Backscatter CSI Acquisition for Long-Range Wireless Power Transfer
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Solution Overview
Problem
Existing wireless power transfer systems face inefficiencies due to insufficient power link budgets and energy harvesting range limitations in RFID and semi-passive IoT devices, particularly in multi-path environments, where channel state information (CSI) measurement is energy-intensive and unreliable.
Innovation Solution
A method and apparatus for channel estimation and CSI acquisition at the reader side through frequency spreading and shifting of backscatter signals, allowing efficient energy transfer by optimizing frequency and spatial beamforming without additional energy expenditure at the RFID tag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI measurement is performed using CSI-RS-based methods in existing wireless power transfer systems, then channel state information can be obtained, but the measurement process consumes excessive energy and provides unreliable results in multi-path environments
Solution Approach 1:
The patent inverts the traditional CSI measurement approach by having the reader device perform channel estimation instead of the RFID tag. The reader transmits probe signals and estimates the channel based on backscatter signals received from the tag, thereby avoiding energy-intensive measurements at the tag while maintaining measurement reliability through frequency spreading techniques
Solution Approach 2:
The patent introduces frequency spreading as an intermediary technique that modulates probe signals across multiple frequencies before transmission. This frequency-spread signal serves as a mediator that enables reliable channel estimation at the reader without requiring the RFID tag to perform energy-intensive measurements, thus resolving the contradiction between measurement reliability and energy consumption
2Measurement precision
If frequency spreading is applied to backscatter signals for CSI estimation, then channel state information accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent segments the channel estimation process into distinct phases: transmitting frequency-spread probe signals, receiving backscatter signals, and performing correlation-based channel estimation at the reader. This segmentation allows the complex frequency spreading operation to be confined to the reader device with sufficient processing power, while the simple RFID tag only needs to perform backscatter modulation
3Length of stationary object
If energy transfer is performed at higher power levels to extend harvesting range, then the energy harvesting range increases, but the power link budget efficiency decreases
Solution Approach 1:
The patent implements feedback-based power adaptation where the reader device performs channel estimation using frequency-spread backscatter signals, then uses the obtained CSI to adaptively adjust the power level and frequency of energy transfer signals. This feedback mechanism enables the system to transmit energy at optimal power levels rather than always using high power, thereby extending harvesting range while maintaining power link budget efficiency
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
Enhances energy transfer efficiency and range by accurately determining optimal frequencies and beamforming parameters, overcoming the limitations of CSI-RS-based measurements and interference, thus improving power harvesting for RFID and IoT devices.
Implementation Method 1
receive, from an energy harvesting (EH) device, a backscatter signal over a plurality of frequencies based on a transmitted signal at a first frequency
Data Source
AI summary
The apparatus may be a reader device configured to transmit a first signal at a first frequency for a backscattering from an energy harvesting (EH) device over a plurality of frequencies, to receive, from an EH device, a backscatter signal over a plurality of frequencies based on a transmitted signal at a first frequency. The apparatus may further be configured to obtain channel state information (CSI) based on the backscattering of the first signal and to transmit an energy signal for the EH device via at least one frequency based on the CSI based on the backscatter signal. In an aspect of the disclosure, the apparatus may be an EH device configured to receive a transmitted signal at a first frequency and backscatter the transmitted signal over a plurality of frequencies and receive, from the reader, an energy signal based on the backscatter signal.