A thorough site survey is the foundational step for any successful WLAN design, especially in complex, high-density environments. It identifies sources of interference, structural obstacles, and existing RF patterns, allowing for a data-driven design that meets capacity and coverage requirements. The other options represent common mistakes: high transmit power can cause excessive co-channel interference, using a single channel cripples capacity, and over-deployment can lead to excessive co-channel interference and client roaming issues.

This scenario describes a classic sticky client or mis-association problem. Excellent signal strength with poor performance often means clients are ‘stuck’ to a distant AP with a strong signal (e.g., from another floor) instead of roaming to a closer, more appropriate AP. This forces the client to use lower data rates and can cause intermittent connectivity. While a faulty cable (B) is possible, it would likely affect the AP’s coverage cell more broadly, not just client performance. The spectrum analyzer ruled out D, and A would cause broader issues.

The most common cause of interference is co-channel contention. Both Wi-Fi (802.11b/g/n/ax) and Bluetooth/BLE share the 2.4 GHz ISM band (2.400 – 2.4835 GHz). While they use different modulation and access methods, their transmissions can physically overlap and corrupt each other’s data frames. Wi-Fi power can be a factor (A), but the fundamental issue is spectrum sharing. Channel bonding (C) is a 5 GHz and 6 GHz concept, not typically affecting the entire 2.4 GHz band used by BLE.

A key advancement in WPA3-Enterprise is the support for the 192-bit security suite, aligned with the Commercial National Security Algorithm (CNSA) suite. This provides stronger cryptographic tools (like 384-bit hashing) for environments handling highly sensitive data (e.g., government, finance). Option D describes the SAE handshake, which is for WPA3-Personal (to protect against offline dictionary attacks). Option C describes Enhanced Open, and option A is misleading as WPA2 already uses AES.

For a long-distance point-to-point link, the primary goals are to focus RF energy precisely at the distant receiver and to maximize sensitivity to incoming signals from that specific direction. A high-gain, directional antenna (like a parabolic dish or a high-gain panel) with a narrow beamwidth accomplishes both. It concentrates the signal, increasing effective range and reducing interference from other directions. Omnidirectional (B) or wide-beamwidth (C) antennas waste energy in all directions, reducing link budget.

VLANs are a Layer 2 segmentation tool. Their primary purpose in WLANs is to separate traffic logically (e.g., guest traffic, employee traffic, IoT device traffic) over the same physical APs and switches. This enhances security by isolating broadcast domains and allows for different policy enforcement (like firewalls and QoS) per network segment. VLANs do not inherently increase bandwidth (A), improve RF coverage (C), or handle client load-balancing (D), which are functions of RF design and controller features.

Signal-to-Noise Ratio (SNR) is the difference between the desired signal strength (here, a good -65 dBm) and the background noise floor. A strong signal with a very low SNR (5 dB is poor) means the noise floor is also very high (approximately -70 dBm in this case). This indicates significant ambient noise or interference from non-Wi-Fi sources (e.g., microwaves, cordless phones, Bluetooth) or co-channel Wi-Fi interference, which will severely degrade throughput and reliability. The problem is environmental, not related to client distance (A), AP power (B), or hardware failure (D).

Wi-Fi Multimedia (WMM) is the Wi-Fi Alliance certification for QoS based on the IEEE 802.11e standard. It is the correct and standard mechanism for prioritizing traffic over the air. WMM defines four access categories (Voice, Video, Best Effort, Background) and uses Enhanced Distributed Channel Access (EDCA) to give higher-priority traffic a better chance to transmit. DiffServ (A) is a Layer 3/IP QoS method used on wired networks. FIFO (B) is no prioritization, and STP (D) is a network loop prevention protocol.

Warehouses with metal shelving create a highly reflective and multipath-prone RF environment. The integrated omnidirectional antennas on standard indoor APs are often ill-suited for this. Deploying APs with external, directional antennas (like patch or yagi antennas) allows you to shape the RF coverage to propagate down aisles, penetrate shelving more effectively, and control multipath. This is a critical design choice for performance. While the other items (A, B, D) may be part of a project, they do not directly address the unique RF propagation challenge.

A thorough site survey is the foundational step for any successful WLAN design, especially in complex, high-density environments. It identifies sources of interference, structural obstacles, and existing RF patterns, allowing for a data-driven design that meets capacity and coverage requirements. The other options represent common mistakes: high transmit power can cause excessive co-channel interference, using a single channel cripples capacity, and over-deployment can lead to excessive co-channel interference and client roaming issues.0