中文摘要：

将蜂窝用户作为中继节点协作终端直通通信，能够以较低的成本提高频谱利用率，解决网络覆盖和服务质量问题。本文针对蜂窝用户作为双向中继节点的系统场景，提出了一种基于网络编码的终端直通通信中最优功率分配和最佳中继选择算法。该算法在终端直通链路发射总功率一定的前提下，以终端直通链路信道容量最大为目标，对终端直通链路上的节点进行了最优功率分配，选出了最佳中继节点。仿真结果表明，本文提出的传输方案与其它方案相比可以显著提高终端直通链路的信道容量。

英文摘要：

Cellular users can be regarded as relay nodes in cooperation with the Device-to-Device （D2D） communication so as to lower the cost, improve spectrum efficiency and solve the problems of network coverage, as well as improving service quality. In this paper an optimal power allocation and optimal relay selection algorithm based on network coding is proposed for using cellular users in the bidirectional relay nodes system. By fixing the total power of the D2D link to be transmitted, this algorithm optimizes the transmission power of each node, and selects the relay node which can maximize the channel capacity of the D2D link as the best relay node. Simulation results show that compared with other protocols, the proposed protocol can significantly improve the channel caoacitv of the D2D link.