Abstract

This paper considers non-orthogonal multiple access (NOMA)-based coordinated direct and relay transmission (CDRT) system, where the base station (BS) directly communicates with the nearby users while it requires the help of a dedicated relay to communicate with the cell-edge users. We derive exact closed form expression for the outage probabilities experienced by the downlink users and the system outage probability of the considered CDRT network with full-duplex relaying (FDR) technique. Further, we derive approximate closed form expressions for the ergodic rates achieved by the users. The channel of all the links experience Nakagami fading distribution and the analysis takes into account the residual interference generated due to the imperfect successive interference cancelation (I-SIC) technique. We provide numerical and simulation results to identify the impact of key system parameters on the outage and ergodic rate performance of the users and the system outage performance. The outage and ergodic rate performance of users in the considered FDR-based NOMA-CDRT system has been observed to be significantly improved compared to a FDR-based OMA (orthogonal multiple access)-CDRT system. It is observed that random selection of NOMA power allocation coefficients at the BS leads to higher outage for the near users compared to the far users. We determine numerical results for the NOMA power allocation coefficient that leads to equal outage performance for both the users. Finally, we derive analytical expression for the optimal power allocation (OPA) coefficient at the BS that minimizes the system outage probability. Through extensive numerical and simulation studies, we establish that OPA can lead to significant reduction of system outage probability compared to random selection of power allocation coefficients at the BS.

中文翻译：

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基于全双工的协调直接和中继传输（CDRT）系统中的非正交多路访问：性能分析和优化

摘要

本文考虑了基于非正交多址（NOMA）的协调直接和中继传输（CDRT）系统，其中基站（BS）直接与附近的用户通信，而它需要专用中继与小区进行通信-边缘用户。对于全下行中继（FDR）技术，我们针对下行链路用户所经历的中断概率以及所考虑的CDRT网络的系统中断概率，得出了精确的封闭式表达式。此外，我们推导用户所达到的遍历率的近似封闭形式表达式。所有链路的信道都经历了Nakagami衰落分布，并且分析考虑了由于不完善的连续干扰消除（I-SIC）技术而产生的残留干扰。我们提供数值和仿真结果，以识别关键系统参数对用户的中断和遍历率性能以及系统中断性能的影响。与基于FDR的OMA（正交多址访问）-CDRT系统相比，在基于FDR的NOMA-CDRT系统中，用户的中断和遍历速率性能已得到显着改善。观察到，与远方用户相比，BS处随机选择NOMA功率分配系数会导致近方用户出现更高的中断。我们确定NOMA功率分配系数的数值结果，以使两个用户的断电性能均等。最后，我们在BS处获得了最佳功率分配（OPA）系数的解析表达式，该系数使系统中断的可能性最小。