OFDM-OOK Wake-Up Signal Synchronization Under Selective Fading
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Solution Overview
Problem
The centralized frequency domain spectrum of low power wake-up signals leads to reduced receiving performance due to frequency selective fading, particularly when the centralized frequency encounters fading, impacting the effectiveness of wake-up signals in network devices.
Innovation Solution
The implementation of orthogonal frequency division multiplexing (OFDM) waveforms with on-off keying (OOK) symbols, where each OOK symbol corresponds to a time domain sequence that randomizes the frequency domain amplitude, preventing excessive spectrum centralization and enhancing receiving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the frequency domain spectrum of the low power wake-up signal is excessively centralized, then the signal power is concentrated on a center frequency, but the receiving performance is greatly reduced when frequency selective fading occurs
Solution Approach 1:
The patent applies segmentation by dividing the centralized frequency spectrum into multiple orthogonal frequency division multiplexing (OFDM) subcarriers. Instead of concentrating all signal power on a single center frequency, the wake-up signal is segmented across multiple frequency sub-channels, which prevents the entire signal from being affected by fading at any single frequency point.
Solution Approach 2:
The patent transitions from a one-dimensional centralized frequency approach to a multi-dimensional frequency distribution approach using OFDM. By spreading the signal across multiple frequency dimensions (subcarriers) and utilizing time-domain sequences for further dispersion, the system achieves better reliability without sacrificing power efficiency.
2Reliability
If time domain sequences are used for frequency domain amplitude randomization, then the spectrum is dispersed and frequency selective fading impact is avoided, but the signal structure becomes more complex
Solution Approach 1:
The patent changes the parameters of the wake-up signal by introducing time-domain sequences with specific mathematical properties (such as Zadoff-Chu sequences or pseudo-random sequences). These sequences modify the frequency domain characteristics through amplitude randomization, dispersing the spectrum while maintaining controlled signal structure that can be efficiently processed.
Solution Approach 2:
The patent uses predefined time-domain sequences that can be generated through mathematical formulas rather than storing complex signal structures. This allows the system to achieve spectrum dispersion through systematic generation of sequences, reducing the complexity of signal structure while maintaining the desired frequency domain characteristics.
Data Source
AI summary
A communication method and system, the method including receiving, by a terminal device or a chip in the terminal device, a synchronization parameter related to a synchronization signal, receiving a low power wake-up signal, the low power wake-up signal includes the synchronization signal, the low power wake-up signal includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain, carrying a plurality of on-off keying (OOK) symbols, each OOK symbol corresponds to one time domain sequence associated with frequency domain amplitude randomization, and the synchronization signal is indicated by at least one of OOK symbols, determining, based on the synchronization parameter, time domain sequences corresponding to OOK symbols carried on the plurality of OFDM symbols, and performing auxiliary synchronization on the terminal device based on the time domain sequences corresponding to the OOK symbols carried on the plurality of OFDM symbols.