Dong Zheng, Chen He, Zhang Jian-Kang
School of Information Science and Engineering, Shandong University, Qingdao 266237, China.
Department of Information Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
Entropy (Basel). 2023 Sep 12;25(9):1325. doi: 10.3390/e25091325.
This paper develops and optimizes a non-orthogonal and noncoherent multi-user massive single-input multiple-output (SIMO) framework, with the objective of enabling scalable ultra-reliable low-latency communications (sURLLC) in Beyond-5G (B5G)/6G wireless communication systems. In this framework, the huge diversity gain associated with the large-scale antenna array in the massive SIMO system is leveraged to ensure ultra-high reliability. To reduce the overhead and latency induced by the channel estimation process, we advocate for the noncoherent communication technique, which does not need the knowledge of instantaneous channel state information (CSI) but only relies on large-scale fading coefficients for message decoding. To boost the scalability of noncoherent massive SIMO systems, we enable the non-orthogonal channel access of multiple users by devising a new differential modulation scheme to ensure that each transmitted signal matrix can be uniquely determined in the noise-free case and be reliably estimated in noisy cases when the antenna array size is scaled up. The key idea is to make the transmitted signals from multiple geographically separated users be superimposed properly over the air, such that when the sum signal is correctly detected, the signal sent by each individual user can be uniquely determined. To further enhance the average error performance when the array antenna number is large, we propose a max-min Kullback-Leibler (KL) divergence-based design by jointly optimizing the transmitted powers of all users and the sub-constellation assignments among them. The simulation results show that the proposed design significantly outperforms the existing max-min Euclidean distance-based counterpart in terms of error performance. Moreover, our proposed approach also has a better error performance compared to the conventional coherent zero-forcing (ZF) receiver with orthogonal channel training, particularly for cell-edge users.
本文开发并优化了一种非正交、非相干的多用户大规模单输入多输出（SIMO）框架，目标是在超5G（B5G）/6G无线通信系统中实现可扩展的超可靠低延迟通信（sURLLC）。在此框架中，利用大规模SIMO系统中与大规模天线阵列相关的巨大分集增益来确保超高可靠性。为了减少信道估计过程引起的开销和延迟，我们提倡采用非相干通信技术，该技术不需要瞬时信道状态信息（CSI），而是仅依赖大规模衰落系数进行消息解码。为了提高非相干大规模SIMO系统的可扩展性，我们通过设计一种新的差分调制方案来实现多用户的非正交信道接入，以确保每个发射信号矩阵在无噪声情况下能够唯一确定，并且当天线阵列规模扩大时在有噪声情况下能够可靠估计。关键思想是使来自多个地理上分离用户的发射信号在空中适当叠加，这样当正确检测到和信号时，每个用户发送的信号就能唯一确定。为了在阵列天线数量较大时进一步提高平均误码性能，我们通过联合优化所有用户的发射功率以及它们之间的子星座分配，提出了一种基于最大最小库尔贝克-莱布勒（KL）散度的设计。仿真结果表明，所提出的设计在误码性能方面显著优于现有的基于最大最小欧几里得距离的对应设计。此外，与具有正交信道训练的传统相干迫零（ZF）接收机相比，我们提出的方法也具有更好的误码性能，特别是对于小区边缘用户。
