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Difficulty: MediumWireless Network Deployment and Standards

A network administrator is deploying a wireless network across a multi-story office building. Due to high access point density, multiple access points on different floors must share the same 5 GHz5\text{ GHz} channel, resulting in co-channel interference (CCI) and contention delays. Which feature introduced in the IEEE 802.11ax standard enables access points to identify overlapping basic service sets and transmit simultaneously over shared channels when preamble energy levels are below a color-aware threshold?

  1. BSS ColoringAnswer
  2. B
    Dynamic Frequency Selection (DFS)
  3. C
    Orthogonal Frequency-Division Multiple Access (OFDMA)
  4. D
    Explicit Transmit Beamforming

Answer

BSS Coloring is the Wi-Fi 6 (802.11ax) spatial reuse mechanism designed to differentiate traffic from overlapping basic service sets on the same channel.
The correct option is BSS Coloring. In IEEE 802.11ax (Wi-Fi 6), BSS Coloring adds a 6-bit identifier (color code) to the preamble of wireless frames. This mechanism enables wireless devices to distinguish between frame transmissions from their own network and neighboring overlapping networks on the same channel. When a frame from an overlapping network is detected with a different 'color', the receiver can adjust its adaptive signal detection threshold, enabling simultaneous transmissions (spatial reuse) and significantly mitigating co-channel interference.

Step-by-Step Solution

1
Identify the primary network performance issue
Co-channel interference (CCI) caused by overlapping access points operating on identical frequency channels.
When access points share a channel, legacy Wi-Fi contention (CSMA/CA) forces devices to defer transmission whenever any preamble on that channel is detected above the clear channel assessment (CCA) threshold.
2
Analyze the features introduced in IEEE 802.11ax for spatial reuse
802.11ax introduces BSS Coloring, which attaches a 6-bit color field to the PHY header of frames.
This allows a client or AP to distinguish between its own basic service set (my BSS) and a neighboring BSS (overlapping BSS). If the frame is from an overlapping BSS and below a secondary energy threshold, the device can transmit concurrently.

Key Concept

BSS Coloring and Spatial Reuse in IEEE 802.11ax
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Topics

Wireless Network Deployment and Standards

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