The OSN3500 use to connect between the GSM network, and the connections between the BSC & MSC was as the following:
GPMS (GOIU Board)-- ODF-- OSN (SLT12-1--PQ1)-- DDF (E1)-- M.W
M.W-- DDF (E1)-- OSN (PQ1)-- (Optical Board)-- ODF-- GTCS (GOIU Board)-- MSC
At the commissioning process, and after I configured the traffics for the OSN3500, I got there alarms reported for the PQ1 “TU_AIS, BIP_EXC, and V5_VCAIS alarms” that cleaned after 16 seconds, and at this time the optical boards (SLT1 or SLQ1) report RLOF & RLOS Alarm and switching to the protection board and with unstable process, this process is repeat for all time.
Note: The Optical Board in OSN is 1+1 linear protection with the GOIU boards in BSC.
RLOF, RLOS, TU_AIS, BIP_EXC, and V5_VCAIS alarms
This because there are some signals that used between the GPMS & GTCS such SS7 signaling (The control plane links refer to the SS7 signaling links, which consist of MTP2 links, MTP3 links, and SCCP subsystem), so when the link failure between MSC & BSC it will result alarms and more messages retransmissions between BSC and MSC. This result in frequent initial establishments, link congestion and link unstableness
So if the connections between GPMS & GTCS is ok and there are loop for one ATER in GPMS or GTCS so this generated messages in layer-2 every near 15second in layer2 that result from MTP-3 Test Alarm so after 24H “Or less” the BSC will be have more alarms and so the BSC will be busy in this time and result the call will drop and at this time the Optical Board “GOIU” on the BSC will be unstable and switch for each time “near 16second” that cased also switch and unstable for the Optical Boards in SDH that connected to these board.
Note: If there messages for the MTP in the two layers, so it means no connections between the two sides. But if there only message for MTP-3 so it means this side can receive the signal but can not process it.
1. I checked the Optical Boards in OSN, and stop the protection and the result is same.
2. I removed one board and put only the active board and the result was same.
3. I checked the fibers connections and it was ok.
4. I checked the configuration and it was ok.
5. I analyzed the history alarm to get the answer but it not indicates any problem related to OSN.
6. So after I checked and analyzed the BSC history alarms I got there are a more MTP Link alarms:
- MTP3 Link Test Failure: That repeated every 1.2 Sec for un-connection ATER Interface.
- And other alarms related in MTP3.
At the commissioning, this alarm is normal for the connections between OSN & GSM if there some ATER or A Interfaces is not connect or looped. But we suggest to not looped the ATER or A Interfaces that have signaling when the traffics existing and used.