Packet Data Unit transmissions on P25 GRN

[citabria]

Hi Guys,

I've been monitoring the P25 GRN with an open source P25 analyzer and I've noticed PDU response packets coming off the voice channels every so often. The packets fall into the following categories:-

DUID:- 0x0C (Packet data uni or Multi packet Trunking signalling block)
Response Packet (Type 0x03)
Response Class: 0x00
Response Type: 0x01
Response Status: 0x06

The only information that can be deduced from this is that it is a system initiated Positive ACK sent in response to an inbound data packet from a radio - in this case it was SID: 0x20340d (Or in Motorola speak RID: 21100477) which was affiliated to TG: 11021 at the time.

Does anyone know what even these positive ACKs are in response to? I can attempt monitoring the input channel, but of course thats a hit and miss affair (ie, the MR needs to be close, and on the correct channel etc)

Cheers,
Matt

[Bigfella237]

The new P25 GRN is a PDS (Packet Data capable System), it does have an ARS (Automatic Registration Service) server so it can pass TMS (Text Messaging Service) messages and location (GPS) data, not to mention OTAP & OTAR (not that anyone is using them AFAIK) and of course it could simply have been a page sent to another radio or an emergency button activation, so the acknowledgment could really have been to any one of a number of things?

Andrew

[citabria]

The new P25 GRN is a PDS (Packet Data capable System), it does have an ARS (Automatic Registration Service) server so it can pass TMS (Text Messaging Service) messages and location (GPS) data, not to mention OTAP & OTAR (not that anyone is using them AFAIK) and of course it could simply have been a page sent to another radio or an emergency button activation, so the acknowledgment could really have been to any one of a number of things?

Andrew

Thats my question - which one is it...

By definition, all P25 trunk systems must be capable of sending packet data, since its part of the P25 trunking standard.

Yes, of course it could be any of those (TMS, GPS, Page, OTAR, etc) - the whole point of this thread is to find out which one it is.

The example I listed above happens at very regular intervals (down to the second) so I suspect its GPS location data - but can anyone confirm?

[Bigfella237]

~ I suspect its GPS location data - but can anyone confirm?

Being on a Sheriff's dept talkgroup, I suspect you're right but no, I can't confirm?