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Difficulty: HardWireless Principles and Architecture

A network engineer is optimizing a high-density 5 GHz wireless deployment in a large corporate conference hall. During testing, wireless clients experience significant performance degradation and latency due to co-channel interference (CCI) caused by adjacent access points operating on overlapping RF cells using the same 20 MHz channels. The engineer must reduce CCI while keeping all access points active to handle client capacity. Which action on the Wireless LAN Controller (WLC) directly resolves this issue?

  1. Decrease the Transmit Power Control (TPC) maximum power threshold on the WLC to shrink the RF cell size of each access point.Answer
  2. B
    Enable 80 MHz channel bonding across all 5 GHz radios to increase the total number of non-overlapping channels available in the RF group.
  3. C
    Reconfigure the access points from Centralized Local mode to FlexConnect mode so that Radio Resource Management (RRM) operates independently on each AP.
  4. D
    Lower the mandatory basic data rates on the WLC to allow beacon and management frames to cover a larger physical area.

Answer

Decrease the Transmit Power Control (TPC) maximum power threshold on the WLC to shrink the RF cell size of each access point.
Decreasing the Transmit Power Control (TPC) maximum power limit forces the Wireless LAN Controller to restrict the output power of individual AP radios. This reduces each AP's RF coverage cell radius, minimizing signal overlap with neighboring APs on the same channel and reducing co-channel interference (CCI) in high-density environments.

Step-by-Step Solution

1
Analyze the primary cause of wireless performance degradation in high-density environments.
Co-channel interference (CCI) occurs when multiple access points using the same frequency channel are located close enough for their RF coverage cells to overlap, forcing clients and APs to wait for the medium to clear.
Wi-Fi uses CSMA/CA, so APs on the same channel share contention domains if they hear each other above the clear channel assessment threshold.
2
Evaluate how Transmit Power Control (TPC) affects RF cell boundaries and co-channel overlap.
Lowering the maximum allowed transmit power via TPC shrinks the physical RF cell boundary of each AP.
Smaller RF cell footprints reduce the coverage overlap between APs operating on identical channels while preserving total network capacity through dense AP placement.
3
Identify why alternative configuration options fail to mitigate CCI.
Channel bonding decreases the total count of non-overlapping channels, FlexConnect affects traffic switching rather than RRM calculations, and lowering basic rates increases cell size and management overhead.
Only TPC power reduction directly curtails the physical reach of the RF signal causing CCI.

Key Concept

Wireless Radio Resource Management (RRM) and Co-Channel Interference (CCI) mitigation in high-density WLAN deployments.
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Topics

Wireless Principles and Architecture

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