  This article re-examines the fundamental notion of interference in wireless
networks by contrasting traditional approaches to new concepts that handle
interference in a creative way. Specifically, we discuss the fundamental limits
of the interference channel and present the interference alignment technique
and its extension of signal alignment techniques. Contrary to this traditional
view, which treats interference as a detrimental phenomenon, we introduce three
concepts that handle interference as a useful resource. The first concept
exploits interference at the modulation level and leads to simple multiuser
downlink precoding that provides significant energy savings. The second concept
uses radio frequency radiation for energy harvesting and handles interference
as a source of green energy. The last concept refers to a secrecy environment
and uses interference as an efficient means to jam potential eavesdroppers.
These three techniques bring a new vision about interference in wireless
networks and motivate a plethora of potential new applications and services.
