In the framework of Next-Generation Networks (NGNs), the IP-based Radio Access Networks (RANs) component, though representing one of the most attractive aspects of NGNs, is also the weakest part. The wireless interface is in fact the critical factor in end-to-end Quality of Service (QoS) support due in particular to the fluctuations of radio channel conditions and consequent errors. Moreover, the problems arising from the highly varying traffic, wireless transmitter energy consumption (e.g., [ODR05, Ber07]), and the highly desirable user mobility create needs to be addressed before wireless broadband Internet services can be widely and successfully deployed.