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
The wifi direct supports concurrent hosting and client capabilities on single interface. Which means, the device will act as an AP, allowing other devices to connect to it as clients, And also connect to another AP as a client. And can share internet connection by driving the internet traffic between the interfaces. However, current implementations of wifi direct on android are specific to the phone and not part of andorid sdk. So there is not much clarity if they support concurrency. This capability is not limited by hardware.
Well You might be interested in looking at AllJoyn. It is qualcoms SDK for android OS which includes wi-fi peer-to-peer implementations by creating adhoc connections. This is same as Wi-Fi Direct.