基于直传和全双工中继的CR-NOMA系统中断性能分析及功率分配研究

非正交多址接入(NOMA)是5G网络的关键候选技术之一，与认知无线电(CR)技术相结合形成的CR-NOMA系统，能够实现更高的频谱效率、更大的吞吐量和更低的传输延迟。本文将协调直传和中继传输(CDRT)技术引入CR-NOMA系统，其中CDRT表示次级源(SS)直接与近端用户通信，而仅通过中继与远端用户通信。在非理想串行干扰消除(SIC)和全双工(FD)中继情况下，推导了NOMA用户中断概率(OP)的精确闭式表达，并获得了在干扰温度限制(ITC)或者SS发射功率趋近于无穷时，用户OP的渐近表达式。此外，基于用户公平性和OP性能，提出用户功率分配因子优化算法。蒙特卡洛仿真验证了理论分析与实验结果的一致性。经过所提算法优化后，用户之间的公平性增加，系统总速率明显增大。

Outage Performance Analysis and Power Allocation Research of CR-NOMA System on Coordinated Direct and FD Relay Transmission

Non-orthogonal multiple access (NOMA) is one of the key candidate technologies of 5G network. The CR-NOMA system formed by the combination of cognitive radio (CR) technology can achieve higher spectrum efficiency, greater throughput and lower transmission delay. In this paper, coordinated direct and relay transmission (CDRT) technology is introduced into CR-NOMA system, where CDRT means that the secondary source (SS) communicates directly with near user and only with far user through relay. In the case of non-ideal successive interference cancellation (SIC) and full-duplex (FD) relay, the exact closed expression of NOMA user outage probability (OP) is derived, and the approximate expression of user OP is obtained when the ITC or the transmission power of the SS approaches infinity. In addition, based on user fairness and OP performance, a user power allocation factor optimization algorithm is proposed. Monte Carlo simulation verifies the consistency between theoretical analysis and experimental results. After the optimization of the proposed algorithm, compared with the fixed power allocation scheme, the fairness of user OP performance is enhanced and the system rate is significantly increased.