The cell coverage shrinks as the
loading increases, this is called cell breathing.
In the uplink, as more and more UE are
served by a cell, each UE needs to transmit higher power to compensate for the
uplink noise rise. As a consequence, the UE with weaker link (UE at greater
distance) may not have enough power to reach the NodeB – therefore coverage
shrinkage.
In the downlink, the NodeB also needs
to transmit higher power as more UE are being served. As a consequence UE with
weaker link (greater distance) may not be reachable by the NodeB.