Harris VDOC

[synegy3488]

This is a long shot -- does anyone have a capture log (from DSDPlus (with maximum verbosity) or other SDR tool) of a Harris system running with VDOC?

 

[SPECIAL_EYE]

What is VDOC my system might be running if it is what I think it is.

 

[medic550]

P25 VDOC (Voice and Data on Control)

 

[SPECIAL_EYE]

Can I figure it out with DSD or OP25 if my system has it?

 

[synegy3488]

Can I figure it out with DSD or OP25 if my system has it?

That is exactly what I'm also trying to determine; what tell-tale changes are made to the CC when a channel is operating in VDOC mode. Knowing Harris the change is probably super-subtle, they don't tend to implement manufacturer specific opcodes.

 

[120Comm]

Used to have some of those near me but they have all been converted to control + 1 voice channel (2 freqs) now. I suspect that won't help you, but if you want me to get some capture via DSD+ or something like that, let me know and I'll see if I can get near enough to a site to log it.

 

[SPECIAL_EYE]

P25 VDOC (Voice and Data on Control)

So if Medic550 is say ing Voice and Data on Control, does that mean it a small system with Voice and Data sharing the CC? If so my system is much bigger.

 

[120Comm]

So if Medic550 is say ing Voice and Data on Control, does that mean it a small system with Voice and Data sharing the CC? If so my system is much bigger.

Doesn't have to mean a small system. The one I'm talking about is (I think) one of the largest Harris systems out there. Or it's at least decently large - ~400 sites in 2 zones. Anyway, in my experience, VDOC is used in areas where you don't have many frequencies available or don't anticipate heavy traffic. The control channel is interrupted to carry voice or data traffic, and then resumes once the traffic is done.

 

[SPECIAL_EYE]

OK one way you could find out if a channel was using VDOC (or not) is with Unitrunker (UT). In my case version 2.0.0.73, have not tested newer.

Install and or open UT, make settings for the current control channel (CC) channel, DSD has a good spectrum display for that finding CC if not known.

Once UT is running hit the lightning bolt (clear hits), note this clears hits for all channels. Leave it run for as long as you like periodically checking the Channel tab, note the hit count on the current CC.

Each time you close UT it makes a back up copy of the previous session, then starts a new session (log). I clearded my hits an hour or so ago and have zero hits on the CC.

 

[SPECIAL_EYE]

In my last post (to late to edit) hits are voice call hits on the channel.

 

[TRENT310]

Doesn't have to mean a small system. The one I'm talking about is (I think) one of the largest Harris systems out there. Or it's at least decently large - ~400 sites in 2 zones. Anyway, in my experience, VDOC is used in areas where you don't have many frequencies available or don't anticipate heavy traffic. The control channel is interrupted to carry voice or data traffic, and then resumes once the traffic is done.

The biggest issues with VDOC sites in our system here is that other non-Harris manufacturer radios were having trouble actually cross-band roaming to the site and then staying on that site, because the CC dropout triggers a roam when it should actually trigger the subscriber radio queueing up user requests made during that time including emergency declaration/ERTT requests, and waiting up to as long as the site's time out timer for the CC to return, then transmit those queued requests inbound the usual ALOHA way. One more is getting upgraded this week leaving 2 afterwards in the system. Wish I had made some raw I/Q WAV recordings to pick apart now, for the request in this post. From a capacity perspective a VDOC and 2 channel site still has equivalent traffic handling capacity, but the 2-channel sites would be more P25 TIA standards compliant since VDOC is basically a proprietary equivalent to SCAT (on EDACS). Harris native radios display a unique icon on the display when they are registered to a VDOC site, which is why we're trying to figure out which identifying message is sent to Harris subscriber radios so it can behave properly.

Those sites bark out lots of MFID A4 opcodes which DSD+ doesn't understand, and some of those are interpreted as CRC error (but for the same amount of errors every time, it's a misinterpretation of the proprietary format TSBK when all the other TSBK before and after decode fine). I've been trying to ask Andy to change that behaviour and just display some raw hex output especially when the software is run with -v4 switches for highest console verbosity. Same with the extended format voice grants and updates, because cross-region I-calls for example re-iterate the WACN and SysID (aka Regions) and that doesn't fit in the compact format trunking message blocks.

 

[synegy3488]

Those sites bark out lots of MFID A4 opcodes which DSD+ doesn't understand, and some of those are interpreted as CRC error (but for the same amount of errors every time, it's a misinterpretation of the proprietary format TSBK when all the other TSBK before and after decode fine). I've been trying to ask Andy to change that behaviour and just display some raw hex output especially when the software is run with -v4 switches for highest console verbosity. Same with the extended format voice grants and updates, because cross-region I-calls for example re-iterate the WACN and SysID (aka Regions) and that doesn't fit in the compact format trunking message blocks.

Okay so you are saying sites in VDOC mode *are* actually transmitting non-standard (i.e. non-$00 MFID) TSBKs, and that the CC data stream contains TSBKs with a $A4 MFID?

That's very interesting. And I also wish you had I/Q recordings...