The use of massive multiple-input multiple-output (MIMO) to serve a crowd of user equipments (UEs) is challenged by the deficit of pilots. Assuming that the UEs are intermittently active, this problem can be addressed by a shared access to the pilots and a suitable random access (RA) protocol. The strongest-user collision resolution (SUCRe) is a previously proposed RA protocol that often privileges the UEs closer to the base station (BS). In contrast, we propose a novel RA protocol using a decentralized pilot power allocation method that aims at a fairer performance. The proposed access class barring with power control (ACBPC) protocol allows each UE to estimate, without additional overhead, how many UEs collided for the chosen pilot and calculate an ACB factor, which is then used to determine the pilot retransmission probability in the next protocol step. The results show that the proposed ACBPC protocol is superior to SUCRe in terms of providing a fair connectivity for very crowded networks, although still being distributed and uncoordinated as the original SUCRe protocol.

中文翻译：

---

在大规模 MIMO 拥挤的机器类型网络中实现公平的随机访问性能

使用大规模多输入多输出 (MIMO) 为大量用户设备 (UE) 提供服务受到导频不足的挑战。假设 UE 间歇性地处于活动状态，这个问题可以通过对导频的共享访问和合适的随机访问 (RA) 协议来解决。最强用户冲突解决 (SUCRe) 是先前提出的 RA 协议，该协议通常为靠近基站 (BS) 的 UE 提供特权。相比之下，我们提出了一种使用分散式导频功率分配方法的新型 RA 协议，旨在获得更公平的性能。提议的接入类禁止功率控制 (ACBPC) 协议允许每个 UE 在没有额外开销的情况下估计有多少 UE 为所选导频发生冲突并计算 ACB 因子，然后用于确定下一个协议步骤中的导频重传概率。结果表明，所提出的 ACBPC 协议在为非常拥挤的网络提供公平连接方面优于 SUCRe，尽管仍然像原始 SUCRe 协议那样是分布式和不协调的。