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Difficulty: MediumWireless Network Deployment and Standards

A network administrator is auditing a wireless network installation across a single-floor office facility operating on the 2.4 GHz2.4\text{ GHz} spectrum. The audit reveals that three adjacent access points (APs) along a main hallway are configured to use 20 MHz20\text{ MHz} channel widths on channels 11, 33, and 55, respectively. Users connected in this hallway experience frequent frame collisions, high latency, and degraded throughput due to spectral overlap. Which of the following channel assignment adjustments should the administrator make to resolve this interference?

  1. Assign the three access points to channels 11, 66, and 1111, respectively.Answer
  2. B
    Assign the three access points to channels 22, 44, and 66, respectively.
  3. C
    Increase the channel width on all three access points to 40 MHz40\text{ MHz} while retaining channels 11, 33, and 55.
  4. D
    Reconfigure the access points to operate on channels 11, 55, and 99, respectively.

Answer

Reconfigure the access points to use channels 1, 6, and 11, respectively, which are the standard non-overlapping channels in the 2.4 GHz band.
In 2.4 GHz Wi-Fi deployments, standard 20 MHz channels require a minimum of 5 channel increments between center frequencies to prevent spectral overlap. Selecting channels 1, 6, and 11 provides complete frequency separation and eliminates adjacent-channel interference.

Step-by-Step Solution

1
Analyze the spectral properties of 2.4 GHz Wi-Fi channels.
Each 2.4 GHz channel is spaced 5 MHz apart, but a standard 802.11 20 MHz channel requires a spectral footprint of 20 to 22 MHz.
Adjacent channel assignments such as channels 1, 3, and 5 overlap heavily in frequency space, causing severe adjacent-channel interference (ACI).
2
Identify non-overlapping channel combinations for the 2.4 GHz band.
Channels 1, 6, and 11 have center frequencies of 2412 MHz, 2437 MHz, and 2462 MHz, providing 25 MHz separation between center frequencies.
This 25 MHz spacing ensures zero spectral overlap between adjacent AP coverage cells when using 20 MHz channel widths.

Key Concept

2.4 GHz Non-Overlapping Channel Planning
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Topics

Wireless Network Deployment and Standards

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