RFCo-BF vs. Co-SR: Wi-Fi 8 Multi-AP Coordination Compared
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Introduction : In legacy Wi-Fi generations, Access Points (APs) operated like independent islands, competing for the same airwaves and often causing interference for one another. Wi-Fi 8 (IEEE 802.11bn) changes this paradigm through the Multi-AP Coordination (MAPC) framework. Two of the most important coordination techniques in this Wi-Fi 8 framework are Coordinated Beamforming (Co-BF) and Coordinated Spatial Reuse (Co-SR). Let us understand how these technologies work and explore differences between them.
Coordinated Beamforming (Co-BF)
It is “interference nulling” strategy. In a typical crowded environment, when a neighboring AP-1 transmits, its signal spills over into your area covered by AP-2, creating noise (interference) for client devices falling under AP-2 coverage.
With Co-BF, two APs work as a team. Before transmitting, they share Channel State Information (CSI). If AP-1 knows that its signal will interfere with a device connected to AP-2, it mathematically “steers” its signal (beamforming) to create a null point exactly where that foreign device is located. By “quieting” the interference in specific directions, Co-BF allows both APs to serve their respective clients with much higher signal quality, especially for devices sitting at the edge of a room or coverage zone.
Image Courtesy : Rohde & Schwarz
Coordinated Spatial Reuse (Co-SR)
It is “simultaneous transmission” strategy. In older Wi-Fi versions, if an AP detected that a neighbor was using the channel, it would wait its turn. This “listen-before-talk” approach is polite but slow.
In Co-SR, APs communicate to find a “sweet spot” of power levels. They exchange information about their transmit power and sensitivity. If the APs are far enough apart (or have enough wall insulation between them), they can agree to transmit at the same time on the same channel. One AP-1 may agree to lower its power slightly to ensure it doesn’t Overwhelm the other AP-2. This effectively doubles the capacity of the spectrum in that area, as two separate conversations are happening simultaneously without overlapping.
Image Courtesy : Rohde & Schwarz
Difference between Co-BF and Co-SR
Following table compares Coordinated Beamforming and Spatial Reuse techniques used in Wi-Fi 8.
| Feature | Coordinated Beamforming (Co-BF) | Coordinated Spatial Reuse (Co-SR) |
|---|---|---|
| Primary Mechanism | Interference Nulling: Steering signals away from “foreign” devices. | Power Control: Balancing signal strength to allow overlapping talk. |
| Core Philosophy behind the feature | ”I will avoid hitting your devices with my noise." | "We will both talk quietly enough to not disturb each other.” |
| Main Benefit | Better Signal Quality (SINR): Dramatically reduces the noise floor. | Higher Capacity: More data can be sent across the network at once. |
| Data Requirement | Requires precise and frequent Channel State Information (CSI). | Requires exchange of Transmit Power and Reuse Parameters. |
| Timing | Transmissions don’t necessarily have to start/end together. | Transmissions are typically synchronized to start and end at the same time. |
| Implementation Complexity | Very High: Requires complex sounding and feedback from STAs. | Moderate: Relies more on AP to AP communication and triggering. |
| Best for application | Improving performance for “cell edge” users in dense areas. | Increasing total throughput in enterprise and campus environments. |
Summary
While both techniques fall under the Wi-Fi 8 MAPC framework, they solve different problems. Co-BF is like using a laser pointer to hit a target while carefully avoiding a neighbor’s eyes, whereas Co-SR is like two people in a library having whispered conversations at the same time; they are sharing the same room (frequency), but because they’ve coordinated their volume (power), they don’t interfere with each other. Collectively, these innovations make Wi-Fi 8 the most socially intelligent wireless standard ever built.
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