Flexible multiple terahertz subchannel wireless transmission adopting hybrid SC-QPSK and SC-16QAM modulation

Against the backdrop of rapid advancements in the sixth-generation (6G) communication technologies, terahertz (THz) communication has emerged as a pivotal enabler for future high-speed wireless systems, owing to its exceptional capabilities in high-data-rate transmission, ultra-wide bandwidth, abundant spectral resources, and enhanced signal security. However, as multi-user application scenarios become increasingly complex, conventional communication architectures face growing limitations in scaling system capacity and spectral efficiency. To address the growing requirements of modern communication systems for high data rates, large bandwidth, and support for multi-user scenarios, we propose a scheme that enables the simultaneous transmission of multiple independent THz subchannels via digital subcarrier multiplexing (DSCM). The proposed architecture allows flexible control of key parameters, including the number of subchannels, their frequency spacing, carrier frequencies, bandwidth allocation, and modulation formats, thereby facilitating efficient multiple-THz subchannel wireless transmission. In transmitter digital signal processing, single-sideband (SSB) modulation is employed to generate the digital baseband DSCM signal, followed by up-conversion in both the digital and analog domains to convert it to THz DSCM signals. Experimental validation is conducted within a 220 GHz all-electronic communication system, utilizing a single-input single-output (SISO) wireless link. The results demonstrate that when multiple THz subchannels are synchronously transmitted using either single-carrier-based quadrature phase shift keying modulation (SC-QPSK) or single-carrier-based 16-ary quadrature amplitude modulation (SC-16QAM), the system can successfully support 13 and 11 subchannel signal transmission with bit error rates (BER) maintained below the soft-decision forward error correction (SD-FEC) threshold of 2 × 10^-2. Furthermore, experimental evaluation of a hybrid configuration comprising four SC-QPSK- and eight SC-16QAM-modulated subchannels confirms that all subchannels achieve BERs below 2 × 10^-2, indicating robust performance under hybrid SC-QPSK and SC-16QAM modulation schemes.