The growing interest in new applications involving co-located heterogeneous requirements, such as the Industrial Internet of Things (IIoT) paradigm, poses unprecedented challenges to the uplink wireless transmissions. Dedicated scheduling has been the fundamental approach used by mobile radio systems for uplink transmissions, where the network assigns contention-free resources to users based on buffer-related information. The usage of contention-based transmissions was discussed by the 3rd Generation Partnership Project (3GPP) as an alternative approach for reducing the uplink latency characterizing dedicated scheduling. Nevertheless, the contention-based approach was not considered for standardization in LTE due to limited performance gains. However, 5G NR introduced a different radio frame which could change the performance achievable with a contention-based framework, although this has not yet been evaluated. This paper aims to fill this gap. We present a contention-based design introduced for uplink transmissions in a 5G NR IIoT scenario. We provide an up-to-date analysis via near-product 3GPP-compliant network simulations of the achievable application-level performance with simultaneous Ultra-Reliable Low Latency Communications (URLLC) and Federated Learning (FL) traffic, where the contention-based scheme is applied to the FL traffic. The investigation also involves two separate mechanisms for handling retransmissions of lost or collided transmissions. Numerical results show that, under some conditions, the proposed contention-based design provides benefits over dedicated scheduling when considering FL upload/download times, and does not significantly degrade the performance of URLLC.

翻译：随着工业物联网等涉及共址异构需求的新应用日益受到关注，上行无线传输面临前所未有的挑战。专用调度一直是移动无线电系统用于上行传输的基本方法，网络根据缓冲相关信息为用户分配无竞争资源。第三代合作伙伴项目讨论了使用竞争性传输作为替代方案，以减少专用调度所带来的上行延迟。然而，由于性能提升有限，竞争性方法未在LTE标准化中被考虑。但5G NR引入了不同的无线帧结构，可能改变竞争性框架可实现的性能，尽管这一点尚未得到评估。本文旨在填补这一空白。我们提出了一种针对5G NR工业物联网场景中上行传输的竞争性设计方案。通过符合3GPP近产品级的网络仿真，提供了同时承载超可靠低延迟通信与联邦学习流量时的应用层性能最新分析，其中竞争性方案应用于联邦学习流量。研究还涉及两种处理丢失或冲突传输重传的独立机制。数值结果表明，在某些条件下，当考虑联邦学习上传/下载时间时，所提出的竞争性设计方案相比专用调度具有优势，且不会显著降低超可靠低延迟通信的性能。