Method and system for geolocating a terminal of a wireless communication system

Patent metadata

Field	Value
Publication number	US-11835638-B2
Application number	US-201917253114-A
Country	US
Kind code	B2
Filing date	Jun 17, 2019
Priority date	Jun 18, 2018
Publication date	Dec 5, 2023
Grant date	Dec 5, 2023

Abstract

A method for geolocating a terminal of a wireless communication system. The terminal includes a positioning device for obtaining a precise geographical position of the terminal. An access network of the communication system estimates an approximate geographical position of the terminal. In order to limit the size of the messages exchanged between the terminal and the access network, only a truncated part of the information about the precise geographical position of the terminal is transmitted by the terminal to the access network. The access network determines the precise geographical position of the terminal by combining the truncated information received from the terminal with the approximate geographical position estimated by the access network.

First claim

The invention claimed is:

1. A method for geolocating a terminal of a wireless communication system, the wireless communication system comprising an access network configured to estimate an approximate geographical position of the terminal, the terminal comprising a positioning device to obtain a precise geographical position of the terminal, a precision obtained by the terminal being better than the precision of the approximate geographical position estimated by the access network, the precise and approximate geographical positions comprising a latitude and a longitude as geographical coordinates, the method comprising:
calculation by the terminal of truncated information on the precise geographical position by breaking down the precise geographical position into a first part and a second part, the first part varying less quickly than the second part when the terminal moves, the truncated information representing the second part of the precise geographical position;
transmission by the terminal of the truncated information in a message to the access network;
estimation of the approximate geographical position of the terminal by the access network;
extraction by the access network of the truncated information from the message received from the terminal;
determination by the access network of the precise geographical position of the terminal from the truncated information and from the approximate geographical position; and
wherein:
the latitude and the longitude, each corresponding to a value encoded respectively in N and M bits;
a latitude Lat 1 and a longitude Lng 1 of the precise geographical position obtained by the terminal being written in a form:
Lat 1 =N 1 ×2 n +n 1

Lng 1 =M 1 ×2 m +m 1

where N 1 , n 1 n, M 1 , m 1 and m are positive integer numbers, n 1 and m 1 corresponding respectively to the n least significant bits of the latitude Lat 1 and to the m least significant bits of the longitude Lng 1 of the precise geographical position obtained by the terminal;
a latitude Lat 2 and a longitude Lng 2 of the approximate geographical position estimated by the access network being written in a form:
Lat 2 =N 2 ×2 n +n 2

Lng 2 =M 2 ×2 m +m 2

where N 2 , n 2 , M 2 and m 2 are positive integer numbers, n 2 and m 2 corresponding respectively to the n least significant bits of the latitude Lat 2 and to the m least significant bits of the longitude Lng 2 of the approximate geographical position estimated by the access network;
the truncated information comprises the n least significant bits of the latitude Lat 1 and the m least significant bits of the longitude Lng 1 of the precise geographical position obtained by the terminal;
the determination by the access network of the precise geographical position of the terminal from the truncated information and from the approximate geographical position comprises:
determination of the latitude Lat 1 as a function of N 2 , n 1 , and a difference between n 1 and n 2 , and
determination of the longitude Lng 1 as a function of M 2 and of m 1 , and a difference between m 1 and m 2 .

2. The method of claim 1 , wherein:
the numbers n and m are chosen so that the precision of the approximate geographical position estimated by the access network, regardless of the geographical position of the terminal, satisfies a following formulae:
|Lat 1 −Lat 2 |<2 (n−1)

|Lng 2 −Lng 2 |<2 (n−1)

the determination by the access network of the latitude Lat 1 of the precise geographical position of the terminal is in accordance with:

Lat
1

=

{

(

N
2

+
1

)

×

2
n

+

n
1

⁢

if
⁢

(

n
1

-

n
2

)

≤

(

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1

)

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2

(

n
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1

)

(

N
2

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1

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×

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if
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≥

Assignees

• Sigfox

Inventors

• Hubert Loïc

Classifications

• G01S5/0054 Primary

  of actual mobile position, i.e. position calculation on base station · CPC title

• G01S5/0036

  of measured values, i.e. measurement on mobile and position calculation on base station · CPC title

• G01S5/018

  Involving non-radio wave signals or measurements · CPC title

• G01S5/0205

  Details · CPC title

• H04W64/00 Primary

  Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management · CPC title