Wake-up Radio Preamble Design for Low Power Wi-Fi
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Solution Overview
Problem
Current wireless communication interfaces face challenges in reducing power consumption while maintaining connectivity, especially in wireless devices like mobile and wearable devices, as they require balancing power usage with connectivity distance, speed, and duration.
Innovation Solution
The implementation of a low-power wake-up receiver (WURx) in conjunction with a main Wi-Fi radio, allowing the WURx to remain active in a wake-up radio mode while the main radio enters a power save state, using orthogonal frequency division multiplexing (OFDM) symbols and On-Off Keying (OOK) modulation for low-power wake-up packet transmissions, and supporting both low and high data rate transmissions through optimized preamble sequences and pulse generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the main Wi-Fi radio enters a power save state, then power consumption is reduced, but wake-up capability is lost
Solution Approach 1:
The wireless communication system is divided into two separate radio components: a main Wi-Fi radio and a wake-up radio (WURx). The main radio handles high-rate data communication while the WURx handles low-power wake-up signal reception. This segmentation allows each component to be optimized for its specific function, with the WURx consuming significantly less power while the main radio can enter sleep mode without losing wake-up capability.
Solution Approach 2:
The wake-up radio acts as an intermediary component between the external environment and the main Wi-Fi radio. It receives wake-up packets from access points or other devices and triggers the main radio to wake up from its power save state. This intermediary approach allows the system to maintain wake-up capability while the main radio remains inactive, solving the contradiction between power savings and reliability.
2Use of energy by moving object
If a low-power wake-up receiver is used, then power consumption is reduced, but data transmission rate is limited
Solution Approach 1:
The system segments the communication functions by assigning wake-up signal reception to the low-power WURx and high-rate data transmission to the main Wi-Fi radio. The WURx uses simple OOK modulation and minimal processing to detect wake-up packets, consuming very little power. When a wake-up signal is detected, the main radio activates and handles all high-rate data communication, thus avoiding the limitation of low transmission rates while maintaining low power consumption during idle periods.
Solution Approach 2:
The system employs periodic action by having the WURx continuously monitor for wake-up signals in a low-power state, while the main radio periodically enters and exits power save states. This periodic operation pattern allows the system to maintain readiness for wake-up events without continuously operating the high-power main radio, achieving both low average power consumption and maintained data transmission capability when needed.
3Reliability
If the main radio remains active, then wake-up and communication capabilities are maintained, but power consumption increases
Solution Approach 1:
The communication system is segmented into two functional units: the WURx for wake-up signal detection and the main Wi-Fi radio for data communication. This segmentation enables the main radio to enter power save states without compromising overall communication capability, as the WURx continues to monitor for wake-up signals. When communication is needed, the WURx triggers the main radio to activate, ensuring communication capability is maintained only when necessary, thus reducing overall power consumption.
Solution Approach 2:
The WURx serves itself and the main radio by independently monitoring for wake-up signals and automatically triggering the main radio when needed. This self-service mechanism eliminates the need for the main radio to remain continuously active, as the WURx handles the wake-up detection function. The main radio can therefore enter power save states, reducing power consumption while the WURx ensures communication capability is restored when required.
Data Source
AI summary
Logic may define one or more wake-up preambles suitable for high data rates for a wake-up radio (WUR) packet. Logic may define wake-up preamble with different counts of symbols. Logic may generate a wake-up preamble as two microsecond pulses of orthogonal frequency-division multiplexing (OFDM) symbols in a four megahertz (MHz) bandwidth. Logic may generate and receive a high data rate (HDR) WUR preamble or a low data rate (LDR) WUR preamble. The HDR preamble may signal a data rate of 250 kilobits per second and the LDR preamble may signal a data rate of 62.5 kilobits per second. The HDR preamble bit count may be twice a bit count of the LDR preamble. The HDR preamble may be 32 bits. The duration of transmission of the HDR may be 64 microseconds and duration of transmission of the LDR may be 128 microseconds.