Description
802.11ac (Wi-Fi 5, ratified 2013) widened channels to 80 MHz (and optionally 160 MHz) at 5 GHz and added MU-MIMO downlink. For CSI research the headline change is resolution: an 80 MHz 802.11ac channel reports up to 256 OFDM subcarriers vs ~56 on 802.11n, which means much sharper time-of-flight / angle-of-arrival estimates and finer-grained motion sensing. nexmon-csi on Broadcom (especially Raspberry Pi 3B+/4 with BCM43455c0, ASUS RT-AC86U) made this practical on commodity hardware.
Specs / capabilities
- 5 GHz only
- 20 / 40 / 80 / (160) MHz channels — 64 / 128 / 256 / (512) OFDM subcarriers
- Up to 8x8 MU-MIMO (downlink)
- Beamforming feedback (compressed CSI) defined in standard, but research uses raw per-frame CSI
- PHY rate up to 6.93 Gbps (theoretical)
Tooling
- nexmon-csi on Broadcom BCM43455c0 / BCM4366c0
- picoscenes platform
Used by (papers)
- 2019+ papers using Raspberry Pi or commodity routers as CSI sensors
- Baseline for sub-cm ranging / FTM-style work