tag:blogger.com,1999:blog-1988432060681510848.post1268535367184442411..comments2024-03-25T23:51:47.067-05:00Comments on Revolution Wi-Fi: Wireless QoS Part 1 - Background InformationAndrew von Nagyhttp://www.blogger.com/profile/12658799453646609565noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-1988432060681510848.post-10317215920087416572013-09-03T06:51:27.485-05:002013-09-03T06:51:27.485-05:00Its clear now,, Thanks for the reference Andrew.
...Its clear now,, Thanks for the reference Andrew.<br /><br />-JeevanAnonymoushttps://www.blogger.com/profile/10089598057372425588noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-1468222685067066342013-08-30T20:32:16.564-05:002013-08-30T20:32:16.564-05:00Hi Jeevan,
The contention window (random backoff t...Hi Jeevan,<br />The contention window (random backoff timer) can be skipped only when the transmitter determines through CCA (both physical and virtual NAV) that the medium is idle for a period of time equal to or greater than one InterFrame Space (DIFS, or AIFS when WMM is in-use) immediately prior to when a frame has been queued for transmission. If the frame gets queued and the medium is busy and the transmitter has to wait, then the contention window must be used. For more information refer to 802.11-2012 section 9.2.2 and Figure 9-3.<br /><br />The benefit of skipping the contention window is that if the network is relatively idle, then a bit of overhead can be cut out of the process without too much risk of causing collisions. But as the network gets busier, the contention window helps to randomly space out the transmissions so they don't cause collisions (because the busy medium from a prior frame transmission serves to align all other transmitters who are waiting for their turn).<br /><br />Cheers,<br />AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-90317206319985900442013-08-30T06:57:05.237-05:002013-08-30T06:57:05.237-05:00Hi Andrew,
In recap you mentioned that,
"If...Hi Andrew, <br />In recap you mentioned that,<br /> "If the medium was idle prior to the frame being queued, the random backoff timer is skipped."<br /><br />I was wondering when this situation is hit. I think we trigger the CCA function only if we have some frame in TX queue. Please correct me if I am wrong<br /><br />-Thanks<br />JeevanAnonymoushttps://www.blogger.com/profile/10089598057372425588noreply@blogger.com