356a Sesión de Tesos en Wi-Fi: WLANPros Wi-Fi Design [Chanels, DFS, AFC, CCC, CCI, ACI, OBSS]

Posted on July 25, 2026July 25, 2026 by Ferney Muñoz

Hello, good morning, afternoon, or evening to everyone around the world! Welcome to Session 356 of Tesos en Wi-Fi, part of the free Wireless LAN Professionals Wi-Fi Design Class. Today, on Saturday, July 25th, I decided to celebrate my birthday doing what I love most: sharing Wi-Fi knowledge with all of you 100% free!. The Frame Types Burden: Why most airtime isn’t actually carrying data, but small management and control frames. OFDM Subcarriers & Channel Bonding: How 20 MHz channels divide into 64 subcarriers, and the price we pay in spectrum congestion when bonding into 40, 80, or 160 MHz wide channels. Interference Realities: The technical differences between Co-Channel Interference (CCI), Adjacent Channel Interference (ACI), and Overlapping Basic Service Sets (OBSS). DFS & AFC Rules: How Dynamic Frequency Selection protects radar systems, and how Automatic Frequency Coordination manages standard-power 6 GHz APs. Wi-Fi 6 OFDMA Mechanics: How Resource Units allow up to 9 client devices to transmit simultaneously, shifting Wi-Fi from single-device contention to efficient spectrum scheduling.

Chat Notes:

00:35:46 Martin Ericson: No, DFS was not required or used in the original U-NII-2A allocation. [1, 2]
When the FCC originally created the U-NII bands in 1997, the 5.250–5.350 GHz band did not mandate DFS. Instead, Wi-Fi devices operating in this band were restricted to a lower maximum power output of 250 mW to avoid interfering with nearby radar. [1, 2, 3, 4, 5]

00:36:09 Ferney Muñoz: Youtube video clic here. Channel Switch Announcements | Ferney Muñoz | WLPC Prague 2023

00:36:22 Martin Ericson: The requirement for DFS came later through regulatory updates to prevent interference with military, weather, and airport radar systems: [1, 2, 3, 4, 5]
The 2003 Overhaul: Following the FCC 03-287 Report and Order, the FCC harmonized rules with international standards. This update introduced the U-NII-2C (Extended) band and formally mandated DFS for both U-NII-2A and U-NII-2C. [1, 2, 3, 4, 5]

00:39:10 Ferney Muñoz: Youtube video clic here. DFS – The Untold Story | David Coleman | WLPC Phoenix 2020

00:45:35 Ferney Muñoz: Youtube video clic here. Throughput Testing and Active Survey Analysis | Ferney Muñoz | WLPC Phoenix 2026

01:21:28 Ferney Muñoz: Youtube video clic here. Preferred Scanning Channels | Ferney Muñoz | WLPC Prague 2024

01:35:51 Martin Ericson: Wi-Fi Fine Timing Measurement (FTM) is a protocol defined in the IEEE 802.11-2016 standard that measures the physical distance between wireless devices by calculating signal travel time. Key aspects include sub-meter accuracy, round-trip time calculation, and independence from standard router connections. [1, 2, 3, 4]