Alvarion BreezeACCESS VL 5.4 System Manual page 91

Operation and Administration
The previous parameters define a sub band of frequencies between the Sub
Band Lower Frequency and the Sub Band Upper Frequency using the
Scanning Step resolution. The Frequency Subset Definition option enables
defining a specific subset of frequencies within this sub band to be used
during scanning. When selected, a list of all valid frequencies in the band
is displayed, and an index is given to each frequency. The current defined
subset is also displayed. The defined subset can be modified by entering a
list of desired indexes, separated by commas (no spaces). Enter A to select
all frequency in the subset.
The default is A, which is the list that includes all indexes of frequencies
defined by the previous parameters.
Best AU Parameters (SU)
An SU that can communicate with more than one AU using the same
ESSID may become associated with the first AU it "finds", not necessarily
the best choice in terms of quality of communication or other factors such
as number of SUs serviced by each AU. The same limitation also exists if
only one AU in the neighborhood has an ESSID identical to the one used
by the SU, since it is not always necessarily the best choice.
The topology of a fixed access network is constantly changing. Changes in
base station deployment and subscriber density can accumulate to create
substantial changes in SU performance. The quest for load sharing
together with the desire to create best throughput conditions for the SU
created the need for the Best AU feature, to enable a SU to connect to the
best AU in its neighborhood.
When the Best AU feature is used, each of the AUs are given a quality
mark based on the level at which it is received by the SU. The SU scans for
a configured number of cycles, gathering information from all the AUs it
can communicate with. At the end of the scanning period, the SU reachs a
Best AU decision according to the information gathered. The AU with the
highest quality mark is selected as the Best AU, and the SU will
immediately try to associate with it. The quality mark given to each AU
depends on the level at which it is received by the SU.
The Best AU selection mechanism can be overridden by defining a specific
AU as the preferred AU.
NOTE:
Although the SU selects the Best AU based on long-term conditions prior to the decision
time, it may not always be connected to the instantaneous Best AU at any given time. Note
also that the decision is done only once during the scanning interval. The decision may not
remain the optimal one for ever. If there are significant changes in deployment of
neighboring AUs and the SUs served by them, overall performance may be improved if the
applicable SUs are reset intentionally so as to re-initiate the Best AU decision process.
The Best AU Parameters menu includes the following options:
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