System and method for proximity motion detection in a wireless network

• US 7,209,751 B2
• Filed: 03/30/2004
• Issued: 04/24/2007
• Est. Priority Date: 03/30/2004
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Nishida, Yoshifumi, Shionozaki, Atsushi
• Primary Examiner(s): Vuong; Quochien B.
• Assistant Examiner(s): Wendell; Andrew
• Application Number:
  US10/814,419
• Publication Number:
  US 20050221829A1
• Time in Patent Office: 1,120 Days
• Field of Search: 455/430, 455/438, 455/440, 455/506, 455/556.1, 455/513, 455/67.11, 455/456.1, 370/332, 370/333, 342/458, 342/461, 342/450, 342/451, 342/465
• US Class Current: 455/456.1
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

Systems and Methods are described for determining proximity motion of a mobile wireless device around a fixed target node. The present invention provides a method of regressively analyzing the signal strength on a receiver node, which may be either the mobile wireless device or the fixed target node, as a function of time to determine the proximity of the sending node, which may be either the mobile wireless device or the fixed target node, to the receiving node. The method includes detecting motion of mobile wireless device with a fixed wireless device within a proximity range of less than about 15 cm, and more preferably within around 5 cm. The system provides accurate proximity motion sensing that is not susceptible to multipath effects, and which can be implemented in a wide variety of wireless applications.

Claims

1. A system for detecting motion of a wireless device, comprising:

a first wireless device configured for communicating wirelessly with at least a second wireless device;

at least one of said wireless devices configured as a beacon sender for sending beacon frames containing signal strength information;

at least one of said wireless devices configured as a beacon receiver for receiving said beacon frames;

a computer processor associated with one of said wireless devices and configured for processing said signal strength information; and

programming executable on said computer processor for performing acts comprising;

calculating, from said signal strength information, differences in signal strength for a plurality of signal strength samples accumulated during a sampling period;

performing a regression analysis on said differences in signal strength with respect to the number of samples in said plurality of signal strength samples;

calculating, as a result of said regression analysis, a coefficient of determination;

calculating, as a result of said regression analysis, a regression coefficient; and

generating and outputting a proximity motion detection signal in response to determining that the regression coefficient is approximately equal to or greater than the quotient of (i) change in signal strength from start to end of the sampling period divided by (ii) the number of said plurality of signal strength samples, and further in response to determining that the coefficient of determination exceeds a threshold value.

2. A system as recited in claim 1, wherein said regression analysis is performed without regard to transmit power of the wireless devices.

3. A system as recited in claim 1, wherein said beacon frames comprise IEEE 802.11 network formatted data frames.

4. A system as recited in claim 1:

wherein said computer processor and said programming are associated with said beacon receiver.

5. A system as recited in claim 1:

wherein said computer processor and said programming are associated with said beacon sender; and

wherein said beacon receiver is configured to send said signal strength information to said beacon sender for processing.

6. A system as recited in claim 1, wherein said beacon frames are transmitted by the beacon sender at a predetermined transmission interval.

7. A system as recited in claim 6, wherein said predetermined transmission interval is at or less than approximately 100 milliseconds.

8. A system as recited in claim 1, wherein said programming further carries out the act of tuning an interval frequency for transmitting the beacon frames.

9. A system as recited in claim 1, wherein said programming is configured to detect motion in response to a defined signal strength change within the given time interval.

10. A system as recited in claim 9, wherein motion is detected if said signal strength change of approximately 20 dB arises within less than or equal to a time interval of approximately one second.

11. A system as recited in claim 1, wherein proximity motion occurs when said first wireless device moves toward said second wireless device to within less than or equal to approximately 15 centimeters.

12. A system as recited in claim 1, wherein proximity motion occurs when said first wireless device moves toward said second wireless device to within less than or equal to approximately 5 centimeters.

13. A system as recited in claim 12:

wherein proximity motion occurs when said first wireless device moves toward said second wireless device from a distance equal to or greater than approximately 30 centimeters to less or equal to approximately 15 centimeters.

14. A method of detecting motion between a first wireless device and a second wireless device, comprising:

monitoring signal strength information for a signal transmitted between said first wireless device and said second wireless device;

calculating, from said signal strength information, differences in signal strength for a plurality of signal strength samples accumulated during a sampling period;

performing a regression analysis on said differences in signal strength with respect to the number of samples in said plurality of signal strength samples;

calculating, as a result from said regression analysis, a regression coefficient;

calculating, as a result from said regression analysis, a coefficient of determination; and

generating and outputting a proximity motion detection signal in response to determining that the regression coefficient is approximately equal to or greater than the quotient of (i) change in signal strength from start to end of the sampling period divided by (ii) the number of said plurality of signal strength samples, and further in response to determining that the coefficient of determination exceeds a threshold value.

15. A method as recited in claim 14, wherein proximity motion occurs when said first wireless device moves toward said second wireless device to within less than or equal to approximately 15 centimeters.

16. A method as recited in claim 14, wherein the proximity motion occurs when said first wireless device moves toward said second wireless device to within less than or equal to approximately 5 centimeters.

17. A method as recited in claim 14:

wherein at least one of said wireless devices is configured as a beacon sender for sending beacon frames containing signal strength information; and

wherein at least one of said wireless devices is configured as a beacon receiver for receiving said beacon frames.

18. A method as recited in claim 14, wherein proximity motion occurs when said first wireless device moves toward said second wireless device from a distance equal to or greater than approximately 30 centimeters to less or equal to approximately 15 centimeters.

19. A method as recited in claim 14:

wherein said regression analysis is performed without regard to transmit power of the wireless devices.

20. A method as recited in claim 17, wherein said beacon frames comprise IEEE 802.11 network formatted data frames.

21. A method as recited in claim 17, wherein said beacon receiver is configured for processing said signal strength information.

22. A method as recited in claim 17:

wherein said beacon sender is configured for processing said signal strength information; and

wherein said beacon receiver is configured to send said signal strength information to said beacon sender for processing.

23. A method as recited in claim 17, wherein said beacon frames are sent by the beacon sender at a predetermined transmission interval.

24. A method as recited in claim 23, wherein said predetermined transmission interval is at or less than approximately 100 milliseconds.

25. A method as recited in claim 17, further comprising tuning an interval frequency for sending the beacon frames.

26. A method as recited in claim 17 further comprising detecting motion in response to a defined signal strength change within the given time interval.

27. A method as recited in claim 26, wherein motion is detected if said signal strength change of approximately 20 dB arises within less than or equal to a time interval of approximately one second.

28. A method of detecting motion between a first wireless node and a second wireless node, comprising:

continuously monitoring beacon frames transmitted by said second wireless node to said first wireless node;

accumulating signal strength information contained in the beacon frames transmitted by said second wireless node;

calculating, from said accumulated signal strength information, differences in signal strength for a plurality of signal strength samples accumulated during a sampling period;

performing a regression analysis on said differences in signal strength with respect to the number of samples in said plurality of signal strength samples;

calculating, as a result of said regression analysis, a coefficient of determination;

calculating, as a result of said regression analysis, a regression coefficient; and

generating and outputting a proximity motion detection signal in response to determining that the regression coefficient is approximately equal to or greater than the quotient of (i) change in signal strength from start to end of the sampling period divided by (ii) the number of said plurality of signal strength samples, and further in response to determining that the coefficient of determination exceeds a threshold value.

29. A method as recited in claim 28, wherein the threshold value for the coefficient of determination is approximately 0.70.

30. A method as recited in claim 28, wherein the threshold value for the coefficient of determination is approximately 0.75.

31. A method of detecting motion of a mobile wireless device with respect to a stationary wireless device in a wireless network, the method comprising:

calculating signal strength differences between the mobile wireless device and the stationary wireless device as the mobile wireless device approaches the stationary wireless device for a plurality of samples;

performing a regression analysis on said signal strength differences with respect to said plurality of samples;

calculating, from said regression analysis, a coefficient of determination,

calculating, from said regression analysis, a regression coefficient; and

determining that the mobile wireless device has moved into proximity with the stationary wireless device and outputting a proximity motion detection signal in response to determining that the regression coefficient is approximately equal to or greater than the quotient of (i) change in signal strength from start to end of the sampling period divided by (ii) the number of said plurality of signal strength samples, and further in response to determining that the coefficient of determination exceeds a threshold value.

32. A method as recited in claim 31, wherein the stationary wireless device and the mobile wireless device are configured in IBSS mode and wherein the mobile wireless device is configured as an access point node.

33. A method as recited in claim 31, wherein calculating the signal strength difference between the mobile wireless device and the fixed wireless device is performed with respect to accumulated signal strength information within a plurality of recorded signal strength samples.

34. A method as recited in claim 33, wherein said regression analysis comprises performing a linear regression analysis on the difference in signal strengths on the signals transmitted between the mobile wireless device and the fixed wireless device with respect to the number of samples to determine said regression coefficient of the signal strengths.

35. A method as recited in claim 34, wherein said regression analysis comprises performing a linear regression analysis on the difference in signal strengths on the signals transmitted between the mobile wireless device and the fixed wireless device with respect to the number of samples to determine said coefficient of determination of the signal strength.

36. A method as recited in claim 31, wherein the threshold value for the coefficient of determination is approximately 0.70.

37. A method as recited in claim 31, wherein the threshold value for the coefficient of determination is approximately 0.75.