ANALYSING EFFECTS OF MALFUNCTIONS ON THE PERFORMANCE OF UMTS RADIO ACCESS NETWORKS

1. ANALYSING EFFECTS OF MALFUNCTIONS ON THE PERFORMANCE OF UMTS RADIO ACCESS NETWORKS Author: Antti Keintola Supervisor: Professor Sven-Gustav Häggman Instructor: M.Sc. Anna Merjamaa

2. Agenda • Background • Research problem and objectives • Methods • Analysis • Results • Summary

3. Background • 3G networks are launched all over the world • Technology is complex and still somewhat immature • Not much experience in operating and troubleshooting the network • Networks are not performing at the optimal level • Faults and failures occur • Troubleshooting is time consuming and finding the root cause is difficult • Performance statistics is sometimes the only source of information available

4. Research problem and objectives • What faults contribute most on the performance degradation? • Is it possible to find the cause of the failure by inspecting statistics? • What actions should be performed to improve performance?

5. Methods • Counter data was collected from a live network • 7 RNCs, 1906 Node Bs • 28 day period • Only daily statistics, not hour or quarter data available • Improvements made simultaneously • Data analysed with spreadsheet tool • Laborious, slow • Need for dedicated tool

6. Methods • Key Performance Indicators defined: • Call Completion Success Rate (CCSR) • Accessibility • Retainability • CCSR = Accessibility * Retainability

7. Analysis – network • The net degradation of performance were calculated and dominant days were identified • Detailed analysis focused on days highlighted with red and yellow

8. Analysis – accessibility • Accessibility was studied first • Almost all accessibility failures related to RRC rejects

9. Analysis – RRC at RNC level • Six distinct faults were identified by analysing RNC RRC statistics

10. Analysis – retainability • Speech and packet drops were studied separately

11. Analysis – Radio Access Bearers • Drop rate analysis were done at RNC level • Basically RAB releases were investigated

12. Results – accessibility failures • Following defects were identified and their net contribution to the overall performance were calculated • Transmission fault affects three out of seven RNCs, hence higher figure • Software and hardware defects have small impact on the overall performance

13. Results – accessibility failures

14. Results – retainability failures • Speech calls • Packet connections

15. Results – retainability failures

16. Summary • Defects with significant impact on the network performance were identified • Impacts on the performance were calculated • Man-made defects have more severe impacts than software or hardware faults • The reasons for man-made faults should be worked out • Working instructions and procedures should be revised and improved • Need for dedicated tool to analyse data from customer network

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