Distance determination of a mobile device

• US 9,706,358 B2
• Filed: 04/12/2013
• Issued: 07/11/2017
• Est. Priority Date: 04/12/2013
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Sen, Souvik, Lee, Jeongkeun
• Primary Examiner(s): Doan, Phuoc H
• Application Number:
  US14/783,179
• Publication Number:
  US 20160037302A1
• Time in Patent Office: 1,551 Days
• Field of Search: 4554562, 4554561, 455517, 340 103, 375227, 375221, 370329
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 4/023 using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds
• CPC Class Codes: H04W 64/003 locating network equipment
• CPC Class Codes: H04W 88/02 Terminal devices
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A first energy of a signal received from a mobile device is computed at a device based on information available at a physical (PHY) layer of the mobile device. A second energy of the received signal is computed. A path-loss exponent of the received signal is computed based on a line-of-sight (LoS) factor (lfactor) of the signal. A distance of the mobile device to the device is computed based on the first energy, the second energy, and the path-loss exponent of the received signal.

Claims

1. A device comprising a signal processing unit to:

compute a first energy of a signal received from a mobile device based on information available at a physical (PHY) layer of the mobile device;

compute a second energy of the received signal;

compute a path-loss exponent of the received signal based on a line-of-sight (LoS) factor (lfactor) of the signal; and

compute a distance of the mobile device to the device based on the first energy, the second energy, and the path-loss exponent of the received signal.

2. The device of claim 1, wherein the second energy is computed based on energy of the signal when the mobile device is 1 meter from the device.

3. The device of claim 1, wherein the PHY layer information comprises channel state information (CSI), wherein the CSI includes a power delay profile (PDP) for the signal.

4. The device of claim 3, wherein the PDP includes energy corresponding to a plurality of paths of the signal incident at a receiver of the device at increasing time delays, and wherein the plurality of paths includes a direct path of the signal and at least one reflected path of the signal.

5. The device of claim 4, wherein energy corresponding to a first component of the PDP is identified as energy of the direct path (EDP), and wherein energy corresponding to other components of the PDP is ignored.

6. The device of claim 5, wherein the lfactor is computed based on a ratio of the EDP to received signal strength indicator (RSSI) of the signal, and wherein the lfactor is inversely proportional to the path-loss exponent.

7. The device of claim 6, wherein the distance is computed according to a solution of:

P_R=P₀−

10γ

log(d),

wherein P_R is the first energy of the received signal computed based on the PHY layer information,

wherein P₀ is the second energy based on at least one of energy of the received signal at a distance of 1 m from the device, and transmit power of the mobile device,

wherein γ

is the path-loss exponent of the received signal based on the lfactor and the EDP, and

wherein d is the distance of the mobile device to the device.

8. The device of claim 7, wherein the lfactor is computed according to a solution of:

9. The device of claim 1, wherein the device comprises at least one of a wireless access point (AP) and a cellular base station.

10. The device of claim 1, wherein the second energy is computed based on a transmit power of the mobile device.

11. The device of claim 1, wherein the signal is a direct path signal received from the mobile device, and wherein the direct path signal is extracted from the PHY layer information of the mobile device.

12. The device of claim 11, wherein non-direct path signal received from the mobile device is ignored, wherein the non-direct path signal includes reflected path signals.

13. A method for determining a distance of a mobile device from a wireless access point (AP), the method comprising:

computing, by a signal processing unit of the AP, a first energy of a received signal transmitted from the mobile device based on information available at a physical (PHY) layer of the mobile device;

computing, by the signal processing unit, a second energy of the received signal;

computing, by the signal processing unit, a path-loss exponent of the received signal based on a line-of-sight (LoS) factor (lfactor) of the received signal; and

computing, by the signal processing unit, a distance of the mobile device to the AP based on the first energy, the second energy, and the path-loss exponent of the received signal.

14. The method of claim 13,

wherein the second energy is computed based on at least one of energy of the signal when the mobile device is 1 meter from the AP and transmit power of the mobile device, and

wherein the PHY layer information comprises channel state information (CSI), wherein a power delay profile (PDP) of the signal is obtained based on the CSI.

15. The method of claim 14, wherein the PDP comprises an energy of the direct path (EDP) and an energy of at least one reflected path of the signal.

16. The device of claim 15, wherein the lfactor is computed based on a ratio of the EDP of the signal to a received signal strength indicator (RSSI) of the signal, and wherein the lfactor is inversely proportional to the path-loss exponent.

17. A non-transitory computer-readable storage medium comprising instructions that, when executed by a processor of a based station, cause the processor to:

compute a first energy of a signal received from a mobile device based on information available at a physical (PHY) layer of the mobile device, wherein the PHY layer information includes channel state information (CSI);

compute a second energy of the received signal;

compute a path-loss exponent of the received signal based on a line-of-sight (LoS) factor (lfactor) of the signal and energy of direct path (EDP) of the signal, wherein the lfactor is computed based on a ratio of the EDP to received signal strength indicator (RSSI) of the signal; and

compute a distance of the mobile device to the base station based on the first energy, the second energy, and the path-loss exponent of the received signal.

18. The non-transitory computer-readable storage medium of claim 17, wherein the lfactor is inversely proportional to the path-loss exponent.