Real-Time CSI from Commercial 5G Radio Unit (RU)

This video shows the measured channel state information (CSI) at a commercial base station from a smartphone when the user is standing and walking.

In 5G O-RAN systems, CSI provides a fine-grained description of the radio channel conditions between a user equipment (UE) and the base station. CSI can be obtained through the uplink sounding reference signals (SRS), which are periodically transmitted by the UE to allow the base station to measure channel characteristics such as amplitude, phase, and frequency response across multiple antennas and subcarriers. This rich channel feedback is essential for key 5G functionalities including beamforming, link adaptation, and interference management, enabling more efficient and reliable wireless communication.

Beyond communication optimization, CSI offers unique potential for sensing and detection. Since wireless signals propagate through the surrounding environment and are affected by movement, orientation, and human activities, CSI inherently captures subtle changes in the physical world. This means that variations in uplink CSI patterns can be used to detect the presence of devices, monitor user mobility, and even infer fine-grained activities such as gestures, walking, or breathing. Leveraging CSI for device and user activity detection opens the door to a new class of applications that combine communication and sensing in an integrated 5G framework.

The integration of AI amplifies this potential by enabling data-driven modeling of the highly complex and dynamic relationship between CSI measurements and real-world activities. It can automatically extract features from high-dimensional CSI data, learn robust patterns, and perform accurate classification or prediction without requiring handcrafted signal models. In practice, this can enable real-world applications such as secure device authentication, occupancy detection for smart buildings, non-intrusive health monitoring, and enhanced situational awareness in wireless networks. By combining CSI with AI, 5G systems are evolving from pure communication infrastructures into intelligent sensing platforms.