Getting proper Wi-Fi coverage
Note: This content focuses on Wi-Fi network design in North America. Restrictions and requirements for network design may differ in other countries.
The physical layout of your school or offices, and how people interact in those spaces, are critical to how you design your network. For example, in a small business, users may move around the building throughout the day, meeting in conference rooms or in offices. In this scenario, network access comes from:
Low-bandwidth activities (for example, checking mail and calendars and browsing the Internet)
High-bandwidth activities (for example, using collaboration tools like voice or voice plus video like FaceTime or Cisco Jabber or WebEx)
When users engage in high-bandwidth activities, Wi-Fi coverage is the highest priority. A Wi-Fi design for this type of environment could include a small number of access points (APs) on each floor to provide coverage for the offices, but you might also consider additional APs for areas where large numbers of employees gather, such as conference rooms.
The number of available channels is also important, so you need to consider the frequency ranges of Wi-Fi networks. There are two options:
5 GHz: At least eight nonoverlapping channels are always available, though the number varies among vendors and from country to country. Because microwave ovens, cordless phones, and many other devices share the same frequencies as the 2.4 GHz band, the 5 GHz band is much better suited for Wi-Fi usage. Because 5 GHz signals don’t penetrate walls and other barriers as well as 2.4 GHz signals do, which results in a smaller coverage area, 5 GHz networks are optimal for a high density of devices in an enclosed space, such as a classroom or meeting room.
2.4 GHz: There are 11 channels available for use in North America. Many of these channels overlap with each other, which can introduce interference. To avoid channel interference in your network, use channels 1, 6, and 11, which don’t overlap.
Important: Wireless coverage should be present 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.
When designing your networks, it’s a good idea to understand how Apple devices scan for a better connection, so that you can plan wisely:
Know the trigger threshold for iOS and iPadOS devices: The trigger threshold is the signal level (in decibel-milliwatts) at which a client begins scanning for a better connection. iOS and iPadOS use –70 dBm as the trigger. Therefore, for example, if you design 5 GHz cells with a –67 dBm overlap, the devices will remain connected to the current basic service set identifier (BSSID) longer than you expect. When the threshold is crossed, and iPadOS initiate a scan to find other possible candidates (BSSIDs) for the current wireless network’s identifying name (ESSID).
Know how iOS and iPadOS devices see cell boundaries: The antennas on a portable computer are much larger and more powerful than those on a smartphone or tablet, so iOS and iPadOS devices see different cell boundaries than expected. It’s always best to measure using the target device.