Integration of Communication and Sensing in 6G: a Joint Industrial and Academic Perspective (2106.13023v1)

Abstract: 6G will likely be the first generation of mobile communication that will feature tight integration of localization and sensing with communication functionalities. Among several worldwide initiatives, the Hexa-X flagship project stands out as it brings together 25 key players from adjacent industries and academia, and has among its explicit goals to research fundamentally new radio access technologies and high-resolution localization and sensing. Such features will not only enable novel use cases requiring extreme localization performance, but also provide a means to support and improve communication functionalities. This paper provides an overview of the Hexa-X vision alongside the envisioned use cases. To close the required performance gap of these use cases with respect to 5G, several technical enablers will be discussed, together with the associated research challenges for the coming years.

• The paper presents a unified framework that integrates communication, sensing, and localization as fundamental 6G capabilities through the Hexa-X initiative.
• It employs advanced frequency bands, joint communication and sensing strategies, and reconfigurable intelligent surfaces to achieve sub-centimeter accuracy and near-instantaneous feedback.
• The study identifies challenges like hardware limitations and signal distortions, emphasizing the need for robust, AI-enhanced algorithms for future 6G deployments.

Integration of Communication and Sensing in 6G: Technical Insights and Future Directions

The advancement towards the sixth generation (6G) of wireless communication underscores a critical transition: the seamless integration of communication, localization, and sensing functionalities. This paper, centered around the Hexa-X initiative, provides an exhaustive perspective on the potential integration of these functionalities, the technical enablers required, and the challenges anticipated in the development and deployment of 6G systems.

Overview

The Hexa-X project, a collaboration between academia and industry, aims to define and realize the vision for 6G networks. A distinguishing feature of 6G is the planned integration of high-resolution localization and sensing within conventional communication networks. Unlike 5G, which considered localization as an auxiliary service layered upon communication, 6G envisions these components as fundamental and integrated from inception. This integration targets use cases demanding extreme performance metrics, such as sub-centimeter accuracy in localization and near-instantaneous sensing and communication feedback.

Key Use Cases

Hexa-X outlines five primary categories for potential 6G use cases: massive twinning, immersive telepresence, cooperative robots (cobots), local trust zones, and smart trust zones in cities. Each of these areas presents unique and stringent requirements for precision, latency, reliability, and availability. For instance, in the domain of massive twinning, 6G would enable real-time digital twins for smart cities and manufacturing that incorporate real-time positional data, demanding high granularity and accuracy.

Technical Enablers

1. Advanced Frequency Utilization: The extension to higher frequency bands, particularly the upper millimeter-wave (mmWave) and terahertz (THz) ranges, will provide the bandwidth necessary for high-resolution sensing and localization. These bands facilitate finely-tuned directional communications and enhance data rates, essential for real-time, data-intensive applications like augmented reality and autonomous navigation.
2. Joint Communication and Sensing (JCS): The concept of JCS transcends basic JRC functionalities by embedding radar, communication, and sensing capabilities into a unified system architecture. It utilizes shared hardware and waveforms to support tasks such as simultaneous localization and mapping (SLAM), relying on dynamic spectrum sharing to maximize spectrum efficiency and ensure fidelity.
3. Reconfigurable Intelligent Surfaces (RIS): RIS can dynamically alter their reflective properties, channeling radio waves to enhance signal reception and facilitate advanced sensing capabilities. This technology offers potential solutions to non-line-of-sight (NLoS) scenarios, significantly boosting both communication quality and localization accuracy.
4. Algorithmic Enhancements: The development of sophisticated algorithms leveraging AI will be critical. These algorithms will need to manage the intricate interplay between communication, localization, and sensing data across diverse environments. AI-driven approaches can compensate for hardware imperfections and adapt to rapidly changing environmental conditions.

Challenges

Several challenges loom in the path toward these envisioned advancements. Notably, hardware limitations, especially at higher frequencies, introduce significant obstacles. For example, phase noise and nonlinearities can compromise the accuracy of Doppler and angular measurements. Moreover, the characteristics of radio propagation at THz frequencies, such as penetration ability and multipath resolution, must be thoroughly understood and accurately modeled to enable effective deployment.

Implications for Future Research

The findings in this paper highlight the need for a holistic approach to 6G development where communication, sensing, and localization are designed in tandem from the system's inception. Addressing the research challenges identified, such as improving the robustness of algorithms against hardware faults and advancing RIS technology, will be pivotal.

In conclusion, the paper outlines a comprehensive path for integrating communication and sensing in 6G, with a focus on technological innovation and collaborative efforts. The Hexa-X project sets an ambitious but coherent direction for research and development, emphasizing that 6G will not just evolve from existing networks but will redefine the way communication systems are conceptualized and built.