Low-power Spike-based Wearable Analytics on RRAM Crossbars

Abstract--This work introduces a spike-based wearable analytics system utilizing Spiking Neural Networks (SNNs) deployed on an In-memory Computing engine based on RRAM crossbars, which are known for their compactness and energy-efficiency. Given the hardware constraints and noise characteristics of the underlying RRAM crossbars, we propose online adaptation of pre-trained SNNs in real-time using Direct Feedback Alignment (DFA) against traditional backpropagation (BP). Direct Feedback Alignment (DFA) learning, that allows layer-parallel gradient computations, acts as a fast, energy & area-efficient method for online adaptation of SNNs on RRAM crossbars, unleashing better algorithmic performance against those adapted using BP. Through extensive simulations using our in-house hardware evaluation engine called DF A Sim, we find that DFA achieves upto 64.1% lower energy consumption, 10.1% lower area overhead, and a 2.1 reduction in latency compared to BP, while delivering upto 7.55% higher inference accuracy on human Figure 1: Pictorial depiction of SNNs used in wearables for temporal activity recognition (HAR) tasks. Pre-trained SNNs in the cloud are adapted online according to the constraints of resource-constrained edge devices.