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Point coordination function
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<h2 id="pcf-interframe-space">PCF Interframe Space</h2> <p><i>PCF Interframe Space (PIFS)</i> is one of the interframe space used in <a href="/facts/IEEE_802.11/ryEGu6Vq">IEEE 802.11</a> based <a href="/facts/Wireless_LAN/ooq0WA45"> Wireless LANs</a>. PCF enabled access point wait for PIFS duration rather than DIFS to occupy the wireless medium. PIFS duration is less than DIFS and greater than SIFS (DIFS > PIFS > SIFS). Hence AP always has more priority to access the medium. </p><p>PIFS duration can be calculated as follows: </p><p>PIFS = SIFS + Slot time<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p> <table><tbody><tr><th>Standard</th><th>Slot time (μs)</th><th>PIFS (μs)</th></tr><tr><td><a href="/facts/IEEE_802.11-1997/VtAWQ3bQ">IEEE 802.11-1997</a> (FHSS)</td><td>50</td><td>78</td></tr><tr><td><a href="/facts/IEEE_802.11-1997/VtAWQ3bQ">IEEE 802.11-1997</a> (DSSS)</td><td>20</td><td>30</td></tr><tr><td><a href="/facts/IEEE_802.11b/WcN5bIIS">IEEE 802.11b</a></td><td>20</td><td>30</td></tr><tr><td><a href="/facts/IEEE_802.11a/mDQTdNEH">IEEE 802.11a</a></td><td>9</td><td>25</td></tr><tr><td><a href="/facts/IEEE_802.11g/DYaeYj0q">IEEE 802.11g</a></td><td>9 or 20</td><td>19 or 30</td></tr><tr><td><a href="/facts/IEEE_802.11n/3gXmkz43">IEEE 802.11n</a> (2.4 GHz)</td><td>9 or 20</td><td>19 or 30</td></tr><tr><td><a href="/facts/IEEE_802.11n/3gXmkz43">IEEE 802.11n</a> (5 GHz)</td><td>9</td><td>25</td></tr><tr><td><a href="/facts/IEEE_802.11ac/aTk3NvIk">IEEE 802.11ac</a></td><td>9</td><td>25</td></tr></tbody></table> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Contention_free_pollable/yXVCz9IL">Contention free pollable</a></li> <li><a href="/facts/Distributed_Coordination_Function/U9hyUV18">Distributed Coordination Function</a></li> <li><a href="/facts/IEEE_802.11e/8VHQHs8W">Hybrid Coordination Function</a></li> <li><a href="/facts/DIFS/wq4F0IhA">DIFS</a></li> <li><a href="/facts/Short_Interframe_Space/Wxoe2Dok">Short Interframe Space</a></li> <li><a href="/facts/Arbitration_inter-frame_spacing/po8GdrMA">Arbitration inter-frame spacing</a></li> <li><a href="/facts/Reduced_Interframe_Space/p16pb8I9">Reduced Interframe Space</a></li> <li><a href="/facts/Extended_Interframe_Space/fPHhAoll">Extended Interframe Space</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://web.archive.org/web/20061111215717/http://www.wi-fiplanet.com/tutorials/article.php/1548381">802.11 Medium Access Methods on wi-fiplanet.com</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Point Coordination Function (PCF)". wireless-center.net. Archived from the original on February 1, 2009. Retrieved 2008-02-26. <a href="https://web.archive.org/web/20090201053710/http://wireless-center.net/WLANs-WPANs/1436.html" target="_blank">https://web.archive.org/web/20090201053710/http://wireless-center.net/WLANs-WPANs/1436.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"IEEE 802.11-2007 Standard" (PDF). Archived from the original (PDF) on October 13, 2008. <a href="https://web.archive.org/web/20081013101112/http://standards.ieee.org/getieee802/download/802.11-2007.pdf" target="_blank">https://web.archive.org/web/20081013101112/http://standards.ieee.org/getieee802/download/802.11-2007.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> </ol>