Figure 4 shows the daily traffic profile of a major operator, where the traffic in peak hours can be 10 times higher than the one in off-peak periods. Realizing the potential in these slow traffic variations, vendors and operators have recently started to bundle traffic of certain transceivers , and switch others off in order to save energy. Beyond these basic techniques, self organizing networks can be exploited to adapt the network topology to slow traffic variations. Furthermore, highly dynamic load variations should be addressed by energy efficient radio resource management strategies.