A Real-Time Software-Defined Radio Platform for Sub-Terahertz Communication Systems

Wireless communication in the sub-terahertz and terahertz (THz) bands (broadly from 100 GHz to 10 THz) is a critical building block of the future generations of telecommunication and networking due to the large available bandwidth at these frequencies and the opportunities it brings for ultra-broadband communication and sensing systems. Alongside the high data rates offered by this band, the huge bandwidth can be shared more generously across multiple users with hopes of reducing network congestion. With the recent improvements being made on the electronics side such as high-speed data converters and high-frequency oscillators, several testing platforms for experimental THz communication have been recently developed. However, these are mostly device technology demonstrators, channel sounders, or physical-layer testbeds, which do not support real-time digital signal processing (DSP). Such platforms have supported the large body of THz research focused on studying the channel or developing physical layer solutions. However, the lack of real-time DSP capabilities prevents the testing of upper networking protocols, on which the research community is only now starting to focus. While real-time networking platforms, namely, software-defined radio (SDR) platforms, developed for lower frequency systems could be utilized, their very low bandwidth misses the point of moving to the sub-THz and THz bands. To fill the gap, in this paper, we design an SDR platform able to process multi-GHz of baseband bandwidth in real-time by leveraging the state of the art in radio-frequency systems on chip (RFSoC), a custom frequency-multiplexing analog network and a multi-phase implementation of an orthogonal frequency-division modulation (OFDM) physical layer. As an instantiation of the platform, we demonstrate a real-time link at 135 GHz with 8 GHz of bandwidth supporting a bit-rate of 33 Gbps when frequency-multiplexing four 2-GHz-wide channels, each with 64-sub-carrier OFDM. Finally, we identify immediate next steps and cross-layer challenges foreseen when implementing wireless communication and sensing systems at frequencies above 100 GHz.