The construction of preamble sequences for channel estimation by superposition of orthogonal pilots can improve performance of massive grant-free uplink from machine-type devices. In this letter, a technique is proposed to obtain full benefit from these "pilot mixtures" in presence of a base station with a massive number of antennas. The proposed technique consists of combining pilot mixtures with an intra-slot successive interference cancellation (SIC) algorithm, referred to as inner SIC, to increase the number of decoded messages per slot. In framed systems, the synergic effect of inner SIC and of an outer SIC algorithm across slots, typical of coded random access protocols, allows achieving a very high reliability with a low number of packet replicas per active user.

翻译：通过叠加正交导频构建的信道估计前导序列可提升海量免授权上行传输的性能。针对配备大规模天线阵列的基站场景，本文提出一种充分利用这些"导频混合信号"优势的技术方案。该技术将导频混合信号与称为内层SIC的时隙内连续干扰消除算法相结合，显著提升了每时隙解码消息数量。在分帧系统中，内层SIC与编码随机接入协议特有的跨时隙外层SIC算法产生协同效应，使得在每位活跃用户仅需少量数据包副本的情况下即可实现超高可靠性传输。