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Difficulty: MediumWireless Principles and Architecture

A network administrator observes severe latency and frequent frame retries on an enterprise floor using a 2.4 GHz wireless deployment. Spectrum analysis reveals high co-channel interference (CCI) among neighboring access points. Which operational characteristic of the 2.4 GHz band primarily causes this channel reuse constraint when compared to the 5 GHz band?

  1. The 2.4 GHz spectrum offers only three non-overlapping 20 MHz channels in standard deployments, restricting spatial frequency reuse.Answer
  2. B
    2.4 GHz radio signals experience higher free-space path loss and attenuation through solid walls than 5 GHz radio signals.
  3. C
    Access points operating in the 2.4 GHz band automatically disable DTLS encryption on CAPWAP control tunnels when client density rises.
  4. D
    The 2.4 GHz spectrum relies on Dynamic Frequency Selection (DFS) to assign adjacent access points to identical broadcast channels.

Answer

The 2.4 GHz spectrum offers only three non-overlapping 20 MHz channels in standard deployments, restricting spatial frequency reuse.
In 802.11 wireless networks using the 2.4 GHz ISM band, 20 MHz channels are spaced only 5 MHz apart. Consequently, only channels 1, 6, and 11 do not overlap with each other. In dense multi-AP deployments, having only three usable non-overlapping channels causes neighboring access points to operate on the same channel, generating high co-channel interference (CCI). In contrast, the 5 GHz band provides a much larger selection of non-overlapping channels, enabling far more flexible channel reuse.

Step-by-Step Solution

1
Analyze the channel spacing and bandwidth in the 2.4 GHz Wi-Fi spectrum.
The 2.4 GHz ISM band allocates channels spaced 5 MHz apart, while standard 802.11 channels require 20 MHz of channel width.
Understanding channel width requirements identifies how channels overlap.
2
Determine the maximum number of non-overlapping channels in 2.4 GHz.
Only 3 channels (channels 1, 6, and 11) can operate simultaneously in the same physical space without overlapping frequencies.
This strict limit creates spatial planning constraints for network designers.
3
Compare with 5 GHz channel availability to assess co-channel interference causes.
Because 5 GHz supports over 20 non-overlapping 20 MHz channels, 2.4 GHz environments suffer far more co-channel interference (CCI) in dense deployments.
The constraint of having only 3 non-overlapping channels directly leads to high CCI in multi-AP designs.

Key Concept

2.4 GHz vs 5 GHz Non-Overlapping Channels and Co-Channel Interference
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Topics

Wireless Principles and Architecture

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