For a research project, I must work on the design of 3G/WiMAX Access Point (AP) protocols. I have access to 2 Android smartphones.
Android devices can become WiFi hotspots for other devices, allowing WiFi tethering.
In this scheme, does the Android devices behave like a regular WiFi AP (like the one present in your home WLAN) or does it just forward the connection from the AP it is connected to ?
Similarily, is there a way of turning one of my smartphone into a 3G/WiMAX AP, so that the other can connect to it as if it was a 3G/WiMAX tower ? If so, can you provide some references and resources that would allow to do that ?
EDIT:
Ok so the keyword is "AP mode", it is a mode available in some Wireless Network Drivers like ath9k, bcm but is absent from most others. It is used to turn the device into an AP (or more accurately a simulated one).
The answer of the first question "Does it behave like an AP?" is Yes: the Android device can behave exactly like an AP (management frames, ack, etc.) AND internaly it forwards the connection from the real AP.
The answer to the second question "Can we turn it on ?" is "It depends on your wireless driver, and thus on your wireless card". Some drivers (ath9k, bcmon) have the options, some others don't. You will have to search for your network card name and check it out.
In my case, I wanted to change the behaviour of on AP (by modifying the driver / kernel), but found out that my driver is a firmware (and proprietary). I ended up adding an USB Wifi adapter that is supported by the driver ath9k (open-source driver for Atheros chipsets).
It behaves like a 'regular' AP, taking into account that both Android and WiFi are constantly evolving and hence the definition of regular may be a moving target.
You can test the behaviour by finding a location with no 2G/3G/4G etc coverage and run a local network with your phone as the AP for multiple devices. An long distance flight for example (where devices on flight laws allow...).
For testing I am not aware of any free or open source 3G network elements yet, but there are some 2G open source projects it might be worth you looking at:
The former has definitely mentioned plans for an open RNC (3G access point) but it is not clear what stage these are at.
Turning a smartphone into a 3G access point (RNC) is definitely not going to be just a matter of developing an app. Given the hardware is probably all there, I am sure it is technically possible if you are prepared to write a lot of low level software, but I think you would probably find it much easier to look at the approaches the above project have taken and see what their plans are for 3G.