Alvarion BreezeACCESS VL System Manual page 221

Modulation PHY Rate
Level (Mbps)
8 54
7 48
6 36
5 24
4 18
3 12
2 9
1 6
When the above mentioned retransmission percentages are reached, the Adaptive
Modulation algorithm will lower the modulation. If the connection is stable on a
particular modulation, the unit will periodically check whether it can further
increase the modulation (except on modulation 8), by sending a number of test
packets using this higher modulation and checking the retransmission rate.
The user can configure a Packet Thershold to Test Up Rate parameter to define
the number of successfully transmitted frames after which the unit will test the
higher modulation. The number of frames used for this test can also be
configured by the user via the Packet No On Upper Rate parameter.
4.2.6.5.8.1 Adaptive Modulation Option
The Adaptive Modulation Option enables or disables the Adaptive Modulation
decision algorithm. When enabled, the algorithm supports decrease/increase of
transmission's modulation levels between the lowest possible level to the value
configured for the Maximum Modulation Level parameter. If the Maximum
Modulation Level is set at the lowest possible level, the Adaptive Modulation
algorithm has no effect.
The default selection is Enable.
4.2.6.5.8.2 History Size
This option indicates the number of entries used by the Adaptive Modulation
algorithm to compute the transmission time.
The available range is between 15 and 25.
The default value is 15.
Operation and Administration
Table 4-13: Retransmission Percentage Equivalence
PHY Rate Difference Compared
to Previous Modulation (Mbps)
54-48=6
48-36=12
36-24=12
24-18=6
18-12=6
12-9=3
9-6=3
Menus and Parameters
Retransmission Percentage
Equivalent to PHY Rate Difference
6/54=11%
12/48=25%
12/36=33%
6/24=25%
6/18=33%
3/12=25%
3/9=33%
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