What are the possible causes for a Drop Call on a UMTS network?

There are several reasons for RAB Drop in WCDMA network.

·         Poor Coverage (DL / UL)

·         Pilot Pollution / Pilot Spillover

·         Missing Neighbor

·         SC Collisions

·         Delayed Handovers

·         No resource availability (Congestion) for Hand in

·         Loss of Synchronization

·         Fast Fading

·         Delayed IRAT Triggers

·         Hardware Issues

·         External Interference

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What are the possible causes for a lower PSR?

There are several different reason for low Paging Success Ratio

- Non-continuous RF Coverage – UE going in and out of coverage area frequently
- Very High ‘Periodic Location Update Timer’ – Keeping UEs in VLR long time after it moved out of coverage
- Lower Paging Channel Power
- Access Channel Parameter Issues
- Delayed Location Update when crossing the LA / CN Boundaries

Also Check

E Book on GPRS and EDGE Performance

What is G-RAKE Receiver?

How WCDMA OSS Works?

Doc For This with Below Containing :

• Cell & Channel Management
• Adjacent Cell Configuration Management
• Radio Network Optimization
• WCDMA Neighboring Cell Support (WNCS)
• WCDMA Measurement Result Recording (WMRR)
• Alarms Status Matrix
• Alarm Log Browser
• Alarm List Viewer
• Element Manager
• RNC Element Manager
• RBS Element Manager
• Bulk Configuration C

Doc Link : WCDMA OSS DOC

What is Paging Success Ratio? What is the typical PSR that you have seen in a WCDMA UMTS network?

Paging Success Ratio:

Its Paging Responces to the Paging Attempts in WCDMA UMTS network.

Typical Value for Good WCDMA Cellular Network is greater than 90%. 

What are the possible causes for an IRAT Failure?

There are several reasons for IRAT failure in cellular network optimization.
Major 4 reasons which played good role in WCDMA Optimization.

·         Missing 2G relations

·         Non availability of 2G Resources

·         Poor 2G Coverage

·         Missing 3G Relations

What is the typical event sequence of IRAT Handover from 3G to 2G

Simple IRAT Handover Flow

Event 2d –entering into compressed mode –measurement of 2G candidates – Event 3a –Verification of 2G resources

Handover from UTRAN Command from 3G RNC to UE

Download Complete UMTS CS Call Flow

What are the typical KPIs you use to measure a network and what criteria?

• Access failure rate (≤ 2%).
• Call setup time (CS: over 95% of the time < 6-second for mobile-to
• PSTN, 9-second for mobile-mobile.  PS: over 95% of the time < 5 second).
• Dropped call rate (≤ 2%).
• BLER: over 95% of the blocks ≤ 2%.
• Average DL/UL throughput for PSD: 210kbps for loaded, 240kbps for unloaded.

Find the complete UMTS KPI from Here

Information on UMTS KPI BenchMark