# Forum

## cfp values and pifs values

• dear sir ,i need to know the correct range of values for pifs and cfp max duration and cfp repetion interval and also the maximum possibility of nav value

• Hi ,

PIFS = SIFS + SLOTTIME

802.11 b PIFS [Short Preamble ] = 30 ms
802.11 b PIFS [Long Preamble ] = 30 ms
802.11 g PIFS [Short Preamble ] = 19 ms
802.11 g PIFS [Long Preamble ] = 30 ms
802.11 a PIFS = 25 ms

Maximum values of NAV is 32767/32 ms

I dont have clue on the other two questions.
Hope some Big Guys Come with the Answer.

• balajiupputuri,

Here are my calculations on the CFP repetition interval:

Beacon Period (int: 2 bytes) * DTIM Interval (int: 1 byte) * CFPRate (int: 1 byte)

MAX CFP repetition interval:

65535 * TU * 255 * 255 = 4,261,478,800 TU (TU = 1024 micro seconds)

MIN CFP repetition interval:

1 * TU * 1 * 1 = 1 TU

###

CFPMaxDuration int: 2 byte = 65535 TU

###

Does anyone agree or disagree?

Thanks,

moe

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