Understanding Capacity Plus trunking

[inigo88]

Note how the 3rd bit alternates as if it is a channel indicator. Also look at this different type of CSBK=62 ..
...

The first 4 bits are also 11x0 (where x alternates).

Sorry for the false alarm Ian, I noticed last night that they alternated while still saying the same thing in the message body. So the "message type" theory is out.

I think you are absolutely right that it is a TDMA slot indicator. When I run DSD on this system, much of the repeater activity is just Capacity Plus CSBK data (necessitating running it using "dsd -xr -fr" so it doesn't try to decode the CSBK data as voice). On screen it looks like this:

CSBK [Slot 0] Slot 1
CSBK Slot 0 [Slot 1]
CSBK [Slot 0] Slot 1
CSBK Slot 0 [Slot 1]
...

So I would surmise that bit 2 being set to "0" indicates the first TDMA channel slot, and "1" indicates the second TDMA channel slot (or vice versa).

Regards,

Inigo

 

[Jay911]

Here's some more fodder for you guys to explore. I've played around with it a bit and think I have figured out at least which frequencies belong to which locations.

I am reasonably certain that 452.4375 and 462.5375 belong together. Both are giving out color code 7, and similar rest LCNs. Interestingly enough, 452.4375 was spending a TON of time spitting out dozens of idle and "rest LCN" messages a second. This was not your typical half-second blip every two seconds - it was a 5-second-or-more long burst, with several seconds of quiet in between. I'm wondering if it was doing this while its partner (462.5375) was actually performing the voice call. Or is it maybe a link channel between the two systems?

Logic would follow that the other two channels I am able to track, 462.2375 and 463.9375, belong together as well. They both use color code 8 and report similar rest LCNs.

I think the reason I get varying levels of success in receiving the signals is an overwhelming amount of interference. A lot of these frequencies are common/itinerant channels in Canada and have dozens of licensed users in a particular geographical area.

As I mentioned earlier, I am getting what I think is an intruding signal on 463.9375 - if you browse the logs, searching for "colour code 1" will identify it. The groups/radio IDs shown there (2, 4, and 14) are the only ones not in the 200s or 300s in my logging.

There is a fifth frequency on which I've heard no data today - 463.7875. I might have to wait until crews return to work after the Easter weekend to see if that channel is in use. I have data from earlier in the week giving it a color code of 7, but I'd rather watch it a bit longer (and in comparison to other signals, as inigo suggested) to be sure.

If you think this particular discussion serves no purpose to deciphering CP itself and would be better served in its own thread in my locale, let me know and I'll start one there.

 

[dtscho]

I am trying to program a Capacity Plus system using the CPS. I am getting an "Out of Range" error on the TRBO radio. What are the possible causes of this? I'm assuming two of the causes could be wrong color code and incorrect member order of the Capacity Plus voice channel list. Anything else I should look at?

Thanks,
Dave

 

[Forts]

The only time I have seen that was when I was indeed out of range of the system. Perhaps you are missing a frequency in the channel pool.

 

[KatinEdmonton]

Your post regarding freq in 400MHz

Jay, I noticed some time back you had talked about some interference on your channels. You mentioned they were around 463-468 or so. (I work for a two way radio company and specialize in frequency management so I understand where your coming from). Have you tried looking up spectrum direct and see what/who they are allocated to in your area?(it's a free site and easy to use). If it is in the 400 band, the law only (Industry Canada) mandates a 10 k radius at best. As well if you and they are using Canada Wide or Alberta Wide Freq, you are out of luck, because they will allow anyone to use them, provided they let them know (IC). The best you can do is actually apply to have a dedicated freq for your location. If you are using a trunked system, a dedicated conventional or a rigging system, then you will have a better case if IC does see you have interference, cause that means someone is using that band illegally. (you probably know all this if you are in communications or a Firefighter), other wise I hope this helps. Your post caught my eye, because I grew up in Bragg Creek. Thanks K

 

[Jay911]

Hello,
It's not my system that I'm monitoring - it's a system near where I work. I have no control over what frequencies they use.

I am well aware of the TAFL and the IC online lookup functions on Spectrum Direct - I use it very often, for both scanner purposes and handling the radio licenses for my volunteer fire department.

The itinerant frequencies in use at the warehouse operation I have/had been monitoring are licensed to several dozen different entities, well inside the 10 km radius you specify. Most use conventional analog with either a CTCSS or DCS tone. There are a couple which are within one or two blocks of the warehouse, making it especially hard to work out the TRBO system as the conventional users cause RFI.

As for Bragg Creek, I've spent the past 21 years here, previously in Pickering, Ontario before that. Beautiful country - I have a view of the mountains, so I can see the nasty weather come right at us the downside being that most "interesting" comms are directly behind me towards the city.

 

[Forts]

I've come across a few new systems that I have popped up in my area, and they are different somehow... In both cases the channel I'm sitting on is spitting out a steady stream of data, no breaks or pauses in it at all. From the data I've gathered it looks somewhat like Capacity Plus but DMR Decoder doesn't see it as such. Here are some samples of the data I'm seeing, repeating over and over...

Unknown CSBK : CSBKO=1 + FID=6 0000010000000000000000000000000000000000000000000000000000001110
Short LC : Unknown SLCO=10 000010011110000001010000

Unknown CSBK : CSBKO=12 + FID=6 0000000000000111011110110000101100000000000000000000000000000000
Unknown CSBK : CSBKO=3 + FID=6 0000011111010011111011000000011111010100101100000010000000000010

Unknown CSBK : CSBKO=12 + FID=6 0000010000000111010010010000101100000000000000000000000000000000
Short LC : Unknown SLCO=9 000101010100000000010000

Unknown CSBK : CSBKO=12 + FID=6 000000000000001111110101000010110000000000000000 0000000000000000
Unknown SLCO=9 000101010100000000010000

Any thoughts? I haven't logged any user traffic on these systems yet (they may still be in the setup stages, I don't know). Different flavour of Capacity Plus? Or maybe Connect Plus? I've got lots of logs if anyone wants to see anything further.

 

[Forts]

One more question for the group. On another unknown system I would see statements like this:

10:20:59 AM DMR Data Frame
CACH : TACT AT=1 Ch 2 Last fragment of LC
Slot Type : Colour Code 3 CSBK
Capacity Plus CSBK : CSBKO=62
Activity Update : Group 16 call on LCN 4
10:20:59 AM Short LC : Capacity Plus Act_Updt - Rest Channel is LCN 4

If the group call is taking place on LCN 4.... how can LCN 4 be the rest channel? And from this info would the assumption be that the frequency be logged is or is *not* LCN 4?

I think I need to spend some time logging a known system and see what info is displayed.

 

[JRayfield]

There is no 'rest channel' in Connect Plus systems, like there is in Capacity Plus systems. Connect Plus systems use a dedicated control 'channel' (actually, one time slot on a repeater is used as a 'control channel').

John Rayfield, Jr.
CETma
W0PM

One more question for the group. On another unknown system I would see statements like this:

10:20:59 AM DMR Data Frame
CACH : TACT AT=1 Ch 2 Last fragment of LC
Slot Type : Colour Code 3 CSBK
Capacity Plus CSBK : CSBKO=62
Activity Update : Group 16 call on LCN 4
10:20:59 AM Short LC : Capacity Plus Act_Updt - Rest Channel is LCN 4

If the group call is taking place on LCN 4.... how can LCN 4 be the rest channel? And from this info would the assumption be that the frequency be logged is or is *not* LCN 4?

I think I need to spend some time logging a known system and see what info is displayed.

 

[inigo88]

Hey Forts,

Good to see this thread revived! I gave up DMR decode hunting for a little while because with one computer, I can't figure out the best way to run DSD (to actually listen to talkgroup traffic) and DMRDecode (to log the talkgroup ID). Any idea how to accomplish this to actually identify talkgroup IDs?

Regarding your first question, the continuous control channel variant is mototrbo Connect Plus (like John said). Maybe we should start a new thread and analyze it there (so we don't mix the message formats up in the same thread?).

Regarding your observation on the rest channel being sometimes assigned as the current active LCN, I have observed this too! It is the reason why I thought originally that we didn't have the message format correct. However I've noticed that it only does this for short voice transmissions, and if they're longer the rest channel will bump to a new LCN. I've been able to verify this by hearing the "beacon" bursts on the new frequency corresponding to the assigned rest LCN using a second scanner when this happens (leaving the discriminator tapped scanner hooked to DMRDecode on the original frequency). Therefore, I'm inclined to believe that we have the format right, but that the in-use repeater doesn't always transmit a new rest LCN if the transmission is quick enough. In this case the rest channel beacon bursts resume on the original frequency when the voice transmission ceases.

 

[IanWraith]

I have created a new forum thread on this subject.

Ian

 

[Forts]

Hey Forts,

Good to see this thread revived! I gave up DMR decode hunting for a little while because with one computer, I can't figure out the best way to run DSD (to actually listen to talkgroup traffic) and DMRDecode (to log the talkgroup ID). Any idea how to accomplish this to actually identify talkgroup IDs?

For now, I think we are pretty much stuck with using multiple tapped scanners and multiple PC's at the same time. The only way we could get around this is if there was in easy way in DSD and DMR Decode to select different audio inputs and run them simultaneously on the same computer.

Regarding your first question, the continuous control channel variant is mototrbo Connect Plus (like John said). Maybe we should start a new thread and analyze it there (so we don't mix the message formats up in the same thread?).

Ahh ok... I suspected as much. I've got a few of those popping up around here now.

Regarding your observation on the rest channel being sometimes assigned as the current active LCN, I have observed this too! It is the reason why I thought originally that we didn't have the message format correct. However I've noticed that it only does this for short voice transmissions, and if they're longer the rest channel will bump to a new LCN. I've been able to verify this by hearing the "beacon" bursts on the new frequency corresponding to the assigned rest LCN using a second scanner when this happens (leaving the discriminator tapped scanner hooked to DMRDecode on the original frequency). Therefore, I'm inclined to believe that we have the format right, but that the in-use repeater doesn't always transmit a new rest LCN if the transmission is quick enough. In this case the rest channel beacon bursts resume on the original frequency when the voice transmission ceases.

Ok, that makes sense. In the examples I posted the transmissions were indeed very brief. Thanks for the info.

 

[Forts]

I have created a new forum thread on this subject.

Ian

Great! Hopefully we can sort thru those systems a little bit too...

 

[IanWraith]

Hello All

Have any of you ever seen a single frequency Capacity Plus system ?

A new DMR system has appeared here which according to the online licence documents is assigned a single frequency pair (i.e an input and output) and belongs to a local hospital. When I started monitoring it I was amazed to see it is a Capacity Plus system. The LCN is channel 2 until there is a voice call when it is channel 1. Can anyone explain the advantages (if there are any) of using Capacity Plus on a single frequency ?

Regards

Ian

 

[Forts]

No idea why that would be... unless the licensing documentation is incomplete and there are indeed other frequency pairs to be used. I don't see any benefit to doing that over just having a regular conventional TRBO channel using both time slots. Weird!

 

[IanWraith]

Yes and its not a huge hospital which previously made do with a single VHF simplex channel. A much larger hospital (but one in another health service admistrative region) near here has just installed a standard single frequency DMR repeater which is what I would have expected the other one to do also.

 

[JRayfield]

Trunking provides for using talkgroups that 'span' both channels, so channel scanning doesn't have to be done. 'Scanning' talkgroups is much better than scanning channels or time slots.

John Rayfield, Jr. CETma

Hello All

Have any of you ever seen a single frequency Capacity Plus system ?

A new DMR system has appeared here which according to the online licence documents is assigned a single frequency pair (i.e an input and output) and belongs to a local hospital. When I started monitoring it I was amazed to see it is a Capacity Plus system. The LCN is channel 2 until there is a voice call when it is channel 1. Can anyone explain the advantages (if there are any) of using Capacity Plus on a single frequency ?

Regards

Ian

 

[IanWraith]

Trunking provides for using talkgroups that 'span' both channels, so channel scanning doesn't have to be done. 'Scanning' talkgroups is much better than scanning channels or time slots.

Nice to have an explanation. Thanks John.

Ian

 

[dasnps]

I am currently running DMRDecode on a TRBO site nearby. I am not sure as to what type of site this actually is, but I am getting some results that say Capacity Plus Full Link Control, but then shows an LCN of 0. Any ideas as to why this is showing this? It isn't possible in the software, as far as I know, to even have an LCN of 0.

CACH : TACT Ch 2 Continuation fragment of LC
Slot Type : Colour Code 2 Terminator with LC
Capacity Plus Full Link Control LC : FLCO=4
Group Address 39 Source Address 655 LCN 0
1:20:09 PM DMR Data Frame
CACH : TACT AT=1 Ch 1 Continuation fragment of LC
Slot Type : Colour Code 2 Idle
1:20:09 PM DMR Data Frame
CACH : TACT Ch 2 Last fragment of LC
Slot Type : Colour Code 2 Terminator with LC
Capacity Plus Full Link Control LC : FLCO=4
Group Address 39 Source Address 655 LCN 0

 

[Forts]

Are you using the latest greatest version of DMRDecode (v58) ? Do you happen to know how many frequencies are in use for this system? Perhaps it's a large system and DMRd is mis-interpreting the LCN's. Capacity Plus LCN's go from 1 to 12.