After reading a lot about the CSMA/CA process, I was not able to wrap my head around the slot time.
What is the slot time (i understand it's a period)?
But like, what is it?
1 us, 1 sec, 2 sec ? (I was looking to understand how the slot time is decided).
Just like other IFS decided for each PHY, does the slot time also depend on PHY?
Is there a table I can refer to?
Any help is appreciated.
The slot duration depends on the the modulation type, the band (2.4 or 5 GHz), what types of clients are Associated, channel spacing (MHz), and what the STA's Short Time Slot Subfield is set to.
It is measured in micro-seconds (μs).
Slot time for DSSS and HR is 20 μs - 5μs for turn around time + 15 for energy detect time.
9 μs for ERP (with 20 MHz spacing) - the difference from DSSS being due to the shorter energy detect time .
Look for CCA_Time in the 802.11 standard (Table 19-.6).
The short slot time of 9μs is used when only ERP stations are associated to the BSSS.
Figure 8 on page 15.
Good point risshu.
That is a really good document, but it is assuming only 20 MHZ channel spacing, so it only mentions 9 and 20 usec durations.
When 802.11p is ratified (with its 10 MHz spacing), another possibility from the standard will probably kick in.
Good to know!
Thank you Howard.
I went through the doc but missed this table section.
Thank you Risshuu.
Are there values specified for .11 ac?
/n and /ac are both 9 μsec.