MARCS-IP Mobiles/Portables - Communications With The System?

[AE8I]

These questions pertain to other than voice transmissions originating from MARCS-IP mobile/portable radios. Generally speaking, are the radios continually communicating with the system, or are these communications relatively infrequent, such as when the mobiles/portables are powered up?

In addition, do MARCS-IP mobile/portable non-voice transmissions appear randomly across all available system input frequencies, or do they typically occur on the repeater input frequency offset by 45 MHz from the control channel frequency currently in use by the system?

 

[wa8pyr]

These questions pertain to other than voice transmissions originating from MARCS-IP mobile/portable radios. Generally speaking, are the radios continually communicating with the system, or are these communications relatively infrequent, such as when the mobiles/portables are powered up?

In addition, do MARCS-IP mobile/portable non-voice transmissions appear randomly across all available system input frequencies, or do they typically occur on the repeater input frequency offset by 45 MHz from the control channel frequency currently in use by the system?

Data transmissions from radios to the system are usually rather infrequent but this can can vary. Typically, radios send data to the system upon power-up; when switching sites; when the PTT is pressed; call alerts; and if/when using status or messaging functions (very short canned messages which can be defined as anything an agency needs such as on scene, in service and so on).

This only happens on the control channel input of the site a specific radio is affiliated to. Responses from the system are on the output side of the control channel.

Ohio MARCS also has a feature called Integrated Voice & Data which can use some voice channels of a site for more extensive data use such as Over The Air Rekeying (OTAR, installing new encryption keys remotely), Over The Air Programming (OTAP), unit-to-unit text messaging, geo-location, and mobile data terminals. However, IV&D is slow and not well suited for graphics-intensive functions, so it's rarely used for mobile data terminals. It's also rarely used for text messaging (which is far easier on a personal cell phone). In addition, IV&D is a low-priority use; as voice traffic increases, the availability of channels for data is reduced.

 

[AE8I]

Thank you, Tom. Your response is very helpful.

Concerning geo-location, is that only accomplished through IV&D, or is that information also provided on occasion to the system, via the input control channel frequency?

 

[kf8yk]

GPS tracking aka automatic vehicle location (AVL) is only provided through IV&D.

I don't know of any agencies actually using IV&D AVL on MARCS due to the $$$. Most agencies who track their fleet are using cellular data, either standalone trackers or in conjunction with their CAD mobile data terminals.

 

[wa8pyr]

Thank you, Tom. Your response is very helpful.

Concerning geo-location, is that only accomplished through IV&D, or is that information also provided on occasion to the system, via the input control channel frequency?

If I recall correctly, geo-location (for GPS equipped radios) via the control channel only happens when a radio user presses the emergency button; there is no geo-location for portable radios through the system.

To complicate matters, it's rather costly to get your applications (CAD, AVL, logging, etc) connected to the system so you can receive canned status and messaging or AVL/GPS; a border firewall and router are required at the system, and on the CEN (Customer Enterprise Network). They're also pretty picky about what and through whom the customer communicates to the outside world. Then you have to hope that your applications are compatible with the incoming data.

As KF8YK noted, true AVL (for vehicles) can be done via IV&D, but nearly everyone does it with cellular. There are a few agencies using IV&D out there, but my guess is it's for pretty simple stuff.

 

[AE8I]

Very good - thanks to both of you for your responses.

 

[scannerboy02]

Hamilton County FD units (via the HCCC) are using MARCS for MDT's. I have all of the MDT radios labeled and watch them as they transmit and receive on the system. This is actually how I know a big call is about to be dispatched, I can see when the MDT's are sent data calls in a big cluster. The more data calls in a row the bigger the dispatch is going to be.

Cincinnati Fire was also using MARCS for MDT's up until about a year ago.

 

[AE8I]

How do you distinguish MDT traffic from other traffic, or are you saying Hamilton County FD uses MARCS exclusively for MDTs, hence any traffic must be MDT?

 

[wa8pyr]

How do you distinguish MDT traffic from other traffic, or are you saying Hamilton County FD uses MARCS exclusively for MDTs, hence any traffic must be MDT?

Scanners will just skip over the data transmissions, but if you watch the system with an application like Pro96Com or Unitrunker, the IV&D channels will show up as a Data transmission with only a user radio ID but no talkgroup. There's really no way to tell what the traffic is (MDT, OTAP, OTAR, AVL, etc) by watching, only that it's a data transmission.

Scannerboy02 most likely has knowledge of Hamilton County operations and knows that they use MARCS for their MDT traffic.

 

[scannerboy02]

Scanners will just skip over the data transmissions, but if you watch the system with an application like Pro96Com or Unitrunker, the IV&D channels will show up as a Data transmission with only a user radio ID but no talkgroup. There's really no way to tell what the traffic is (MDT, OTAP, OTAR, AVL, etc) by watching, only that it's a data transmission.

Scannerboy02 most likely has knowledge of Hamilton County operations and knows that they use MARCS for their MDT traffic.

What he said ;-)

 

[AE8I]

I am aware of Pro96Com but have never used it, and I had no success in getting Unitrunker to work properly, for whatever reason. Perhaps it's time I try Pro96Com or retry Unitrunker, to see what I've been missing.