Opportunistic beamforming (OBF) is an attractive research topic in wireless communications, which can provide multi-user diversity with a low complexity. The conventional OBF technique requires a large number of waiting users, and cannot simultaneously support multiple users. In order to solve the mentioned problem, this paper proposes a downlink multi-user multi-weight opportunistic beamforming non-orthogonal multiple access (MW-OBF-NOMA) system. An objective function is formulated to maximize the sum spectrum efficiency (SE) of the proposed system, however, it is a non-convex issue and intractable to derive an optimal solution. To solve this non-convex issue, we divide it into two sub-optimal issues and solve them one-by-one. Based on the solutions of the two sub-optimal issues, a joint iterative resource allocation algorithm is presented. Moreover, we discuss the influences of signal-to-noise ratio (SNR) estimation, and deduce a closed-form expression of bit error ratio (BER). Numerical results show that our proposed system can simultaneously serve multiple users without extra resources, and achieve an improved sum SE with a low complexity.

中文翻译：

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非正交多用户多权重机会波束成形系统的联合迭代优化资源分配算法

机会波束成形（OBF）是无线通信中一个有吸引力的研究课题，它可以提供低复杂度的多用户分集。传统的OBF技术需要大量等待用户，无法同时支持多个用户。为了解决上述问题，本文提出了一种下行多用户多权重机会波束成形非正交多址（MW-OBF-NOMA）系统。制定了一个目标函数来最大化所提出系统的总频谱效率 (SE)，但是，这是一个非凸问题，并且难以推导出最佳解决方案。为了解决这个非凸问题，我们把它分成两个次优问题，一一解决。基于两个次优问题的解，提出了一种联合迭代资源分配算法。此外，我们讨论了信噪比 (SNR) 估计的影响，并推导出了误码率 (BER) 的封闭式表达式。数值结果表明，我们提出的系统可以在没有额外资源的情况下同时为多个用户提供服务，并以低复杂度实现改进的和 SE。