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US5613205A
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System and method of locating a mobile terminal within the service area of a cellular telecommunication system
Assignee: Telefonaktiebolaget LM Ericsson AB
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Filing: 1995-03-31
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Granted: 1997-03-18
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Expires: 2015-03-31
Abstract
Abstract A mobile terminal locator for locating a mobile terminal in a cellular telecommunication system having a plurality of base stations and associated cells. The mobile terminal locator identifies a plurality of candidate handoff cells having sufficient signal strength to maintain a call with the mobile terminal, and forces sequential handoffs of the mobile terminal from its serving cell to the plurality of candidate handoff cells. The locator then measures signal strength and propagation delay between the mobile terminal and each base station associated with each of the plurality of candidate handoff cells and between the mobile terminal and the serving base station. Either the signal strength, the propagation delay, or both are then used to calculate a distance between the mobile terminal and each base station associated with each of the plurality of candidate handoff cells and between the mobile terminal and its serving base station. From the calculated distances, a plurality of arcs of possible locations of said mobile terminal are then defined, the arcs being centered on the serving base station and each base station associated with each of the plurality of candidate handoff cells. Finally, the mobile terminal locator calculates an intersection point of the plurality of arcs of possible locations, the intersection point defining the location of the mobile station. The locator may operate in cellular telecommunication systems with or without synchronized timing reference signals from the base stations.
Inventors
- 👤 Daniel Dufour
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 02:13
CPC Classifications
H; H04; H04W; H04W64/00; G; G01; G01S; G01S5/00; G01S5/02; G01S5/14
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
213 words
A method of locating a mobile terminal in an unsynchronized cellular telecommunication system having a plurality of unsynchronized base stations and associated cells, said mobile terminal being served by one of said plurality of base stations, said method comprising the steps of: identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal; forcing sequential handoffs of said mobile terminal from said serving cell to said plurality of candidate handoff cells having sufficient signal strength to maintain a call; measuring signal strength and propagation delay between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; defining a plurality of arcs of possible locations of said mobile terminal, said arcs being centered on said serving base station and each unsynchronized base station associated with each of said plurality of candidate handoff cells; and calculating an intersection point of said plurality of arcs of possible locations, said intersection point defining the location of said mobile station.
Claim 2
Independent Claim
213 words
A method of locating a mobile terminal in an unsynchronized cellular telecommunication system having a plurality of unsynchronized base stations and associated cells, said mobile terminal being served by one of said plurality of base stations, said method comprising the steps of: identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal; forcing sequential handoffs of said mobile terminal from said serving cell to said plurality of candidate handoff cells having sufficient signal strength to maintain a call; measuring signal strength and propagation delay between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; defining a plurality of arcs of possible locations of said mobile terminal, said arcs being centered on said serving base station and each unsynchronized base station associated with each of said plurality of candidate handoff cells; and calculating an intersection point of said plurality of arcs of possible locations, said intersection point defining the location of said mobile station.
Claim 3
Dependent Claim
51 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 1 wherein the step of identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal includes identifying an initial search list comprising the serving cell's neighbor list.
Claim 4
Dependent Claim
88 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 2 wherein the step of identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal includes the steps of: measuring the signal strength between the mobile terminal and each unsynchronized base station associated with each of said cells in the serving cell's neighbor list; and making a list of the measured cells having sufficient signal strength to maintain a call with said mobile terminal.
Claim 5
Dependent Claim
32 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 3 further comprising the step of prioritizing said cells in said list of candidate cells for handoff.
Claim 6
Dependent Claim
61 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 1 wherein said step of calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes calculating said distances utilizing said measured propagation delays.
Claim 7
Dependent Claim
61 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 1 wherein said step of calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes calculating said distances utilizing said measured signal strength.
Claim 8
Dependent Claim
69 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 1 wherein said step of calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes calculating said distances utilizing a combination of said measured propagation delay and said measured signal strength.
Claim 9
Dependent Claim
51 words
The method of locating a mobile terminal in an unsynchronized cellular telecommunication system of claim 1 wherein said step of calculating an intersection point of said plurality of arcs of possible locations includes utilizing a geographic intersection technique from the group consisting of arculation, triangulation, and defining a probability density function.
Claim 10
Dependent Claim
226 words
A mobile terminal locator for locating a mobile terminal in an unsynchronized cellular telecommunication system having a plurality of unsynchronized base stations and associated cells, said mobile terminal being served by one of said plurality of base stations, said mobile terminal locator comprising: means for identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal; means for forcing sequential handoffs of said mobile terminal from said serving cell to said plurality of candidate handoff cells having sufficient signal strength to maintain a call; means for measuring signal strength and propagation delay between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; means for calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; means for defining a plurality of arcs of possible locations of said mobile terminal, said arcs being centered on said serving base station and each unsynchronized base station associated with each of said plurality of candidate handoff cells; and means for calculating an intersection point of said plurality of arcs of possible locations, said intersection point defining the location of said mobile station.
Claim 11
Dependent Claim
226 words
A mobile terminal locator for locating a mobile terminal in an unsynchronized cellular telecommunication system having a plurality of unsynchronized base stations and associated cells, said mobile terminal being served by one of said plurality of base stations, said mobile terminal locator comprising: means for identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal; means for forcing sequential handoffs of said mobile terminal from said serving cell to said plurality of candidate handoff cells having sufficient signal strength to maintain a call; means for measuring signal strength and propagation delay between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; means for calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station; means for defining a plurality of arcs of possible locations of said mobile terminal, said arcs being centered on said serving base station and each unsynchronized base station associated with each of said plurality of candidate handoff cells; and means for calculating an intersection point of said plurality of arcs of possible locations, said intersection point defining the location of said mobile station.
Claim 12
Dependent Claim
44 words
The mobile terminal locator of claim 9 wherein the means for identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal includes means for identifying an initial search list comprising the serving cell's neighbor list.
Claim 13
Dependent Claim
80 words
The mobile terminal locator of claim 10 wherein the means for identifying a plurality of candidate handoff cells having sufficient signal strength to maintain a call with said mobile terminal includes: means for measuring the signal strength between the mobile terminal and each unsynchronized base station associated with each of said cells in the serving cell's neighbor list; and means for making a list of the measured cells having sufficient signal strength to maintain a call with said mobile terminal.
Claim 14
Dependent Claim
22 words
The mobile terminal locator of claim 11 further comprising means for prioritizing said cells in said list of candidate cells for handoff.
Claim 15
Dependent Claim
54 words
The mobile terminal locator of claim 9 wherein said means for calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes means for calculating said distances utilizing said measured propagation delays.
Claim 16
Dependent Claim
54 words
The mobile terminal locator of claim 9 wherein said means for calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes means for calculating said distances utilizing said measured signal strength.
Claim 17
Dependent Claim
62 words
The mobile terminal locator of claim 9 wherein said means for calculating a distance between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes means for calculating said distances utilizing a combination of said measured propagation delay and said measured signal strength.
Claim 18
Dependent Claim
41 words
The mobile terminal locator of claim 9 wherein said means for calculating an intersection point of said plurality of arcs of possible locations utilizes a geographic intersection technique from the group consisting of arculation, triangulation, and defining a probability density function.
Claim 19
Dependent Claim
68 words
The mobile terminal locator of claim 9 wherein said means for measuring signal strength and propagation delay between the mobile terminal and each unsynchronized base station associated with each of said plurality of candidate handoff cells and between the mobile terminal and said serving base station includes means for measuring said signal strength and said propagation delay without synchronizing said base stations to transmit synchronized timing reference signals.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-03-17 | 2000-09-16 | 2001-03-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-03-17 | 2004-09-16 | 2005-03-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-03-17 | 2008-09-16 | 2009-03-18 | $7700.00 | Window Closed / Lapsed |