描述了基于放大转发中继underlay 模式下的D2D 传输模型，研究了用户最大发射功率受限前提下利用
单向放大转发中继的D2D 通信系统功率分配方法. 首先从D2D 系统端到端信干噪比表达出发，推导出D2D 链
路和蜂窝上下行链路的可达和速率，据此建立了可达和速率的联合功率优化模型，根据功率约束条件将双目标优
化模型转化为单目标优化模型；然后采用Pareto 优化方法最大化可达和速率，并提出相应的低复杂度实现算法.
仿真结果表明：在中低信噪比区域，基于放大转发中继辅助的D2D 通信性能显著优于传统D2D 通信模式，采用
Pareto 功率优化方法可进一步提升D2D 通信以及蜂窝上下行链路的系统可达和速率.
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.
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