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

Abstract

This study addresses the critical challenge of maintaining linearity and high precision in Digital-to-Analog Converters (DACs) for prospective Terahertz (THz) IoT transceivers. The paper introduces a novel signal processing technique called Modified Pulse-width Modulation (MPWM) to overcome the speed and accuracy limitations of standard PWM-DACs in high-order modulation schemes. The research culminates in the presentation of a specialized RISC-V System-on-Chip (SoC) architecture that successfully integrates the high-resolution MPWM-DAC for future THz communication systems.

Report

Key Highlights

• THz IoT Focus: The research aims to augment communication capacity and spectral efficiency for future Internet-of-Things (IoT) devices utilizing Terahertz (THz) frequencies.
• DAC Bottleneck: Identifies the inherent limitations (insufficient conversion speed and precision) of conventional Pulse-width Modulation-based DACs (PWM-DACs) when dealing with complex, high-order modulation schemes required by THz communications.
• MPWM Innovation: Introduces the Modified Pulse-width Modulation (MPWM) methodology to enhance both the conversion speed and accuracy of DACs.
• Performance Metrics: Comparative assessments show that MPWM-DACs achieve enhanced speed over standard PWM-DACs and greater accuracy compared to Pulse-count Modulation DACs (PCM-DACs).
• RISC-V Integration: The final implementation is presented as a RISC-V System-on-Chip (SoC) specifically incorporating the MPWM-DAC structure for THz applications.

Technical Details

• Domain: High-frequency, mixed-signal transceiver design for Terahertz wireless communication.
• Problem Statement: High-resolution DACs contribute significantly to limiting linearity at high frequencies necessary for complex modulation in THz transmitters.
• Core Solution: The MPWM framework provides adjustable options, resulting in a highly adaptable DAC suitable for diverse application scenarios.
• Implementation Details: The study involves a comprehensive examination of the core principles, spectrum characteristics, and evaluation metrics of the MPWM method, followed by experimental validation.
• System Architecture: The RISC-V SoC acts as the foundational platform, embedding the optimized MPWM-DAC to achieve the requisite high-resolution output for THz signaling.

Implications

• Enabling THz Communication: By providing a solution to the critical speed and precision trade-off in THz DACs, this work removes a major hurdle toward realizing viable THz transceiver chips for high-speed wireless networks (e.g., 6G).
• Advancing Digital-to-Analog Conversion: The MPWM methodology demonstrates that PWM-based converters can be highly optimized to compete effectively in high-resolution, high-frequency domains, offering efficiency and affordability previously limited to lower-performance applications.
• RISC-V in Specialized Hardware: The integration of the MPWM-DAC within a RISC-V SoC further validates the RISC-V architecture as a flexible, customizable core capable of driving complex, highly specialized communication and hardware acceleration systems necessary for next-generation IoT and wireless infrastructure.