Integrated Sensing and Communications Over the Years: An Evolution Perspective

TL;DR

Integrated Sensing and Communications (ISAC) addresses spectrum efficiency and hardware cost by co-designing sensing and communication. The paper presents a multi-dimensional evolution—from RF to optical ISAC, single-cell to multi-cell architectures, and single- to multi-modal sensing with edge intelligence—highlighting architectural choices, waveform design, and cross-domain coordination. It synthesizes security/privacy concerns and standardization progress across 3GPP, IEEE, and ITU to outline a practical roadmap toward 6G ISAC deployments. The work emphasizes unified co-design frameworks, AI-enabled edge perception, and task-oriented ISAC as key directions for scalable, deployment-ready systems. Overall, the survey provides a cohesive narrative linking spectrum expansion, network scale, sensing modalities, security, and standardization to guide future ISAC research and standards.

Abstract

Integrated Sensing and Communications (ISAC) enables efficient spectrum utilization and reduces hardware costs for beyond 5G (B5G) and 6G networks, facilitating intelligent applications that require both high-performance communication and precise sensing capabilities. This survey provides a comprehensive review of the evolution of ISAC over the years. We examine the expansion of the spectrum across RF and optical ISAC, highlighting the role of advanced technologies, along with key challenges and synergies. We further discuss the advancements in network architecture from single-cell to multi-cell systems, emphasizing the integration of collaborative sensing and interference mitigation strategies. Moreover, we analyze the progress from single-modal to multi-modal sensing, with a focus on the integration of edge intelligence to enable real-time data processing, reduce latency, and enhance decision-making. Finally, we extensively review standardization efforts by 3GPP, IEEE, and ITU, examining the transition of ISAC-related technologies and their implications for the deployment of 6G networks.

Figures (14)

• Figure 1: Structure of the Survey
• Figure 2: Optical ISAC is categorized into VLC, FSO, and Photonic Sensing
• Figure 3: The figure illustrates orthogonal resource allocation in ISAC. In the time division section, a 10-ms radio frame allocates subframes for V2V/V2I communication and sensing. The frequency division section depicts uplink ISAC, where the UE transmits joint S&C signals to the BS, optimized for sensing. In the spatial division section, ISAC beamforming with sidelobe control in a 10-antenna MIMO radar serves a UE at $-50^\circ$, maintaining a wide radar beam. Sidelobe levels fluctuate between $-40$ dB and $-20$ dB in the UE's direction. The code division section employs three-dimensional complementary coded scrambling to mitigate fading and interference, enhancing radar performance and data rates in multi-user environments.
• Figure 4: Topologies of single-cell networks, including collaboration between BS and UEs, and BS collaboration with target monitoring terminals.
• Figure 5: Topologies of multi-cell Network, illustrating: collaboration of RRUs in C-RAN, coordination among multiple BSs for joint monostatic and bistatic sensing, integration of monostatic and bistatic sensing at a single BS, and cooperation between macro and micro BSs.