The 6 GHz spectrum has opened new possibilities for wireless communication, supporting the latest advancements like Wi-Fi 6E and the upcoming Wi-Fi 7. However, with greater access comes the challenge of managing a crowded frequency band while ensuring fair coexistence with existing users. This is where Automated Frequency Coordination (AFC) steps in, acting as a smart, real-time traffic controller for the 6 GHz band.

AFC is crucial for protecting incumbent users—licensed services like fixed microwave links, satellite operations, and public safety communications that have long relied on the 6 GHz band. Without effective coordination, interference from unlicensed devices could disrupt these essential services.

Objective:

In this blog, we’ll take a closer look at the mechanics of AFC, its role in managing spectrum access, and its overall impact on wireless connectivity. We’ll also cover the various types of 6 GHz access points—Standard Power and Low Power APs—and the wide range of 6 GHz client devices. By the end, you’ll gain a deeper understanding of how AFC helps protect incumbents from potential Wi-Fi interference and how access points communicate with the AFC system to maintain efficient and reliable use of the 6 GHz spectrum.

Role of Automated Frequency Coordination (AFC)

Automated frequency coordination (AFC) systems are known by different names in different frequency bands. As per FCC, AFC is a system that automatically determines and provides a list of which frequencies are available for use by SP access points operating in the 5.925-6.425 GHz and 6.525-6.875 GHz bands at a given location.

AFC facilitates spectrum sharing by carrying out the following core functions:

• • Protect incumbent licensees or other users from interference caused by entrants with lower priority (and, in some cases, coordinate among users with the same priority).
  • Ensures that only authorized devices are used.
  • AFC-enabled devices (APs and clients) will be able to provide a far better user experience, especially in outdoor environments like open-air stadiums, urban areas, and last-mile connectivity.
  • Facilitate more optimal use of the spectrum resources.

6GHz Channel

Before learning about AFC operations, let’s understand about the 6GHz frequency in Wi-Fi. The 6GHz Wi-Fi band, introduced with Wi-Fi 6E and expanded further in Wi-Fi 7, marks a major leap in wireless networking by offering up to 1200MHz of clean, wide-open spectrum—from 5925 MHz to 7125 MHz in regions where the full band is allowed. This translates to 59 non-overlapping 20MHz channels, with every 4th channel designated as a Preferred Scanning Channel (PSC) to speed up network discovery. The below mentioned picture will depict the 6GHz channel in detail.

Image Courtesy: WIK Consult, July 2023

The adoption of Automated Frequency Coordination (AFC) in the 6GHz band solves many of the issues experienced with Dynamic Frequency Selection (DFS) in the 5GHz band. DFS was implemented to protect radar and weather systems by requiring Wi-Fi devices to detect and avoid active frequencies, but this often led to unreliable connections and false detections that disrupted user experience. In contrast, AFC provides a more reliable and pre-coordinated method of protecting incumbent users—such as fixed microwave and satellite services—by determining safe channels and power levels based on device location and regulatory data. This approach eliminates unexpected channel switching and improves overall stability, making 6GHz Wi-Fi far more efficient, predictable, and user-friendly for modern high-speed networks.

6GHz incumbents details are mentioned below:

The below image will give an overview of 6GHz band usage and how Wi-Fi shares the spectrum with the incumbents,

The Low Power Indoor Access points can operate in all the 6GHz UNII bands and there is no AFC required. The Standard Power Access Points can only operate in UNII-5 & UNII-7 and it should operate under AFC guidelines.

AFC Device Types and Classes:

6GHz Indoor Devices:

LPI AP 6ID:

• • Low Power APs, which are meant to be used only in INDOOR locations.
  • Must have Integrated Antennas.
  • Cannot be used in a weatherized enclosure.
  • Should not be battery-powered.
  • No need to connect with the AFC.
  • There are restrictions on power spectral density (PSD = 5dBm/MHz) and maximum EIRP (Effective Isotropic Radiated Power) to control signal strength. (i.e., 30dBm EIRP at 320MHz, 24dBm EIRP at 80MHz and 18dBm EIRP at 20MHz).
  • 6ID – 6GHz Indoor Device.

LPI Clients:

Subordinate Devices 6PP

• • This will operate under a LPI AP.
  • This should not have a direct connection to the internet. All the communication should go through the LPI AP.
  • Wi-Fi Extenders, Mesh Node APs will come under this category.
  • 6PP – 6GHz Portable Peer.

Indoor Clients 6XD

• • This will operate under the control of a LPI AP or a LPI Subordinate device.
  • 6XD – 6GHz Extended Device.

6GHz Outdoor Devices:

Standard Power AP 6SP:

A Standard Power Access Point (6SD) is managed by AFC (Automated Frequency Coordination), requiring the AP to regularly consult a central database to ensure protection for incumbent 6 GHz services. These checks (i.e Channel, Bandwidth, GPS, Transmit Power, etc) must be conducted daily to comply with FCC regulations.

The AP must also provide necessary information to connected clients, enabling them to adjust their EIRP (Effective Isotropic Radiated Power) to at least 6 dB lower than the levels authorized by the AFC for the Standard Power Access Point.

Standard-power access points operating in the 6 GHz band are allowed a maximum EIRP of 36 dBm (with PSD = 23dBm/MHz), regardless of channel bandwidth. For outdoor deployments, there is an additional requirement that the EIRP in directions above a 30-degree elevation angle must not exceed 21 dBm.

These values may be reduced based on local regulations or specific coordination with the AFC system.

Standard Power Clients 6FX:

Standard Power Clients (6FX) are Wi-Fi 6E devices that operate in the 6 GHz band, and they are specifically designed to connect to Standard Power Access Points (6SD), which require AFC (Automated Frequency Coordination) coordination.

Key Features of 6FX Devices:

• Standard Power Operation: 

  • Like Standard Power APs (6SD), 6FX clients can operate at higher power levels compared to Low Power Indoor (LPI).
  • They follow the same AFC-controlled settings that the Standard Power AP uses for managing transmit power and frequency usage.

• AFC-Managed:

  • 6FX clients do not interact directly with the AFC system. Instead, they rely on the Standard Power AP to provide the necessary information, such as the allowed channels and transmission power.
  • The AP ensures that the client is operating in compliance with AFC rules, including power restrictions.

• EIRP (Effective Isotropic Radiated Power) Adjustment:

  • The Standard Power AP will also instruct connected 6FX clients to adjust their EIRP if needed. This might involve lowering their EIRP to at least 6 dB below the level authorized for the Standard Power AP, ensuring safe operation and no interference with other services.

• Indoor/Outdoor Usage:

  • Since 6FX clients operate with Standard Power APs, they are permitted to work outdoors as well as indoors, unlike LPI clients which are restricted to indoor use.
  • They can be used in environments like stadiums, parks, or public hotspots where broad coverage and higher power are needed.

Fixed Client 6FC:

• • Fixed Location Use: Designed for fixed, stationary installations.
  • Standard Power Operations: Typically connects to a Standard Power APs (6SD).
  • Does Not Require Mobility: Unlike portable clients (e.g., 6PP or 6XD), 6FC devices do not need to support mobility or roaming features.
  • Reliable, High-Power Usage: Can operate at higher power levels compared to mobile devices, as they are stationary and used in environments where more stable, reliable connections are required.
  • Indoor or Outdoor Use: Can be installed in both indoor and outdoor environments, depending on the type of connected Standard Power AP.
  • Fixed Position: Since these devices are stationary, they do not need to adjust their transmit power dynamically (unless specified by the AFC system).
  • Works with AFC-Managed APs: These clients connect to Standard Power APs that are managed by AFC, ensuring proper frequency coordination to avoid interference.
  • EIRP Adjustment: The AP communicates with 6FC devices to ensure the client’s EIRP remains within AFC-approved levels, typically ensuring that it stays 6 dB lower than the maximum allowable EIRP for the AP.

Dual Client 6CD:

• • Dual-Mode Operation: 6CD devices can operate both indoor and outdoor within the 6 GHz band but must comply with the power regulations of the AP they are connected to an LPI AP or a Standard Power AP.
  • When Connected with a SP AP, 6CD Client’s Tx Power is limited to 6dB below the SP AP and it should not to exceed a limit of 30 dBm EIRP and a power spectral density limit of 17 dBm EIRP in any 1-megahertz band.
  • When connected with a LPI AP or Subordinate Devices, 6CD Client is restricted to a maximum EIRP of +24 dBm and a power spectral density limit of −1 dBm EIRP within any 1-megahertz bandwidth.
  • Dynamic EIRP Adjustment: These clients can adjust their EIRP (Effective Isotropic Radiated Power) depending on whether they are inside or outside. The AP will provide the necessary instructions for power levels, ensuring compliance with regulatory rules.
  • Dual Connectivity: Can connect to LPI APs for indoor use or Standard Power APs for outdoor use. This gives them more flexibility in how they connect based on the environment.
  • AFC Coordination: For outdoor usage, the 6CD device must work under the control of a Standard Power AP that is managed by the AFC (Automated Frequency Coordination) system, ensuring that no interference occurs with incumbent services.
  • Indoor and Outdoor Usage: It is not restricted to indoor or outdoor usage alone — it can switch between both depending on the connected access point’s regulations.
  • Subordinate to AP: Like other client devices, 6CD does not have a direct connection to the AFC system but follows the instructions and frequency management provided by the AP.
  • Versatile Use Case: These clients are great for environments where devices might need to switch between indoor and outdoor locations (e.g., smartphones, laptops, or IoT devices in variable environments).

VLPI:

• • Extremely Low Power Use: VLPI devices are designed for very low power operation, typically lower than regular LPI devices. This ensures minimal interference and is especially useful in environments with dense device deployment.
  • Indoor-Only Operation: Just like LPI devices, VLPI devices are restricted to indoor environments only. They cannot be used in outdoor or weather-exposed areas.
  • Limited EIRP (Effective Isotropic Radiated Power): VLPI devices are subject to stringent EIRP limitations to ensure they emit very low power signals, minimizing interference with nearby devices and networks.
  • AFC Independence: VLPI devices do not require coordination with the AFC system for frequency management since they operate at such low power that they are unlikely to interfere with incumbent services.
  • Integrated Antennas: These devices are likely to have integrated antennas, just like LPI devices, to ensure efficient, localized coverage and avoid excessive radiation.
  • Restricted to Specific Use Cases: VLPI devices are often used in highly localized or dense indoor environments, such as office buildings, homes, or small-scale enterprise networks, where the power needs to be limited and coverage is highly localized.
  • Usage is allowed in Europe regions

The type of 6GHz device can be found under the 6GHz operation information → Regulatory Info

AFC Architecture:

Databases: A database server that is managed by an NRA and that maintains the information necessary for the calculation of Available Spectrum.

AFC system: A system that automatically determines and provides lists of which frequencies are available for use by access points operating in the 5.925-6.425 GHz and 6.525-6.875 GHz bands.

AFC Master/Standalone AP: A Standard Power Access Point which communicates with the AFC System directly and operates based on the information of Available Spectrum provided by the AFC System.

AFC Managed AP: A Standard Power Access Point which does not communicate with the AFC System directly and operates based on the information of Available Spectrum provided by the AFC System via the Proxy.

AFC Proxy: An entity engaging in communications with the AFC System on behalf of one or more Non-Standalone APs.

AFC Operational Flow:

The AFC device must connect/communicate with an AFC system at least once in a day to get the information about the spectrum and to ensure that they are operating in the allocated frequency bands without interrupting the incumbents/licensed frequency users.

AFC devices need to communicate with the AFC system at least once to know:

• • Spectrum Availability: The spectrum can change dynamically based on the presence of incumbent users. AFC systems ensure that devices only use frequencies where they won’t cause interference.

  • Regulatory Compliance: Compliance with regulations (e.g., FCC or ETSI) mandates that devices check for available spectrum to ensure they operate within permissible limits and protect licensed users.

  • Efficient Frequency Usage: The AFC system helps devices use spectrum more efficiently by providing up-to-date information on where and when certain frequencies are available for use.

  • Periodic Communication:
    In many cases, this communication happens periodically, not just once. AFC devices may need to check the AFC system regularly (e.g., daily) to ensure that their operation is still in compliance with the latest spectrum availability and to avoid causing interference to other systems.

An Available Spectrum Inquiry Request message is transmitted by an AFC Device to an AFC System to retrieve Available Spectrum information, while an Available Spectrum Inquiry Response message is sent by the AFC System in reply to the inquiry made by the AFC Device.

AFC URL Format:

The structure of an AFC URL is as follows:

Format: $BASE_URL/$METHOD

• • $BASE_URL includes at least the host name of the AFC System, along with an optional path component that may consist of one or more path segments.

  • $METHOD refers to a pair of a Request message and a Response message, as defined in Section 4 of the AFC System to AFC Device Interface Specification

For communication between the AFC System and AFC Device, HTTP v1.1 with TLS v1.2 should be used. Both entities must negotiate a ciphersuite to secure the communication. The following ciphersuites must be supported by both the AFC Device and the AFC System:

• • TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256

  • TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

Stronger ciphersuites may be negotiated and used if both sides support them.

JSON Formats of Available Spectrum Request/Response Messages:

The following JSON object is an example of an Available Spectrum Request message for an AP. The AP inquires regarding spectrum availability on both a frequency and channel basis. Followed by the Available Spectrum Response Message for the AP from the AFC system

In this example request scenario, the AP queries spectrum availability on a frequency basis throughout U-NII 5. It also requests channel availability for all 80 MHz channels in U-NII 5 & 7, and for 160 MHz channels in U-NII 5 only.

Automated Frequency Coordination (AFC) is a crucial innovation for optimizing the 6 GHz spectrum, allowing Wi-Fi access points to operate efficiently while safeguarding incumbent services. By intelligently managing spectrum access, AFC reduces interference, enhances network reliability, and supports next-generation wireless technologies. However, its implementation comes with challenges, such as transmit power restrictions on Wi-Fi devices, which can limit coverage and impact advanced features like OFDMA etc, potentially affecting overall network efficiency. Despite these limitations, AFC remains a key enabler of high-performance, interference-free wireless communication in the evolving 6 GHz landscape.

References

• 1. IEEE 802.11ax 2021
  2. AFC System to AFC Device Interface Specification v1.5 WiFi Alliance.
  3. WInnForum AFC webinar
  4. Unlicensed Use of the 6 GHz Band