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Paul Gardner-Stephen paul at servalproject.orgHi Sylvain, On Thu, Sep 1, 2011 at 10:51 PM, Sylvain Munaut <246tnt at gmail.com> wrote: > 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). Most interesting! > Then you have to come up with a protocol that with those primitives > can build a stable mesh network. Well, once there is a stable packet transport, then it is fairly easy to build the mesh on top. > 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. Indeed. The Serval mesh software is being setup so that it can use any link-layer, including such a GSMish one as you have described. That part is the easy part from my perspective. > You could probably get some inspiration from the specs of TETRA DMO > mode since what you want is essentially a DMO mode for GSM. Yes, in some ways that is what we want. We also need to deal with bridging to WiFi and some other odd bits and pieces. Paul. > Cheers, > > Sylvain >