摘要： 对D2D（Device to Device）通信系统的容量扩展问题进行了研究，提出了一种双向中继辅助的D2D通信系统，该系统采用非正交多址接入（Non-Orthogonal Multiple Access，NOMA）。首先分析了各信号的信干噪比（SINR），接着详细计算了每个信号的累积分布函数（Cumulative Distribution Function，CDF）和概率密度函数（Probability Density Function，PDF），并据此推导出了系统遍历总容量的解形式。除此之外，还分析了OMA系统的遍历总容量，与NOMA系统进行对比。仿真结果表明，NOMA系统的可达速率优于OMA系统，双向中继能够比传统的单向中继获得更高的容量。
(1.College of Telecommunications＆ Information Engineering，Nanjing University of Posts and Telecommunications，Nanjing 210003，China；2.Key Lab of Broadband Wireless Communication and Sensor Network Technology，Ministry of Education，Nanjing University of Posts and Telecommunications，Nanjing 210003，China)
Abstract： A two-way relay-assisted device to device (D2D) communication system using non-orthogonal multiple access (NOMA) is proposed to solve the capacity scaling for D2D communication system. Firstly, the signal to interference noise ratio (SINR) of each signal is analyzed, and according to the cumulative distribution function (CDF) and probability density function (PDF) of each signal, the solution form of the ergodic sum capacity of the system is obtained. In addition, the ergodic sum capacity of orthogonal multiple access (OMA) system is analyzed and compared with NOMA system. Simulation results show that compared with OMA system, the achievable capacity of the system can be improved when NOMA is used, and the two-way relay scheme can make the system obtain higher capacity than the traditional one-way relay scheme.
Key words : device to device （D2D）；non-orthogonal multiple access （NOMA）；two-way relay；ergodic sum capacity
