User's Manual

Chapter 4 - Operation and Administration
BreezeNET B System Manual
4-58
Performance Parameters
The Performance Parameters menu enables defining a series of
parameters that control the method by which traffic is transmitted
through the BreezeNET B wireless link.
The Performance Parameters menu provides the following parameters:
Maximum Modulation Level
When the Adaptive Modulation Adaptation (see
Adaptive Modulation
Algorithm on page 4-60) is enabled, it changes the modulation level
dynamically according to link conditions to increase the probability of
using the maximum possible modulation level at any given moment.
Although the algorithm will avoid using modulation levels that are too
high for the prevailing link conditions, it might be desired under certain
conditions to limit the use of higher modulation levels. If the link
quality is not sufficient, it is recommended that the maximum
modulation level be decreased, since higher modulation levels elevates
the error rate. In such conditions, a higher Maximum Modulation Level
increases the number or retransmissions before the modulation level is
being reduced by the Adaptive Modulation Algorithm. A high number of
retransmissions reduce the overall throughput of the link.
The link quality can be estimated based on the SNR measurement of the
RB at the BU, which can be viewed in the MAC Address Database
option in the Site Survey menu, and on the SNR measurement of the
BU at the RB, which can be viewed using the Continuous Link Quality
Display option. If the measured SNR is less than a certain threshold, it
is recommended that the maximum modulation level be decreased in
accordance with Table 4-9, using the values of typical sensitivity. It is
recommended to add a 2 dB safety margin to compensate for possible
measurement inaccuracy or variance in the link quality.
NOTE
The SNR measurement at the BU is accurate only when receiving transmissions from
the applicable RB. If necessary, use the Ping Test utility in the Site Survey menu to
verify data transmission.
When the Adaptive Modulation Algorithm is disabled, this parameter
will serve to determine Fixed Modulation Level used for transmissions.
The default is Modulation Level 7.