My layman understanding of the old GSM network is that cells have a control channel that is used to set up calls (and initially also transfer SMS, before it bec

My layman understanding of the old GSM network is that cells have a control channel that is used to set up calls (and initially also transfer SMS, before it became popular enough to DOS the cells) and then a bunch of channels for handling the actual calls. It may well be that the control channel's initial "wakeup" transmission is done at a very high power to ensure the phone receives it clearly, and then after some back and forth the two adjust their power levels and move to a different channel for the actual call.