An overview to synchronization in SDH network and introduction to Symmetricom TS3600 PRC

1. Synchronization in GrameenPhone Network Presented by: Md. Asif Matin Rocky

2. The Objective of Network Synchronization If the node clocks in a telecommunication network operate asynchronously then the transmit and receive rates of telecommunication systems in each node would be different to the other nodes. In this case causing data errors commonly referred to as “slips”. Slips per day = frequency difference x traffic frames/second x seconds/day (86400) The object of network synchronization is therefore to avoid and to minimize slips. This can only be achieved by synchronizing all the node clocks, and hence all the telecommunication systems, to the nearly master clock.

3. Overhead byte for synchronization in STM frame Fig. 8 Assignment of SSM bit patterns (TR3272EU00TR_0401 Synchronization, 10) S1 byte, the quality of Synchronization Message, indicates the type of clock source used to time the transmitted STM-n signal.

4. Assignment of SSM bit patterns SSM (Synchronization Status Message): Contains the timing quality of the reference timing of a received STM signal. It is 4 bits wide. Q6 DNU 1111 Q4 4.6x10℮-6 (lowest quality) SEC 1011 Q3 2x10℮-08 per day SSU Local 1000 Q2 1x10℮-09 per day SSU Transit 0100 Q1 1x10℮-11 PRC (highest quality) 0010 Q5 Quality unknown 0000 Q-level Accuracy Description S1 byte, bit 5-8

5. Reason: Timing loops occur, when a chain of slave-clocks forms a loop, so that the active reference input of any of the clocks is actually locked indirectly to the output of that same clock. Result: The clocks on the timing loop then are not locked to a PRC anymore, the loop’s clock frequency diverges, thus causing catastrophic degradation of traffic performance . Timing Loop

6. Potential Timing Loop Holdover P2 selected P2 selected P2 selected P2 selected P1 selected P1 selected Sync loop created (NE04-NE03-NE01-NE02-NE04) Priority 1 Signal, P1  Priority 2 Signal, P2 

7. Better Design Priority 1 Signal, P1  Priority 2 Signal, P2  Holdover P2 selected P2 selected P2 selected P2 selected No Sync Loop for Every Possible Fiber Cut P1 selected

9. Antenna and TS 3600 installed at LKB

10. Hardware View Power Source B Power Source A IF Cable to roof antenna 2 MHz output (Wire wrap type) Ethernet port LCT port

12. The TimeSource 3600 tracks all satellites within its field of view. The performance of each tracked satellite is observed and compared to the others, and available for use in the timing solution. A satellite with unacceptable performance data is dropped from the timing solution. GPS Tracking

13. Key features Power redundancy: Has two separate power sources A and B. Bit rate: 2.048 Mb/s Frequency accuracy: 1x10 GPS Holdover Stability: 1x10 for 72 hours. 1x10 for 30 days. Efficiency: Low installation cost and maintenance free. High Performing: BESTIME technology. -12 -11 -10

15. Block Diagram

16. PRC PRC PRC PRC PRC PRC DHKJT DHLKB SYJGB CGPTL BSCOS BOBET Method of Distribution P1 P2 P3

18. TimeScan NMS

19. TimeScan Craft

20. Ethernet Administration

21. 1) Trouble shooting with Front panel alarms: Front panel alarms Alarm handling The system has been in holdover per the user alarm setting, or there is a hardware fault. n/a. Output signal is PRS. System is in warm-up mode or is not powered. OFF Status SYS A GPS event, which has existed per the user alarm setting, has escalated to a major alarm. A minor GPS event has occurred. GPS successfully tracking satellites. System is not powered. OFF Status GPS Description Status Name

22. Description Status Name Antenna failed. An event (GPS error, temperature error) escalated to a minor alarm. A software download is required. Power A or B has failed. There is no minor alarm OFF Alarms MIN The system has been in holdover per the user alarm setting. There is no major alarm OFF Alarms MAJ A major alarm has occurred due to any hardware fault. There is no critical alarm OFF Alarms CRIT Alarm handling

24. Thank You !