This letter presents a group-based data transmission protocol for small-sized ultra-reliable and low latency communication (URLLC) services. For the users within the same group, the semi-persistent scheduling (SPS) and grant-free based scheduling schemes are adopted for their initial transmission and retransmission to reduce signaling overhead consumption, respectively. We further investigate the optimal number of consecutive slots within one group and derive a closed-form optimal configuration to maximize the utilization of retransmission resources. Results show that the proposed protocol can significantly reduce the control signaling while guaranteeing the stringent latency and reliability requirements.

中文翻译：

---

面向小型URLLC服务的基于组的数据传输协议

这封信提出了一种用于小型超可靠低延迟通信 (URLLC) 服务的基于组的数据传输协议。对于同一组内的用户，其初传和重传分别采用半持久调度（SPS）和基于无授权的调度方案，以减少信令开销消耗。我们进一步研究了一组内连续时隙的最佳数量，并推导出一种封闭形式的最佳配置，以最大限度地利用重传资源。结果表明，所提出的协议可以显着减少控制信令，同时保证严格的延迟和可靠性要求。