Backscatter Devices Transmitting OFDM Packets via Impedance Modulation
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Solution Overview
Problem
The power requirements for transmitting OFDM signals in wireless communication, particularly in IoT and ubiquitous sensing scenarios, are prohibitive due to the lack of power scaling in analog RF components, which hinders efficient communication from sensors and mobile devices.
Innovation Solution
The implementation of backscatter devices that decouple digital baseband functions from power-consuming RF components, using helper devices to provide carrier signals, allowing backscatter devices to modulate antenna impedance with low-power inphase and quadrature bits to transmit OFDM packets, thereby reducing power consumption by orders of magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OFDM signals are transmitted using conventional RF components, then communication compliance with Wi-Fi and LTE standards is achieved, but power consumption becomes prohibitive
Solution Approach 1:
The patent extracts the power-consuming RF signal generation function from the backscatter device and places it in a helper device. The backscatter device retains only the essential impedance modulation function, which consumes minimal power. This extraction resolves the contradiction by maintaining OFDM communication compliance through the helper device's RF capabilities while achieving ultra-low power consumption in the backscatter device.
Solution Approach 2:
The helper device acts as an intermediary that provides the carrier signal and handles RF signal generation. The backscatter device modulates this carrier signal by varying its impedance based on baseband data, enabling OFDM transmission without requiring its own RF signal generation capabilities. This intermediary approach allows communication standard compliance while dramatically reducing power consumption.
2Reliability
If analog RF components are used for OFDM transmission, then signal quality is maintained, but power scaling benefits are lost
Solution Approach 1:
The system segments the transmission function into two parts: RF signal generation (handled by the helper device with its analog RF components) and data modulation (handled by the backscatter device through impedance control). This segmentation allows the helper device to maintain signal quality using full-capability RF components while the backscatter device operates at ultra-low power by only controlling impedance based on baseband data.
3Reliability
If full RF signal generation is implemented in backscatter devices, then transmission capability is improved, but device complexity increases
Solution Approach 1:
The complex RF signal generation components are extracted from the backscatter device and relocated to the helper device. The backscatter device is simplified to contain only an antenna and impedance control circuitry that responds to baseband data. This extraction maintains full transmission capability through the helper device while dramatically reducing the backscatter device's complexity and component count.
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
This approach enables ultra-low power communication, allowing backscatter devices to transmit data compliant with Wi-Fi and LTE standards, improving battery life and facilitating IoT and ubiquitous sensing by reducing the need for power-hungry RF components.
Implementation Method 1
a backscatter device configured to backscatter the carrier signal to form a backscatter signal including orthogonal frequency division multiplexing (OFDM) packets
Data Source
AI summary
Examples described herein include backscatter devices which may transmit orthogonal frequency division multiplexing (OFDM) signals. Techniques for complex analog backscatter are described. Examples of impedance circuitry are described which may be used to provide real and imaginary components of impedance in accordance with inphase and quadrature bits.