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Software Defined Radio is opening up many new possibilities for amateur digital modes. One family of technologies that interests me is cellular. 2G GSM voice/sms and 2.5G GPRS data has been proven to work with OpenBTS on a USRP SDR using licensed cellular bands. Can this technology be used by amateurs? Could an amateur cellular network be deployed sometime in the future?

Note: I know that there are many small practical considerations to doing this. Cellular technologies are heavily patented, but patents on many older GSM technologies have recently expired. Also, some deployment tweaks will be needed to adhere to amateur regulations, such as disabling encryption. Answers should focus on the fundamentals of amateurs using cellular technologies via sdr and not these small hangups.

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  • $\begingroup$ If you want to avoid "small hangups" like if it's legal or not, what else is there? $\endgroup$ – Phil Frost - W8II Nov 20 '13 at 21:55
  • $\begingroup$ @PhilFrost I've reworded the section about patent legality $\endgroup$ – JC Hulce Nov 20 '13 at 22:05
  • $\begingroup$ Still not sure what questions are left. Could you take a cellular network and change the frequency to amateur bands? Sure. Are amateurs capable, technically and mentally, of operating such a network? That's really another issue, but a quite subjective one... $\endgroup$ – Phil Frost - W8II Nov 21 '13 at 15:12
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Yes it can be done, and there are some huge advantages:

  • Better use of bandwidth
  • Existing chipsets/support/implementation
  • Low power

In fact there's little reason why one couldn't essentially replace DSTAR and competing systems with a standard based on GSM and GPRS technologies. Even for those parts that are patented, the patents running out means we'd be using technology that's advanced well beyond DSTAR and similar systems, and it's completely open.

It would take a few individuals building up an example design and example infrastructure for it to be picked up widely. But once that happened you could build a cellular network over Amatuer Radio frequencies, and you could expand functionality to support specific Amateur Radio needs such as public safety and emergency communications.

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  • $\begingroup$ Of course I'd have to say that if amateur radio is just another cellular network, then it would share the weaknesses of cellular networks we have now, and thus, not so great for emergency communications. Amateur radio is robust in its decentralized, ad-hoc, simple nature, traits not shared by cellular networks. $\endgroup$ – Phil Frost - W8II Oct 23 '14 at 14:04
  • $\begingroup$ @PhilFrost Yes. And given that it's a continuum, one could choose to mix and match traits and technology which would produce a radio that better meets their particular needs. $\endgroup$ – Adam Davis Oct 23 '14 at 14:19
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    $\begingroup$ Ironically the proprietary digital modes some hams are using on the air, like DSTAR, are patent-encumbered as well! See ham.stackexchange.com/questions/809/… for more on the AMBE patents. Given the economies of scale, it may even be cheaper to obtain properly-licensed chips implementing GSM than it is right now for AMBE. (Of course, I've also heard it's notoriously hard for mere mortals to get datasheets on cell technology…) $\endgroup$ – natevw - AF7TB Feb 29 '16 at 21:56
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Honestly, the key technology to making this work has been around for quite a while, and that is the phone patch. Essentially, you can get on a repeater and dial a person from said repeater. The area of operations is fairly limited for such, but it has been done. And an SDR might help with this process, but it isn't required.

As far as digital, the key thing to remember is that Amateur bands prohibit encryption. Most of the useful things that one does over a cellular network require encryption of some form. Thus, it isn't likely to be of huge use. But yes, in principal it could be done.

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