Backscatter 2K-PSK Modulation for Orthogonal Multi-Device Access
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Solution Overview
Problem
Existing backscattering techniques face challenges in using licensed frequency spectrum and managing interference in environments with multiple devices operating in close proximity, particularly with non-orthogonal modulation methods like OOK and FSK, which are not spectrally efficient.
Innovation Solution
Employing 2K-Phase Shift Keying (PSK) modulation and multiple access techniques, where backscattering devices modulate impedance switching based on predefined sequences and rates aligned with subcarrier spacing, enabling orthogonal frequency domain signals and suppressing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If OOK or FSK modulation is used for backscattering, then the system is simple to implement, but spectral efficiency is poor and interference management is difficult
Solution Approach 1:
The patent changes the modulation parameter from simple OOK/FSK to 2K-PSK, where K information bits are encoded into 2K phase states. This parameter change dramatically improves spectral efficiency while maintaining implementation feasibility through structured codebooks and impedance switching.
Solution Approach 2:
The patent employs periodic impedance switching at rates synchronized with the OFDM symbol structure. The switching pattern follows periodic sequences that align with subcarrier spacing, enabling orthogonal signal separation and improving spectral efficiency through structured periodic modulation.
2Quantity of substance
If multiple backscattering devices operate in close proximity, then device density increases, but interference between devices worsens
Solution Approach 1:
The patent segments the frequency spectrum into orthogonal subcarriers and assigns different devices to different subcarrier sets. Each device modulates impedance at rates corresponding to specific subcarrier spacings, creating orthogonal frequency-domain signals that can coexist without interference, thus enabling high device density.
Solution Approach 2:
The patent moves the differentiation between multiple devices from time domain to frequency domain by using orthogonal frequency division multiplexing principles. Devices are separated by assigning them to different frequency subcarriers and using frequency-synchronized impedance switching, allowing simultaneous operation without interference.
3Adaptability or versatility
If licensed frequency spectrum is used, then spectrum availability is improved, but spectral efficiency requirements become more stringent
Solution Approach 1:
The patent implements 2K-PSK modulation where each symbol carries 2K bits of information through phase changes. This high-order modulation parameter dramatically increases spectral efficiency, making licensed spectrum usage viable by maximizing information throughput per Hertz of bandwidth.
Solution Approach 2:
The patent uses periodic impedance switching synchronized to OFDM symbol boundaries and subcarrier spacing. This periodic structure enables efficient spectral utilization by concentrating signal energy in orthogonal frequency bins, meeting the stringent spectral efficiency requirements of licensed spectrum operations.
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
Achieves spectrally efficient and interference-free communication, allowing multiple devices to operate simultaneously by generating orthogonal 2K-PSK signals, enhancing reception sensitivity and spectral efficiency.
Implementation Method 1
a passive or semi-passive transmitter generates a transmit signal by using an antenna mismatched to the incoming wireless carrier, thus reflecting or backscattering the incoming wireless signal
Implementation Method 2
modulating an impedance of the antenna between a first impedance value and a second impedance value at a switching rate that is R times a subcarrier spacing
Implementation Method 3
Passive and semi-passive transmitters transmit a signal using a technique referred to as backscattering. With backscattering, generation of the RF carrier is delegated to an external node that is not power constrained
Data Source
AI summary
Systems and methods are disclosed for transmission and reception of backscattering signals using 2K Phase Shift Keying (PSK) (2K-PSK) modulation and/or multiple access techniques.