Apparatus and method for locating mobile and portable radio terminals in a radio network

• US 5,293,645 A
• Filed: 10/04/1991
• Issued: 03/08/1994
• Est. Priority Date: 10/04/1991
• Status: Expired due to Term

• Current Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Microelectronics Technology, Inc.
• Inventors: Sood, Prem L.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Charouel, Lisa
• Application Number:
  US07/771,195
• Time in Patent Office: 886 Days
• Field of Search: 455/11.1, 455/12.1, 455/13.1, 455/15, 455/20, 455/24, 455/33.1, 455/33.2, 455/33.3, 455/53.1, 455/54.1, 455/54.2, 455/56.1, 455/67.6, 379/58, 379/59, 379/60, 379/61, 379/63, 342/357, 342/126, 342/127, 342/450, 342/451, 342/457, 340/988, 340/991, 340/992, 340/993
• US Class Current: 455/456.2
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0226 Transmitters
• 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

A system for locating a movable radio terminal within a cellular telephone network, or other radio network, which includes a plurality of base stations that transmit synchronized timing reference signals. A receiver in the network receives transmissions from the radio terminals to be located that include information compiled at the radio terminal indicating relative propagation delays in receipt of the timing reference signals from at least three base stations. A processor coupled with the receiver, processes the transmissions indicating relative propagation delays to identify a geographic location of the radio terminal. A complementary radio terminal receives the timing reference signals from base stations, including a designated base station and compiles information indicating propagation delays, relative to the propagation delay of the timing reference signal from the designated base station, from at least two additional base stations. The radio terminal transmits the information compiled so that a station receiving the transmission may locate the radio terminal in response to the information and the known locations of base stations in the network.

Claims

1. An apparatus for locating a radio terminal in a radio network, comprising:

a plurality of base station in the radio network, each including a transmitter and a receiver communicating with the radio terminal if the radio terminal is located within an operating range of one of the plurality of base stations and transmitting a timing reference signal substantially synchronized with the timing reference signals transmitted by other base stations in the plurality of base stations, wherein the radio terminals includes a processor for compiling information indicating relative propagation delays of the timing reference signals from at least three base stations in the plurality of base stations;

means, in the radio network, for receiving transmissions from the radio terminal to be located, the transmissions including the information compiled at the radio terminal indicating the relative propagation delays in receipt of the timing reference signals by the radio terminal; and

means coupled with the means for receiving, for processing the transmissions indicating the relative propagation delays to identify a geographic location of the radio terminal.

2. The apparatus of claim 1, including an additional base station having a transmitter and a receiver in the radio network, and wherein the means for receiving comprises the receiver in the additional base station.

3. The apparatus of claim 1, further including:

means mounted in respective base stations in the plurality of base stations, for synchronizing the timing reference signal of the respective base station with a master timing reference signal.

4. The apparatus of claim 1, wherein the means for processing includes:

means, responsive to the information indicating relative propagation delays, for determining estimated propagation distances to the radio terminal from at least three base stations in the plurality of base stations; and

means, responsive to the estimated propagation distances and known locations of the plurality of base stations, for identifying the geographic location for the radio terminal.

5. The apparatus of claim 1, further including:

means for supplying a master timing reference signal to the plurality of base stations; and

means, mounted in respective base stations in the plurality of base stations, for synchronizing the timing reference signal of the respective base station with the master timing reference signal.

6. The apparatus of claim 5, wherein the means for supplying includes a direct communication link to the plurality of base stations.

20. The apparatus of claim 1, wherein the plurality of base stations comprise a cellular radio network.

7. An apparatus for locating a radio terminal in a radio network, comprising:

a plurality of base stations, each including a transmitter transmitting a timing reference signal, wherein the radio terminal includes a processor for compiling information indicating relative propagation delays of the timing reference signals from at least three base stations in the plurality of base stations;

means for supplying a master timing reference signal to the plurality of base stations;

means mounted in respective base stations in the plurality of base stations, for synchronizing the timing reference signal of the respective base station with the master timing reference signal;

a receiver in the plurality of base stations, adapted to receive transmissions from the radio terminal to be located, the transmissions including the information compiled at the radio terminal indicating the relative propagation delays of the timing reference signals by the radio terminal, relative to the propagation delay from a designated base station in the plurality of base stations; and

means coupled with the receiver, for processing the transmissions indicating the relative propagation delays to identify a geographic location of the radio terminal.

8. The apparatus of claim 7, wherein the means for supplying includes a direct communication link to the plurality of base stations.

9. The apparatus of claim 7, wherein the means for processing includes:

means, responsive to the information indicating relative propagation delays, for determining estimated propagation distances to the radio terminal from the designated base station, and at least two additional base stations in the plurality of base stations; and

means, responsive to the estimated propagation distances and known locations of the plurality of base stations, for identifying the geographic location for the radio terminal.

10. For use in a radio network including a plurality of base stations transmitting synchronized timing reference signals, a radio terminal comprising:

a receiver receiving the timing reference signals from base stations in the plurality of base stations, including a designated base station, in a region near the receiver;

means coupled with the receiver, for compiling information indicating propagation delays, relative to the propagation delay of the timing reference signal from the designated base station, of the timing reference signals from at least two additional base stations in the plurality of base stations in the region near the receiver; and

a transmitter, coupled with the means for compiling, for transmitting information indicating the relative propagation delays of the timing reference signals, so that the radio terminal may be located in response to the transmission and known locations of the base stations in the plurality of base stations.

11. A method for locating a movable radio terminal in a radio network including a plurality of base stations transmitting timing reference signals, comprising:

synchronizing the timing reference signals in the plurality of base stations;

receiving a transmission from the movable radio terminal including information indicating relative propagation delays of the timing reference signals from at least three base stations to the movable radio terminal;

processing the information to determine estimated propagation distances to the movable radio terminal from at least three base stations in the plurality of base stations; and

locating the movable radio terminal in response to the estimated propagation distance and known locations of the base stations in the plurality of base stations.

12. The method of claim 11, wherein the step of synchronizing comprises:

synchronizing the timing reference signals of the respective base stations in the plurality of base stations with a master timing reference signal.

13. The method of claim 11, wherein the step of synchronizing comprises:

supplying a master timing reference signal to the plurality of base stations; and

synchronizing the timing reference signals of the respective base stations in the plurality of base stations with the master timing reference signal.

14. For a radio network including a plurality of base stations transmitting synchronized timing reference signals, a method for providing information from a movable radio terminal from which its location may be identified, comprising:

receiving, at the movable radio terminal, the timing reference signals from at least three base stations in the plurality of base stations;

identifying, at the movable radio terminal, a designated base station in the plurality of base stations;

determining, at the movable radio terminal, propagation delays of the received timing reference signals relative to the time of receipt of the timing reference signal from the designated base station; and

transmitting, from the movable radio terminal, the information indicating the relative propagation delays.

15. An apparatus for locating a radio terminal in a radio network, comprising:

a plurality of base stations for the radio network, each including a transmitter transmitting a timing reference signal substantially synchronized with the timing reference signals transmitted by other base stations in the plurality of base stations, wherein the radio terminal includes a processor for compiling information indicating relative propagation delays of the timing reference signals from at least three base stations in the plurality of base stations;

a receiver, mounted in at least one base station in the plurality of base stations, to receive transmissions from the radio terminal to be located, the transmissions including the information compiled at the radio terminal indicating relative propagation delays in receipt of the timing reference signals by the radio terminal; and

means, coupled with the receiver, for processing the transmissions indicating the propagation delays to identify a geographic location of the radio terminal.

16. The apparatus of claim 15, further including:

means, mounted in respective base stations in the plurality of base stations, for synchronizing the timing reference signal of the respective base station with a master timing reference signal.

17. The apparatus of claim 15, wherein the means for processing includes:

means, responsive to the information indicating relative propagation delays, for determining estimated propagation distances to the terminal from at least three base stations in the plurality of base stations; and

means, responsive to the estimated propagation distances and known locations of the plurality of base stations, for identifying the geographic location for the radio terminal.

18. The apparatus of claim 15, further including:

means for supplying a master timing reference signal to the plurality of base stations; and

means, mounted in respective base stations in the plurality of base stations, for synchronizing the timing reference signal of the respective base station with the master timing reference signal.

19. The apparatus of claim 18, wherein the means for supplying includes a direct communication link to the plurality of base stations.