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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 ...
Collision Avoidance: if another node was heard, we wait for a period of time (usually random) for the node to stop transmitting before listening again for a free communications channel. Request to Send/Clear to Send (RTS/CTS) may optionally be used at this point to mediate access to the shared medium.
This time period is called a beacon period (BP). At the beginning of each BP, there is a beacon generation window consisting of w + 1 {\displaystyle w+1} slots each of length aSlotTime . Each station calculates a random delay uniformly distributed in [ 0 , w ] {\displaystyle [0,w]} and is scheduled to transmit a beacon when the delay timer expires.
Slot time (μs) DIFS (μs) IEEE 802.11-1997 (FHSS) 50 128 IEEE 802.11-1997 (DSSS) 20 50 IEEE 802.11b: 20 50 IEEE 802.11a: 9 34 IEEE 802.11g: 9 or 20 28 or 50
This protocol was designed under the assumption that all nodes have the same transmission ranges. RTS/CTS frames can cause the exposed terminal problem in which a wireless node that is nearby, but is associated with another access point, overhears the exchange and then is signaled to back off and cease transmitting for the time specified in the RTS.
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).
IEEE 802.11s is a wireless local area network (WLAN) standard and an IEEE 802.11 amendment for mesh networking, defining how wireless devices can interconnect to create a wireless LAN mesh network, which may be used for relatively fixed (not mobile) topologies and wireless ad hoc networks.
The use of TXOPs reduces the problem of low rate stations gaining an inordinate amount of channel time in the legacy 802.11 DCF MAC. A TXOP time interval of 0 means it is limited to a single MAC service data unit (MSDU) or MAC management protocol data unit (MMPDU). The levels of priority in EDCA are called access categories (ACs).