Method of measuring a distance between two radio-communication devices and device adapted to implement one such method

• US 20090270042A1
• Filed: 12/23/2005
• Published: 10/29/2009
• Est. Priority Date: 01/03/2005
• Status: Active Grant

• Current Assignee: Orange S.A.
• Original Assignee: Orange S.A.
• Inventors: Schwoerer, Jean, Miscopein, Benoit, Evennou, Frederic
• Granted Patent: US 8,521,091 B2
• Time in Patent Office: Days
• US Class Current: 455/67.110
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The invention relates to a method of measuring a distance between two radio-communication devices (1, 2), consisting in measuring a radio signal exchange delay. According to the invention, the time-of-flight of the signals is calculated from the exchange delay and subsequently corrected using an analysis of a single channel measuring frame that is transmitted between the two devices. The corrected time-of-flight corresponds to the shortest propagation path followed by the radio signals. In the majority of radio transmission medium configurations, the corrected time-of-flight is a straight line measurement of the distance separating the two devices (1, 2).

Claims

1. A method of measuring a distance between two radiocommunication devices, comprising the following steps:

a—

by a first of the two devices;

transmission of a radio signal requesting a measurement of an exchange delay between the two devices;

b—

by the second device;

reception of the request signal and, after an intermediate delay known to both devices, the sending of an acknowledgement radio signal; and

c—

by the first device;

reception of the acknowledgement signal;

measurement of the time between the transmission of the request signal and the reception of the acknowledgement signal, then storage of said time and exchange delay; and

calculation of a first time of flight of the request and acknowledgement signals based on the exchange delay and the intermediate delay,

characterized in that the method also comprises a transmission, by the second device, of a channel measurement frame adapted so that the first device;

determines, from various radio signals received corresponding to the channel measurement frame, a difference in time of flight between a propagation path corresponding to said first time of flight and the shortest propagation path followed by the radio signals transmitted between the two devices; and

calculates of a second time of flight from the first time of flight and the difference in time of flight.

2. The method as claimed in claim 1, wherein at least one of the request and acknowledgement radio signals comprises a short frame.

3. The method as claimed in claim 1, wherein the propagation path corresponding to the first time of flight is followed by a main part of the energy of the request radio signal and of the acknowledgement signal.

4. The method as claimed in claim 1, also comprising a transmission, by the first device to the second device, of a signal comprising an indication of the second time of flight.

5. The method as claimed in claim 1, wherein the steps a to c are repeated, and wherein the first time of flight (T_OF1) is updated each time the steps a to c are executed.

6. The method as claimed in claim 5, wherein the steps a to c are repeated after the difference between the first and second times of flight has been determined.

7. The method as claimed in claim 5, wherein the channel measurement frame is transmitted by the second device after the acknowledgement signal, with a waiting time from the transmission of the acknowledgement signal is greater than or equal to a determined guard time.

8. The method as claimed in claims 7, wherein the steps a to c are repeated before the guard time has elapsed from the transmission of a first acknowledgement signal by the second device.

9. The method as claimed in claim 1, wherein several first reception instants are identified by the first device, respectively for first radio signals corresponding to the channel measurement frame that have followed the same propagation path as the acknowledgement signal, and wherein second instants of reception of second radio signals corresponding to said frame and which have followed other propagation paths between the two devices are identified by said first device from different first reception instants.

14. The method as claimed in claim 1, wherein the channel measurement frame is transmitted by the second device after the acknowledgement signal, with a waiting time from the transmission of the acknowledgement signal is greater than or equal to a determined guard time.

15. A radiocommunication device adapted to implement those steps of the method of measuring distance between two devices as claimed in any one of claims 1 to 14, that are carried out by the first of the two devices.

16. A radiocommunication device adapted to implement those steps of the method of measuring distance between two devices as claimed in any one of claims 1 to 14, that are carried out by the second of the two devices.

17. A communication system comprising at least two radiocommunication devices wherein said first and second radiocommunication are adapted to implement the method of measuring distance between said first and second radiocommunication devices as claimed in any one of claims 1 to 14.

10. (canceled)

11. (canceled)

12. (canceled)