P25 repeaters

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Re: P25 repeaters

Postby Wowbagger » Thu Aug 20, 2009 1:55 pm

MattSR wrote:Like any software project, (especially one like OP25) this project has people with all sorts of eclectic skills.

Join the mailing list and you'll see exactly how/what I contribute. Surely your employer won't discipline you for reading up on our efforts.


It's not a question of that - it's the questions of:
1) Potential "contamination" of our closed-source code with GPL code. Yes, I am disciplined enough to not do so on purpose, but, having seen a GPL implementation, it is possible I might accidentally come close with our implementation.
2) Potential "contamination" the other way: there's almost no safe way they could ever accept anything put high-level specifications from me, as I've "seen too much" that is under NDA.
These opinions are mine, not Aeroflex's - if you want service info, manual, or other official support please contact Aeroflex directly.

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Re: P25 repeaters

Postby MattSR » Thu Aug 20, 2009 8:47 pm

I wouldn't be worried about number 1 - Aeroflex's framework would be vastly different and more mature than OP25/GNUradio since the latter are only part time "enthusiast" type projects. Your analyzers appear to be designed and built/coded to a spec - OP25 is more 'beta' software at this stage, and as you said its a matter of professionalism for yourself also.

Point number 2 is the one that intrigues me - OP25 has been implemented from the TIA/ETSI specs and publicly available information such as the Daniels P25 training manual - nothing more.. Apart from the DVSI stuff, is there anything else that's encumbered by NDA/patents?

As much as we need good contributors, at the end of the day, its a not-for-profit, research project - if its going to threaten your income or career then its simply not worth it. Morally and ethically, you could contribute things are that are public knowledge, but it could be a potential minefield for you if anyone wanted to play hardball.

Cheers,
Matt

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Re: P25 repeaters

Postby Wowbagger » Thu Aug 20, 2009 8:55 pm

MattSR wrote:Point number 2 is the one that intrigues me - OP25 has been implemented from the TIA/ETSI specs and publicly available information such as the Daniels P25 training manual - nothing more.. Apart from the DVSI stuff, is there anything else that's encumbered by NDA/patents?


Oh, things like how Motorola does their ADP encryption, modulation parameters on some of the derivative protocols like Wide-Pulse and LSM - and other things that I really cannot talk about.

Perhaps it is just an over-abundance of caution on my part, but I'd rather not have even "the appearance of impropriety".
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Re: P25 repeaters

Postby MattSR » Thu Aug 20, 2009 10:30 pm

OK cool, that puts my mind at rest. I expected as much re the wide pulse/LSM/other proprietary stuff

Yes - ADP algorithm isn't part of the P25 spec, so I would automatically consider that to be proprietary. Here's where it gets tricky though. the Keyfill interface/protocol *is* part of the publicly available spec, and several manufacturers have developed keyloaders to fill P25 radios. Would it then be considered a breach of Motorola's IP to design a KFD that can load a 40-bit key using the TIA102-AACD specs? Since the spec itself is public, I wouldn't think so - all you're doing is loading an arbitrary 40-bit key into a subscriber unit, all the proprietary stuff is done inside the radio.. Just as long as you didn't use the word "ADP" it should be fine..

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Re: P25 repeaters

Postby Wowbagger » Fri Aug 21, 2009 7:23 am

MattSR wrote:OK cool, that puts my mind at rest. I expected as much re the wide pulse/LSM/other proprietary stuff

Yes - ADP algorithm isn't part of the P25 spec, so I would automatically consider that to be proprietary. Here's where it gets tricky though. the Keyfill interface/protocol *is* part of the publicly available spec, and several manufacturers have developed keyloaders to fill P25 radios. Would it then be considered a breach of Motorola's IP to design a KFD that can load a 40-bit key using the TIA102-AACD specs? Since the spec itself is public, I wouldn't think so - all you're doing is loading an arbitrary 40-bit key into a subscriber unit, all the proprietary stuff is done inside the radio.. Just as long as you didn't use the word "ADP" it should be fine..


Actually, there are 2 key fill algorithms: the APCO-25 specified one, which is really a subset of the OTAR commands, and a Motorola proprietary one, that most certainly ISN'T documented outside of Motorola. Many of the old keyfill devices didn't have the P25 algorithm, only the Motorola one, which was called ASN.

Since many of our customers had only the older KFDs, and needed to be able to keyload the 2975 in order to test the encryption of their radios, we had to support ASN. So, we began negotiations with Motorola to get the ASN protocol license. Dealing with Motorola's contracts people is part of where my "abundance of caution" comes from - the amount of recycled male bovine cattle feed we dealt with was truly unbelievable.

Meanwhile, while trying to understand the APCO-25 Key Fill protocol, I had, incidentally, reverse engineered much of the ASN protocol as well - I had just a couple of questions that were not clear from the process.

We finally got all the legal "i"'s dotted and "t"'s crossed, and Motorola delivered the "documentation" on ASN - a photocopy of couple of pages of handwritten notes. Had I not already worked out most of the protocol it would not have been sufficient to implement the protocol.
These opinions are mine, not Aeroflex's - if you want service info, manual, or other official support please contact Aeroflex directly.

MattSR
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Re: P25 repeaters

Postby MattSR » Fri Aug 21, 2009 9:09 am

Hehe I'm not surprised - just as the P25 CAI evolved from ASTRO VSELP, P25-KFD probably evolved from ASN legacy mode.

In any case, its a very common style of interface thats been documented in many engineering textbooks since before 2 way radios started using encryption... All they're really patenting is the protocol process/opcodes/framing etc...

Cheers,


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