BSS Coloring and Spatial Reuse

Drag two same-channel APs, give each a BSS color and set the OBSS PD level, and see when Wi-Fi 6 spatial reuse lets one AP talk over the other, what it costs, and how a color collision is fixed.

How to use this tool controls and what to look for

Drag two same-channel APs and their clients around the floor, give each a BSS color, and see when AP A may talk over AP B's frames and what that does to both clients' speed.

Controls to change

  • Neighbor AP B is: compare a Wi-Fi 6 or 7 neighbor, which sends a color, with a Wi-Fi 5 neighbor, which doesn't.
  • AP A's BSS color: set each AP's color, 1 to 63. Give both the same color to see a collision.
  • Spatial reuse (OBSS PD): turn spatial reuse on or off.
  • OBSS PD level: raise it from −82 to −62 dBm to ignore stronger neighbor frames; the chart shows the transmit power it costs.
  • AP transmit power: change both APs' normal transmit power, which also moves the rings.
  • AP spatial streams: switch the reference power in the limit between 21 dBm (1 or 2 streams) and 25 dBm (3 or more).
  • Color Switch Countdown: with a collision, choose how many beacons announce the new color before AP A switches.

What to look for

  • The dBm bar under the floor: coloring only helps when AP B's frame lands between −82 dBm and the OBSS PD level.
  • The flowchart ticks each decision AP A makes; click another branch to change the setup.
  • The speed bars: reuse raises total speed, but each client loses SINR. Drag a client away from its AP to see reuse make things worse.
  • Same color: no reuse, and card 5 shows the BSS Color Change Announcement countdown that fixes it.

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About this tool

Wi-Fi 6 added a BSS color, a number from 1 to 63 in the preamble of every frame, so a radio can tell within about 32 microseconds whether a frame comes from its own network or a neighbor on the same channel. With spatial reuse (OBSS PD), an AP may ignore a neighbor's frame that is weaker than its OBSS PD level, somewhere between −82 and −62 dBm, and transmit over it, as long as it lowers its transmit power by as many dB as it raised the threshold. This simulator lets you drag two access points and their clients around a floor, change their colors, the OBSS PD level and transmit power, and see when spatial reuse raises throughput, when it hurts, and how an AP fixes a color collision with a BSS Color Change Announcement.

What you'll learn

  • Where the BSS color sits in the Wi-Fi 6 and Wi-Fi 7 preamble, and how a station classifies a frame as intra-BSS or inter-BSS
  • Why BSS coloring only helps when a neighbor's frames arrive between −82 dBm and the OBSS PD level
  • The IEEE 802.11 rule that trades a higher OBSS PD level for lower transmit power, and what it costs your own and the neighbor's clients
  • What a BSS color collision breaks and how the BSS Color Change Announcement countdown fixes it

Common questions

Does BSS coloring increase Wi-Fi throughput?
Only in a narrow band of cases. An AP can talk over a neighbor's frame only if that frame is below its OBSS PD level, and then only at reduced power, which lowers its own clients' SINR and adds interference for the neighbor's clients. With APs far apart it changes nothing, and with APs close together the neighbor's frames are too strong to ignore.

Should I set the OBSS PD level to −62 dBm?
A higher OBSS PD level lets an AP ignore more of its neighbors, but the standard makes it lower its transmit power by the same number of dB, so its clients get a lower MCS. Vendors usually pick the level automatically; in a dense design it is still better to separate same-channel APs with channel planning and power.

What happens when two access points use the same BSS color?
Each takes the other's frames for its own, so neither can use spatial reuse, and clients may set the wrong NAV or doze at the wrong time. The AP detects the collision itself or from client reports, then announces a new color in its beacons for a few beacon intervals and switches.

Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.