MP.11 and MP.11/a Quick Install Guide
Chapter 5. Web Interface
51
The Roaming feature lets the SU monitor local SNR and data rate for all frames received from the current Base
Station. As long as the average local SNR for the current Base Station is greater than the slow scanning
threshold, and the number of retransmitted frames is greater than the slow scanning threshold given in
percentage, the SU does not scan other channels for a better Base Station.
•
The
slow scanning
procedure starts when the average local SNR for the current Base Station is less than or
equal to the slow scanning threshold and the number of retransmitted frames is greater than the slow
scanning threshold given in percentage. During the slow scanning procedure the SU scans the whole list of
channels while maintaining the current session uninterrupted.
•
Fast Scanning
is the scanning procedure performed under emergency conditions, when the average local
SNR for the current Base Station is very low, below the fast scanning threshold, and the number of
retransmitted frames is greater than the fast scanning retransmission threshold give in %, so that the current
session should terminate as soon as possible. During this procedure, the SU scans other channels as fast as
possible.
Roaming can only occur if the slow scanning or fast scanning procedure is started, under the following conditions:
1. If the roaming is started from the slow-scanning procedure (when the slow scanning procedure has completed
scanning all of the channels), the SU selects the Base Station with the best SNR value on all available
channels. The SU roams to the best Base Station only if the SNR value for the current Base Station is still
below the slow scanning SNR threshold, and best Base Station offers a better SNR value for at least roaming
threshold than the current Base Station. During roaming, the SU first ends the current session and starts the
registration procedure with the best Base Station.
2. If the roaming is started from the fast-scanning procedure (emergency conditions), the SU selects the first
Base Station that offers better SNR than the current Base Station, and starts a new registration procedure
with the better Base Station without ending the current session. The current Base Station automatically ends
the session with the SU that roamed to another Base Station after 30 seconds.
