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802.11 Beacon frame. A beacon frame is a type of management frame in IEEE 802.11 WLANs. It contains information about the network. 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 the IEEE 802.11 wireless LAN protocols (such as Wi-Fi), a MAC frame is constructed of common fields (which are present in all types of frames) and specific fields (present in certain cases, depending on the type and subtype specified in the first octet of the frame). Generic 802.11 Frame
Timing synchronization is achieved by stations periodically exchanging timing information through beacon frames. In (intra) BSS, the AP sends the TSF information in the beacons. In Independent Basic Service Set (IBSS, ad-hoc), each station competes to send the beacon. Each station maintains a TSF timer counting in increments of microseconds (μs).
According to the 802.11 standards, a delivery traffic indication message (DTIM) period value is a number that determines how often a beacon frame includes a DTIM, and this number is included in each beacon frame. A DTIM is included in beacon frames, according to the DTIM period, to indicate to the client devices whether the access point has ...
This mode is optional, and only very few APs or Wi-Fi adapters actually implement it. [citation needed] APs send beacon frames at regular intervals (usually every 100 TU or 0.1024 second). Between these beacon frames, PCF defines two periods: the Contention Free Period (CFP) and the Contention Period (CP). In the CP, DCF is used.
Current 802.11 standard defines "frame" types for use in management and control of wireless links. IEEE 802.11w is the Protected Management Frames standard for the IEEE 802.11 family of standards. Task Group 'w' worked on improving the IEEE 802.11 Medium Access Control layer. [ 1 ]
IEEE 802.15.4 protocol stack. Devices are designed to interact with each other over a conceptually simple wireless network.The definition of the network layers is based on the OSI model; although only the lower layers are defined in the standard, interaction with upper layers is intended, possibly using an IEEE 802.2 logical link control sublayer accessing the MAC through a convergence sublayer.
When stations hear the beacon frame, they start their network allocation vector for the duration of the contention free period of the repetition period. Since most APs have logical bus topologies (they are shared circuits) only one message can be processed at one time (it is a contention based system), and thus a media access control technique ...