How It Works

Wi-Fi Sensing Technology

Devices flashed with the TOMMY firmware form a mesh network and exchange packets. Channel State Information (CSI) can be extracted from received packets using specific reference signals or pilot tones within the packet structure. CSI provides detailed data about how the Wi-Fi signal traveled from transmitter to receiver, including:

• Signal amplitude: Strength of the received signal across different subcarriers
• Phase information: Phase shifts of the signal at different frequencies
• Frequency response: How the channel affects different frequency components
• Multipath characteristics: How signals reflect, scatter, and diffract in the environment

How Movement Affects the Signal

When someone moves through a Wi-Fi zone, the signal is affected in the following ways:

• Direct path blocking: Movement directly between transmitter and receiver
• Multipath changes: Reflections off walls, furniture, and the person's body change
• Doppler effects: Moving objects cause frequency shifts in reflected signals
• Scattering: The human body scatters Wi-Fi signals in characteristic ways

Motion Detection Process

1. Baseline Establishment: TOMMY learns the normal Wi-Fi signal patterns for a static environment
2. Continuous Monitoring: Real-time analysis of CSI data as packets are exchanged
3. Change Detection: Algorithms identify when signal patterns deviate from the baseline
4. Motion Classification: Changes are analyzed to determine if they indicate movement

Limitations and Considerations

Current Limitations

• Movement only: Cannot detect stationary presence (planned for Q1 2026)
• All motion detected: No distinction between humans, pets, or objects (planned for Q1 2026)

Environmental Factors

The environment affects sensing accuracy and range. Several factors can enhance or limit TOMMY's motion detection capabilities:

• Walls and building materials: Different materials affect signal penetration differently. Drywall allows signals to pass through, while concrete and brick can significantly reduce range. Thicker walls require devices to be placed closer together.

• Room size and layout: Larger spaces may require more devices to maintain adequate coverage. Open floor plans generally provide better signal propagation than spaces with many small rooms.

• Furniture placement: Dense furniture arrangements can create signal shadows or dead zones. Device placement can help overcome these obstacles.

• Reflective surfaces: Mirrors, large windows, and metal surfaces can cause signal reflections that create multipath effects. While multipath effects are used for detection, excessive reflections can sometimes cause false positives outside the detection area.

• Large metal objects: Appliances, filing cabinets, and other large metal objects can block or redirect Wi-Fi signals, potentially creating blind spots or false positives.

• Device spacing: The distance between TOMMY devices affects both network reliability and sensing range. Devices placed too far apart may have reduced motion detection abilities.

• Interference: Other Wi-Fi networks, Bluetooth devices, and electronic equipment operating on similar frequencies can introduce noise that affects CSI data quality.