Abstract: In this paper, we describe the D2D communication strategy assisted by a relay node using a
one-way amplify-and-forward (AF) protocol for the underlay mode. Based on this strategy we propose a
joint-power allocation scheme to maximize the rate of both D2D and cellular link with the constraint of peruser’s
maximum transmit power. To achieve this goal, we derive an expression for the achievable sum-rate
of each link according to the signal-to-interference-plus-noise expressions of end-to-end uplink and downlink.
According to these expressions, we set up an optimization model for jointly power allocation to maximum an
achievable sum-rate. For this model, we transform the dual-objective function into a single-objective function
and propose a low complexity joint-power allocation scheme by using the Pareto-optimal method to maximize
the achievable sum-rate. Numerical results show that a higher gain of the sum-rate of the D2D link can be
obtained by using the relay aided strategy in low and intermediate signal-to-noise regimes as compared with
that of the traditional D2D mode. It is also shown that the power optimal scheme can further be improved for
the achievable sum-rate of D2D and cellular links by using the Pareto-optimal method.

Key words: D2D communication, amplify-and-forward, achievable sum-rate, joint-power allocation, Paretooptimal