Multiple-Input Multiple-Output (MIMO) is a wireless communication technique that uses multiple antennas at both the transmitter and receiver simultaneously to transmit and receive data across spatially diverse signal paths. In WiFi/CSI sensing research, MIMO is significant because it multiplies the volume and spatial richness of CSI measurements available for analysis — for example, a system with multiple transmit and receive antenna pairs yields CSI across numerous antenna-subcarrier combinations, substantially improving the granularity and robustness of sensing tasks such as people counting, localization, and activity recognition. Key variants relevant to the field include Single-Input Multiple-Output (SIMO) and Multiple-Input Single-Output (MISO) as reduced configurations, as well as Massive MIMO found in newer standards, though commodity WiFi sensing research most commonly exploits the 2×2 or 3×3 MIMO configurations available in off-the-shelf 802.11n/ac chipsets such as those targeted by tools like the nexmon CSI Extractor.
Source Papers
- A Novel Device-Free Counting Method Based on Channel Status Information ↗ — A Novel Device-Free Counting Method Based on Channel Status
- CRPF-QC: An Efficient CSI Recurrence Plot-Based Framework for Queue Counting ↗ — CRPF-QC: An Efficient CSI Recurrence Plot-Based Framework fo
- Channel State Information from Pure Communication to Sense and Track Human Motion: A Survey ↗ — Channel State Information from Pure Communication to Sense a
- Free Your CSI ↗ — Free Your CSI