That’s the thing, we don’t have those in alcatel.
Let’s try to guess.. the MS starts with a channel request on RACH, the “Channel Required” reaches the BSC, and then is counted as a “random access attempt”.
The BSC sends a Channel Activation to the BTS, if the SDCCH is not congested. Counted as a “SDCCH Request”.
The BTS replies with a Channel Activation Ack (not counted)
Then the BSC sends a Immediate Assign Command, counted as a “SDCCH allocated”.
Maybe in your formula, this is the ratio CHANNEL ACTIVATION / CHANNEL REQUIRED ?
I really cannot be sure… this indicator is not provided by alcatel. it can be computed manually though.