Transmission Interface Handling DS1 1544 kbit/s
UAST ceases
UAST ceases when available state is declared. Each direction (upstream
and downstream) is supervised independently of the other.
54.3.4
Supervision of Transmission Quality
The function is initiated when the AO DP is enabled from the BSC.
The configuration of quality supervision can only be performed when
the AO DP is in state “Disable”. The reporting to the BSC is performed
when the AO DP is in state “Enable”.
Quality supervision consists of six supervision functions:
•
BFF (Bit Fault Frequency)
•
DF (Disturbance Frequency)
•
SF (Slip Frequency)
•
ES (Errored Seconds)
•
SES (Severely Errored Seconds)
•
UAS (Unavailable Seconds)
Bit Fault Frequency supervision
The number of bit errors in the received 1544 kbit/s signal is used to
establish an error rate. The CRC-6 sequence is used to obtain the
number of bit errors. In this method, the distribution of errors in the
time is considered. Bursts of faults decrease the number of CRC errors
detected compared to what would have been detected with an equal
distribution of faults in time.
The probability of bit faults appearing in bursts is greater than the
probability of detecting single isolated bit faults. This probability
increases with the real bit error rate, and with the length of the time
period over which the real bit fault frequency is calculated.
In the used method, the number of CRC-6 errors is counted during the
base interval. Then, a translation to bit fault frequency is performed.
The bit fault frequency is supervised and reported as the mean bit error
ratio in ppm (parts per million) during the BI (Base Interval).
Disturbance Frequency supervision
This supervision monitors detected fault situations which are regarded
as disturbances upon detection. Upon detection the following events are
regarded as disturbances:
•
LOF (Loss Of Frame) alignment
•
LOS (Loss Of Signal)
•
AIS (Alarm Indication Signal)
•
RAI (Remote Alarm Indication) received from remote end
EN/LZT 720 0008
P2A
2001-11-28
429 (485)
© Ericsson Radio Systems AB
— All Rights Reserved —
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Summary of Contents for RBS 2106
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