6GOPENVERSO-NET: A sub-THz link prototype for XR applications
Extended reality (XR) can provide immersive technologies and experiences by combining physical and virtual worlds through extensive video processing and data fusion, becoming one of the most prominent enablers of 6G services such as immersive gaming/entertainment, telesurgery, immersive learning and communications, and holographic teleconferencing. However, XR requires very high data rates, precise synchronization for 3D video, and stringent latency constraints, among others, and the improvements in terms of reliability, latency, and energy consumption introduced by the evolution of 5G systems through releases 15 and 16 are not aligned with the specific needs of XR applications.
High-frequency bands, such as the terahertz (THz) range (0.1–10 THz), provide much larger bandwidths and integrated sensing capabilities, facilitating the development of emerging applications like XR. In addition, the development of Integrated Sensing and Communication (ISAC) technologies, which encompass communication and sensing functionalities, leads to synergies and improved system performance that are particularly appealing for XR.
The design and development of the sub-THz link prototype demonstrates that affordable infrastructure can be deployed to support future 6G services. This ISAC system performs radar capabilities and very-high data rate transmission based on non-expensive commercial off-the-shelf (COTS) components, which significantly reduce the cost with respect to monolithic solutions of traditional vendors.
The following diagram shows the system blocks. Both OFDM-based transmitter and receiver have been developed and implemented on the same RFSoC platform, to avoid synchronization issues. A conventional OFDM waveform has been adapted to the specifications of the project to include object detection and movement. The IF (intermediate frequency), designed and implemented during the execution of the project, pass the baseband signals to the sub-Thz converters, which operate at 91.525 GHz. As the system requires a large bandwidth of more than 1.5 GHz, four 400 MHz signal flows combine to form the total flow to avoid additional processing challenges. The radar processing subsystem processes the received signal and provides detection information, and the communication data can be processed by upper layers.
Use case validation
The prototype was validated at Gradiant’s premises through the detection of static and moving targets. Regarding static target detection, the system successfully detects a metal box and a column which are located at 4.75 m and 3.1 m respectively from the antennas. By performing range-Doppler analysis, we can observe that both objects are correctly detected at the right distance. The radar system can also detect slow movement up to 1 cm/s. We can then detect a person breathing within the range of the transmitted signal by identifying the periodic movement of the chest. This movement can also be detected by monitoring phase changes in the received signal, whose phase shifts positively when the chest moves towards the radar and negatively when it moves away. This video provides further details on the use case results.
