  We consider the problem of spectrum sharing in device-to-device communication
systems. Inspired by the recent optimality condition for treating interference
as noise, we define a new concept of "information-theoretic independent sets"
(ITIS), which indicates the sets of links for which simultaneous communication
and treating the interference from each other as noise is
information-theoretically optimal (to within a constant gap). Based on this
concept, we develop a new spectrum sharing mechanism, called
"information-theoretic link scheduling" (ITLinQ), which at each time schedules
those links that form an ITIS. We first provide a performance guarantee for
ITLinQ by characterizing the fraction of the capacity region that it can
achieve in a network with sources and destinations located randomly within a
fixed area. Furthermore, we demonstrate how ITLinQ can be implemented in a
distributed manner, using an initial 2-phase signaling mechanism which provides
the required channel state information at all the links. Through numerical
analysis, we show that distributed ITLinQ can outperform similar
state-of-the-art spectrum sharing mechanisms, such as FlashLinQ, by more than a
100% of sum-rate gain, while keeping the complexity at the same level. Finally,
we discuss a variation of the distributed ITLinQ scheme which can also
guarantee fairness among the links in the network and numerically evaluate its
performance.
