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This paper presents a ferroelectric FET (FeFET)-based processing-in-memory (PIM) architecture to accelerate the inference of deep neural networks (DNNs). We propose a digital in-memory vector-matrix multiplication (VMM) engine design utilizing the FeFET crossbar to enable bit-parallel computation and eliminate analog-to-digital conversion in prior mixed-signal PIM designs. A dedicated hierarchical network-on-chip (H-NoC) is developed for input broadcasting and on-the-fly partial results processing, reducing the data transmission volume and latency. Simulations in 28-nm CMOS technology show 115× and 6.3× higher computing efficiency (GOPs/W) over desktop GPU (Nvidia GTX 1080Ti) and resistive random access memory (ReRAM)-based design, respectively. INDEX TERMS Deep neural network (DNN), ferroelectric FET (FeFET), processing-in-memory (PIM).

This paper introduces a heterogeneous spiking neural network (H-SNN) as a novel, feedforward SNN structure capable of learning complex spatiotemporal patterns with spike-timing-dependent plasticity (STDP) based unsupervised training. Within H-SNN, hierarchical spatial and temporal patterns are constructed with convolution connections and memory pathways containing spiking neurons with different dynamics. We demonstrate analytically the formation of long and short term memory in H-SNN and distinct response functions of memory pathways. In simulation, the network is tested on visual input of moving objects to simultaneously predict for object class and motion dynamics. Results show that H-SNN achieves prediction accuracy on similar or higher level than supervised deep neural networks (DNN). Compared to SNN trained with back-propagation, H-SNN effectively utilizes STDP to learn spatiotemporal patterns that have better generalizability to unknown motion and/or object classes encountered during inference. In addition, the improved performance is achieved with 6x fewer parameters than complex DNNs, showing H-SNN as an efficient approach for applications with constrained computation resources.

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Spiking neural network (SNN) uses biologically inspired neuron model coupled withSpike-timing-dependent-plasticity (STDP) to enable unsupervised continuous learning in artificial intelligence (AI) platform. However, current SNN algorithms shows low accuracy in complex problems and are hard to operate at reduced precision. This paper demonstrates a GPU-accelerated SNN architecture that uses stochasticity in the STDP coupled with higher frequency input spike trains. The simulation results demonstrate 2 to 3 times faster learning compared to deterministic SNN architectures while maintaining high accuracy for MNIST (simple) and fashion MNIST (complex) data sets. Further, we show stochastic STDP enables learning even with 2 bits of operation, while deterministic STDP fails.