Beacon frame

Beacon frames are transmitted periodically; they serve to announce the presence of a wireless LAN and to provide a timing signal to synchronise communications with the devices using the network (the members of a service set).

In an infrastructure basic service set (BSS), beacon frames are transmitted by the access point (AP).

For the 2.4 GHz spectrum, when having more than 15 SSIDs on non-overlapping channels (or more than 45 in total), beacon frames start to consume significant amount of air time and degrade performance even when most of the networks are idle.

Infrastructure network access points send beacons at a defined interval, which is often set to a default 100 TU which is equivalent to 102.4 ms.

After an ad hoc station receives a beacon frame from a peer, it waits a random amount of time.

This increases load on the network and decreases throughput for users, but it does result in a quicker association and roaming process.

Radio NICs generally scan all RF channels searching for beacons announcing the presence of a nearby access point.