Chapter 3 Wi-Fi 24
Important: Avoid using hidden Service Set Identiers (SSIDs), because Wi-Fi devices must actively
seek out hidden SSIDs. This leads to delays when rejoining the SSID, potentially impacting data
ow and communications. There’s also no security benet in hiding the SSID. Users tend to
change location frequently along with their Apple devices, so hidden SSIDs often delay network
association time and hinder roaming performance. This practice may use more power than a
broadcast SSID and may aect device battery life.
2.4 GHz vs. 5 GHz
Wi-Fi networks operating at 2.4 GHz provide 11 channels in North America. However, due
to channel interference considerations, only channels 1, 6, and 11 should be used in a
network design.
5 GHz signals don’t penetrate walls and other barriers as well as 2.4 GHz signals, which results
in a smaller coverage area. Therefore, use 5 GHz networks when you design for a high density
of devices in an enclosed space, such as in classrooms or large meeting rooms. The number of
channels available in the 5 GHz band varies among vendors and from country to country, but at
least eight channels are always available.
5 GHz channels are non-overlapping, which is a signicant departure from the three non-
overlapping channels available in the 2.4 GHz band. When you design a Wi-Fi network for a
high density of Apple devices, the additional channels provided at 5 GHz become a strategic
planning consideration.
Important: Wireless coverage should be ubiquitous throughout the workspace. If legacy devices
are in use, both Wi-Fi bands—802.11b/g/n 2.4 GHz and 802.11a/n/ac 5 GHz—should be central to
the design plan.
Design considerations
There are three main considerations when you design your Wi-Fi networks.
Design for coverage
The physical layout of the building may have an impact on your Wi-Fi network design. For
example, in a small business environment, users may meet with other employees in conference
rooms or in oces. As a result, users move around the building throughout the day. In this
scenario, the majority of network access comes from low bandwidth activities such as checking
mail, calendars, and Internet browsing, so Wi-Fi coverage is the highest priority. A Wi-Fi design
could include a small number of access points on each oor to provide coverage for the oces.
Additional access points might be considered for areas where large numbers of employees
gather, such as a large conference room.
Design for capacity
Contrast the scenario above with a school that has 1000 students and 30 teachers in a two-story
building. Every student is issued an iPad, and every teacher is issued both a MacBook Air and an
iPad. Each classroom holds approximately 35 students, and classrooms are next to each other.
Throughout the day, students conduct research on the Internet, watch curriculum videos, and
copy les to and from a le server on the Local Area Network (LAN).
100% resize factor
