LiFi-Powered RF Backscatter for Battery-Free IoT Tags
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Solution Overview
Problem
Existing RF backscatter systems for IoT devices face limitations such as short transmission range and low data rate due to limited energy harvesting and the presence of power-hungry components like oscillators, which deplete batteries quickly and are environmentally harmful.
Innovation Solution
A hybrid system combining LiFi and RF backscatter technologies, where LiFi transmitters generate optical signals with downlink data and chirp signals to power and communicate with IoT tags, which process these signals to support battery-free or low-power operation, using a chirp signal to modulate RF backscatter for uplink communication, eliminating the need for oscillators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If RF backscatter systems use oscillators for communication, then data transmission is enabled, but energy consumption increases and battery life decreases
Solution Approach 1:
The patent extracts the oscillator function from the IoT tag and relocates it to the base station. The tag only needs to modulate the backscattered RF signal by switching between reflective and absorptive states, while the base station generates and processes the chirp signal, eliminating the need for a local oscillator in the tag.
Solution Approach 2:
The base station performs multiple functions: it generates the RF carrier signal, modulates the chirp signal, and processes the backscattered signal. This multi-functionality consolidates power-hungry operations in a centralized location with adequate power supply, allowing the tag to operate with minimal energy consumption.
2Ease of operation
If RF backscatter systems use power-hungry components, then communication functionality is improved, but environmental impact increases due to battery disposal
Solution Approach 1:
The system enables self-powered operation where the IoT tag harvests energy from the ambient RF environment and uses it to modulate the backscattered signal. The tag does not require an external power source or battery, making it environmentally friendly while maintaining full communication functionality.
3Power
If LiFi transmitter generates optical signals with downlink data and chirp signals, then energy is provided to IoT tags, but system complexity increases
Solution Approach 1:
The patent combines downlink data transmission and energy provision into a single LiFi optical signal. The optical signal contains both the chirp signal (used for uplink communication) and downlink data, allowing the tag to simultaneously harvest energy and receive communication signals without requiring separate systems.
Solution Approach 2:
The LiFi optical signal serves dual purposes: it provides energy to power the tag's operations and carries downlink communication data. This multi-functionality reduces the number of separate components needed, offsetting the complexity of integrating LiFi with RF backscatter.
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
The system achieves longer transmission range and increased data rate with reduced energy consumption, enabling battery-free or low-power IoT devices by offloading oscillator functions to the LiFi transmitter and minimizing power-hungry components.
Implementation Method 1
a LiFi, 'Light Fidelity', transmitter configured for generating and transmitting an optical signal
Implementation Method 2
converting the optical signal into an electrical signal
Implementation Method 3
harvesting energy from the DC component into the harvester
Implementation Method 4
the RF antenna generates an RF signal by multiplying its reflection coefficient by the RF carrier
Data Source
AI summary
The present invention is related to a low-power backscatter system comprising a LiFi, “Light Fidelity”, transmitter configured for generating and transmitting an optical signal comprising a sequence of a downlink data signal and a chirp signal and an IoT, “Internet of Things”, tag.