Extended reality (XR) is a key innovation of 5G-advanced and beyond networks. The diverse XR use-cases, including virtual reality, augmented reality, and mixed reality, transform the way humans interact with surrounding environments. Thus, XR technology enables true immersive experiences of novel services spanning, e.g., e-commerce, healthcare, and education, respectively. However, the efficient support of XR services over existing and future cellular systems is highly challenging and requires multiple radio design improvements, due to the unique XR traffic and performance characteristics. Thus, this article surveys the state-of-art 3GPP standardization activities (release-18) for integrating the XR service class into the 5G-advanced specifications, highlighting the major XR performance challenges. Furthermore, the paper introduces valuable insights and research directions for supporting true XR services over the next-generation 6G networks, where multiple novel radio design mindsets and protocol enhancements are proposed and evaluated using extensive system level simulations, including solutions for application-native dynamic performance reporting, traffic-dependent control channel design, collaborative device aggregation for XR capacity boosting and offload, respectively.

翻译：扩展现实（XR）是5G-Advanced及未来网络的关键创新。涵盖虚拟现实、增强现实和混合现实等多种XR用例，正在改变人类与周围环境的交互方式。因此，XR技术能够实现跨越电子商务、医疗保健和教育等领域的全新沉浸式服务体验。然而，由于XR业务流量与性能特性的独特性，在现有及未来蜂窝系统上高效支持XR服务面临巨大挑战，需要多项无线设计改进。本文综述了3GPP在将XR服务类别集成至5G-Advanced规范中的最新标准化活动（Release-18），重点分析了XR性能的主要挑战。此外，本文提出了在下一代6G网络中支持真正XR服务的宝贵见解与研究方向，设计并评估了多种新型无线设计思路与协议增强方案，包括面向应用原生的动态性能报告、业务流量相关的控制信道设计、用于XR容量增强与负载分流的协作设备聚合等解决方案，并通过大规模系统级仿真进行了验证。