RET system
RET system consists on Actuators connected directly to the phase shifter inside the antennas.
In Data networks like UMTS and HS where the cell is 'breathing' the shrinkage factor is a known fact.
Every data usage will cause the actual size of the cell to change, trying to keep enough energy and to supply sufficient QOS to the users.

Having centralized controlled motor ready to change the elevation of the lobe allows the operator to optimize the size of the cells according to the needs.

Traffic jam on the highway?
Expand the cell to allow more people to talk.

Lunch in the near mall?
Fine tune the size of the cell to allow customers to use their PDA's