This can be accounted
in the DCF model by simply setting, in Eq. (31), W0=CWmin instead of W0=CWmin+1.
Finally, since, according to the standard specification, a contending station will wait for an
ACK_Timeout greater than an EIFS, before reattempting to transmit10, then
(41) ?? + = c c T T
The throughput shall be computed as in the usual case, but with the new values defined
in Eqs. (39), (40) and (41):
( )c success idle s success idle
success
T P P T P P
] P [ E P S
??’ ??’ + +
=
1 ??
(42)
We point out that, in practical cases (e.g., the 802.11b parameters ??“ we recall that
CWmin=31 in this case), the difference between the results computed via Eq. (42) and that
computed via the more approximate expression in Eq. (37) are negligible.
4.3.3.2 Delay Performance
In saturation conditions, the total delay experienced by a frame is not meaningful. The time
elapsed from the time instant when the frame is inserted in the transmission buffer to the
time instant when it is successfully transmitted depends on how long the system has
remained in saturation conditions, and consequently how congested the transmission buffer
has become (this in turn depends on how much greater is the offered load with respect to
the saturation throughput bound).
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