Non-orthogonal multiple access (NOMA) is an emerging technology for massive connectivity in machine-type communications (MTC). In code-domain NOMA, non-orthogonal spreading sequences are uniquely assigned to all devices, where active ones attempt a grant-free access to a system. In this paper, we study a set of user-specific, non-orthogonal, binary spreading sequences for uplink grant-free NOMA. Based on Golay complementary sequences, each spreading sequence provides the peak-to-average power ratio (PAPR) of at most 3 dB for multicarrier transmission. Exploiting the theoretical connection to Reed-Muller codes, we conduct a probabilistic analysis to search for a permutation set for Golay sequences, which presents theoretically bounded low coherence for the spreading matrix. Simulation results confirm that the PAPR of transmitted multicarrier signals via the spreading sequences is significantly lower than those for random bipolar, Gaussian, and Zadoff-Chu (ZC) sequences. Also, thanks to the low coherence, the performance of compressed sensing (CS) based joint channel estimation (CE) and multiuser detection (MUD) using the spreading sequences turns out to be superior or comparable to those for the other ones. Unlike ZC sequences, the binary Golay spreading sequences have only two phases regardless of the sequence length, which can be suitable for low cost MTC devices.

中文翻译：

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用于上行链路无授权 NOMA 的二进制 Golay 扩展序列和 Reed-Muller 码

非正交多路访问 (NOMA) 是一种用于机器类通信 (MTC) 中大规模连接的新兴技术。在码域 NOMA 中，非正交扩展序列被唯一分配给所有设备，其中活动设备尝试对系统进行无授权访问。在本文中，我们研究了一组用户特定的、非正交的、二进制扩展序列，用于上行链路无授权 NOMA。基于 Golay 互补序列，每个扩频序列为多载波传输提供最多 3 dB 的峰均功率比 (PAPR)。利用与 Reed-Muller 码的理论联系，我们进行了概率分析以搜索 Golay 序列的置换集，该置换集在理论上呈现出扩展矩阵的有界低相干性。仿真结果证实，通过扩频序列传输的多载波信号的 PAPR 明显低于随机双极、高斯和 Zadoff-Chu (ZC) 序列的 PAPR。此外，由于低相干性，使用扩频序列的基于压缩感知 (CS) 的联合信道估计 (CE) 和多用户检测 (MUD) 的性能证明优于或可与其他序列相媲美。与ZC序列不同，二进制Golay扩频序列与序列长度无关，只有两个相位，可以适用于低成本的MTC设备。使用扩频序列的基于压缩感知 (CS) 的联合信道估计 (CE) 和多用户检测 (MUD) 的性能结果证明优于或可与其他的性能相媲美。与ZC序列不同，二进制Golay扩频序列与序列长度无关，只有两个相位，可以适用于低成本的MTC设备。使用扩频序列的基于压缩感知 (CS) 的联合信道估计 (CE) 和多用户检测 (MUD) 的性能结果证明优于或可与其他的性能相媲美。与ZC序列不同，二进制Golay扩频序列与序列长度无关，只有两个相位，可以适用于低成本的MTC设备。