Traffic offloading via device-to-device (D2D) communications
has been proposed to alleviate the traffic burden
on base stations (BSs) and to improve the spectral and energy
efficiency of cellular networks. The success of D2D communications
relies on the willingness of users to share contents. In
this paper, we study the economic aspect of traffic offloading via
content sharing among multiple devices and propose an incentive
framework for D2D assisted offloading. In the proposed incentive
framework, the operator improves its overall profit, defined as
the network economic efficiency (ECE), by encouraging users
to act as D2D transmitters (D2D-Txs) which broadcast their
popular contents to nearby users. We analytically characterize
D2D assisted offloading in cellular networks for two operating
modes: 1) underlay mode and 2) overlay mode. We model the
optimization of network ECE as a two-stage Stackelberg game,
considering the densities of cellular users and D2D-Tx’s, the
operator’s incentives and the popularity of contents. The closedform
expressions of network ECE for both underlay and overlay
modes of D2D communications are obtained. Numerical results
show that the achievable network ECE of the proposed incentive
D2D assisted offloading network can be significantly improved
with respect to the conventional cellular networks where the D2D
communications are disabled