Alvarion BreezeACCESS II System Manual page 162

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Based on the RSSI information responses from the SUs, the AU
performs a calculation of the SU Rx Power Average Delta, defined as
the average difference for all SUs between the last RSSI at the SU and
the previous (one before last) RSSI. The average is calculated only for
SUs that responded to both of the last two polling message. The average
is calculated as:
SURSSIn(t) - The last RSSI value received from responding
SU number n.
SURSSIn(t-1) - The previous RSSI value received from responding
SU number n.
N - The number of SUs that responded to both last and previous polling
requests.
A Tx Power Level Decrease major severity alarm is generated if the
decrease in the SU Rx Power Average Delta is higher than the value of
the configurable SU Rx Power Decrease Threshold parameter:
-(SU Rx Power Average Delta) > SU Rx Power Decrease Threshold.
The alarm is generated only if the number of SUs used in calculating the
SU Rx Power Average Delta (responded to both of the last two polling
messages) is at least 5.
NOTE:
SUs with SW version below 4.3 will respond to the polling message. However,
the last RSSI value will not be included in the response message. Therefore,
this test is not applicable to cells where all SUs use SW version below 4.3.
The AU also gathers for all responding SUs the RSSI level at which each
SU was received by the AU. Based on these measurements, the AU
performs a calculation of the AU Rx Power Average Delta, defined as
the average difference for all responding SUs between the last RSSI at
he AU and the previous (one before last) RSSI:
Σ
n=1-N [AURSSIn(t) - AURSSIn(t-1)]/N, where:
AURSSIn(t) - The last RSSI value at which the responding SU number n
was received by the AU.
AURSSIn(t-1) - The previous RSSI value at which the responding SU
number n was received by the AU.
An Rx Signal Strength Decrease major severity alarm is generated if
the decrease in the AU Rx Power Average Delta is higher than the
value of the configurable AU Rx Power Decrease Threshold parameter:
-(AU Rx Power Average Delta) > AU Rx Power Decrease Threshold.
The alarm is generated only if the number of responding SUs used in
calculating the AU Rx Power Average Delta (responded to both of the
last two polling messages) is at least 5.
Manual Revision: 3.0
BreezeACCESS Version 4.3 Operations and Administration
Σ
n=1-N [SURSSIn(t) - SURSSIn(t-1)]/N, where: