiry signal including a transponding station identification corresponding to the transponding station;

transmitting the enquiry signal from the interrogating station to the transponding station;

transmitting individual wake-up messages from the interrogating station to each radio unit, each wake-up message including a corresponding radio unit identification;

placing each radio unit in a faster wake-up mode for determining a location of the transponder station than in a non-location determining mode;

transmitting a reply signal from the transponding station to the radio units in response to the transponding station hearing the transponding station identification in the enquiry signal and the radio units receiving the wake-up messages, the reply signal including the transponding station identity;

operating each radio unit to identify the transponding station from the reply signal and to determine a received signal strength of the reply signal in response to receiving the rely signal and being placed in the faster wake-up mode;

relaying the transponding station identification and the determined received signal strengths of the relay signal together with the set of radio unit identifications from the radio units and the interrogating station to the central station; and

operating the central to compute the location of the transponding station relative to the location of each radio unit in response to receiving the transponding station identification and the determined received signal strengths of the relay signal together with the set of radio unit identifications.