What is Wi-Fi?
Wi-Fi is the Wi-Fi Alliance's trademark for wireless LAN (WLAN) products built on the IEEE 802.11 standards. The IEEE writes the technical standards; the Wi-Fi Alliance tests products for interoperability and lets the ones that pass carry the Wi-Fi CERTIFIED label. The name is a brand, not an acronym: it doesn't stand for "Wireless Fidelity".
A Wi-Fi network has an access point, often built into a SOHO wireless router, that broadcasts a network name called the SSID. Clients connect, authenticate, and then get an IP address, usually from DHCP. Devices take turns on the shared radio channel (802.11 uses CSMA/CA), so every client on an access point shares its capacity.
Wi-Fi generations
| Name | IEEE standard | Bands | Theoretical max |
|---|---|---|---|
| None | 802.11a | 5 GHz | 54 Mbps |
| None | 802.11b | 2.4 GHz | 11 Mbps |
| None | 802.11g | 2.4 GHz | 54 Mbps |
| Wi-Fi 4 | 802.11n | 2.4 and 5 GHz | 600 Mbps |
| Wi-Fi 5 | 802.11ac | 5 GHz | About 6.9 Gbps |
| Wi-Fi 6 | 802.11ax | 2.4 and 5 GHz | About 9.6 Gbps |
| Wi-Fi 6E | 802.11ax | Adds 6 GHz | About 9.6 Gbps |
| Wi-Fi 7 | 802.11be | 2.4, 5 and 6 GHz | About 46 Gbps |
The older 802.11a, b and g standards never got official generation numbers. Real-world throughput is a fraction of these maximums. Newer generations still connect older devices on the same band, at the older device's speed.
The three bands
| 2.4 GHz | 5 GHz | 6 GHz | |
|---|---|---|---|
| Range | Longest, best through walls | Medium | Shortest |
| Non-overlapping 20 MHz channels (US) | 3 (1, 6 and 11) | About two dozen, many needing DFS | 59 |
| Congestion | Crowded: neighbors, Bluetooth, microwave ovens | Less crowded | Least crowded |
| Devices | Almost all, including many IoT devices | Most laptops and phones | Wi-Fi 6E and Wi-Fi 7 only |
Wi-Fi security
- WPA3: replaces the pre-shared key handshake with SAE, which resists offline password guessing. The Wi-Fi Alliance requires it on 6 GHz.
- WPA2 with AES (CCMP): the minimum acceptable choice, for devices that can't do WPA3.
- WEP and WPA with TKIP: broken and obsolete; never use them.
- Personal vs. Enterprise: Personal uses one shared passphrase; Enterprise authenticates each user through 802.1X and a RADIUS server.
On a SOHO router, also change the default admin password, turn off WPS and keep the firmware updated.
Troubleshooting Wi-Fi
- Check that Wi-Fi is on, airplane mode is off, and the device is joining the right SSID.
- For authentication failures, re-enter the passphrase or forget the network and rejoin, and confirm the device supports the security type, such as WPA3.
- If the device has a 169.254.x.x (APIPA) address, it joined the network but didn't get a DHCP lease: check the router's DHCP service.
- For slow or intermittent connections, check signal strength and distance, then look for interference and channel overlap with a Wi-Fi analyzer. Move to a less crowded channel or band.
- Update the wireless adapter driver and the access point firmware, and restart both.
For the CompTIA A+ exams
Wi-Fi shows up in both cores. In Core 1 (220-1201), objective 2.2 covers the 2.4, 5 and 6 GHz frequencies, channels and the 802.11 standards; 2.6 covers setting up SOHO wireless networks; 2.8 includes the Wi-Fi analyzer; and 5.5 covers problems such as intermittent wireless connectivity, slow speeds and authentication failures. In Core 2 (220-1202), objective 2.3 covers wireless security protocols such as WPA2, WPA3 and TKIP, and 2.10 covers securing SOHO wireless networks. Learn which standard uses which band, and that Wi-Fi 6E and Wi-Fi 7 are the generations that reach 6 GHz.