802.11 standards and frequency bands
The major 802.11 standards differ by frequency band, maximum speed, and the technologies they introduced. 802.11b was the first widely adopted standard at 2.4 GHz with a maximum of 11 Mbps. 802.11a ran at 5 GHz with 54 Mbps but cost more and had shorter range. 802.11g brought 54 Mbps to 2.4 GHz and added backward compatibility with 802.11b.
802.11n (Wi-Fi 4) introduced MIMO, using multiple antennas simultaneously to multiply throughput, and supported both 2.4 GHz and 5 GHz. Maximum theoretical throughput reached around 600 Mbps. 802.11ac (Wi-Fi 5) dropped 2.4 GHz support entirely and focused on 5 GHz with wider channels and MU-MIMO for multi-user scenarios, reaching multi-gigabit theoretical speeds. 802.11ax (Wi-Fi 6 and Wi-Fi 6E) added the 6 GHz band, introduced OFDMA for more efficient use of spectrum in dense environments, and further improved multi-user performance.
The 2.4 GHz band has longer range and better wall penetration than 5 GHz but is heavily congested because consumer devices, Bluetooth, microwaves, and baby monitors all compete on it. The 5 GHz band has more available channels, less interference, and higher throughput, but does not travel as far. 6 GHz (Wi-Fi 6E and Wi-Fi 7) offers significant spectrum with almost no legacy interference.
Channel planning and wireless security
On 2.4 GHz, channels 1 through 11 are available in North America but they overlap with adjacent channels. Only channels 1, 6, and 11 are far enough apart to be non-overlapping. Adjacent access points must use these three channels only. Using any other combination, like 1, 4, and 8, causes co-channel interference that degrades performance across the entire area.
On 5 GHz, there are up to 23 non-overlapping 20 MHz channels, making channel planning far simpler and allowing denser AP deployments without interference.
Wireless security evolved from catastrophically broken to genuinely secure. WEP used a 40-bit RC4 key that can be cracked in minutes with freely available tools. Never use WEP. WPA improved on WEP with TKIP but is also deprecated. WPA2 uses AES-CCMP encryption and is the current minimum acceptable standard. WPA2-Personal uses a pre-shared key. WPA2-Enterprise uses 802.1X with a RADIUS server for per-user authentication. WPA3 replaces the PSK exchange with SAE (Simultaneous Authentication of Equals), which prevents offline dictionary attacks even if the handshake is captured.
Wireless topology and how to choose the correct answer
BSS (Basic Service Set): one access point and its associated clients. The SSID is the network name broadcast in beacon frames. BSSID is the MAC address of the access point radio.
ESS (Extended Service Set): multiple access points sharing the same SSID, connected by a wired distribution system. Users can roam between APs seamlessly because the SSID is the same. APs should overlap in coverage by about 20 percent and use different non-overlapping channels.
Autonomous APs: self-contained, configured individually. Lightweight APs: split operation between the AP and a Wireless LAN Controller (WLC) via CAPWAP tunnels. The WLC handles configuration, roaming, and RF management centrally.
Standard selection questions: 5 GHz only = 802.11a or 802.11ac. 2.4 and 5 GHz = 802.11n or 802.11ax. Non-overlapping 2.4 GHz channels = 1, 6, 11 only.