From: David A. B. <dbu...@jc...> - 2010-07-24 17:03:46
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Paul - I think the idea of building a handset for an ISM band is interesting, but I don't think that 915 is a good choice. First, the bandwidth may be too narrow to support the frequency duplexing that is common in most cellular protocols. Second, such systems would be useful only in ITU region 2 and a few other oddball countries out there, like Australia, who don't strictly follow the standard ITU bandplans. A better band might be 2.4 GHz. There's plenty of bandwidth and it's much more standardized across the globe. The down side is that you lose about 60% of your range by moving to a higher frequency. You might make some of that up with higher antenna gain at the basestation. Your other big problem, in any ISM band, is that you will suffer horrible interference from 802.11 networks, other unlicensed IP radios, CCTV networks, remote-controlled airplanes and all kinds of other random junk, especially if you try to operate over any significant distances. Cellular networks run on licensed spectrum for good reason: you need to be able to control you uplink band over very large areas. It's not all about greed and social control. Really. All that said, if you really want a handset for a non-standard band, it's probably possible without "rolling your own". You just need to know a handset maker and China and be prepared to order at least 10,000 of them. -- David On Jul 23, 2010, at 5:28 PM, Paul Gardner-Stephen wrote: > Hello, > > I would also like to pitch in with my support for a software mobile > phone. > > In addition to the obvious GSM applications, I see a further benefit > in that it allows use of the ISM915 band that lies between the up and > down bands for mesh telephony. > At servalproject.org we already have a P2P mesh mobile telephony > architecture which we have proved, and could be used as an > interconnect for networks of OpenBTSs. > In fact, as soon as I can find some funding to do so, we will begin > working on doing just that. However, the ISM915 side of things does > require the same kind of crazy baseband processor coding as would > implementing the GSM protocols themselves, but the value would be in > the extended mesh range that would result. > This could be used for stand-alone mesh mobile networks, but also to > extend the range of the OpenBTS by using GSM as far as possible, with > the mesh forming an annulus of extended best-effort coverage beyond > that. > > If anyone is interested in doing their PhD in this space, or otherwise > contributing to such an effort, I would be delighted to hear from you. > > On a related note, what does the OpenMoko use for the baseband radio? > It it open or closed source? > > Paul. > > ---------------------------------------------------------------------- > -------- > This SF.net email is sponsored by Sprint > What will you do first with EVO, the first 4G phone? > Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first > _______________________________________________ > Openbts-discuss mailing list > Ope...@li... > https://lists.sourceforge.net/lists/listinfo/openbts-discuss David A. Burgess Kestrel Signal Processing, Inc. |