The Call Setup Success Rate (CSSR) is calculated by taking the number of the unblocked call attempts divided by the total number of call attempts. A call setup is an exchange of signaling information in the call process that leads to Traffic Channel (TCH) seizure.
The Dropped Call Rate (DCR) - also called Call Drop Rate - is the number of dropped calls divided by the total number of call attempts. A dropped call is a call that is prematurely terminated before being released normally by either the caller or called party (i.e., the call is dropped before the exchange of Released Message 'RL_M' and Released Complete Message 'RLC_M' in the signaling flow).
The Standalone Dedicated Control Channel Congestion Rate is defined as the probability of failure of accessing a Standalone Dedicated Control Channel (SDCCH) during call set up. The SDCCH is used in the GSM system to provide a reliable connection for signalling and SMS (Short Message Service) messages.
The Traffic Control Channel Congestion Rate is the probability of failure of accessing a traffic channel during call setup. Traffic Control Channels (TCCH) are responsible for transferring control information between mobiles and the BTS.