After checking out your web site, I see you're trying to use standard off-the-shelf hardware. In that case, this is the wrong avenue to pursue. I think a better idea, without knowing anything about the deep technical details, would be to drop the phone-to-phone mesh network effort and focus instead on creating some sort of BTS-in-a-box that can be deployed by airdrop or whatever, using low power components capable of being maintained on solar alone. The mesh networking could come into play here, where perhaps a BTS-to-BTS mesh can be developed (again, I don't even know if this is possible, but this seems to be a better avenue to pursue if stock cell phones are a goal). There is at least one group working to deploy OpenBTS-based hardware in extremely remote locations running under very limited power budgets. This kind of solution could use 100% stock phone hardware. While carrier-grade BTS hardware is ridiculously expensive, it doesn't have to be that way for this kind of use case. Also, in an emergency situation like the Haiti earthquake, which was your inspiration, are you really going to be concerned with all the strict legalities involved, or are you going to be more concerned with saving lives? Let's see. Tens of thousands dead and injured, and more deaths by the minute. So, we better make sure our hardware is 100% compliant with local laws and difficult to deploy since it needs custom software and possible hardware mods to function. Or, maybe, just maybe, in this type of disaster scenario, since the local cellular service is down anyway, easily deploy a legally questionable but 100% workable solution many times faster. As an aside, I read an article in an amateur radio magazine back in the 1980s by someone who designed a portable solar-powered packet radio repeater with stock hardware of the time. He use an old ammo box to hold everything and powered it with a solar panel and motorcycle battery. It was self-contained, had no overheating issues (he checked), and was just cool. Scott On Thu, Sep 1, 2011 at 7:11 AM, Paul Gardner-Stephen <paul(a)servalproject.org

You have to essentially stick with GSM mostly so: - Same modulation GMSK - Same frame structure of 4.615ms - Same bursts : 156.25 bits - Same channel coding for CCH and TCH - Same channel spacing of 200kHz This way you can mostly reuse the GSM primitives offered by the baseband DSP. Then you have to create new primitives so that phones can do between them what they would do with a BTS - Transmit a FCCH / SCH ( so that a phone can become 'local master' and provide sync to other phones ) - RX RACH requests ( so that a phone that's 'local master' can answer incoming requests for channels ) Both of theses actually already exist (I coded them). Then you have to come up with a protocol that with those primitives can build a stable mesh network. And this latter part doesn't actually require any messing with osmocom-bb at first, you should design and simulate it fully _first_. And then once you have it you can start implementing it on real hardware. You could probably get some inspiration from the specs of TETRA DMO mode since what you want is essentially a DMO mode for GSM. Cheers, Sylvain

You can't do it like that here (like you could with Wifi). Because the mesh network itself is gonna have to provide negatiation and everything _to_ establish reliable packet transport. (neighbor discovery, master election, organization or the nodes in 'micro network' for sync etc etc ...). All that needs to be figured out first, because when you power up a phone, it doesn't have _anything_ and before it can even think about exchanging packet, it'll have to find some other node to provide sync ... (and then whenever a node is changed / moved / ... adapt) Cheers, Sylvain

Hi Paul, another point to assess is if it is feasible at all to use these devices with a to-be-developed p2p protocol in terms of practicability to operate them in the field as you intend. Because there is still the issue of power consumption you can not get around so easily. GSM phones can maintain their high standby-times only by relying on stable basestations to be able to switch off their transceivers for most of the time. As Sylvain stated there has to be a master kind of imitating the BS for its neighbours to sync on. This master most certainly had to send a beacon all the time so its battery would drain quickly. The operation time in master mode would be significantly less than the usual speech-time of that phone, so not much more than very few hours. As there is only a short radio range, all participating devices had to act as a master for some time of their operation and suffer from this energy consuming mode, especially in loosely covered areas where are no or few other devices reachable. It's just my view that this should be considered, too, before making huge efforts to implement sth. like this for the intended purpose. Of course it would be a cool addon to osmocom-bb and this shouldn't keep anybody from doing this for the sake of rising to the challenge. ;-) Regards, Mad