The performance of grant-free random access (GF-RA) is limited by the number of accessible random access resources (RRs) due to the absence of collision resolution. Compressive sensing (CS)-based RA schemes scale up the RRs at the expense of increased non-orthogonality among transmitted signals. This paper presents the design of multi-sequence spreading random access (MSRA) which employs multiple spreading sequences to spread the different symbols of a user as opposed to the conventional schemes in which a user employs the same spreading sequence for each symbol. We show that MSRA provides code diversity, enabling the multi-user detection (MUD) to be modeled into a well-conditioned multiple measurement vectors (MMVs) CS problem. The code diversity is quantified by the decrease in the average Babel mutual coherence among the spreading sequences. Moreover, we present a two-stage active user detection (AUD) scheme for both wideband and narrowband implementations. Our theoretical analysis shows that with MSRA activity misdetection falls exponentially while the size of GF-RA frame is increased. Finally, the simulation results show that about 82% increase in utilization of RRs, i.e., more active users, is supported by MSRA than the conventional schemes while achieving the RA failure rate lower bound set by random access collision.

中文翻译：

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用于基于压缩感知的无授权通信的多序列扩展随机接入 (MSRA)


由于缺乏冲突解决，无授权随机接入 (GF-RA) 的性能受到可访问随机接入资源 (RR) 数量的限制。基于压缩感知 (CS) 的 RA 方案扩大了 RR，但代价是传输信号之间的非正交性增加。本文提出了多序列扩频随机接入（MSRA）的设计，它采用多个扩频序列来扩频用户的不同符号，而不是用户对每个符号采用相同扩频序列的传统方案。我们证明 MSRA 提供了代码多样性，使多用户检测 (MUD) 能够建模为条件良好的多测量向量 (MMV) CS 问题。码分集通过扩频序列之间的平均 Babel 互相关性的降低来量化。此外，我们提出了一种适用于宽带和窄带实现的两阶段活动用户检测（AUD）方案。我们的理论分析表明，随着 MSRA 活性的增加，误检率呈指数下降，而 GF-RA 框架的大小则增加。最后，仿真结果表明，在实现随机接入冲突设定的RA失败率下限的同时，MSRA比传统方案支持约82%的RR利用率增加，即更多的活跃用户。