Alvarion BreezeACCESS EZ AU-EZ, System Manual

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Chapter 4 - Operation and Administration Menus and Parameters
BreezeACCESS EZ AU-EZ 108 System Manual
2 dB safety margin to compensate for possible measurement inaccuracy or
variance in the link quality.
When the Adaptive Modulation Algorithm is disabled, this parameter will serve to
determine Fixed Modulation Level used for transmissions.
The minimum and maximum values for the Maximum Modulation Level are
defined by the Sub-Band in use. For information on how to view the Sub-Bands
supported by the unit and the supported parameters' values and options, refer to
Section 4.2.2.4 . Currently, all Sub Bands support the entire range of modulation
levels, from 1 to 8.
The default is the highest supported Modulation Level.
4.2.6.5.6 Control Modulation Level
This feature controls the modulation for ACK frames sent by the unit. The ACK
modulation can either be set dynamically based on the modulation of the frame it
acknowledges or it can be enforced to modulation level 1. The latter is particularly
useful for asymmetric links.
For instance, if one unit in the link is capable of receiving frames in modulation 8,
while the other can only receive in modulation 2, in theory one of the units should
send its data traffic using modulation 8. However, unless it receives the
corresponding ACK feedback in modulation 2 or 1, it will not be able to
synchronize and will bring its own Tx modulation down as a result. Setting the
ACK modulation to level 1 at the other side of the link will fix this, allowing the
unit to acknowledge that frames sent in modulation 8 are successfully received.
NOTE
The SNR measurement at the AU is accurate only when receiving transmissions from the
applicable SU.
Table 4-11: Recommended Maximum Modulation Level
SNR Maximum Modulation Level
SNR > 23 dB 8
21 dB < SNR < 23 dB 7
16 dB < SNR < 21 dB 6
13 dB < SNR < 16 dB 5
10 dB < SNR < 13 dB 4
8 dB < SNR < 10 dB 3
7 dB < SNR < 8 dB 2
6 dB < SNR < 7 dB 1