Android as SIP to GSM gateway

Question

Soon I could use a SIP to GSM gateway, because I'll need to make phone calls from Germany to a mobile phone in Czech Republik. Hence, I thought about implementing one.

Now, the questions are:

• Does such a solution already exist (for a reasonable price)?
• Is it possible to redirect a (voice) stream to a GSM connection with the available Android APIs (SDK or NDK)?

Ideas, suggestions, comments are highly welcome.

Answer 1

To date most android devices are not architected in a way where both sides of the in-call audio are available to apps running under linux on the application processor. Instead, the in call audio seems to be private to the radio processor.

Answer 2

It's not possible to use Android as a SIP GSM Gateway. It is possible to make calls but the API won't let you redirect incoming audio to another stream or send your desired stream as outgoing audio. It will be limited to device microphone/speaker and bluetooth/wired headsets.

The Android Telephony package passes the complete control of radio device to Radio Daemon (rild) library which would not allow you to change the audio streams as mentioned above. Even, rild is vendor-dependent propertiary software and is not opensource, so using Custom ROMs would not help.

For more technical info, see here .

Answer 3

You can use asterisk with chan_mobile and connect your android (or any old mobile phone) to it via bluetooth. This is reasonably priced if using a Raspberry Pi.

Strictly speaking this does not satisfy the Android requirement, but rather uses any mobile + bluetooth + asterisk as a GSM gateway.

http://www.stocksy.co.uk/articles/Networks/use_an_old_mobile_phone_as_a_gsm_gateway_in_asterisk/

Answer 4

You can solder the adapter, which turns the microphone input on the headset into a line input. In the headphone jack, such an adapter is inserted, which physically routs the audio output to the headphones into the microphone input of the smartphone. Together with the application, you just need to show the electrical scheme to solder such an adapter or sell an adapter on the Internet.

Answer 5

如果您使用计算机管理 sip 呼叫，您可以“传输”语音并使用蓝牙控制您的手机。

Answer 6

This is not a question for Android but rather to the gateway side. Android will be dialing out using SIP through a 3rd party app or through the one provided in its SDK, but then the transcoding and redirection over GSM is done on the gateway side.

Answer 7

There is a solution can make your Android phones work as SIP GSM Gateway for calls termination and origination

http://pure-voip.com/