Irregular repetition slotted aloha (IRSA) is a massive random access protocol which can be used to serve a large number of users while achieving a packet loss rate (PLR) close to zero. However, if the number of users is too high, then the system is interference limited and the PLR is close to one. In this paper, we propose a variant of IRSA in the interference limited regime, namely Censored-IRSA (C-IRSA), wherein users with poor channel states censor themselves from transmitting their packets. We theoretically analyze the throughput performance of C-IRSA via density evolution. Using this, we derive closed-form expressions for the optimal choice of the censor threshold which maximizes the throughput while achieving zero PLR among uncensored users. Through extensive numerical simulations, we show that C-IRSA can achieve a 4$\times$ improvement in the peak throughput compared to conventional IRSA.

翻译：非规则重复时隙ALOHA（IRSA）是一种大规模随机接入协议，可在达到近乎零丢包率（PLR）的同时服务大量用户。然而，当用户数量过多时，系统将受限于干扰，丢包率趋近于1。本文提出一种适用于干扰受限场景的IRSA变体——审查式IRSA（C-IRSA），其核心机制是信道状态较差的用户主动审查自身，避免发送数据包。我们通过密度演化理论分析了C-IRSA的吞吐性能，并推导出审查阈值最优选取的闭式表达式，该阈值可在未审查用户间实现零丢包率的同时最大化系统吞吐量。大量数值仿真表明，与传统IRSA相比，C-IRSA在峰值吞吐量方面可实现4倍的提升。