PCM SYNCH NO USABLE PCM REFERENCE
The synchronization reference from the PCM network is faulty (for example, too much jitter/wander) or missing. More information can be found in Transmission System Supervision in the CPI for the relevant RBS.
The alarm is raised if the following applies:
– TF has been trying to synchronize with the PCM reference for more than 5 minutes after initial startup.
– TF has detected that the PCM reference has drifted more than 80 ppb during the last 48h.
– If a second PCM reference is not available and the TF did not recover before the holdover period expired (that is, the AO TF EC2:1 alarm was active for too long.)
– The holdover period depends on how long it takes for the variance of the TF estimated frequency to exceed a variance limit for a class 1 alarm. The limit is set to ensure that the frequency at the antenna does not exceed the 50 ppb accuracy limit.
– Explanation:When the reference quality of the PCM is outside specification of G.823 and G.824, the BTS goes into holdover and the TF starts to estimate its own frequency quality. The trigger to go into holdover and start the estimation is when short-term wander on the PCM reference is more than 6 ppm for 25 seconds. The estimation process, using a Kalman filter, causes the variance of the estimated frequency to increase with time.
– The alarm is raised after about 24 h when the temperature varies within +-10°C if the following conditions are fulfilled:
– RBS with DUG or DXU excluding DXU-01, DXU-03, DXU-11
– More than 72 hours of operation locked to PCM, with temperature supervision.
– PCM reference traceable to G.812 Type II/Stratum 2
– The alarm is raised after about 60 minutes if the above conditions are not fulfilled.
Only when TF mode is master or stand-alone.