A Low-Power Sparse Convolution Accelerator with Idle-First-Task-Assignment for Edge Vision

Abstract

In recent years, edge-vision monitoring systems for applications such as smart animal husbandry have faced strict tripartite constraints: maintaining input resolution under extremely limited transmission bandwidth and strict power budgets. Conventional dense convolutional neural networks (CNNs) cannot satisfy the resource limits of such constrained IoT nodes. To address this challenge, this paper presents a low-power sparse convolution accelerator for edge devices, fabricated and validated in a 16 nm process. First, the accelerator adopts a bitmap-based format for compression in both data transmission and computation, effectively reducing memory and bandwidth overhead. Second, to mitigate load imbalance in sparse computation, an Idle-First-Task-Assignment (IFTA) dynamic scheduling strategy is proposed, significantly reducing processing-element (PE) idle time and improving multiplier utilization. In addition, a dedicated dataflow is designed to support and accelerate depthwise separable convolution (DWConv), which is widely used in lightweight networks. Experimental results show that the chip occupies only 0.5~mm$^2$ core area and consumes as little as 12--16~mW. On ImageNet, for sparse VGG16 and MobileNetV2, the proposed accelerator achieves 6.5$\times$ and 2.8$\times$ speedups, respectively, over traditional dense accelerators, and also delivers significant performance gains over the existing sparse accelerator.