With the advent of 6G networks, offering ultra-high bandwidth and ultra-low latency, coupled with the enhancement of terminal device resolutions, holographic communication is gradually becoming a reality. Holographic digital twin (HDT) is considered one of key applications of holographic communication, capable of creating virtual replicas for real-time mapping and prediction of physical entity states, and performing three-dimensional reproduction of spatial information. In this context, integrated sensing and communication (ISAC) is expected to be a crucial pathway for providing data sources to HDT. This paper proposes a four-layer architecture assisted by ISAC for HDT, integrating emerging paradigms and key technologies to achieve low-cost, high-precision environmental data collection for constructing HDT. Specifically, to enhance sensing resolution, we explore super-resolution techniques from the perspectives of parameter estimation and point cloud construction. Additionally, we focus on multi-point collaborative sensing for constructing HDT, and provide a comprehensive review of four key techniques: node selection, multi-band collaboration, cooperative beamforming, and data fusion. Finally, we highlight several interesting research directions to guide and inspire future work.

翻译：随着6G网络提供超高带宽与超低时延，加之终端设备分辨率的提升，全息通信正逐步成为现实。全息数字孪生（HDT）被视为全息通信的关键应用之一，能够创建虚拟副本以实时映射和预测物理实体状态，并实现空间信息的三维复现。在此背景下，集成感知与通信（ISAC）有望成为向HDT提供数据源的重要途径。本文提出了一种ISAC辅助的四层HDT架构，通过融合新兴范式与关键技术，实现低成本、高精度的环境数据采集以构建HDT。具体而言，为提升感知分辨率，我们从参数估计与点云构建两个角度探讨了超分辨率技术。此外，我们聚焦于构建HDT的多点协同感知，并对节点选择、多频段协作、协同波束成形及数据融合四项关键技术进行了全面综述。最后，我们指出了若干具有前景的研究方向，以引导和启发未来的工作。