This brief examines current research on cooperative device-to-device
(D2D) communication as an enhanced offloading technology to improve the
performance of cognitive radio cellular networks. By providing an
extensive review of recent advances in D2D communication, the authors
demonstrate that the quality of D2D links significantly affects
offloading performance in cellular networks, which motivates the design
of cooperative D2D communication. After presenting the architecture of
cooperative D2D communication, the challenges of capacity maximization
and energy efficiency are addressed by optimizing relay assignment,
power control and resource allocation. Furthermore, cooperative D2D
communication is enhanced by network coding technology, and then is
extended for broadcast sessions. Along with detailed problem formulation
and hardness analysis, fast algorithms are developed by exploiting
problem-specific characteristics such that they can be applied in
practice.