A RISC-V SOC for Terahertz IoT Devices: Implementation and design challenges

Terahertz (THz) communication is considered a viable approach to augmenting
the communication capacity of prospective Internet-of-Things (IoT) resulting in
enhanced spectral efficiency. This study first provides an outline of the
design challenges encountered in developing THz transceivers. This paper
introduces advanced approaches and a unique methodology known as Modified
Pulse-width Modulation (MPWM) to address the issues in the THz domain. In this
situation involving a transceiver that handles complex modulation schemes, the
presence of a mixed signal through a high-resolution digital-to-analog
converter (DAC) in the transmitter greatly contributes to the limitation in
maintaining linearity at high frequencies. The utilization of Pulse-width
Modulation-based Digital-to-Analog Converters (PWM-DACs) has garnered
significant attention among scholars due to its efficiency and affordability.
However, the converters' performance is restricted by insufficient conversion
speed and precision, especially in the context of high-resolution, high-order
modulation schemes for THz wireless communications. The MPWM framework offers a
multitude of adjustable options, rendering the final MPWM-DAC highly adaptable
for a diverse array of application scenarios. Comparative performance
assessments indicate that MPWM-DACs have enhanced conversion speed compared to
standard PWM-DACs, and they also provide greater accuracy in comparison to
Pulse-count Modulation DACs (PCM-DACs). The study presents a comprehensive
examination of the core principles, spectrum characteristics, and evaluation
metrics, as well as the development and experimental validation of the MPWM
method. Furthermore, we present a RISC-V System-on-Chip (SoC) that incorporates
an MPWM-DAC, offering a highly favorable resolution for THz IoT communications.