Well... I've purchased 2 camera, one was intended to be placed at the end of my garden.
I've placed a wifi extender in my garden to ensure I've a good signal. I understand now that it was useless, as the base is not powerfull enough to cover the distance and there is no connection to my main wifi network.
By the way, the camera are working fine when I'm close to the base, but on the 1st floor of my house it is not (base is in the cellar).