Edge computing-enabled crowd density estimation based on lightweight convolutional neural network

In public areas, crowd stampedes and incidents generate huge negative impacts on public security. Accurate and efficient crowd density estimation is critical to monitor crowd status for developing evacuation strategies. The existing crowd density estimation methods are established based on complex deep-learning algorithms which are usually more accurate, but, on the other side, they require much more computational resources. Consequently, cloud-computing is the only option for deploying crowd density estimation algorithms, which needs tremendous resources for real-time video data transmission and the malfunction and delay of internet service may cause wrong and delayed estimation results. Edge computing is a novel concept of accomplishing computing tasks only relying on the computational resources of edge devices. Estimating crowd density on edge devices rather than conveying images to cloud server for further analysis has several advantages, including 1) reducing network bandwidth pressure from remote transmission; 2) avoiding risks of leaking privacy on images; and 3) improving computation efficient. This study designs an edge computing-enabled crowd density estimation model based on the residual bottleneck block and dilated convolution. The experiments are designed and conducted on public crowd data sets to verify accuracy, storage cost and computation efficiency of our model. According to the experimental results, the proposed model achieves a considerable improvement in operational efficiency, while keep the accuracy at the same level with the complex deep-learning algorithms. Furthermore, the proposed model is implemented on a real edge device to detect real-world crowd density in a Beijing subway station.