This paper proposes a unified semi-blind detection framework for sourced and unsourced random access (RA), which enables next-generation ultra-reliable low-latency communications (URLLC) with massive devices. Specifically, the active devices transmit their uplink access signals in a grant-free manner to realize ultra-low access latency. Meanwhile, the base station aims to achieve ultra-reliable data detection under severe inter-device interference without exploiting explicit channel state information (CSI). We first propose an efficient transmitter design, where a small amount of reference information (RI) is embedded in the access signal to resolve the inherent ambiguities incurred by the unknown CSI. At the receiver, we further develop a successive interference cancellation-based semi-blind detection scheme, where a bilinear generalized approximate message passing algorithm is utilized for joint channel and signal estimation (JCSE), while the embedded RI is exploited for ambiguity elimination. Particularly, a rank selection approach and a RI-aided initialization strategy are incorporated to reduce the algorithmic computational complexity and to enhance the JCSE reliability, respectively. Besides, four enabling techniques are integrated to satisfy the stringent latency and reliability requirements of massive URLLC. Numerical results demonstrate that the proposed semi-blind detection framework offers a better scalability-latency-reliability tradeoff than the state-of-the-art detection schemes dedicated to sourced or unsourced RA.

翻译：本文提出了一种面向有源随机接入（RA）和无源随机接入的统一半盲检测框架，能够支持海量设备下的下一代超可靠低延迟通信（URLLC）。具体而言，活跃设备以无授权方式传输上行接入信号，以实现超低接入延迟。同时，基站在无需显式信道状态信息（CSI）的条件下，旨在强干扰环境中实现超可靠数据检测。我们首先设计了一种高效的发射机方案，在接入信号中嵌入少量参考信息（RI）以解决未知CSI带来的固有模糊性。在接收端，我们进一步开发了一种基于连续干扰消除的半盲检测方案，其中采用双线性广义近似消息传递算法进行联合信道与信号估计（JCSE），并利用嵌入的RI消除模糊性。特别地，引入秩选择方法和RI辅助初始化策略，分别降低算法计算复杂度和提升JCSE可靠性。此外，集成四项使能技术以满足大规模URLLC对延迟和可靠性的严苛要求。数值结果表明，与专用于有源或无源随机接入的现有检测方案相比，所提出的半盲检测框架在可扩展性-延迟-可靠性折衷方面具有更优性能。