Description
A CSI monitor station is a host (typically Raspberry Pi, OpenWrt router, or Linux laptop) running a CSI-extraction NIC in monitor mode: it observes Wi-Fi traffic between other parties without participating, and logs per-frame CSI for sensing analysis. This is the "passive sniffer" deployment pattern that the thesis architecture relies on — fixed monitor stations placed at known coordinates around the monitored area continuously log CSI from any cooperating Wi-Fi traffic in the room. Distinct from an access-point because it never serves clients; only listens.
Specs / capabilities
- Any CSI-capable NIC (intel-5300, atheros-csi-tool, nexmon-csi, picoscenes) in monitor mode
- Passive: does not transmit, does not associate
- Channel-locked (typically locked to the deployment AP's channel)
- Logs CSI to local storage or streams over Ethernet to a central collector
Quirks / known issues
- Must be channel-locked → cannot follow channel hops
- Some NICs decimate CSI in monitor mode vs associated mode (Intel 5300 reports the same 30 subcarriers either way)
- Time-of-day clock drift between distributed monitors is a real problem; PTP / GPSDO can help
Used by (papers)
- Distributed CSI deployments
- Thesis-style "fixed sensor at known coordinates" architecture