Backscatter Tag Using Commodity WiFi Radios
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Solution Overview
Problem
Current backscatter communication systems require specialized hardware and consume significant power, and they face challenges with signal-to-noise ratio due to self-interference from original transmissions, making them unsuitable for deployment using commodity devices like smartphones and tablets.
Innovation Solution
A backscatter tag communication system that uses a receiver to map and frequency shift WiFi packets, generating a single sideband spectrum compatible with the 802.11b protocol, allowing decoding by standard WiFi receivers and reducing power consumption by eliminating unnecessary hardware and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If specialized hardware is used for backscatter communication, then communication capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes standard WiFi radios perform backscatter communication functions in addition to their normal WiFi communication functions. The receiver can decode both regular WiFi packets and backscattered packets using the same hardware, eliminating the need for specialized backscatter hardware while maintaining communication capability
Solution Approach 2:
The invention uses commodity WiFi radios that replicate the functionality of specialized backscatter hardware through software processing. The standard radio captures and processes backscattered signals using algorithms that mimic specialized hardware behavior, achieving the same communication capability without dedicated components
2Reliability
If continuous wave signal generators are used for excitation, then backscatter signal generation is improved, but power consumption increases
Solution Approach 1:
The system uses existing WiFi network infrastructure and standard WiFi radios to provide the excitation signals and decode backscattered signals. The commodity devices themselves serve the function of signal generation and detection, eliminating the need for separate dedicated signal generators and reducing overall system power consumption
Solution Approach 2:
Standard WiFi radios perform multiple functions including receiving excitation signals, generating local oscillators for backscatter modulation, and decoding backscattered packets. This multi-functionality eliminates dedicated signal generation hardware and reduces power consumption by using integrated circuits designed for general WiFi operation
3Reliability
If full duplex hardware add-on is used for backscatter, then backscatter communication is enabled, but device complexity and cost increase
Solution Approach 1:
The patent enables standard WiFi radios to handle both transmit and receive operations for backscatter communication using the same hardware components. The radio performs full-duplex operation through software control and signal processing algorithms, eliminating the need for separate full-duplex hardware add-ons while maintaining communication capability
4Reliability
If self-interference from original transmissions is present, then signal-to-noise ratio deteriorates, but communication range is limited
Solution Approach 1:
The system extracts the backscattered signal from the composite received signal by exploiting the known structure of WiFi packets. The receiver subtracts the expected original transmission signal from the received signal, isolating the backscattered component and improving signal-to-noise ratio, thereby extending communication range
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables low-power, low-interference backscatter communication over extended ranges using commodity devices, achieving efficient data transmission and reducing power consumption, thus addressing the limitations of existing systems.
Implementation Method 1
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
Implementation Method 2
the mapper is further configured to map the at least first subset of the multitude of codewords by changing phases of the at least first subset of the multitude of codewords
Implementation Method 3
Backscatter communication has attracted interest for applications such as implantable sensors, wearables, and smart home sensing because of its ability to offer low power connectivity to these sensors
Data Source
AI summary
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.