Network Impact
How much Wi-Fi traffic and airtime TOMMY uses, with example figures, and how to keep the impact minimal.
TOMMY shares the Wi-Fi channel with everything else on your network, so it is built to take as little of it as possible. This page explains what TOMMY actually sends, what that adds up to in practice, and which settings control it.
What TOMMY sends
TOMMY's traffic falls into two classes:
- Sensing broadcasts. The transmitting devices in a zone broadcast small fixed-size packets (240 bytes) at a steady rate: 30 per second in conservative mode, up to 100 per second in high performance mode. The topology controls how many devices transmit: one in star, all but one in mesh.
- CSI backhaul. Every listening device forwards its channel measurements to the TOMMY server as compact packets of around 600 bytes, one per received broadcast. This traffic rides your regular Wi-Fi connection through the access point.
Example figures
Measured on real zones in star topology with conservative mode, with airtime estimated for a 5 GHz HE20 channel:
| Zone | Traffic | Throughput | Channel airtime |
|---|---|---|---|
| 2 devices (1 transmitter, 1 listener) | 60 pkt/s | ~27 KB/s | ~0.7% |
| 4 devices (1 transmitter, 3 listeners) | 120 pkt/s | ~63 KB/s | ~1.5% |
On a 2.4 GHz HT20 channel the same zones land at roughly 0.8% and 1.8% airtime. For comparison, the 2-device zone moves about as much data as a music stream.
Live estimate in the dashboard
Open Network impact under Stats in the sidebar to see the estimated airtime your zones use per band and channel, with a per-zone breakdown of traffic.
Tips to reduce impact
- Topology sets how many devices transmit. Star keeps it to a single transmitter per zone regardless of zone size, while mesh scales with the number of devices in the zone.
- Performance Mode sets the broadcast rate. Conservative is recommended for most users; higher modes increase Wi-Fi traffic.
- Band matters: zones on 5 GHz (ESP32-C5) run at higher data rates, so the same traffic takes less airtime, and the band is typically far less congested than 2.4 GHz.
- Channels are separate airtime domains. Zones on different bands or access point channels do not compete. On mesh Wi-Fi networks, pin each zone's devices to a different access point than other zones where possible (see the BSSID notes in system requirements). Devices within a zone must share an access point, but spreading zones across access points offloads the traffic. The effect is biggest when the access points run on different channels.
About the estimates
Airtime figures are modelled from packet counts, sizes, and the data rates of the negotiated PHY mode, assuming a strong link between devices and access point. Retransmissions on weak links, router settings, and neighboring networks can shift the real numbers, which is why the dashboard's live estimate is the best reference for your setup.