Linked Capacity + Systems With > 8 Channels Understanding Thread Plus Raw Recordings

[jcardani]

Linked Capacity + Systems With > 8 Channels Understanding Thread Plus Raw Recordings

Hi All

This threads directed to the developers of DSDPlus, WinDSD, and others to implement updates to their program to enable the following of linked capacity plus systems with over 8 channels. Per Eric C., systems over 8 channels are not supported by the DSD programs because there were none at the time to test.

I recorded 7 raw audio files of a local system. Each file is from a different site/channel. See links below:

Site 6 Channel 9 - 10 (Voice traffic)
https://www.dropbox.com/s/7gfoj32uvqh6ggf/DSDPlus-Raw-Input_2015-11-23@210119.wav?dl=0

Site 5 Channel 9 - 10 (Voice traffic)
https://www.dropbox.com/s/p1cbo6oae2l1trd/DSDPlus-Raw-Input_2015-11-23@210404.wav?dl=0

Site 7 Channel 13 - 14 (Voice traffic)
https://www.dropbox.com/s/eqsfrc1crka5da3/DSDPlus-Raw-Input_2015-11-23@210539.wav?dl=0

Site 1 Unknown Chanel > 8 (Voice traffic)
https://www.dropbox.com/s/p61x40ne9h9vjxj/DSDPlus-Raw-Input_2015-11-23@211834.wav?dl=0

Site 1 Unknown Channel > 8 (no voice but several grants)
https://www.dropbox.com/s/r6x52i4w0eu0ycd/DSDPlus-Raw-Input_2015-11-23@211941.wav?dl=0

Site 1 Unknown Channel > 8 (no voice but several grants)
https://www.dropbox.com/s/jhm6vnxjiwzmldl/DSDPlus-Raw-Input_2015-11-23@212714.wav?dl=0

Site 1 Unknown Channel > 8 (no voice but several grants)
https://www.dropbox.com/s/ywphdbnqu5z0p5t/DSDPlus-Raw-Input_2015-11-23@212913.wav?dl=0


The last 3 had lots of grants but no voice. It would be great if someone would let me know the channel numbers for the 4 site 1 recordings if possible.

In addition I believe at least 1 Private call was recorded above.

Hopefully the developers would be able to figure out how to support systems with over 8 channels.

thanks

Joe




Originally Posted by EricCottrell View Post
Hello,

It is a problem with DSDPlus, but likely would also occur with DSD. When Cap+ was being figured out, the biggest system monitored was eight channels (4 repeaters). There is a status message that normally shows activity for channels 1 to 8, and 6 talkgroups. It is known that fields change to show activity for channels 9 to 16, but exact details were difficult to get. Most Cap+ systems are 8 channels or less.

It would be very helpful if you could do a raw recording with DSDPlus when this event occurs, so the developers could see what changes in the messages occur. A recording during peak activity would likely be the best time.

What system is this?

73 Eric

 

[natedawg1604]

Waittt, I thought Fastlane doesn't yet support support the capacity plus trunking protocol AT ALL, regardless of how many channels. Did I miss something here?

 

[DaveNF2G]

Capacity Plus trunking has been supported since before the Fast Lane came out.

 

[jcardani]

I believe that Linked Capacity Plus trunk following is not fully supported but you can definitely see activity on Capacity Plus system with DSDPlus. It does not currently show activity (or even recognize) channel grants to channels 8 through 16. And also if there's more than 6 simultaneous grants at once.

Refer to Eric Cottrell's answer at the bottom of my first post.

I certainly hope that DSDPlus, Eric C, and Denny S use these raw recording in their development to improve Linked Cap+ support.

 

[EricCottrell]

Hello,

Thanks very much for the recordings. I plan to look at them over the holiday weekend.

The first status message has data fields for channel activity for channel 1 through 8 and the first six active talkgroups, so that jives with your observation.

I do have information on the format of the second status message, but the unknown is information on one small data field that determines if it is the first or last status message. If there is only one status message, then both the first and last bits are set. So which bit is used for first and which bit for last is not known.

73 Eric

 

[jcardani]

Hi Eric,

The system is really busy here most of the day and evening so just let me know if you need more recordings.

 

[natedawg1604]

Capacity Plus trunking has been supported since before the Fast Lane came out.

Are you talking about decoding the bits transmitted on a capacity plus frequency, or tracking a talkgroup in real-time across all Cap+ frequencies? I thought all versions of DSD+ released thus far, only support the former at present, along with decoding the audio from individual frequencies. Am I missing something here?

The current FastLane documentation states "Cap+ trunking is less supported (no rest channel following)". Isn't the rest channel the functional equivalent of a control channel, which you have to follow in order to monitor individual talkgroups?

 

[slicerwizard]

Looks to me like you summed up the current state of affairs perfectly.

 

[DSheirer]

I certainly hope that DSDPlus, Eric C, and Denny S use these raw recording in their development to improve Linked Cap+ support.

Thanks for the samples. I'll dig into them when I start the DMR decoder for version 0.3.x.

I have 3 or 4 strong DMR systems local, but none are as busy as what you're describing.

cheers,
Denny

 

[DaveNF2G]

Are you talking about decoding the bits transmitted on a capacity plus frequency, or tracking a talkgroup in real-time across all Cap+ frequencies? I thought all versions of DSD+ released thus far, only support the former at present, along with decoding the audio from individual frequencies. Am I missing something here?

The current FastLane documentation states "Cap+ trunking is less supported (no rest channel following)". Isn't the rest channel the functional equivalent of a control channel, which you have to follow in order to monitor individual talkgroups?

I guess I misunderstood the extent of the "tracking" that I was seeing. I have been able to scan Cap+ systems and my equipment responds as if it was trunktracking, but what is happening is more like tracking LTR-Regular instead of using the actual Cap+ trunking instructions.

 

[jcardani]

Thanks for the samples. I'll dig into them when I start the DMR decoder for version 0.3.x.

I have 3 or 4 strong DMR systems local, but none are as busy as what you're describing.

cheers,
Denny

Thanks Denny! BTW I just emailed you a few questions.

Joe

 

[EricCottrell]

Hello,

All the voice sounded encrypted and I noticed the Privacy bit was set, so it is encrypted. The last three sample were all data transmissions. It also appears this very busy system has a site with 14 channels (7 repeaters).

What would be interesting is a raw capture of a idle rest channel during a quieter time. There is usually a short burst every two seconds or so when the rest channel is idle.

I made some progress in figuring things out. Developers should refer to figure 7 in this patent.
https://www.google.com/patents/US8358968

FL field is: 3 for single block (first and last), 2 for first block, 0 for a continuation block, and 1 for the last block. This is a similar concept as in other DMR multi-block transmissions. I did see a few transmissions where three blocks were send, sequenced 2, 0, and 1. Otherwise a two block sequence is 2, 1.

What the figure does not show is the byte with channel 9 through 16 status is not fixed in the second block. It moves depending on the number of active channel 1 through 8 talkgroups. The figure shows the location if channels one through eight were all active.

I was able to see Channels 9 and higher by counting the number of active status bits for channels 1 through 8, process the same number of talkgroup ids for channels 1 through 8 as the set status bits, count the number of set bits in the next byte for channel 9 through 16 status, then process the same number of talkgroup ids for Channel 9 through 16 as set status bits.

I also occasionally see some data beyond channels 9 through 16, so there appears to be additional data to be figured out.

73 Eric

 

[jcardani]

Hi Eric,

Yes the system is fully encrypted.

I'll try to get some rest channel raw recordings tonight. Do I need to be sitting on a channel higher than 8 for this or can I be on a lower channel? Reason being not all channels are set up for the rest beacon.

Great job on the continued work. You know I get first crack at testing your updates


Thanks!
Joe

 

[jcardani]

Hi Eric,

Here are some additional links to raw recordings I did tonight on Site # 5, Channel 9 - 10.

Had a tough time of this because the rest beacon switches channels fast and like a roulette wheel you never know where it's gonna wind up. And on the not so good ones a grant follows right after the first beacon. But the last and longest one hopefully would be the best example. HTH

First attempt - short and not a good example
https://www.dropbox.com/s/2c1plasvbodyq1x/DSDPlus-Raw-Input_2015-11-25@225501.wav?dl=0

This one has some rest beacons on the channel plus a few grants
https://www.dropbox.com/s/u7epjesc3mz7asz/DSDPlus-Raw-Input_2015-11-25@225704.wav?dl=0

Another one but just grants
https://www.dropbox.com/s/v89q1vz1d3ya8gm/DSDPlus-Raw-Input_2015-11-25@230756.wav?dl=0

Again just grants
https://www.dropbox.com/s/86ohnrble41g8of/DSDPlus-Raw-Input_2015-11-25@231024.wav?dl=0

This one is the best example - lots of beacons and grants, and long!
https://www.dropbox.com/s/q04kqvbtnguc1uu/DSDPlus-Raw-Input_2015-11-25@231844.wav?dl=0

 

[jcardani]

Hi Eric,

Did the latest raw recording help? Did you figure this out yet or do you need more recordings? I have not heard any progress lately and just checking.

Thanks for your work on the software! Hope that you can update WIndDSD and release a new version shortly.

Joe