An ACME company employee complained about a recent poor-quality VoIP call while moving around their...

[Reference: Aruba WLAN Validated Reference Design – Voice over WLAN Considerations; Aruba Central UCC visibility guidelines; AOS-S/CX Campus Wired/Wireless Design Guides (Roaming and RF Design sections)., Channel support limitations on 5 GHz (D): Aruba guidance emphasizes enabling and using DFS spectrum (U-NII-2/U-NII-2e) for capacity and better roaming. Clients that do not support these channels see fewer candidate APs, which increases contention on the remaining non-DFS channels and can lead to sticky roaming and packet loss during movement—resulting in poor MOS even if the Central UCC score shows only “fair.”Exact extract: “Client devices that lack DFS (U-NII-2/Extended) support are restricted to a reduced channel set. This limits roam candidates and concentrates airtime utilization, which can degrade real-time applications, including voice, during mobility.”Reference: Aruba RF Planning and Optimization Guide (5-GHz channelization and DFS usage); Aruba Validated Design for High-Density and Real-Time Applications (Client capabilities and roaming)., Why the other options are not the best contributors:, B (CAC level set too low): Aruba’s CAC controls voice call admission based on airtime reservations. If CAC is set too low, calls are prevented from starting rather than allowed to start and then suffer in-call quality issues while roaming.Exact extract: “Call Admission Control rejects new calls when available airtime for voice is insufficient; it does not intentionally degrade admitted calls.”Reference: Aruba Voice and UCC Best Practices (CAC behavior)., C (BSS coloring not enabled): BSS Coloring (802.11ax) can improve spatial reuse in dense deployments, but its absence is not a primary cause of a sudden MOS of ~2.3 during roaming. Aruba documents position it as an optimization, not a prerequisite for acceptable voice quality.Exact extract: “BSS Coloring enhances efficiency in overlapping BSS scenarios; it is an optimization feature and not required for baseline voice operation.”Reference: Aruba 802.11ax (Wi-Fi 6/6E) Feature Overview – OBSS and BSS Coloring., , , ]