Low Power Wide Area Network, such as LoRa is one of the main building blocks of the Internet of Things. One of the main issues is to scale up the number of devices and one strong limitation comes from the downlink communication. In fact, the access point is constrained by the duty cycle, therefore it cannot address a large number of devices. We propose a superposition scheme to transmit multiple packets to multiple devices in the same frequency, time slot, and spreading factor. This scheme is applied to the specific physical layer proposed by LoRa, based on the chirp spread spectrum. Our proposal includes the power allocation scheme and the decoding technique that are very specific to this physical layer and show a significant performance improvement, increasing the number of devices that can be connected at least by ten compared to the classical LoRa-like system.