In this session, which is part of the Wireless LAN Professionals Wi-Fi Design Class, we dive deep into the fundamental operations of Network Interface Controllers (NICs) and how they interpret the wireless environment. We explore the critical process of converting electromagnetic waves into digital ones and zeros, highlighting the complexities that arise from hardware variations. Anatomy of Ethernet vs. Wi-Fi Frames: We break down the structure of frames, including the preamble for synchronization, expanded headers containing up to four MAC addresses in Wi-Fi, and the Frame Check Sequence (FCS) used to verify data integrity. RadioTap Header and Metadata: We explain how the receiving NIC adds essential information not found in the air, such as timestamps, channel stamps, and RSSI readings from its own perspective. Noise, SNR, and MCS: We discuss the challenges NICs face when estimating the noise floor and how the Signal-to-Noise Ratio (SNR) dictates which modulation schemes (MCS) the chipset chooses for data transmission. Survey Methodology and Speed: We address common questions regarding walk speed during site surveys and how scanning multiple channels across 2.4 GHz, 5 GHz, and 6 GHz affects data accuracy and interpolation.

Session Highlights:
01:36:25 – Visual demonstration of wave polarization.
00:12:45 – The structure of Ethernet and Wi-Fi frames.
00:21:03 – Understanding the RadioTap Header.
00:34:31 – Comparison of receive sensitivity across different devices.
00:54:48 – Testing at the Salt Flats: Does walk speed matter?
00:58:59 – Directional variations in survey heat maps.
01:21:59 – How NICs interpret signal and estimate noise.