Repurpose a phone as a repeater?

January 5, 2013 8:04 AM

Now that we all have a handful of old hackable smartphones lying around, is there any way to build our own active repeaters or cell phone to IP gateways?

Googling leads me to believe the answer is no, for a variety of legal and technical reasons, but it really seems like I should be able to hang my old Sprint Palm Pre in the window as a repeater to help with my terrible inside-the-house reception. Or as a cel phone to IP telephony gateway? Is the cell phone part of these devices too locked down?

posted by mzurer to Technology (7 answers total)

Best answer: There's people working on a version of Asterisk (pbx software) for Android which you could use for some kind of repeating. You'd be using it as a gateway between an IP network and the mobile phone network though.

What you cannot do is to use a phone as a cell phone repeater. The main reason is that all the radio and network functions are implemented on a single chip that interfaces with the OS. Neither the Android OS nor IOS "know" how GSM, CDMA, 3G, whatever work on a protocol level. They just tell the chip "make a call to the following number".
Also, those chips are typically not designed for relaying which requires maintaining two duplex links rather than one.
posted by atrazine at 8:25 AM on January 5, 2013

Best answer: You cannot repurpose a phone to act like a cell. The phone is designed to transmit on one set of frequencies and receive on a different set. The cell transmits on the ones the phone receives, and receives the ones the phone transmits. The phone doesn't have the ability to transmit the frequencies which the cell transmits.

Also, the protocol roles of the two are quite different; the phone is missing other hardware which the cell has.
posted by Chocolate Pickle at 8:29 AM on January 5, 2013

On a related note, there is some work being done to implement an open base-station stack based on the Universal Serial Radio Peripheral. There has even been some in-the-wild implementations built with varying levels of success.
posted by TheNewWazoo at 9:38 AM on January 5, 2013

That project is for GSM 2G, which is obsolete and being phased out all over the world. GSM 3G is an entirely different and completely incompatible protocol.
posted by Chocolate Pickle at 11:20 AM on January 5, 2013

Obsolete = available for hobbyists, though, in many cases.
posted by limeonaire at 11:35 AM on January 5, 2013

As well, even the very newest phones support speaking GSM 2G. It's not so much about interoperating with the established carriers as it is interoperating with handsets in the field.
posted by TheNewWazoo at 12:20 PM on January 5, 2013

The OP asked about interoperating with established carriers.
posted by Chocolate Pickle at 1:50 PM on January 5, 2013