Automated Frequency Coordination vs Dynamic Frequency Selection

WiFi technology has grown increasingly sophisticated over the years, leading to new mechanisms for managing radio frequencies and ensuring efficient use of spectrum. Two of the most discussed systems are Automated Frequency Coordination (AFC) and Dynamic Frequency Selection (DFS). Although both are designed to manage spectrum use effectively, they operate in different contexts and use different methods. In this article, we will explore the differences between AFC and DFS, and compare their functionalities, applications, and performance.

To learn more about Automated Frequency Coordination in detail, you can refer to the previous article giving an in-depth explanation of how AFC works and its relevance to WiFi 7.

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What is Automated Frequency Coordination (AFC)?

Automated Frequency Coordination (AFC) is a mechanism used to manage the use of the 6GHz frequency band by WiFi devices, particularly in outdoor environments. The 6GHz band is a new addition to WiFi, offering expanded spectrum that reduces interference and provides greater capacity for high-bandwidth applications.

The main purpose of AFC is to ensure that unlicensed WiFi devices do not interfere with existing licensed users of the 6GHz band, such as fixed-service microwave links, broadcast auxiliary services, and public safety systems. AFC accomplishes this by using an automated database that keeps track of incumbent users and dynamically assigns available frequencies to WiFi devices based on location and other operational parameters. This coordination is crucial for outdoor WiFi 7 deployments, where the risk of interference is significantly higher compared to indoor environments.

What is Dynamic Frequency Selection (DFS)?

Dynamic Frequency Selection (DFS) is a regulatory requirement that applies to certain WiFi devices operating in the 5GHz band. The 5GHz band is used not only by WiFi devices but also by radar systems, such as weather radar and military radar, which have priority over other users of the spectrum. DFS was introduced to ensure that WiFi devices do not interfere with these radar systems.

DFS works by requiring WiFi access points to scan the 5GHz band for radar signals before selecting a channel. If a radar signal is detected, the access point must switch to another channel to avoid interference. This process is dynamic and ongoing, meaning that WiFi devices must continuously monitor the spectrum for radar activity and adjust their channel usage accordingly.

In essence, DFS is designed to ensure that WiFi devices operating in the 5GHz band coexist peacefully with radar systems by dynamically selecting channels that are free from interference.

Key Differences Between AFC and DFS

While both AFC and DFS are designed to manage spectrum use and prevent interference, they differ in several key aspects, including their operational context, method of coordination, and the type of spectrum they manage.

1. Operational Context

• AFC: AFC is used for WiFi devices operating in the 6GHz band. It is particularly important for outdoor deployments, where the risk of interference with incumbent users is higher. AFC is designed to protect licensed services that operate in the 6GHz band, such as fixed microwave links and satellite services.
• DFS: DFS is used for WiFi devices operating in the 5GHz band. It is designed to prevent interference with radar systems that share the same spectrum. DFS is required for both indoor and outdoor access points, but the risk of interference is particularly high in outdoor environments where radar systems are more prevalent.

2. Method of Coordination

• AFC: AFC relies on a centralised database that contains information about incumbent users of the 6GHz spectrum. WiFi devices must query this database to determine which channels are available for use. The AFC system dynamically assigns channels based on the location of the WiFi device and the presence of incumbent users in the area.
• DFS: DFS does not use a centralised database. Instead, WiFi devices must independently scan the 5GHz band for radar signals and select channels that are free from interference. If a radar signal is detected, the device must switch channels to avoid interference. This process is entirely local to the WiFi device and does not involve any external coordination.

3. Type of Spectrum Managed

• AFC: AFC is used to manage the 6GHz band, which is a newly opened spectrum for WiFi use. The 6GHz band offers more channels and greater capacity compared to the 2.4GHz and 5GHz bands, making it ideal for high-bandwidth applications. However, the presence of incumbent users in this band requires careful coordination to avoid interference.
• DFS: DFS is used to manage the 5GHz band, which has been in use for WiFi for several years. The 5GHz band offers higher data rates compared to the 2.4GHz band, but it is shared with radar systems, which have priority over WiFi devices. DFS ensures that WiFi devices do not interfere with these radar systems.

4. Complexity and Implementation

• AFC: The implementation of AFC is more complex compared to DFS, as it requires communication with a centralised database and ongoing coordination with other users of the spectrum. WiFi devices must register with an AFC system, provide their location, and request channel availability information. This adds an additional layer of complexity to the deployment of WiFi access points, particularly in outdoor environments.
• DFS: DFS is relatively simpler to implement, as it does not require any external communication or database queries. WiFi devices simply need to be equipped with the capability to detect radar signals and switch channels as needed. However, the requirement to continuously monitor the spectrum for radar activity can add some overhead to the operation of WiFi devices.

Performance Differences Between AFC and DFS

The differences in how AFC and DFS operate also lead to differences in performance, particularly in terms of spectrum availability, interference management, and overall network efficiency.

1. Spectrum Availability

• AFC: AFC allows WiFi devices to access a wider range of channels in the 6GHz band, which offers more spectrum compared to the 5GHz band. This increased spectrum availability allows for higher data rates, greater capacity, and improved performance, particularly in high-density environments. By coordinating spectrum use with incumbent users, AFC ensures that WiFi devices can make full use of the available spectrum without causing interference.
• DFS: DFS limits the channels that WiFi devices can use in the 5GHz band, as certain channels may be occupied by radar systems. If a radar signal is detected, the WiFi device must switch to another channel, which can lead to disruptions in network performance. Additionally, the need to continuously monitor for radar signals can reduce the overall efficiency of the network.

2. Interference Management

• AFC: AFC provides a more proactive approach to interference management by using a centralised database to determine which channels are available for use. This helps minimise the risk of interference with incumbent users and ensures that WiFi devices operate on frequencies that are free from interference. The use of AFC is particularly beneficial in outdoor environments, where the risk of interference is higher.
• DFS: DFS takes a reactive approach to interference management, as WiFi devices must detect radar signals and switch channels if interference is detected. This can lead to disruptions in network performance, particularly if a radar signal is detected on a channel that is being used for an active WiFi connection. The reactive nature of DFS can make it less effective in managing interference compared to AFC.

3. Network Efficiency

• AFC: By allowing WiFi devices to access more spectrum and proactively coordinating channel use, AFC helps improve overall network efficiency. The availability of more channels in the 6GHz band allows for better distribution of network traffic, reducing congestion and improving performance. Additionally, the centralised coordination provided by AFC ensures that channels are assigned in a way that minimises interference between neighbouring devices.
• DFS: The need to continuously monitor for radar signals and switch channels can reduce the efficiency of WiFi networks using DFS. Channel switching can lead to temporary disruptions in connectivity, which can impact the user experience. Additionally, the limited number of channels available in the 5GHz band can lead to congestion in high-density environments, further reducing network efficiency.

Conclusion

Automated Frequency Coordination (AFC) and Dynamic Frequency Selection (DFS) are both important mechanisms for managing spectrum use in WiFi networks, but they operate in different contexts and use different methods to achieve their goals. AFC is used to manage the 6GHz band, ensuring that WiFi devices can operate without interfering with incumbent users through a centralised database system. DFS, on the other hand, is used for managing the 5GHz band, requiring WiFi devices to dynamically select channels based on the presence of radar signals.

The key differences between AFC and DFS lie in their operational context, method of coordination, and the type of spectrum they manage. AFC provides a more proactive approach to interference management and offers greater spectrum availability, particularly for outdoor WiFi 7 deployments. DFS, while effective in preventing interference with radar systems, takes a reactive approach and can lead to disruptions in network performance.

Ultimately, both AFC and DFS play a crucial role in ensuring that WiFi networks can coexist with other users of the radio spectrum. As WiFi technology continues to evolve, the use of these mechanisms will be essential for managing spectrum use and ensuring reliable and efficient wireless connectivity.

James Smythe( Editor-in-chief )

I am James, a UK-based tech enthusiast and the Editor and Owner of Mighty Gadget, which I’ve proudly run since 2007. Passionate about all things technology, my expertise spans from computers and networking to mobile, wearables, and smart home devices.

As a fitness fanatic who loves running and cycling, I also have a keen interest in fitness-related technology, and I take every opportunity to cover this niche on my blog. My diverse interests allow me to bring a unique perspective to tech blogging, merging lifestyle, fitness, and the latest tech trends.

In my academic pursuits, I earned a BSc in Information Systems Design from UCLAN, before advancing my learning with a Master’s Degree in Computing. This advanced study also included Cisco CCNA accreditation, further demonstrating my commitment to understanding and staying ahead of the technology curve.

I’m proud to share that Vuelio has consistently ranked Mighty Gadget as one of the top technology blogs in the UK. With my dedication to technology and drive to share my insights, I aim to continue providing my readers with engaging and informative content.