Downlink Event Allocation for Battery-Powered IoT Devices
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Solution Overview
Problem
Battery-powered devices in wireless networks face significant power constraints, necessitating techniques to maximize available power and extend their operational lifespan, especially in applications like water and gas metering where batteries may last up to 20 years.
Innovation Solution
Implementing event offsets that allow battery-powered devices to operate in a sleep mode for most of the time, with scheduled wake periods for communication, coordinated by mains-powered devices to minimize overlap and distribute communication events uniformly across a period, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery-powered devices remain awake continuously to maintain network connectivity, then communication reliability is improved, but power consumption increases and battery lifespan decreases
Solution Approach 1:
The patent implements periodic wake-up cycles where battery-powered devices transition between sleep and awake states. Devices wake up at scheduled intervals to check for downlink events, transmit uplink data, and maintain network connectivity, then return to sleep mode. This periodic operation significantly reduces average power consumption while preserving communication reliability through regular connectivity checks.
Solution Approach 2:
The network coordinator pre-calculates and publishes event offsets that indicate when downlink events are expected to occur. Battery-powered devices use this advance information to schedule their wake-up times accurately, ensuring they are awake exactly when needed for communication without unnecessary power consumption during other periods.
2Reliability
If battery-powered devices wake up frequently for communication, then communication reliability is improved, but the duration of sleep mode decreases and power consumption increases
Solution Approach 1:
The system establishes regular periodic cycles where devices alternate between extended sleep periods and brief awake periods for communication. This timing pattern maximizes sleep duration to conserve power while ensuring frequent enough wake-ups to maintain communication reliability through predictable rhythm of activity and rest.
Solution Approach 2:
The network coordinator monitors network conditions and adjusts event offset publications to optimize wake-up scheduling. When network traffic patterns change or connectivity issues are detected, the coordinator modifies the timing and frequency of wake-up cycles dynamically, balancing power conservation with communication reliability through continuous feedback adjustment.
Data Source
AI summary
Techniques for allocating event offsets within a period of transmission are described. A mains-powered device (MPD) may act as a “parent” to one or more battery-powered devices (BPDs). The MPD may assign “event offsets” to each BPD. The event offset is a time by which the BPD's timeslot is “offset” from the start of a periodic cycle of transmissions by the MPD. Thus, each event offset indicates a time that the BPD must be “awake,” i.e., operating its radio receiver and/or performing other functionality. A BPD may spend a substantial fraction of its time in a “sleep” mode, wherein less power is used and fewer functions are performed than during a period of that BPD's event offset. Another BPD may have a different event offset. Communications by the MPD with each child BPD may be substantially uniformly distributed over the period. To increase efficiency, groups of BPDs may receive multicasts.