Android as SIP to GSM gateway

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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.

Ballistics answered 18/1, 2011 at 11:22 Comment(4)

Does Android allow for a "multihomed" setup, i.e. one ethernet interface via WiFi and one via GSM in parallel? – Modernize 18/1, 2011 at 11:52

I've no idea about the abilities of Android, that's why I'm asking. I was hoping to find some experienced Android developer who could point me into the right direction - or tell me that's not possible at all. – Ballistics 18/1, 2011 at 16:11

Forget my question. You do no need a data bearer on GSM, so yo don't need ethernet on GSM. You need a GSM voice bearer. So the question rather would be: does Android allow access to telephony voice payload from applications? – Modernize 21/1, 2011 at 6:35

Yes, that's almost correct. I need to establish a GSM connection and access the incoming and outgoing voice streams from an Android application. – Ballistics 21/1, 2011 at 10:0

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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/

Utah answered 5/7, 2016 at 11:49 Comment(0)

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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.

Cracow answered 9/8, 2018 at 6:46 Comment(0)

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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.

Tobe answered 17/10, 2015 at 15:58 Comment(0)

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in the case you use a computer for managing sip calls, you can "transfer" voice and control your phone with bluetooth.

Saransk answered 5/5, 2011 at 11:41 Comment(0)

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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.

Birdman answered 27/4, 2012 at 15:55 Comment(0)

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

http://pure-voip.com/

Lalitta answered 18/6, 2018 at 12:32 Comment(0)

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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.

Antiperistalsis answered 18/1, 2011 at 12:33 Comment(9)

My goal is to call my Android phone via SIP and let Android forward that call to a different mobile phone. – Ballistics 20/1, 2011 at 14:47

Then I don't understand the issue. If you call via SIP, the other mobile phone needs to receive the call in SIP. If you want the other phone to receive it over GSM - you need a gateway in the middle. – Antiperistalsis 20/1, 2011 at 15:47

I'll do an example: I live in Germany and person P lives in Czech Replublic. My Android phone with CZ SIM card is in CZ and I do have high speed internet in Germany. Now I want to call P on his CZ mobile. My idea now is that I would call my Android phone located in CZ using SIP. The phone would then establish a GSM connection with P and forward all the voice payload in both directions. – Ballistics 21/1, 2011 at 9:58

You probably would come out much easier if you drop the android and gsm requirment. A desktop PC with appropriate interface hardware connected to a fixed telephony line would be much easier to set up, e.g. with asterisk. – Modernize 21/1, 2011 at 21:35

@martin-so are you saying that this would include 3 phones?first would make call from SIP and the other is on GSM .You want an interface between the two phone by creating a gateway – Gonnella 27/1, 2011 at 8:56

@all: Sorry for the delay, I started a new job this month. – Ballistics 9/2, 2011 at 17:4

@Bernd: It depends how expensive a GSM card for PC is. I'll think about it, thanks. – Ballistics 9/2, 2011 at 17:5

@Garima: I'd like to call phone B from phone A. Phone B would then call phone C and forward the voice streams in both directions. Hence, yes there are 3 phones involved. – Ballistics 9/2, 2011 at 17:8

@martin-so basically a call forwrding technique is required on phone C..Sip support is available now in android .. – Gonnella 10/2, 2011 at 8:43

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