Why Legacy 802.11b/g Devices Lose Connectivity with RRM TPC
Short answer
D TPC drastically reduces Tx power in the 2.4 GHz band, causing insufficient coverage for legacy devices.
Question
Key Takeaways
The question tests RRM TPC behavior in high-density designs, highlighting the trap that TPC reduces power to mitigate interference, which can inadvertently create coverage holes for legacy 2.4 GHz devices.
This scenario explains why legacy 802.11b/g devices lose connectivity in a hospital Wi-Fi design using RRM for TPC. It establishes that TPC reducing Tx power in the 2.4 GHz band causes insufficient coverage for legacy clients.
Common mistake: Choosing A (co-channel interference) because it is a common 2.4 GHz issue, ignoring that TPC specifically mitigates this by reducing power, which is the actual cause of the connectivity loss.
Expert Analysis
Why the Answer Is Correct
Option D is correct because RRM's TPC algorithm dynamically adjusts transmit power to minimize co-channel interference, often drastically reducing Tx power in the 2.4 GHz band in high-density environments like hospitals. Since the design only specified a strict RF coverage requirement (-67 dBm) for the 5 GHz spectrum and not 2.4 GHz, TPC can lower 2.4 GHz power to levels insufficient for legacy 802.11b/g devices. These legacy clients often have less sensitive radios, making them particularly vulnerable to low signal strength caused by reduced AP transmit power.
Why the Other Options Are Wrong
Option A is incorrect because while co-channel interference is a problem in 2.4 GHz, TPC actively reduces transmit power to mitigate this interference, rather than allowing it to remain excessive. Option B is incorrect because DCA (Dynamic Channel Assignment) manages channel selection to minimize overlapping channels, making excessive overlapping channels unlikely under RRM control. Option C is incorrect because TPC in a high-density hospital environment reduces transmit power to shrink cell sizes and prevent overlap, not drastically increase it.
Community Comment Notes
Commenters noted that legacy devices "may have less sensitive receivers so if TPC reduces TxP too much in 2.4 GHz, the result is insufficient signal strength," directly supporting Option D. Another user argued for Option A, claiming co-channel interference directly impacts connectivity, but failed to account for TPC's specific mechanism of reducing power to fix that interference, which inadvertently causes the connectivity issue for legacy clients.
Exam Strategy
When analyzing RRM issues, remember that TPC's primary goal is to reduce co-channel interference by lowering transmit power. In high-density designs, if no minimum coverage threshold is enforced for the 2.4 GHz band, TPC can lower power too much for legacy clients.
Community Votes
50% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 3 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 3
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Love2Cod3 👍 1 Answered DD is correct. Considering these are legacy 802.11b/g devices, they may have less sensitive receivers so if TPC reduces TxP too much in 2.4 GHz, the result is insufficient signal strength causing them to be unable to maintain strong enough connection to the APs.
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Jonycici 👍 1 Answered AOption A is more likely because co-channel interference directly impacts connectivity by increasing noise and contention, while TPC adjustments (Option D) are typically controlled to maintain adequate coverage.
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Farhad123 👍 1D is correct
Reader comments & corrections
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