User:Smiljan~enwiki/Sandbox

= Voice call setup success rate =

Definition
CSSR is defined as the ratio of successful normal call connections, divided by the total number of call setup attempts.

The call is considered as initiated if the RRC Connection Request is logged in the tool.


 * Alternative definitions
 * RRC Connection request is favorable for E/// since the problems in FACH channel reading is not taken into account in this case.
 * Technically more correct would be to trigger the even with the Event: Call initiation, equivalent to AT command sent to the UE or pressing the dial button on the phone
 * Depending on the UE, some UEs are logging the initial NAS message before the RRC connection establishment, in those cases the trigger in this message is equivalent to Call initiation message.

The call is considered as successfully established if the Alerting message is logged in the tool.


 * Alternative definitions
 * Some operators would propose to trigger the success event by the reception of the Call connect acknowledge message.
 * No deterioration in the success rate is forseen if this definition would be used. But the call setup time would be affected.
 * Arguments against this approach
 * At that time all the resources for the call are succesfully allocated, the signalling path is established and de facto we are in connected mode. Because of that, the problems in this period should be counted as drop calls, not the accessibility problems.

$$CSSR=\frac{\#SuccessfullyEstablishedCalls}{\#CallAttempts}\times 100$$ $$Innovation=\frac{The art}{of working smart}$$

Measurement method
Drive test will be performed, with “short call” sequence.
 * Event triggers
 * Success: Direct Transfer (Alerting) reception message
 * Initiation: Call attempt message from the UE

KPI classification

 * Recommendation
 * recommended