We consider unsourced random access with MIMO receiver - a crucial communication scenario for future 5G/6G wireless networks. We perform a projection-based decoder analysis and derive energy efficiency achievability bounds when channel state information is unknown at transmitters and the receiver (no-CSI scenario). The comparison to the maximum-likelihood (ML) achievability bounds by Gao et al. (2023) is performed. We show that there is a region where the new bound outperforms the ML bound. The latter fact should not surprise the reader as both decoding criteria are suboptimal when considering per-user probability of error (PUPE). Moreover, transition to projection decoding allows for significant dimensionality reduction, which greatly reduces the computation time.

翻译：本文研究了面向未来5G/6G无线网络关键通信场景的MIMO接收机无源随机接入问题。我们通过投影解码器分析，推导了发射端与接收端均未知信道状态信息（无CSI场景）时的能效可达性界限。与Gao等人（2023）提出的最大似然（ML）可达性界限进行了对比，结果表明新界限在特定范围内优于ML界限。该现象不应使读者感到意外，因为就每用户错误概率（PUPE）而言，两种解码准则均非最优。此外，采用投影解码可显著降低维度，从而大幅减少计算时间。