When designing a dual-band Wi-Fi network, it is a standard best practice to plan the design around the 5 GHz frequency. The 5 GHz band has a shorter wavelength compared to the 2.4 GHz band, resulting in greater signal attenuation and reduced ability to penetrate obstacles. Consequently, its coverage cells are smaller at the same transmission power. By ensuring adequate coverage for the more challenging 5 GHz band, you inherently guarantee sufficient coverage for the 2.4 GHz band, which propagates further. This approach ensures that clients capable of using the higher-performance, less-congested 5 GHz band have reliable service.

A. Different radio frequencies have different propagation characteristics. Lower frequencies (2.4 GHz) travel farther and penetrate objects better than higher frequencies (5 GHz), so coverage is not identical.

B. This statement is incorrect. Higher frequencies like 5 GHz have shorter wavelengths, which results in greater signal loss (attenuation), shorter travel distances, and poorer penetration through walls compared to 2.4 GHz.

D. This statement is factually incorrect. The IEEE 802.11ac standard operates exclusively in the 5 GHz frequency band. Therefore, the premise of the statement is false.

1. Juniper Networks Technical Documentation, "Wi-Fi Fundamentals": In the section discussing RF characteristics, it is explained that "The 2.4 GHz band has only three non-overlapping 20 MHz channels, while the 5 GHz band has 24... The lower frequency of the 2.4 GHz band gives it a longer range and better penetration of solid objects than the 5 GHz band." This supports the reasoning that 5 GHz has a shorter range, making it the critical band for coverage planning. (Reference: Juniper Networks Learning Portal, JNCIA-MistAI Courseware, Module: Wi-Fi Fundamentals).

2. Juniper Networks, "Mist AI and Cloud, Radio Management" Documentation: "Because 5 GHz signals don't travel as far as 2.4 GHz signals, you might need to deploy more APs to provide adequate 5-GHz coverage." This statement directly supports the principle of planning for 5 GHz coverage as it is the more limiting factor in a dual-band design. (Reference: Juniper Mist Documentation, Radio Management, Coverage and Capacity section).

3. IEEE Standard 802.11ac-2013: The official standard specifies the physical layer (PHY) and medium access control (MAC) layer for very high throughput operation. Section "22.1 Overview" explicitly states that the operation is in the frequency bands below 6 GHz, with subsequent sections defining channelization exclusively within the 5 GHz spectrum. This confirms that 802.11ac is a 5 GHz-only standard. (Reference: IEEE Std 802.11ac™-2013, Section 22.1, Page 253).