The Challenges and Emerging Technologies for Low-Power Artificial Intelligence IoT Systems

• Published in: IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2021-12, Vol.68 (12), p.4821-4834
• Main Authors: Ye, Le, Wang, Zhixuan, Liu, Ying, Chen, Peiyu, Li, Heyi, Zhang, Hao, Wu, Meng, He, Wei, Shen, Linxiao, Zhang, Yihan, Tan, Zhichao, Wang, Yangyuan, Huang, Ru
• Format: Article
• Language: English
• Subjects: Artificial intelligence; asynchronous; Batteries; charge-domain; Circuit design; computing in memory; Criteria; Data processing; Energy efficiency; Energy harvesting; energy-efficient; Engines; evaluation criteria; event-driven; Internet of Things; level-crossing ADC; light-duty artificial intelligence; Neural networks; New technology; Power consumption; Power demand; Power management; random sparse events; Sensors; Servers; Service life assessment; Signal processing; spike neural network; Systems design; ultralow power
• ISSN: 1549-8328; 1558-0806
• DOI: 10.1109/TCSI.2021.3095622

The Internet of Things (IoT) is an interface with the physical world that usually operates in random-sparse-event (RSE) scenarios. This article discusses main challenges of IoT chips: power consumption, power supply, artificial intelligence (AI), small-signal acquisition, and evaluation criteria. To overcome these challenges, many works recently aimed at IoT system design have emerged. This work reviews the architecture and circuit innovations that have contributed to IoT developments. This paper does not cover security of IoT. Event-driven architectures and nonuniform sampling ADCs significantly reduce the long-term average power. Besides, embedding AI engines in IoT nodes (AIoT) is one critical trend. The computing-in-memory technique improves the energy efficiency of the AI engine. Asynchronous spike neural networks (ASNNs) AI engines show low power potential. In addition to data processing, small-signal acquisition is also critical. The charge-domain analog-front-end (AFE) techniques such as floating inverter-based amplifiers improve energy efficiency. In addition to the above low power and high energy efficiency technologies, energy harvesting can also enhance the lifetime of AIoT devices. This article discusses recent ambient RF and natural energy harvesting approaches and high-efficiency DC-DC with a wide load range. Finally, novel evaluation criteria are introduced to establish benchmark standards for AIoT chips.