We consider multiple-input multiple output (MIMO) non-orthogonal multiple access (NOMA) downlink channels with zeroforcing beamforming transmission. The base station has multiple transmit antennas while all mobile devices have single receive antenna. With a limited feedback rate, channel direction information (CDI) needs to be quantized and fed back from mobile users to a base station. Thus, the accuracy of the quantized channel state information at the transmitter (CSIT) will depend on the feedback rate. To increase spectral efficiency, 2 active users in some clusters share the same beamforming vector and thus, will interfere fully with each other. Given a total-feedback rate, we analyze the feedback allocation for clusters with single active user and 2 active users. The objective is to either minimize the maximum outage probability or maximize the minimum rate among all active users in a cell. We show that the proposed feedback allocation is close to the optimum. Some numerical examples show that the resulting rate performance with the proposed feedback allocation is increased by 100% over that with the uniform feedback allocation.

中文翻译：

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量化CSIT优化下行MIMO-NOMA反馈速率分配


我们考虑采用迫零波束成形传输的多输入多输出 (MIMO) 非正交多址 (NOMA) 下行链路信道。基站具有多个发射天线，而所有移动设备都具有单个接收天线。在反馈速率有限的情况下，需要量化信道方向信息(CDI)并将其从移动用户反馈到基站。因此，发射机处的量化信道状态信息（CSIT）的准确性将取决于反馈速率。为了提高频谱效率，某些集群中的 2 个活动用户共享相同的波束成形矢量，因此将相互完全干扰。给定总反馈率，我们分析具有单个活跃用户和 2 个活跃用户的集群的反馈分配。目标是最小化最大中断概率或最大化小区中所有活动用户的最小速率。我们表明所提出的反馈分配接近最优。一些数值示例表明，与统一反馈分配相比，所建议的反馈分配所产生的速率性能提高了 100%。