Questions about data capability in P25

[Jay911]

Hi,

I'm researching capabilities of P25 systems in preparation for the new system coming my way. At least one of these things I think has been answered for someone else, as far as my quick search of the forum tells me, but I'm going to ask my questions anyway in case they are unique to my situation.

All of my questions, as far as I believe, come back to one concept - that of sending data over a P25 system. Ultimately, I want to know if what I'm imagining is possible, and/or if additional hardware (i.e. modems, extra radios over and above the one "mobile radio" in a vehicle) is required to make it happen - and, if it would have to be a dedicated talkgroup or if it can "piggyback" on the control channel, so to speak.

There are several different kinds of data that are communicated to end users in my region, through a variety of different methods:

- Alerting fire and EMS agencies to incidents is done, for some, with two-tone (Quik-Call II) voice paging, and for some with Zetron station alerting, and other such technologies.
- Some agencies also get a text notification of the call on a pager or phone - some by POCSAG or Golay paging over a privately-owned and operated (ancient) paging network and frequency, and some by text message sent to the commercial telco's iDEN network for distribution to iDEN phones. (These are also used for regular "paging" i.e. text messaging, not just for call notification.)
- MDT data (call info, GPS/AVL information, etc) is sent over the commercial telco EvDO or similar network.

Does any/all of this have a place in the P25 spec? I guess what I'm asking is, hypothetically/theoretically, could a properly-configured system transport the MDT data over the P25 system, doing away with the telco modem (and airtime/fees, and etc); send text messages (of the equivalent of "pages") to portable/handheld radios; and be up to the task of alerting on-call/callout members of a department to a request for response?

On the last one, I am not necessarily looking for two-tone paging or anything like that - I know that that in particular is not designed in to P25. However, I'm thinking more along the lines of some kind of selective call or group call using Private Call or Call Alert (excuse my Motorola terms - the system I use now is a Smartzone network so that's what I know). Could the system be configured such that all radios for a given department (or duty crew) has a common alert address, so you could hit one button on the dispatcher console and alert all radios (or, again, all duty crew radios) prior to voicing a dispatch?

Thanks in advance,
--j.
Jason Low

 

[bldavis]

So, if I understand correctly, you're asking if paging systems, or MDT/MDC traffic can run over P25 systems.

The answer is yes, it is possible, but manufacturers haven't gotten that far yet, and in some cases, probably won't go that route. P25 is a data spec at its heart, and can send/receive at up to 9600 bps.

Pagers - i.e. the little belt-clip jobs the size of a pack of cigarettes, would be prohibitively expensive to manufacture with a P25 CAI built into them, at least or until someone builds chipsets a whole lot cheaper than the current third generation stuff. And P25 isn't designed to work with unaffiliated devices - devices that don't transmit their identity info, and adding a transmitter makes it that much harder. But I suppose a "monitor only" device listening to a conventional channel is possible. Just improbable.

MDT/MDC - This is being sold now, in a few forms. But for most agencies, 9600bps just isn't fast enough to be useful, which is one of the big drivers of the push towards LTE (broadband cellular data networks) for public safety use.

Station Alerting - Also being done now over P25, either as traditional toned audio, toned audio feeding station elerting equipment, or as IP data feeding station alerting equipment.

Text messaging is just waiting for someone to sell a subscriber unit with a keypad. One way text is already being done (usually dispatch to units).

GPS data - Also being done now, usually in slow data mode (aka, a unit keys up to talk, and also sends GPS coords with the audio) and this is being fed into applications that present officer location maps in dispatch centers or where ever.

As to sending an alert or text message or audio (voice) to a specific station, or user - the data is IP (internet protocol), and so it can be individually directed to anyone or anything you care to give an IP address to, be it a Zetron box, or Battalion Chief, or Engine, or group of people/stations/things. You can even gateway it into other IP based systems, like VoIP telephone systems, chat clients, email, you name it. It's all just waiting for programmers and vendors to whack up something to sell.

Not sure I fully answered your question, but maybe I got you closer.

 

[SCPD]

- Alerting fire and EMS agencies to incidents is done, for some, with two-tone (Quik-Call II) voice paging, and for some with Zetron station alerting, and other such technologies.

A group call is effectively a voice page.

Tone style paging can be done over the control channel. An 8 bit code can be addressed to a group or radio. The meanings of these codes are system defined. The radio can display a predefined text message for a given code.

- Some agencies also get a text notification of the call

- MDT data (call info, GPS/AVL information, etc) is sent over the commercial telco EvDO or similar network.

These require attaching a laptop; the radio becomes an RF modem. Data calls compete with voice traffic. In the case of text paging, not as convenient as an alpha pager or cellphone. Bandwidth is very limiting compared to a 3G network.

 

[Jay911]

Thanks to both of you. I understand things significantly better now. IMO it appears that I will be looking elsewhere than the P25 system for most of these solutions.