Description
Orthogonal Frequency-Division Multiplexing splits a wideband channel into many narrow orthogonal subcarriers, each modulated independently. It is the physical-layer foundation of every Wi-Fi standard from 802.11a onward and is what makes Channel State Information well-defined and rich: one complex channel coefficient per subcarrier per packet. Without OFDM there is no CSI to talk about.
When it's used
- Implicit prerequisite for all WiFi-CSI sensing
- Pilot-aided channel estimation that produces the CSI matrix
- Frequency-selective fading analyses (Fresnel zones, multipath profiling)
- 802.11bf sensing primitives on top of OFDM PHY
Limitations
- Sensitive to inter-carrier interference under high Doppler
- Requires precise CFO/SFO tracking
- High peak-to-average power ratio