This paper considers a cognitive radio inspired uplink communication scenario, where one primary user is allocated with one dedicated resource block, while $M$ secondary users compete with each other to opportunistically access the primary user's channel. Two new designs of NOMA schemes, namely hybrid successive interference cancellation with power adaptation (HSIC-PA) and fixed successive interference cancellation with power adaptation (FSIC-PA), are proposed. The significant advantages of the proposed schemes are two folds. First, the proposed two schemes can ensure that the secondary users are opportunistically served without degrading the transmission reliability of the primary user. Besides, the transmission robustness of the served secondary users can be guaranteed. Specifically, the outage probability error floors can be avoided for the secondary users, which is proved by asymptotic analysis in the paper. Extensive simulation results are also provided to demonstrate the superior performance of the proposed schemes.

翻译：本文考虑一种认知无线电启发的上行通信场景，其中主用户被分配一个专用资源块，而$M$个次用户相互竞争，以机会方式接入主用户的信道。提出了两种新的NOMA方案设计，即混合逐次干扰消除与功率自适应（HSIC-PA）以及固定逐次干扰消除与功率自适应（FSIC-PA）。所提方案的显著优势体现在两个方面。首先，这两种方案能够确保在不降低主用户传输可靠性的前提下，机会性地服务次用户。此外，被服务的次用户的传输鲁棒性也能得到保证。具体而言，次用户的中断概率错误平层可以被避免，本文通过渐近分析证明了这一点。大量仿真结果也展示了所提方案的优越性能。