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.
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 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 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.