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Difficulty: HardWireless Network Deployment and Standards

A network engineer is troubleshooting high latency and packet retransmissions in a densely populated multi-tenant office building. A site survey reveals that four adjacent enterprise access points (APs) in the 5 GHz spectrum were all configured with 80 MHz channel bonding using channels 36, 40, 44, and 48 (UNII-1 band). Because these four 20 MHz sub-channels comprise a single 80 MHz bonded channel, all four access points are competing for the exact same frequency space. Which of the following channel management strategies should the engineer implement to eliminate co-channel interference while maintaining distinct, non-overlapping channels for each access point?

  1. Reduce the channel width of each access point from 80 MHz to 20 MHz and assign distinct channels 36, 40, 44, and 48 across the four access points.Answer
  2. B
    Migrate all four access points to the 2.4 GHz band and assign them to channels 2, 5, 8, and 11 respectively.
  3. C
    Increase the channel width to 160 MHz across all four access points to provide extra throughput capacity for heavy traffic.
  4. D
    Maintain the 80 MHz channel width on channel 36 and increase the power output on all access points to override background noise.

Answer

Reduce the channel width of each access point from 80 MHz to 20 MHz and assign distinct channels 36, 40, 44, and 48 across the four access points.
Reducing the channel width from 80 MHz to 20 MHz separates the single wide channel into four independent, non-overlapping 20 MHz channels (36, 40, 44, and 48). Assigning one distinct 20 MHz channel to each access point completely eliminates co-channel interference (CCI) and resolves contention issues.

Step-by-Step Solution

1
Analyze the existing channel allocation and spectrum usage.
The four access points are operating on an 80 MHz channel width that spans channels 36, 40, 44, and 48 simultaneously, forcing all four APs into the same collision domain.
When channels are bonded into an 80 MHz width, the individual 20 MHz sub-channels no longer function independently.
2
Evaluate channel width modification to create non-overlapping frequency spaces.
Reducing the channel width to 20 MHz yields four individual, non-overlapping channels (36, 40, 44, and 48) in the 5 GHz UNII-1 band.
Operating each AP on a dedicated 20 MHz channel eliminates co-channel contention and allows simultaneous transmissions.

Key Concept

5 GHz Channel Bonding and Co-Channel Interference Mitigation
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Topics

Wireless Network Deployment and Standards

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