Sensing Signals

Description

Sensing signals are a foundational concept in 3GPP's Integrated Sensing and Communication (ISAC) framework, introduced in Release 19. They refer to any transmission on the 3GPP radio interface that can be repurposed or specifically designed for sensing purposes. Unlike conventional communication signals that carry data between users, sensing signals are used to probe the environment, and their reflections are analyzed to extract information about objects, their position, movement, and characteristics. This dual use of the radio interface is a key enabler for ISAC, allowing the same spectrum and infrastructure to support both communication and radar-like sensing functions.

In terms of architecture, sensing signals can be transmitted by various entities within the 3GPP system, including base stations (gNBs) and user equipment (UEs). The choice of transmitter depends on the sensing mode: in monostatic sensing, the same node transmits and receives; in bistatic or multistatic sensing, different nodes transmit and receive. The signals themselves can be existing communication reference signals (e.g., CSI-RS, SRS, DMRS) or new dedicated sensing waveforms defined in specifications such as 22.137 and 22.837. The use of existing signals minimizes overhead and leverages already deployed infrastructure, while dedicated signals offer better sensing performance and flexibility.

The operation of sensing signals involves several key steps. First, the network determines the sensing requirements (e.g., range, velocity, accuracy) and selects appropriate signal parameters such as bandwidth, duration, and periodicity. The sensing transmitter then emits the signal, which propagates through the environment and reflects off objects. The reflected echoes are captured by sensing receivers, which can be co-located with the transmitter or at a different location. The received signals are then processed to estimate parameters like time of arrival, angle of arrival, and Doppler shift, which are used to detect, localize, and track objects. This process is coordinated by the network, often with the help of a sensing function that manages resources and fuses data from multiple receivers.

Sensing signals are crucial for enabling a wide range of applications, including autonomous driving, drone detection, indoor localization, and environmental monitoring. They allow the 3GPP system to provide sensing as a service, integrating it with communication services in a unified framework. The specifications 22.137 and 22.837 define the service requirements and use cases for sensing, ensuring that the technology meets diverse needs. As the technology evolves, sensing signals will become more sophisticated, supporting higher resolution, longer range, and more efficient use of spectrum.

In summary, sensing signals are the radio transmissions that make ISAC possible. They transform the 3GPP network from a pure communication system into a sensing-capable platform, opening new business opportunities and enhancing the value of existing infrastructure. Their design and deployment are central to the success of sensing services in future releases.

Purpose & Motivation

Sensing signals exist to enable the 3GPP system to perform environmental sensing using the same radio interface and spectrum allocated for communication. Traditionally, sensing (e.g., radar) required separate dedicated systems and spectrum, leading to inefficiencies and higher costs. By allowing communication signals to be used for sensing, or by defining new sensing-specific signals, 3GPP aims to integrate sensing as a native service, reducing duplication and enabling new applications. The motivation is to support use cases like autonomous vehicles, where both communication and sensing are needed, and to provide sensing services in areas where traditional radar coverage is limited.

The introduction of sensing signals in Release 19 addresses the limitations of previous approaches that treated sensing and communication as separate domains. It allows the network to dynamically allocate resources for sensing, leveraging the wide bandwidth and advanced antenna systems of 5G and beyond. This integration also facilitates the sharing of sensing data with communication applications, enabling context-aware services. The specifications 22.137 and 22.837 provide the requirements and architectural framework, ensuring interoperability and guiding implementation. Overall, sensing signals are a key enabler for the convergence of sensing and communication in 6G and beyond.