Russell Have you seen this? http://www.findmespot.com/en/ So it works in an emergency...first hand experience (family member in the m= iddle of the desert with a medical emergency). Second...there are cruise ships that have on-board cellular like systems, s= uch as Disney Wave Phone....its a phillips handset, has the ability for SMS= and is short range. Not sure of the other details on it, maybe in a month = I can report more info :-) -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of= RussellMc Sent: Tuesday, April 09, 2013 6:21 AM To: Microcontroller discussion list - Public. Subject: [EE]:: GSM cellular phone - handset to handset communications I'm interested in knowing what it would take at a minimum to enable GSM cel= lphone to cellphone comms among a limited number of phones in the absence o= f a traditional cell-site structure. ie add your own cell-site if necessary= .. That could be tightened up somewhat to say GSM 2G platform or better and co= uld be just SMS, just voice, and ideally SMS and voice and data. Either all phones involved need to be capable of peer to peer communication= s, or a cell site / base station "cellphone tower" is needed. Has anyone here any experience in this area or can comment on the feasibili= ty of using existing in-phone GSM hardware to meet this need. Assume regulatory issues are not of concern (even though in many cases they= will be). A hypothetical example application might be a "flying cell site" that is us= ed in look-down mode from high altitudes to provide search and rescue radio= communications in rugged terrain allowing the use of cellphones by ground = parties - which would otherwise be ineffective in cell-site-less valleys. = If you can talk to the cellphone equipped hiker lying incapacitated with a = broken leg, so much the better. (An extremely experienced wilderness vetera= n died some years ago in NZ after lying incapacitated for several weeks af= ter a fall and not being found until too late. He should have been carrying= a locator beacon, but with a flying cellsite a $25 phone would have saved = his life. This example would easily support the basic "$1000 solution" belo= w (although it would usually done for even more in that application) but so= me applications would benefit from lowest possible cost. Russell "Resources:" The minimum arrangement that I'm currently aware of is to implement a cell = site (or "cellphone tower") using a SDR (Software defined radio) and a comp= uter of some sort. Almost any linux box can be used and I've recently read = of people doing it with a Raspberry Pi. The probably most accessible, but not necessarily the best, solution is the= use of Open BTS (Open Base Transceiver Station) free software (refs below)= with a suitable SDR (Software Defined Radio). The usual hardware starting point is the open source USRP1 - User Software = Defined Radio transceiver. A version of this, the USRPB100 can be bought fully assembled from Ettus Re= search for $US650 retail. Various Ettus Research SDR's here https://www.ettus.com/product/category/USRP_Bus_Series Add an eg Raspberry Pi and probably a GPS timing source, basic power supply= and aerial(s) and you have a workable base for around $US1000 (assuming y= our time is worth zilch). That's a good start , but cheaper still would be better. _____________________ Android SDR anyone :-) Agh: That opened up a whole new line of thought. eg Realtek RTL2832U DVB st= ick gives you an SDR control core for under $20. Looks like it could handle the receive size OK. Transmit? http://wiki.spench.net/wiki/RTL2832U http://www.hamradioscience.com/forum/discussion/88/setting-up-your-rtl2832u= -dongle-for-sdr-use/p1 http://sdr.osmocom.org/trac/wiki/rtl-sdr http://dx.com/p/rtl2832u-r820t-mini-dvb-t-dab-fm-usb-digital-tv-dongle-blac= k-170541 __________________ Open BTS - Wikipedia http://en.wikipedia.org/wiki/OpenBTS OpenBTS (Open Base Transceiver Station) is a software-based GSM access poin= t, allowing standard GSM-compatible mobile phones to be used as SIP endpoin= ts in Voice over IP (VOIP) networks. OpenBTS is the first free software im= plementation of the lower three layers of the industry-standard GSM protoco= l stack. It is written in C++ and released as free software under the terms= of version 3 of the GNU Affero General Public License (AGPL). Good GSM / Open BTS video 5m:34 http://www.youtube.com/watch?v=3DZoWKYJ1ATeE&feature=3Dplayer_embedded USRP Wikipedia http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral USRP1 circuit diagram http://code.ettus.com/redmine/ettus/attachments/download/209/usrp1.pdf http://www.tcmaker.org/wiki/doku.php?id=3Dhamradio:ettus_research_u= srp1 USRP1 for sale $700 https://www.ettus.com/product/details/USRP-PKG The USRP1 is the original Universal Software Radio Peripheral(tm) hardware = (USRP) that provides entry-level RF processing capability. It is intended t= o provide software defined radio development capability for cost-sensitive = users and applications. The architecture includes an Altera Cyclone FPGA, 6= 4 MS/s dual ADC, 128 MS/s dual DAC and USB 2.0 connectivity to provide data to host processors. A modular design allow= s the USRP1 to operate from DC to 6 GHz. The USRP1 platform can support two= complete RF daughterboards. This feature makes the USRP ideal for applicat= ions requiring high isolation between transmit and receive chains, or dual-= band dual transmit/receive operation. The USRP1 can stream up to 8 MS/s to and from host applications, and users can = implement custom functions in the FPGA fabric. _____________________________ 25C3 - Running your own GSM network. Excellent 44 minute video. http://www.youtube.com/watch?feature=3Dendscreen&NR=3D1&v=3De_9hPRF5fzA http://events.ccc.de/congress/2008/wiki/GSM/ Harald Welte This presentation will mark the first public release of a new = GPL licensed Free Software project implementing the GSM fixed network, incl= uding the various minimal necessary functionality of BSC, MSC, HLR. It will= introduce the respective standards and protocols, as well as a short demon= stration of an actual phone call between two mobile phones registered to th= e base station. On the Ethernet/IP based Internet, we are used to Free Soft= ware and general-purpose hardware. The worlds second largest communications network GSM couldn't be any more d= ifferent. Even though the protocols are standardized and publicly available= at the ETSI, all implementations are highly-guarded proprietary secrets of= a few major players in the industry. The hardware is even more closed, as = there is not a single GSM subscriber or base station chipset with even the = least bit of publicly known information. Nonetheless, in recent years there= are a number of different projects working on driving a wedge of Openness = into this world. You might have heard about other projects like the THC GSM= sniffer project (pure wireshark-like functionality) and OpenBTS (a softwar= e defined radio based GSM base station interfacing with the Asterisk VOIP s= erver). This presentation is about yet another new GSM related Open Source = project. A project that follows the GSM specs more closely and actually aim= s at interoperability with existing equipment such as hardware BTS hooked u= p via S2M ... _____________ Raspberry Pi Used To Replace A 30-Foot GSM Base Station And Create A Workin= g Mobile Network Uses Open BTS and a Ettus SDR Excellent links in discussio= n http://techcrunch.com/2012/12/21/raspberry-pi-used-to-replace-a-30-foot-g= sm-base-station-and-create-a-working-mobile-network/ Open BTS source forge redirect page http://wush.net/trac/rangepublic This Trac is the home of the OpenBTS public release, a FOSS version of = Range Network's self-contained SDR/GSM/VoIP stack. GNU Radio http://gnuradio.org/redmine/projects/gnuradio/wiki/OpenBTS Freeswitch http://en.wikipedia.org/wiki/FreeSWITCH FreeSWITCH is free and open source communications software for the creation= of voice and messaging products. It is licensed under the Mozilla Public L= icense (MPL), a free software license. Its core library, libfreeswitch, is = capable of being embedded into other projects, as well as being used as a s= tand-alone application. Open BTS - superb You tube intro video for Open BTS Uses Ettus Research SPR USRP N210, ($US 1500 list) BUT could use eg USRPB100 at $US650 list. Software Radio / OpenBTS - The Well Tempered Hacker Ep 4 16m 20s http://www.youtube.com/watch?v=3DpTb1_v8M6iA Range Networks http://www.rangenetworks.com/ -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t This e-mail (and any attachments) is confidential and may be privileged. A= ny unauthorized use, copying, disclosure or dissemination of this communica= tion is prohibited. 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