Waveform Coded Wake-Up Radio Frame for Energy-Efficient Decoding
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Solution Overview
Problem
Wireless local area network (WLAN) devices with limited power supplies, such as those in IoT applications, face rapid battery depletion due to the lack of an appropriate sleep mode and wake-up mechanism for their WLAN receiver circuits, necessitating an efficient wake-up signal communication method to conserve energy.
Innovation Solution
A waveform coded wake-up radio (WUR) frame format is introduced, using a series of modulated symbols with a guard interval followed by sub-symbols of equal duration, where data bits are represented by different relative energy distributions between the sub-symbols, allowing for efficient decoding using a low coefficient filter and minimizing energy leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the WLAN receiver circuit remains always on to ensure continuous communication capability, then communication reliability is improved, but power consumption increases rapidly depleting the limited battery supply
Solution Approach 1:
The receiver is segmented into two functional parts: a low-power wake-up radio circuit that operates intermittently to detect wake-up signals, and a high-power WLAN receiver circuit that remains dormant until activated. This segmentation allows the system to maintain communication reliability through the wake-up mechanism while dramatically reducing power consumption by keeping the main receiver off most of the time.
Solution Approach 2:
The wake-up radio circuit operates periodically rather than continuously, activating only when needed to detect wake-up signals from the access point. This periodic operation mode enables the receiver to maintain alertness for incoming communications while consuming minimal power during the majority of the time, resolving the contradiction between reliability and energy usage.
2Use of energy by moving object
If a simple wake-up mechanism is implemented to conserve energy, then power consumption is reduced, but the complexity of the communication protocol increases
Solution Approach 1:
The wake-up signal mechanism is extracted as a separate, simplified subsystem from the main WLAN communication protocol. The wake-up radio handles only the critical function of detecting wake-up signals using simple energy detection, while the complex WLAN protocol operations are isolated to the main receiver that activates only when needed. This extraction reduces the overall system complexity by confining complex operations to when they are actually required.
Solution Approach 2:
The wake-up radio circuit is designed as a simple, low-cost component with minimal processing requirements, comparable to a disposable sensor rather than a permanent communication device. It uses basic energy detection mechanisms rather than complex signal processing, reducing both the hardware complexity and power consumption while achieving the necessary wake-up functionality.
3Device complexity
If the wake-up radio uses a low coefficient filter for decoding to reduce complexity, then device complexity is reduced, but energy leakage and interference between symbols increases
Solution Approach 1:
Zero-energy guard intervals are inserted between wake-up symbols as a preliminary action to prevent overlap and interference. This guard interval structure is built into the symbol format beforehand, allowing the simple low-coefficient filter to decode symbols accurately without requiring complex filtering that would increase device complexity, while simultaneously preventing energy leakage and inter-symbol interference.
Solution Approach 2:
Each wake-up symbol is segmented into distinct time portions with zero-energy guard intervals separating the active symbol periods. This segmentation in the time domain allows the receiver to use simple filters while the guard intervals prevent energy from leaking into adjacent symbols, resolving the contradiction between filter simplicity and energy loss prevention.
4Use of energy by moving object
If data bits are represented using on-off keying with waveform coded symbols, then energy efficiency is improved, but the risk of inter-symbol interference increases
Solution Approach 1:
Zero-energy guard intervals are inserted between waveform coded symbols as a preliminary protective measure. These guard intervals create clear temporal separation between symbols, preventing the energy-efficient on-off keying modulation from causing inter-symbol interference while maintaining the energy efficiency benefits of the modulation scheme.
Solution Approach 2:
The zero-energy guard intervals act as a cushioning buffer between adjacent waveform coded symbols, absorbing potential interference and preventing it from affecting adjacent symbols. This beforehand cushioning allows the system to use energy-efficient on-off keying without compromising reliability through inter-symbol interference.
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
The WUR frame format enables accurate and energy-efficient wake-up signal decoding at low-power WUR receivers, reducing the risk of inter-symbol interference and extending battery life in devices with low duty cycles.
Implementation Method 1
modulating the waveform coded symbols onto a carrier frequency and transmitting a wake-up signal that includes the modulated waveform coded symbols in the communications channel
Data Source
AI summary
Methods and systems for waking up a wireless receiving device having a wake-up receiver (WUR) circuit. A series of waveform coded symbols each represent a corresponding data bit from a wake-up frame, each of the waveform coded symbols comprising a guard interval followed by first and second sub-symbols of equal duration wherein the corresponding data bit is represented as a different relative energy distribution between the first and second sub-symbols.