RFID Sensor Network for Wireless Occupancy Detection
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Solution Overview
Problem
Existing occupancy sensors face challenges in achieving high accuracy, privacy preservation, and cost-effectiveness for smart thermostats and energy management systems, particularly in environments where wiring is not feasible and require robustness and minimal implementation burden.
Innovation Solution
An integrated occupancy sensing system utilizing a radio-frequency identification (RFID) sensor network with multimodal sensor fusion, including image and acoustic energy sensors, powered by a photovoltaic cell, which leverages spatiotemporal interactions and machine learning algorithms for accurate occupancy detection without the need for wiring, preserving privacy and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing occupancy sensors are connected to a power source using wiring, then they can operate continuously and detect occupancy, but installation becomes complex and requires electrical outlets
Solution Approach 1:
The patent replaces wired electrical connections with wireless RFID communication. The occupancy sensor node communicates occupancy status wirelessly to the reader, eliminating the need for electrical wiring and outlets for data transmission. This substitution resolves the contradiction by maintaining detection capability while dramatically simplifying installation.
Solution Approach 2:
The patent introduces an RFID reader as an intermediary device that acts as a wireless power source and communication hub. The reader transmits electromagnetic energy that powers the passive sensor node and enables wireless data transmission. This intermediary resolves the contradiction by providing both power and communication without requiring direct wiring to the sensor node.
2Reliability
If occupancy sensors use infrared or ultrasonic technology, then they can detect motion, but they consume significant energy and require frequent battery replacement or wiring
Solution Approach 1:
The patent implements a passive RFID sensor node that harvests electromagnetic energy from the RFID reader's transmission signals. The sensor node uses this harvested energy to power its occupancy detection electronics and wireless communication, eliminating the need for batteries or external power wiring. This self-service approach resolves the contradiction by making the sensor energy-autonomous while maintaining continuous operation.
Solution Approach 2:
The patent employs periodic transmission of electromagnetic energy by the RFID reader, which simultaneously serves as a power source and communication channel. The sensor node periodically wakes up to sense occupancy and transmit data using energy harvested from these periodic transmissions. This periodic operation pattern enables the sensor to function with minimal energy consumption while maintaining reliable detection capability.
3Power
If sensors are placed closer to the transmitter, then power availability increases, but installation flexibility and optimal sensing coverage are reduced
Solution Approach 1:
The patent creates a dynamic power availability model where the sensor node's operational capabilities adapt to its distance from the transmitter. The system adjusts transmission power, sensing frequency, and data reporting intervals based on the harvested energy level. This dynamic adaptation resolves the contradiction by allowing flexible installation positions while maintaining reliable operation through real-time parameter adjustment.
Solution Approach 2:
The patent changes operational parameters (transmission power, sensing interval, data rate) based on the distance between the sensor node and RFID reader. When the node is farther from the transmitter with lower power availability, the system reduces transmission frequency and power consumption. This parameter adaptation enables installation flexibility across various distances while ensuring continuous functionality.
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 system achieves high accuracy in occupancy detection with minimal false alarms, battery-free operation, and reduced implementation costs, enabling efficient energy management and privacy preservation in residential settings.
Implementation Method 1
at least some of the RFID sensors are coupled to a photovoltaic cell configured to harvest at least two sources of energy, including (but not limited to) radio frequency and light
Implementation Method 2
configured to harvest at least two sources of energy, including (but not limited to) radio frequency and light
Data Source
AI summary
An integrated occupancy sensing system includes one or more radio frequency identification (RFID) sensor nodes and one or more base station units. Each of the one or more RFID sensor nodes includes at least one of (1) an image sensor, (2) an acoustic energy sensor, (3) a temperature sensor, (4) an illuminance sensor, or (5) a relative humidity sensor. Each of the one or more base station units is configured to be connected to a power source to emit a continuous wave carrier signal and to receive a reflected signal. Each of the one or more RFID sensor nodes is configured to receive and reflect the continuous wave carrier signal. In response to receiving the reflected signal from the one or more RFID sensor nodes, at least one of the base station units is configured to infer the likelihood of human occupancy in the building.