User guide

Optimizing Performance
6-21
Alvarion
In this type of situations the disappointing network performance might be
caused by the busy wireless traffic in that area, where the CSMA/CA protocol
causes the wireless stations to defer transmissions to often for either:
! Heavy data traffic by other stations in the same wireless cell
! Traffic from stations in neighboring cells, where stations in a location where
wireless cells overlap one another seem to suffer more than the other
stations.
The last example would typically occur only in networks where all Base Stations
have been configured to operate at the same frequency, or at frequencies with
an insufficient channel separation (see Frequency Channel Management).
Influencing the Deferral Behavior
To overcome the performance issue described on previous pages, you can
choose to design a high performance network based on the following principles:
! Add more Base Stations to your network.
! Configure Base Stations in neighboring cells to operate at different
frequency channels with a maximum channel separation (see Frequency
Channel Management).
! Adjust the
Distance Between APs parameter to optimize the load balance of
the number of wireless stations per Base Station (see Distance Between
APs).
Distance between APs is a parameter that must be set on both the wireless stations and
the Base Station. The values that you select must be the same for ALL BreezeNET
equipped devices in your network to avoid unpredictable behavior of your network and
the roaming connectivity of wireless devices.
By changing the Distance between APs parameter from Large to Medium or Small,
you can virtually reduce the receiver sensitivity of the wireless radios, that will
show the following behavior:
! The stations will show a more active roaming behavior and connect to one
of the added Base Stations more quickly.
! Considering the fact that you have added more Base Stations, the deferral
behavior does no longer need to be as strict in environments where the
density of installed Base Stations was fairly low:
" The stations will only defer transmissions when the signal level of a
message sensed on the wireless medium equals or exceeds a
specific level.
" Messages with a low signal level are not likely to be addressed at
the Base Station that services the local cell, since the more active
roaming behavior should have caused the station to connect to
another Base Station.
To support the more active roaming behavior of the wireless stations and to
compensate the lower receiver sensitivity, changing the Distance between APs