An Efficient Algorithm-Hardware Co-Design for Radar-Based Fall Detection With Multi-Branch Convolutions

In this paper, we propose an efficient algorithm-hardware co-design framework to realize radar-based fall detection with limited resources. We first design a compact neural network model named MB-Net with multi-branch convolutions for feature extraction of radar time series data combined with multi-scale wavelet transform. After that, an FPGA-based neural network (NN) accelerator tailored for the proposed network is designed. The proposed NN accelerator replaces the general multipliers with non-exact multipliers to reduce the hardware cost. For the multi-branch convolution layer, a novel layer computing sequence is introduced to improve the efficiency of the processing element (PE) array and reduce the memory footprint. In addition, the average pooling operation in the proposed network is folded into the quantization factors to reduce hardware cost. The experimental findings show that the MB-Net can maintain competitive performance in comparison to state-of-the-art methods while the hardware cost is significantly lower. The proposed network model is implemented in Zynq ZC702 board using only 3615 LUTs, 1843 FFs, 11.5 BRAMs, and 8 DSPs with 0.234 W power consumption. Through algorithm and hardware co-optimization, the fall detection accelerator can achieve 95 $\%$ PE efficiency and takes 0.346 ms latency for a radar sample interference with only 80.96 uJ energy consumption.