  This letter investigates the power control and channel assignment problem in
device-to-device (D2D) communications underlaying a non-orthogonal multiple
access (NOMA) cellular network. With the successive interference cancellation
decoding order constraints, our target is to maximize the sum rate of D2D pairs
while guaranteeing the minimum rate requirements of NOMA-based cellular users.
Specifically, the optimal conditions for power control of cellular users on
each subchannel are derived first. Then, based on these results, we propose a
dual-based iterative algorithm to solve the resource allocation problem.
Simulation results validate the superiority of proposed resource allocation
algorithm over the existing orthogonal multiple access scheme.
