Channel Number
The channel number is a standardized identifier assigned to specific frequency ranges used in wireless communication systems. It enables devices to select and operate on predefined frequency blocks, ensuring interoperability and compliance with regional spectrum regulations.
Scope and Application
Channel numbers are used to define center frequencies in Wi-Fi systems operating in the 2.4 GHz, 5 GHz, and 6 GHz bands. Together with the channel bandwidth, they determine the actual frequency range of transmission.
Common assignments include:
2.4 GHz: Channels 1–13 (5 MHz spacing), with channel 14 allowed only in Japan
5 GHz: Channels 36–64 (UNII-1 and UNII-2A), 100–144 (DFS-required), 149–165 (UNII-3, often outdoor use)
6 GHz: Channels 1–233 for Wi-Fi 6E and Wi-Fi 7, subject to national approval and Automated Frequency Coordination (AFC)
Technical Role and Configuration
The channel number specifies the center frequency, which must align with the selected channel bandwidth and permitted frequency range.
Channel selection affects:
Spectrum efficiency and interference mitigation
Transmit power limits, which vary depending on indoor/outdoor classification
Dynamic Frequency Selection (DFS), mandatory for radar-protected channels in the 5 GHz band
Certain 5 GHz channels (e.g., 52–144) require DFS—a mechanism that continuously monitors the band for radar signals and triggers a channel switch when interference is detected.
Modern devices may dynamically assign channels based on scan results or databases (e.g., AFC systems in the 6 GHz band).
Regulatory Considerations
Channel numbering schemes and availability are defined by regional authorities:
FCC (USA): 47 CFR Part 15, Subparts C and E
ETSI (EU): EN 300 328, EN 301 893, EN 303 687
ISED (Canada): RSS-247
Devices must restrict active channels to those permitted in the selected regulatory domain. For example, channels 12 and 13 are often disabled in U.S. configurations, and DFS compliance must be demonstrated through testing.