Method and system for locating a mobile station
First Claim
1. A method for locating a mobile station based on a mobile communications system, comprising the steps of:
- setting a plurality of two-dimensional search areas each being dissected into a predetermined size narrower than a radio zone of each of a plurality of base stations;
pre-obtaining a positional relationship between said base stations and each of said two-dimensional search areas based on mutual time differences reflecting time differences in radio wave propagation between base stations and said two-dimensional search areas;
transmitting characteristic signals from respective base stations to obtain mutual time differences in the propagation times of said characteristic signals between transmission of said characteristic signals at respective base stations and reception thereof at a mobile station; and
identifying a two-dimensional search area where said mobile station is present by comparing the obtained mutual time differences between said characteristic signals with the pre-obtained positional relationship between said base stations and each of said two-dimensional search areas.
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Abstract
This invention relates to a mobile station locating method for locating a mobile station based on a mobile communications system. Radio zones of base stations are dissected into a plurality of search areas (grid sections). A positional relationship between base stations and a concerned search area is defined by mutual time differences in the radio wave propagation between them. The base stations transmit their characteristic signals. Time differences in the propagation of the characteristic signals are caused between transmission of the characteristic signals at respective base stations and reception at a mobile station. Mutual differences in their propagation times are used to identify a search area where the mobile station is present. Thus, the position of the mobile station can be identified by an area not by a point.
90 Citations
13 Claims
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1. A method for locating a mobile station based on a mobile communications system, comprising the steps of:
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setting a plurality of two-dimensional search areas each being dissected into a predetermined size narrower than a radio zone of each of a plurality of base stations; pre-obtaining a positional relationship between said base stations and each of said two-dimensional search areas based on mutual time differences reflecting time differences in radio wave propagation between base stations and said two-dimensional search areas; transmitting characteristic signals from respective base stations to obtain mutual time differences in the propagation times of said characteristic signals between transmission of said characteristic signals at respective base stations and reception thereof at a mobile station; and identifying a two-dimensional search area where said mobile station is present by comparing the obtained mutual time differences between said characteristic signals with the pre-obtained positional relationship between said base stations and each of said two-dimensional search areas. - View Dependent Claims (2)
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3. A method for locating a mobile station based on a mobile communications system, comprising the steps of:
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setting a plurality of search areas each being narrower than a radio zone of a base station; defining a positional relationship between each base station and a concerned search area based on mutual time differences in a radio wave propagation between base stations and said concerned search area; transmitting characteristic signals from respective base stations to obtain mutual time differences in the propagation of said characteristic signals caused between transmission of said characteristic signals at respective base stations and reception at a mobile station, and identifying a specific search area where said mobile station is present based on said mutual time differences between said characteristic signals, wherein said base stations transmit said characteristic signals to a target search section, which is successively changed, in such a manner that said characteristic signals arrive at the target search area at the same time, while said mobile station sends back a confirmation signal to said base stations when said mobile station receives said characteristic signals simultaneously.
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4. A mobile station locating system for setting a plurality of two-dimensional search areas each being dissected into a predetermined size narrower than a radio zone of each of a plurality of base stations of a mobile communications system and identifying a specific two-dimensional search area where a mobile station is present, characterized by
a base station including: -
characteristic signal generating means for generating a characteristic signal of said base station; characteristic signal synchronizing means for controlling a transmitting time of said characteristic signal in synchronism with transmitting times of other characteristic signals of other base stations; positional information memory means for storing positional information of said plurality of two-dimensional search areas in advance, said positional information including positional data of each two-dimensional search area with respect to said base stations; positional information calculating means for identifying said specific two-dimensional search area where said mobile station is present based on information sent back from said mobile station in response to reception of said characteristic signal, with reference to said positional information stored in said positional information memory means; and shift hysteresis memory means for storing shift hysteresis of said mobile station, and said mobile station including; characteristic signal delay time calculating means for calculating time differences in the propagation of characteristic signals transmitted from respective base stations to the mobile station; positional information output interface means for outputting positional information of said mobile station to said base stations; and positional information notifying means for notifying positional information of said mobile station obtained from said base station. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. A method for locating a mobile station based on a mobile communications system including a plurality of base stations, said locating method comprising the steps of:
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setting a plurality of grid sections each being smaller than a radio zone of each base station; measuring positional relationship of each grid section with respect to said plurality of base stations; memorizing data relating to positional relationship of each grid section with respect to said plurality of base stations; transmitting characteristic signals from respective base stations to obtain mutual time differences in the propagation times of said characteristic signals between transmission of said characteristic signals at respective base stations and reception thereof at a mobile station; and identifying a grid section where said mobile station is present based on the obtained mutual time differences between said characteristic signals and on the memorized positional relationship of each grid section with respect to said plurality of base stations. - View Dependent Claims (12, 13)
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Specification