Method for detecting the location of a mobile terminal

• US 5,666,662 A
• Filed: 07/21/1994
• Issued: 09/09/1997
• Est. Priority Date: 07/23/1993
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Shibuya, Toshiyuki
• Primary Examiner(s): Pham, Chi H.
• Application Number:
  US08/278,516
• Time in Patent Office: 1,146 Days
• Field of Search: 455/33.1, 455/53.1, 455/54.1, 455/54.2, 455/56.1, 455/67.1, 455/67.7, 342/450, 342/457, 342/463-465
• US Class Current: 455/456.4
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 13/78 discriminating between different kinds of targets, e.g. IFF-radar, i.e. identification of friend or foe G01S13/75, G01S13/79 take precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

In location detection of a mobile terminal, a location inquiry signal is transmitted from one or more base stations to the mobile terminal at predetermined intervals. In response to the location inquiry signal, the mobile terminal transmits a location signal including its identification information such as a telephone number. The location signal is received by at least three base stations neighboring to the mobile terminal. The respective distances from that base stations to the mobile terminal are calculated based on the respective field strength values of the location signal received by the base stations, and the location of the mobile terminal is detected based on the calculated distances. More specifically, the location is calculated as an intersection of the respective circles defined by radiuses of the calculated distances from the base stations receiving the location signal.

Claims

1. A method for detecting the location of a mobile terminal in a mobile radio communication system including a plurality of base stations and a plurality of mobile terminals, the method comprising the steps of:

emitting a location inquiry signal from at least one of the base stations through a control channel which is used to transmit the location inquiry signal;

emitting a location signal from each of the mobile terminals receiving the location inquiry signal from the at least one base station, the location signal including identification information of each of the mobile terminals;

receiving the location signal from each of the mobile terminals in at least three base stations neighboring each of the mobile terminals;

calculating the respective distances from the base stations receiving the location signal of a specified mobile terminal, based on the respective field strength values detected from the received location signal, the specified mobile terminal being identified by the identification information included in the location signal; and

calculating the location of the specified mobile terminal among the base stations receiving the location signal of the specified mobile terminal, based on the respective distances from the base stations receiving the location signal to the specified mobile terminal.

2. The method as set forth in claim 1, wherein the location of the specified mobile terminal is calculated as an intersection of the respective circles defined by radiuses of the calculated distances from the base stations receiving the location signal.

3. The method as set forth in claim 1, wherein the mobile radio communication system comprises a portable telephone system comprising a plurality of base stations and a plurality of switching stations, each of the base stations comprising a field strength detector, and each of the switching stations comprising a location detection controller, and the specified mobile terminal comprises a portable telephone set.

4. The method as set forth in claim 3, wherein the detected field strength values are transferred from the base stations receiving the location signal to a switching station connected to that base stations,

the switching station calculating the respective distances based on the respective field strength values, and calculating the location of the portable telephone set among the base stations receiving the location signal, based on the respective distances from the base stations receiving the location signal to the portable telephone set.

5. A method for detecting the location of a mobile terminal in a mobile radio communication system including a plurality of base stations and a plurality of mobile terminals, the method comprising the steps of:

emitting a location inquiry signal from at least one of the base stations at predetermined intervals through a control channel which is used to transmit the location inquiry signal;

emitting a location signal from each of the mobile terminals receiving the location inquiry signal from the at least one base station, the location signal including identification information of each of the mobile terminals;

receiving a location signal from each of the mobile terminals in at least three base stations neighboring each of the mobile terminals;

calculating the respective distances from the base stations receiving the location signal to a specified mobile terminal, based on the respective field strength values detected from the received location signal at the predetermined intervals, the specified mobile terminal being identified based on the identification information included in the location signal;

calculating the location of the specified mobile terminal among the base stations receiving the location signal of the specified mobile terminal, based on the respective distances from the base stations receiving the location signal to the specified mobile terminal at the predetermined intervals; and

storing the locations of the specified mobile terminal at the predetermined intervals.

6. The method as set forth in claim 5, wherein the location of the specified mobile terminal is calculated as an intersection of the respective circles defined by radiuses of the calculated distances from the base stations receiving the location signal.

7. The method as set forth in claim 5, wherein the mobile radio communication system comprises a portable telephone system comprising a plurality of base stations and a plurality of switching stations, each of the base stations comprising a field strength detector, and each of the switching stations comprising a location detection controller, and the specified mobile terminal comprises a portable telephone set.

8. The method as set forth in claim 7, wherein the detected field strength values are transferred from the base stations receiving the location signal to a switching station connected to that base stations,

the switching station calculating the respective distances based on the respective field strength values, and calculating the location of the portable telephone set among the base stations receiving the location signal, based on the respective distances from the base stations receiving the location signal to the portable telephone set.