In Android Is it possible to access the physical layer of 2G/3G to transmit voice/data

I wanted to make an walkie talkie app in android, i know there are a lot of apps like these but they use the Wi-fi or they are just web services. But if we want to like transmit voice/data on 2G/3G frequencies, is there an option in android ? or "is it even legal ?" considering it will be a short range transmission. i know that 2G/3G are not device-device communication systems but if we can directly access the physical layer of 2G/3G(the transmission hardware) of the phone then we can transmit data through it.