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Extended Interframe Space
Extended Interframe space (EIFS) is used in IEEE 802.11 based WLANs. If a previously received frame contains an error then a station has to defer EIFS duration instead of DIFS before transmitting a frame. This is because, although this station was not able to decode the frame, it could be that the intended receiver could decode the frame. It should have the opportunity to return an Acknowledgment frame; the EIFS ensures the transmission of the Ack can proceed without interference from those not able to decode the frame. This duration is calculated by the below method. EIFS = Transmission time of Ack frame at lowest phy mandatory rate + SIFS + DIFS See also * DIFS * RIFS * SIFS References {{reflist E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DCF Interframe Space
The IEEE 802.11 family of standards describe the DCF protocol, which controls access to the physical medium. A station must sense the status of the wireless medium before transmitting. If it finds that the medium is continuously idle for DCF Interframe Space (DIFS) duration, it is then permitted to transmit a frame. If the channel is found busy during the DIFS interval, the station should defer its transmission. DIFS duration can be calculated by the following method. DIFS = SIFS + (2 * Slot time) , 2016, Equation (10-6), page 1332. IEEE 802.11g is backward compatible with IEEE 802.11b IEEE 802.11b-1999 or 802.11b is an amendment to the IEEE 802.11 wireless networking specification that extends throughput up to 11 Mbit/s using the same 2.4 GHz band. A related amendment was incorporated into the IEEE 802.11-2007 standard. .... When these devices are associated with same AP all the timing parameters are changed to 802.11b. See also * SIFS * PIFS * AIFS * RI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reduced Interframe Space
Reduced Interframe Space (RIFS) is one of the new features introduced in IEEE 802.11n to improve its efficiency. RIFS is the time in micro seconds by which the multiple transmissions from a single station are separated. RIFS is used when no SIFS separated response frames are expected from the receiver. The value of RIFS is 2μs for 802.11n phy. The use of RIFS is obsolete from 802.11ac amendment onwards. An 802.11ac station will not transmit frames separated by RIFS. So a 11ac station operating in HT mode sets the RIFS mode field in HT operation element to 0. See also * SIFS - Short Interframe Space * PIFS - PCF Interframe Space * DIFS - DCF Interframe Space * AIFS - Arbitration Interframe Space * PCF - Point Coordination Function Point coordination function (PCF) is a media access control (MAC) technique used in IEEE 802.11 based WLANs, including Wi-Fi. It resides in a point coordinator also known as access point (AP), to coordinate the communication within the network. .. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Short Interframe Space
Short Interframe Space (SIFS), is the amount of time in microseconds required for a wireless interface to process a received frame and to respond with a response frame. It is the difference in time between the first symbol of the response frame in the air and the last symbol of the received frame in the air. A SIFS time consists of the delay in receiver RF, PLCP delay and the MAC processing delay, which depends on the physical layer used. In IEEE 802.11 networks, SIFS is the interframe spacing prior to transmission of an acknowledgment, a Clear To Send (CTS) frame, a block ack frame that is an immediate response to either a block ack request frame or an A-MPDU, the second or subsequent MPDU of a fragment burst, a station responding to any polling a by point coordination function and during contention free periods of point coordination function. Implications for Software Radio Because most Software-Defined Radios use a host computer for processing, the SIFS impose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |