OOK-Spread DFT-s-OFDM Wake-Up Signals for Low-Power NR
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Solution Overview
Problem
Current 3GPP NR receivers face significant energy consumption due to the need for high-precision analog-to-digital conversion and synchronization with existing wake-up signals, and the proposed low-power wake-up receiver solutions have not been deployed in products by network operators.
Innovation Solution
A transmit device using a low-complexity on-off keying (OOK) signal is implemented, which spreads a sequence of bits with a linear phase sequence and discrete Fourier transform precoder to generate an orthogonal frequency-division multiplexing (OFDM) signal, allowing for robust detection with low-precision ADCs and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OFDM-based wake-up signals (MWUS/NWUS) are used, then orthogonality to other signals is maintained, but high-precision analog-to-digital conversion and synchronization are required, increasing energy consumption
Solution Approach 1:
The patent changes the modulation parameter from conventional OFDM to OOK (on-off keying) modulation. This parameter change allows the wake-up signal to be detected by low-power receivers with lower precision ADCs, reducing energy consumption while maintaining reliable signal transmission through amplitude-based detection rather than requiring precise synchronization and high-precision conversion
Solution Approach 2:
The patent introduces a dedicated low-power wake-up receiver (LP-WUR) that is simpler and less expensive than the main radio receiver. This LP-WUR uses low-precision ADCs and can detect the OOK signal without requiring the high-precision components of the main radio, effectively replacing the need for expensive high-precision components in the wake-up signal reception path
2Reliability
If main radio is kept on for wake-up signal detection, then reliable signal reception is ensured, but power consumption increases
Solution Approach 1:
The patent segments the receiver functionality into two separate components: a low-power wake-up receiver (LP-WUR) dedicated to detecting wake-up signals, and the main radio that processes full data communications. This segmentation allows the LP-WUR to operate with minimal power consumption using simple OOK detection, while the main radio remains off during idle periods, ensuring reliable wake-up detection without requiring the main radio to be continuously powered on
Solution Approach 2:
The patent extracts the wake-up signal detection function from the main radio and places it in a separate dedicated receiver (LP-WUR). This extraction allows the main radio to be completely switched off during idle periods, as the LP-WUR independently handles wake-up signal detection using its own simplified architecture with low-precision ADCs, thereby reducing overall power consumption while maintaining detection reliability
3Use of energy by stationary object
If low-power wake-up receiver is introduced, then power saving is achieved, but detection precision requirements are reduced
Solution Approach 1:
The patent changes the detection parameter from high-precision OFDM signal processing to amplitude-based OOK detection. This parameter change enables the LP-WUR to use low-precision ADCs and simpler detection circuits, reducing power consumption while maintaining adequate detection precision through amplitude thresholding rather than requiring high-precision analog-to-digital conversion and synchronization
Data Source
AI summary
An orthogonal frequency-division multiplexing (OFDM) signal is obtained by spreading a sequence of Nbit number of bits to obtain Nsymb number of modulation symbols based on multiplying each bit in the sequence of Nbit number of bits with a corresponding spreading sequence in a sequence of Nbit number of spreading sequences. Each spreading sequence in the sequence of Nbit number of spreading sequences is a linear phase sequence having a constant rotational phase angle Φ. The Nsymb number of modulation symbols are multiplied with a discrete Fourier transform precoder to obtain Nsymb number of Fourier coefficients. The OFDM signal including the Nsymb number of Fourier coefficients mapped onto K number of OFDM subcarriers is transmitted.