To efficiently utilize the scarce wireless resource, the random access scheme has been attaining renewed interest primarily in supporting the sporadic traffic of a large number of devices encountered in the Internet of Things (IoT). In this paper we investigate the performance of slotted ALOHA -- a simple and practical random access scheme -- in connection with the grant-free random access protocol applied for user-centric cell-free massive MIMO. More specifically, we provide the expression of the sum-throughput under the assumptions of the capture capability owned by the centralized detector in the uplink. Further, a comparative study of user-centric cell-free massive MIMO with other types of networks is provided, which allows us to identify its potential and possible limitation. Our numerical simulations show that the user-centric cell-free massive MIMO has a good trade-off between performance and fronthaul load, especially at low activation probability regime.

翻译：为高效利用稀缺的无线资源，随机接入方案近年来重新获得广泛关注，主要因其适用于物联网（IoT）中大量设备产生的突发性业务流量。本文研究了时隙ALOHA——一种简单实用的随机接入方案——在结合免授权随机接入协议应用于用户中心型无蜂窝大规模MIMO时的性能表现。具体而言，我们在假设上行链路集中式检测器具备捕获能力的前提下，推导了系统总吞吐量的解析表达式。此外，本文还通过与其他类型网络架构的对比研究，揭示了该架构的潜在优势与可能存在的局限性。数值仿真结果表明，用户中心型无蜂窝大规模MIMO在性能与前传负载之间取得了良好平衡，尤其在低激活概率场景下表现突出。