DEFINITIONS - 5

directed frame: See: individually addressed.
direct link: A bidirectional link from one quality-of-service (QoS) station (STA) to another QoS STA
operating in the same infrastructure QoS basic service set (BSS) that does not pass through a QoS access
point (AP). Once a direct link has been set up, all frames between the two QoS STAs are exchanged
directly.
directed multicast service (DMS): A service in which the access point (AP) transmits group addressed
frames as individually addressed frames to the requesting non-AP station (STA).
disassociation service: The service that removes an existing association.

distributed coordination function (DCF): A class of coordination function where the same coordination
function logic is active in every station (STA) in the basic service set (BSS) whenever the network is in
operation.
distribution service: The service that, by using association information, delivers medium access control
(MAC) service data units (MSDUs) within the distribution system (DS).
distribution system (DS): A system used to interconnect a set of basic service sets (BSSs) and integrated
local area networks (LANs) to create an extended service set (ESS).
distribution system medium (DSM): The medium or set of media used by a distribution system (DS) for
communications between access points (APs), mesh gates, and portals of an extended service set (ESS).
distribution system service (DSS): The set of services provided by the distribution system (DS) that enable
the medium access control (MAC) to transport MAC service data units (MSDUs) between stations (STAs)
that are not in direct communication with each other over a single instance of the wireless medium (WM).
These services include transport of MSDUs between the access points (APs) of basic service sets (BSSs)
within an extended service set (ESS), transport of MSDUs between portals and BSSs within an ESS,
transport of MSDUs between mesh gates in the same or different mesh basic service sets (MBSSs), transport
of MSDUs between mesh gates and APs, transport of MSDUs between mesh gates and portals, and transport
of MSDUs between STAs in the same BSS in cases where the MSDU has a group destination address or
where the destination is an individual address and the STA is associated with an AP.
NOTE—DSSs are provided between pairs of MACs not on the same instance of the WM.
downlink: A unidirectional link from an access point (AP) to one or more non-AP stations (STAs).
dynamic frequency selection (DFS): Facilities mandated to satisfy requirements in some regulatory
domains for radar detection and uniform channel spreading in the 5 GHz band. These facilities might also be
used for other purposes, such as automatic frequency planning.
dynamic frequency selection (DFS) owner: A station (STA) in an independent basic service set (IBSS) or
off-channel TDLS direct link that takes responsibility for selecting the next channel after radar is detected
operating in a channel. Due to the nature of IBSSs, it cannot be guaranteed that there is a single DFS owner
at any particular time and the protocol is robust to this situation.


downlink: A unidirectional link from an access point (AP) to one or more non-AP stations (STAs).
dynamic frequency selection (DFS): Facilities mandated to satisfy requirements in some regulatory
domains for radar detection and uniform channel spreading in the 5 GHz band. These facilities might also be
used for other purposes, such as automatic frequency planning.
dynamic frequency selection (DFS) owner: A station (STA) in an independent basic service set (IBSS) or
off-channel TDLS direct link that takes responsibility for selecting the next channel after radar is detected
operating in a channel. Due to the nature of IBSSs, it cannot be guaranteed that there is a single DFS owner
at any particular time and the protocol is robust to this situation.
dynamic station (STA) enablement (DSE): The process by which an enabling STA grants permission and
dictates operational procedures to STAs that are subject to its control.
effective isotropic radiated power (EIRP): The equivalent power of a transmitted signal in terms of an
isotropic (omnidirectional) radiator. The EIRP equals the product of the transmitter power and the antenna
gain (reduced by any coupling losses between the transmitter and antenna).
emergency alert system (EAS): A U.S. national public warning system.
enabling station (STA): A registered STA that has the authority to control when and how a dependent STA
can operate. An enabling STA communicates an enabling signal to its dependents over the air. An enabling
STA chooses whether other dynamic STA enablement (DSE) messages are exchanged over the air, over the
distribution system (DS), or by mechanisms that rely on transport via higher layers.
encapsulate: To construct a protected frame from an unprotected frame.
encapsulation: The process of generating a protected frame by encapsulating plaintext data.