What is the purpose of the IEEE 802.11 WLAN superframe?

• A. To synchronize clocks across all devices.
• B. To allocate IP addresses to clients.
• C. To determine channel bandwidth.
• D. To allow fair coexistence between PCF-mode and DCF-mode clients on the network.

Answer: (D)

The WLAN superframe is a timing structure that lets the access point manage who talks and when. It splits time into a contention-free period, where the AP polls stations to give them guaranteed airtime, and a contention period, where devices compete for the medium using CSMA/CA. This setup lets PCF-mode clients (polling-based, deterministic access) and DCF-mode clients (random-access) share the network fairly, avoiding one style starving the other. The focus is on coordinating access so both methods can operate without constant collisions.

The other options describe tasks the wireless medium doesn’t assign via the superframe: clocks are synchronized mainly by beacons, IP addresses are given by DHCP or static config, and channel bandwidth is determined by PHY/regulatory settings rather than the superframe structure.