Method and system to control ambient RF energy for wireless devices

• US 9,397,522 B2
• Filed: 03/08/2012
• Issued: 07/19/2016
• Est. Priority Date: 03/08/2012
• Status: Active Grant

• Current Assignee: Duke University, Ricoh Company Limited
• Original Assignee: Duke University, Ricoh Company Limited
• Inventors: Chemishkian, Sergey, Gudan, Ken, Hull, Jonathan J., Reynolds, Matthew S.
• Primary Examiner(s): Amaya, Carlos
• Application Number:
  US13/415,560
• Publication Number:
  US 20130234536A1
• Time in Patent Office: 1,594 Days
• Field of Search: 307/104
• US Class Current: 1/1
• CPC Class Codes: H02J 50/001 Energy harvesting or scavenging
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence

Abstract

A method and apparatus is disclosed herein for controlling radio-frequency (RF) energy for wireless devices. In one embodiment, the method comprises determining to increase radio-frequency (RF) energy available to power a wireless tag and controlling the RF energy delivered to the wireless tag to provide tag energy, using one or more of: a) increasing transmission RF power of one or more wireless communication devices, b) increasing a duty cycle associated with wireless transmissions of one or more wireless communication devices, and c) decreasing path loss of the power to the wireless tag.

Claims

1. A method to control energy that is available for wireless power harvesting, the method comprising:

determining to increase radio-frequency (RF) energy available to power a wireless tag incorporating wireless power harvesting; and

controlling the RF energy delivered to the wireless tag to provide tag energy by;

increasing a duty cycle associated with wireless transmissions of one or more wireless communication devices by increasing network traffic of the one or more wireless communication devices.

2. The method defined in claim 1 wherein controlling the RF energy is performed further by decreasing path loss of the power to the wireless tag.

3. The method defined in claim 2 wherein controlling the RF energy is performed to maximize average power over time T at the wireless tag according to:

4. The method defined in claim 2, wherein decreasing path loss of the power to the wireless tag comprises selecting wireless communication devices that have lower path loss or dynamically updating the path loss estimate information between each wireless communication device and the wireless tag.

5. The method defined in claim 1 wherein controlling the RF energy is performed further by increasing transmitted power by one or more of (i) increasing transmission RF power of one or more wireless devices or (ii) signaling the one or more wireless communication devices to increase its transmit power.

6. The method defined in claim 1 wherein increasing the duty cycle is performed further by increasing frequency of beacon, Probe, or other periodic pulse/packet output for at least one of the one or more wireless communication devices.

7. The method defined in claim 1 wherein increasing the duty cycle is performed further by changing RF modulations of a transmission by at least one of the one or more wireless communication devices.

8. The method defined in claim 1 further comprising:

maintaining a data structure that stores capabilities for a plurality of wireless communication devices and their respective path loss with respect to providing energy to the wireless tag; and

accessing the data structure in response to determining to increase the RF energy available to power the wireless tag to determine which available wireless communication device(s) to control to increase the RF energy delivered to the wireless tag.

9. The method defined in claim 1 further comprising controlling one or more devices not compatible with Wi-Fi to increase their emissions of RF energy.

10. The method defined in claim 1, wherein increasing network traffic of the one or more wireless communication devices comprises causing the one or more wireless communication devices to stream data.

11. The method defined in claim 10, wherein causing the one or more wireless communication devices to stream data comprises selecting and transmitting data on a subset of antennas of the one or more wireless communication devices to increase the energy being delivered to the wireless tag.

12. The method defined in claim 10, wherein causing the one or more wireless communication devices to stream data comprises selecting and transmitting data on a subset of antennas of the one or more wireless communication devices based on path loss information between each antenna and the wireless tag.

13. The method defined in claim 1, wherein controlling the RF energy is performed further by varying the power spectral density (PSD) of the transmitted signal.

14. A system to control energy that is available for powering wireless tags, the system comprising:

a memory; and

a processor coupled to the memory and operable to;

determine to increase radio-frequency (RF) energy available to power a wireless tag, and

control the RF energy delivered to the wireless tag to provide tag energy by;

increasing a duty cycle associated with wireless transmissions of one or more wireless communication devices by increasing network traffic of the one or more wireless communication devices.

15. The system defined in claim 14 wherein the processor controls the RF energy further by decreasing path loss of the power to the wireless tag.

16. The system defined in claim 14 wherein the processor controls the RF energy to maximize average power over time1 T at the wireless tag according to:

17. The system defined in claim 14 wherein the processor controls the RF energy further by increasing transmitted power by one or more of (i) increasing transmission RF power of one or more wireless devices or (ii) signaling the one or more wireless communication devices to increase its transmit power.

18. The system defined in claim 14 wherein the processor increases the duty cycle further by increasing frequency of beacon, Probe, or other periodic pulse/packet output for at least one of the one or more wireless communication devices.

19. The system defined in claim 14 wherein the memory stores a data structure that includes capabilities for a plurality of wireless communication devices and their respective path loss with respect to providing energy to the wireless tag, and the processor is operable to access the data structure in response to determining to increase the RF energy available to power the wireless tag to determine which available wireless communication device to control to increase the RF energy delivered to the wireless tag.

20. A computer-readable, non-transitory storage medium having stored thereon a computer program which is executable by a computer, the computer program controlling the computer to execute functions of

determining to increase radio-frequency (RF) energy available to power a wireless tag;

and

controlling the RF energy delivered to the wireless tag to provide tag energy by;

increasing a duty cycle associated with wireless transmissions of one or more wireless communication devices by increasing network traffic of the one or more wireless communication devices.