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1 Dropped Calls Classification

The main cases and dropped call causes are listed below.

1.1 Missing Neighbours

Every drop that occurs when there are poor RSCP and/orEc/No levels/quality on the Best Server/AS, with thecontemporary possibility for the UE to perform a SHO on abetter cell that is not declared as a Neighbour for the AScells themselves. An example of dropped call for missingneighbour problem is shown in figure below.

Problem Description: The Active Set best server is cell61888 (SC = 205). During the call sector 62096 (SC = 293)becomes the strongest sector but is not added to the activeset, as the two cells are not defined neighbours. This can beseen in the Serving/Active Set window in TEMS. The cell62096 act as an increasing interferer until eventually the callis released. The release cause is classified as unspecified.

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1.2 Poor Coverage

The Drop occurs in regions where conditions CPICH RSCPand/or CPICH Ec/No are measured in critical values notsuitable for a proper connection. In the table below anexample is shown.

Problem Description: In this case the RF environment asreported by the UE is very poor before the call is dropped.The best server RSCP=-127dBm and Ec/No=-32dB. The

scanner also reports poor radio conditions for the same SCat the same instant i.e. RSCP = -11.97dBm and Ec/Io = -10.69dB. The last message sent is the UL Active SetComplete message sent by the UE. The UE then goes intoidle mode.

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1.3 Bad Radio Environment

Every drop that occurs when Best Server is Missing (Mostlyin good CPICH RSCP conditions). The UE active set updatecannot follow the quick coverage changes. In this case PilotPollution situations are included as well (3 cells in AS and

more than 1 strong SCs is interfering the connection within arange of 5 dB - Ec/No basis evaluation).

Problem Description:The Active Set best servers are cellswith SCs 49 and 303, and all MN (SCs 304, 179 and 180)are close to them on a RSCP basis (from 70dBm to 79dBm). During the call UE is performing a continuous numberof SHOs, affecting both the service continuity and the qualityof the connection (low values of Ec/No on each cell). So, theRadio Environment is not suitable for a good connection andtherefore the dropped call occurs. Sometimes the TEMS Inv.doesnt show the event on the chart, like in this case, so itsadvisable to check the Events and Layer 3 messages: In the

L3 table the RRC Connection Release DL corresponds (intothe Event table) to an RRC Connection Abnormal Releasewith the specification Unspecified.

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