Time-Hopping Wireless Network for Fluorescent Lamp Control
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Solution Overview
Problem
Existing ZigBee-based lighting control systems for low-power wireless networks face high implementation costs and substantial power consumption, despite their advantages in reducing overall power usage through low-power sleep modes and synchronization.
Innovation Solution
A low-power wireless time-hopping network system that uses RF-enabled fluorescent lamp starter units, where the local master unit transmits beacons at pseudo-random intervals, and receiver units operate in low-power sleep mode most of the time, waking up only to listen for beacons and transmit upon command, reducing collisions and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If ZigBee-based lighting control system is used with beacon synchronization, then power consumption is reduced through sleep mode, but implementation cost and protocol overhead increase
Solution Approach 1:
The system segments the beacon transmission function from the coordination function by using a dedicated beacon transmitter unit that can be separate from the coordinator. This allows endpoints to receive beacons for synchronization without requiring full ZigBee protocol stacks, reducing implementation cost while maintaining power savings from sleep mode operation.
Solution Approach 2:
The patent extracts the beacon reception and synchronization function from the full ZigBee endpoint device requirements. Endpoints only need to receive beacons and synchronize their sleep/wake cycles, without needing complete ZigBee protocol implementation, thereby reducing device complexity and cost while preserving energy efficiency.
2Use of energy by moving object
If coordinator transmits beacons at widely spaced intervals for synchronization, then endpoints can spend more time in low-power sleep mode, but communication latency increases
Solution Approach 1:
The system dynamically adjusts beacon transmission intervals based on network conditions and communication requirements. The beacon transmitter can vary the spacing between beacons, allowing the system to optimize between power consumption (wider spacing) and communication latency (narrower spacing) depending on current operational needs.
Solution Approach 2:
The patent employs parameter changes by allowing the beacon interval to be adjusted as a variable parameter rather than a fixed value. This enables the system to change the time parameter of beacon transmission to balance power savings and latency requirements based on specific operational conditions.
3Area of stationary object
If multiple wireless networks operate in the same frequency band, then network coverage is extended, but signal collisions increase
Solution Approach 1:
The system uses periodic beacon transmissions with time-hopping spread spectrum techniques. Each network transmits beacons at periodic intervals but with pseudo-random time offsets, allowing multiple networks to coexist in the same frequency band by distributing their transmissions across different time slots, thereby reducing collisions while maintaining coverage.
Solution Approach 2:
The patent introduces time-hopping spread spectrum as an intermediary mechanism that mediates between multiple networks operating in the same frequency band. This technique spreads each network's signal across the frequency band over time, reducing the probability of simultaneous transmissions and collisions while preserving network coverage area.
Data Source
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AI summary
A low-power wireless network involves a master and a plurality of RF-enabled fluorescent lamp starter units. In each of a plurality of intervals, a starter wakes up and listens for a beacon, regardless of whether a beacon is transmitted during that interval or not. The starter operates in a low power sleep mode during the majority of the interval. The master can transmit during the beacon slot time of any interval, but typically only transmits frequently enough to maintain starter synchronization. If the master wishes to communicate with the starters with reduced latency, then the master can transmit a beacon in the next interval. Beacon slot time is varied within the interval (for example, from interval to interval or from group of intervals to group of intervals) in a pseudo-random time-hopping fashion known to both the starters and the master, thereby reducing persistence of collisions with similar networks.