ok, in ericsson, the data utilization is very efficient.
So just do your standard “voice only” capacity calculation, as you demonstrated. But rather than using 100% utilization, you may want to apply a small margin factor, of about 10-15%.
That gives you the numnber of timeslots needed to carry the current traffic. But of course, for the degrow, you must increase the HR Ratio. So don’t forget to take that into account (as i explained in firdt post)
Now you know the number of physical TS needd for TCH, add 1 BCCH, add x SDCCH.
And on top of all that, depending if your cell is “high traffic” or “low traffic”, add between 3 to 8 timeslots for data. 6 ts for data is a good average.
I’m not sure i would call that retro-engineering… you just look at the current traffic to estimate how many TRX to be removed. That’s straight-forward engineering 😀