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 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