Wake-Up Signal Bandwidth Design for Interference-Resistant Detection
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Solution Overview
Problem
Existing wake-up receivers (WURs) face high vulnerability to interference due to imprecise local oscillator signals, leading to increased power consumption and limited filtering capabilities, which compromises their ability to accurately detect wake-up signals.
Innovation Solution
Generate and transmit wake-up signals (WUS) over a frequency range with a bandwidth larger than twice the information symbol rate, using multiple carrier frequencies or orthogonal frequency division multiplexing, and incorporate pilot signals for frequency synchronization, enabling narrow filtering and reduced interference resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If on-off keying (OOK) is used for wake-up signal transmission to avoid the need for accurate local oscillator signals in the wake-up receiver, then power consumption of the wake-up receiver is reduced, but vulnerability to interference particularly in adjacent frequencies increases
Solution Approach 1:
The patent changes the fundamental parameter of the wake-up signal from simple OOK modulation to spread spectrum modulation (Direct Sequence Spread Spectrum or Frequency Hopping Spread Spectrum). This transformation allows the signal to be transmitted over a much wider bandwidth while maintaining low power consumption in the wake-up receiver, as the receiver only needs to detect the presence of the spread spectrum signal without requiring precise frequency synchronization or accurate local oscillator signals.
Solution Approach 2:
The patent transitions from narrowband OOK signaling to wideband spread spectrum signaling by expanding the frequency dimension. The wake-up signal is modulated across a broad frequency range using pseudorandom codes, which provides inherent resistance to interference through processing gain. The wake-up receiver detects the signal by correlating with the known pseudorandom code, achieving reliable detection without precise frequency reference.
2Use of energy by moving object
If the local oscillator signal of the wake-up receiver is not very accurate to reduce power consumption, then power consumption is reduced, but only modest filtering can be used which increases vulnerability to interference
Solution Approach 1:
The patent fundamentally changes the signal structure from narrowband to wideband spread spectrum, which transforms the interference problem. The wide bandwidth provides processing gain that inherently rejects narrowband interference. The wake-up receiver uses correlation detection with the known pseudorandom code, which provides narrow effective filtering in the correlation domain without requiring narrow analog filters that would demand precise frequency references.
Solution Approach 2:
The patent introduces pseudorandom spreading codes as an intermediary mechanism. These codes modulate the wake-up signal in a pseudorandom manner, spreading the energy across a wide bandwidth. At the receiver, correlation with the known code acts as a matched filter that provides narrow effective bandwidth and high rejection of interference, all while operating with low-power, imprecise local oscillators.
3Reliability
If precise filtering is applied to reduce vulnerability to interference, then immunity to interference is improved, but this would require accurate local oscillator signals which increases power consumption
Solution Approach 1:
The patent changes the filtering approach from requiring narrow analog filters with precise frequency references to using correlation-based digital filtering. The spread spectrum signal structure allows the wake-up receiver to achieve narrow effective filtering through correlation with the known pseudorandom code, eliminating the need for high-Q analog filters that would require accurate local oscillator signals.
Solution Approach 2:
The patent replaces the mechanical/analog filtering system (which requires precise frequency references and high-Q components) with a correlation-based detection system. The wake-up receiver correlates the received spread spectrum signal with a locally generated copy of the pseudorandom code, providing narrow effective filtering and high interference rejection without requiring precise frequency synchronization or accurate local oscillator signals.
Data Source
AI summary
A method for a wake-up transmitter. The method includes generating a wake-up signal (WUS) from a digital WUS sequence having an information symbol rate and a corresponding information symbol bandwidth. The method also includes transmitting the WUS over a frequency range having a signal bandwidth, wherein the signal bandwidth is larger than twice the information symbol rate, and wherein any frequency interval comprised in the frequency range conveys the digital WUS sequence when a width of the frequency interval is at least the information symbol bandwidth.