"Because of the necessity of an individual frequency for every single mobile phone"
I believe that this statement is wrong!
Not that we are in the digital era, each cell phone receives a lot of signal on a frequency. But it just accept only those who are coded for him. And as the messages are all encoded, a cell phone can not easily listen to what other cell phone or device are discussing.
Modifies cell phone exist, and can be bought in China, by example, which have "extended" capacities.
It's like having an ethernet network with a hub instead of a switch as central distributor.
It's like having a 10base-T network. All on the same signal line, and being able to hear everything, but only listening to the packets which are directed to you.