In next generation Internet-of-Things, the overhead introduced by grant-based multiple access protocols may engulf the access network as a consequence of the unprecedented number of connected devices. Grant-free access protocols are therefore gaining an increasing interest to support massive access from machine-type devices with intermittent activity. In this paper, coded random access (CRA) with massive multiple input multiple output (MIMO) is investigated as a solution to design highly-scalable massive multiple access protocols, taking into account stringent requirements on latency and reliability. With a focus on signal processing aspects at the physical layer and their impact on the overall system performance, critical issues of successive interference cancellation (SIC) over fading channels are first analyzed. Then, SIC algorithms and a scheduler are proposed that can overcome some of the limitations of the current access protocols. The effectiveness of the proposed processing algorithms is validated by Monte Carlo simulation, for different CRA protocols and by comparisons with developed benchmarks.

翻译：在下一代物联网中，因联网设备数量空前庞大，基于授权多址接入协议所产生的开销可能淹没接入网络。因此，无授权接入协议在支持间歇性活动的机器类设备的大规模接入方面日益受到关注。本文研究了将编码随机接入与大规模多输入多输出相结合的方案，以设计高可扩展性的大规模多址接入协议，同时兼顾严格的时延与可靠性要求。聚焦物理层的信号处理问题及其对系统整体性能的影响，首先分析了衰落信道中连续干扰消除的关键问题。随后提出了能够克服现有接入协议部分局限性的SIC算法与调度器。通过蒙特卡洛仿真，针对不同CRA协议并与已有基准方法进行对比，验证了所提处理算法的有效性。