I try to create an ad-hoc network between many Android devices, but I can\'t find documentation to do that.
I thought Wifi direct could work for what I want, but is
Ad hoc wifi is disabled in Android. You need to ask Google why they have chosen to do so. If you have access to a device that allow you to install custom Android images, you will be able to patch Android to support it. Or you can root your device and reenable ad hoc Wifi, there are plenty of solutions on the web on how to enable ad hoc on rooted Android devices. This is a software issue, the hardware on every Android device that I know of has support for ad hoc Wifi.