Massive grant-free multiple-access is a valuable research topic for next generation multiple-access, since it significantly reduces the control signaling overhead and transmission latency. This paper constructs a novel uniquely-decodable multi-amplitude sequence (UDAS) set for grant-free multiple-access systems, which can provide high spectrum efficiency (SE) without additional redundancy and realize low-complexity active user detection (AUD). We firstly propose an UDAS-based multi-dimensional bit interleaving coded modulation (MD-BICM) transmitter. Then, this paper presents the detailed definition of UDAS, and provides three conditions for constructing a UDAS set. Following, two kinds of UDAS sets are constructed based on cyclic and quasi-cyclic matrix modes; and some important features of the cyclic/quasi-cyclic UDAS sets are deduced. Besides, we present a statistic of UDAS feature based AUD algorithm (SoF-AUD), and a joint multiuser detection and improved message passing iterative decoding algorithm for the proposed system. Finally, the active user error rate (AUER) and Shannon limits of the proposed system are deduced in details. Simulation results show that the AUER of our proposed system can reach an extremely low value $10^{-5}$, when $E_b/N_0$ is 0 dB and the length of transmit block is larger than a given value (e.g., 784). Meanwhile, the SE of our proposed system can compare with the designed non-orthogonal multiple-access (NOMA) codebooks, verifying the valid and flexible.

翻译：大规模免费赠与多重存取是下一代多重存取的宝贵研究课题,因为它大大降低了UDAS的详细定义,并为构建一个多式存取系统提供了三种条件。随后,根据周期性和准周期性基建了两种UDAS套件,这些套件可以提供高频效率(SE),而无需额外冗余,并实现低复合性UDAS主动用户检测(AUD)系统。此外,我们首先提出了基于UDAS的多维多维分分调调制(MD-BICM)发送器。然后,本文介绍了UDAS的详细定义,并为构建多式存取系统提供了三个条件。随后,两种UDAS套以循环和准周期性存取模式为基础,可以提供高频(SEAUA)系统基于UAUDUD(So-AUD) 有效调试算法(SOF-AUDM) 以及一个联合多用户检测和改进的信息,通过ODUDO值的迭代代换解算法(UAAUA) 和拟议的低式解算算法(SAL-delal-L_SUAUDER) 的预算算算法(SLisl-Lisl) 和低值是我们提议的系统(AUDER-Lisl-Lisl-L) 的系统(AUDR) 的预算算算算算算算算算法的低值。