I've spent the last couple of months reading through the etsi
documents trying to figure out the packet structure of the 'forward to
pc' option on a hytera radio.
Having done some detective work and comparing packets I can decode
radio ID, LLID, and extract SMS data by bit bashing. I would prefer to
actually understand the whole packet structure so I can decode it
properly rather than blindly extracting the useful data.
The packet does at first appear to be a standard etsi packet,
containing all the blocks.
The issue I'm having is the documents and all open source software I
can find deal with the air side blocks, not a network packet.
Take for example the first 8 bits in the packet : "00001001", which
could be any of the following :
1) 1001 = Idle Data
2) Privacy Flag=0, Reserved Flag=0 and FLCO=001001 making up the first
line in a Full LC header.
3) 001001=8 bit ISO/IEC 8859-7
4) 1001 = SAP 9 = Short Data Services over PDP
Without figuring out some basics, like blocktype I can't work out
which interleaving to use (bptc, hamming etc)
Then there is the LLID. All ETSI documents say it should be
24bits+24bits, but I see the CAI in each address making it 28 or 32
bits for each.
I've attached a text file with some example recieved data split into
colums to make comparision easier for myself.
Im not asking for a full packet decode (although I wouldn't say no!),
just a push in the right direction on how to figure out the packet
type (It must be the first thing transmitted right?)
I realise this isn't a DVSwitch question, but I cant think of a more
knowledgeable group of people on the DMR protocol. If you think there
would be a better place to ask this, please let me know!
Thank you for taking the time to read this, I really hope you can help.