Re: [Discuss-gnuradio] The OpenBTS project - an open-source GSM basestation using the USRP and VoIP

[Eric Blossom]

On Thu, Sep 04, 2008 at 09:56:18AM -0700, David Burgess wrote:
> Eric -
>
> Here's what can be released now:
>
>       -- The GMSK radiomodem and its interface to the USRP.  (GSM 05.01, 
> 05.04, 
> 05.05)
>       -- The interface between the GMSK radiomodem and the rest of the GSM 
> stack.
>       -- The FEC coders and decoders used in GSM 05.03.  (Already in CVS, 
> BTW.)
>       -- Most of the TMDA functions of GSM 05.02.
>       -- Serializers and deserializers for L3 messages.  (GSM 04.08)
>       -- The hybrid GSM/SIP control layer.  (GSM 04.08, ITU-T Q.931, IETF 
> RFC-3261, IETF RFC-3550)
>       -- An incomplete SMS stack.

That's great.  Thanks for being explicit.

Will this be licensed under the GPL?


> What's missing:
>
>       -- Parts of the TDMA (GSM 05.02).  This can all be done with tables and 
> isn't that complex.
>       -- The code to organize the FEC components into actual L1 channels 
> (defined in GMS 05.03).  This is straightforward, though, and we will 
> publish some base-class examples.  Once you have the framework in place, 
> this stuff almost writes itself.
>       -- GSM L2, LAPDm, is defined in GSM 04.06.  It borrows heavily from 
> ISDN 
> LAPD (ITU-T Q.921).  Both LAPDm and LAPD are subsets of HDLC.  We will 
> publish a initial .h object framework.  There is also an open-source ISDN 
> LAPD implementation that makes a useful reference.  Our current LAPDm is 
> less than 500 lines of code, so replacing it should not be a huge chore, 
> especially with a .h object framework and example LAPD as a starting point.

Very good.

> I'm sorry to sound coy about this.  It would simply not be prudent to 
> release some of this code into the public right now and it might take over 
> a year for that situation to be resolved.  We don't want to wait another 
> year so we're releasing what we can and hoping enough interested people get 
> involved to replace what's missing.

I can understand that.  Thanks for being forthright about the situation.

Eric