Backscatter communication among commodity WiFi radios

Patent metadata

Field	Value
Publication number	US-10338205-B2
Application number	US-201715676474-A
Country	US
Kind code	B2
Filing date	Aug 14, 2017
Priority date	Aug 12, 2016
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

A backscatter tag communicate device includes, in part, a receiver configured to receive a WiFi packet conforming to a communication protocol defining a multitude of codewords, a mapper configured to map at least a first subset of the multitude of codewords disposed in the packet to a second multitude of codewords defined by the protocol, and a frequency shifter configured to shift a frequency of the second multitude of codewords such that the frequency shifted codewords are characterized by a single sideband spectrum. The communication protocol may be the 802.11b communication protocol. The mapper may optionally map the first subset of the multitude of codewords by changing phases of the first subset of the multitude of codewords.

First claim

What is claimed is:

1. A backscatter tag communicate device comprising:
a receiver configured to receive a WiFi packet conforming to a communication protocol defining a plurality of codewords;
a mapper configured to map at least a first subset of the plurality of codewords disposed in the packet to a second plurality of codewords defined by the protocol;
a frequency shifter configured to shift a frequency of the second plurality of codewords such that the frequency shifted codewords are characterized by a single sideband spectrum;
a first signal splitter configured to split a WiFi signal representative of the WiFi packet into first and second signals;
a first on-off keying block disposed in a first path and adapted to receive the first signal; and
a second on-off keying block disposed in a second path and adapted to receive the second signal.

2. The backscatter tag communication device of claim 1 wherein said communication protocol is the 802.11b communication protocol.

3. The backscatter tag communication device of claim 2 wherein said mapper is further configured to map the at least first subset of the plurality of codewords by changing phases of the at least first subset of the plurality of codewords.

4. The backscatter tag communication device of claim 1 further comprising:
a delay element adapted to delay the first signal to generate a third signal.

5. The backscatter tag communication device of claim 4 further comprising a coupler configured to:
receive an output of the first on-off keying block;
receive a delayed output of the second on-off keying block;
shift a phase of the delayed output of the second on-off keying block; and
combine the output of the first on-off keying block with the phase-shifted delayed output of the second on-off-keying block, said combined output being the single sideband signal of the backscatter tag communication device.

6. The backscatter tag communication device of claim 5 further comprising:
a second signal splitter adapted to receive the WiFi signal from a receive antenna and supply the received WiFi signal to the first signal splitter; and
a signal integrator adapted to integrate the WiFi signal received from the second splitter and deliver the integrated signal to a control logic.

7. The backscatter tag communication device of claim 6 further comprising:
a multiplexer configure to select between an oscillating signal or a delayed replica of the oscillating signal in response to a select signal the multiplexer receives from the control logic.

8. The backscatter tag communication device of claim 7 wherein said multiplexer is further configure to deliver the selected signal to the control logic.

9. A method of communication via a backscatter tag, the method comprising:
receiving a packet conforming to a WiFi communication protocol defining a plurality of codewords;
mapping at least a first subset of the plurality of codewords disposed in the packet to a second plurality of codewords defined by the protocol;
shifting a frequency of the second plurality of codewords such that the frequency shifted codewords are characterized by a single sideband spectrum;
splitting a WiFi signal representative of the WiFi packet into first and second signals using a first signal splitter;
supplying the first signal to a first on-off keying block disposed in a first path; and
supplying the second signal to a second on-off keying block disposed in a second path.

10. The method of claim 9 wherein said communication protocol is the 802.11b communication protocol.

11. The method of claim 10 further comprising:
mapping the at least first subset of the plurality of codewords to a second plurality of codewords by changing phases of the at least first subset of the plurality of codewords.

12. The method of claim 9 further comprising:
delaying the first signal to generate a third signal.

13. The method of claim 12 further comprising:
receiving an output of the first on-off keying block;
receiving a delayed output of the second on-off keying block;
shifting a phase of the delayed output of the second on-off keying block; and
combining the output of the first on-off keying block with the phase-shifted delayed output of the second on-off-keying block to generate the single sideband signal at an output of the backscatter tag.

14. The method of claim 13 further comprising:
splitting the received the WiFi signal from a receive antenna using a second splitter;
supplying a first WiFi signal split by the second splitter to the first signal splitter; and
integrating the second WiFi signal split by the second splitter; and
delivering the integrated signal to a control logic.

15. The method of claim 14 further comprising:
selecting between an oscillating signal or a delayed replica of the oscillating signal in response to a control signal supplied by the control logic.

16. The method of claim 15 further comprising:
delivering the selected signal to the control logic.

Assignees

• Univ Leland Stanford Junior

Inventors

• Zhang Pengyu
• Bharadia Dinesh
• Joshi Kiran
• Katti Sachin

Classifications

• H04B5/00

  Near-field transmission systems, e.g. inductive or capacitive transmission systems · CPC title

• H04B5/0031

  Electricity · mapped topic

• H04L27/066 Primary

  Carrier recovery circuits (H04L27/2271 takes precedence) · CPC title

• G01S13/758

  using a signal generator powered by the interrogation signal · CPC title

• G01S13/00 Primary

  Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified · CPC title