marcs and tdma and datanet...whats going w/ it lately?

[dizwiz]

Ok, sorry if this topic has been covered, but what's been going on with this.

Last I heard some cuyahoga county area marcs users were getting phase 2 tdma radios, however those radios are still phase 1 capable and until all phase 1 only radios were phased out, that the users would all continue to use phase1....and hence my psr500 would still work.

Also I heard they will be using new 700/mhz freq

Will psr800 monitor marcs tdma?

Now. I have a question that's prob. Not been asked yet...

Once marcs goes tdma, starting w/ given regions, then the whole system, will marcs datanet freq also go away? Ie. Will the data currently going out through seperate 800 mhz datanet frequencies start going out w/ the datastream of the tdma transmission?

 

[jackj]

The way I understand TDMA vs FDMA is that the two multiplexing systems are NOT compatible. Radios can be purchased that will work on either system but older radios that are only FDMA won't work on a TDMA system. I believe that if MARCS were to change over to TDMA, they would have to do it all at once or loose interoperability during the change over period.

 

[kf8yk]

Last I heard some cuyahoga county area marcs users were getting phase 2 tdma radios, however those radios are still phase 1 capable and until all phase 1 only radios were phased out, that the users would all continue to use phase1....and hence my psr500 would still work.

Only the APX series of Motorola radios can do TDMA and they require the purchase of an optional software feature to do it. The APX is fairly new & there are not a lot of them in use but with the pricing at or below the older XTS/XTL series any agency buying radios now is likely to choose the APX.

For TDMA to work several items have to be in place: The portable/mobile radio has to have a TDMA software feature purchased, the system has to have the TDMA software feature purchased, the talkgroup has to be programmed for TDMA, and all the radios participating in the call have to be TDMA capable. If just one radio affiliated to that talkgroup is not TDMA capable the transmission will 'fallback' to FDMA mode. TDMA & FDMA radios can exist on the same system with no problems.

A lot of the agencies that will be using the Cuyahoga 700 MHz system have plenty of XTS/XTL radios, so their talkgroups will be FDMA for quite a while.

Also I heard they will be using new 700/mhz freq

The 700 MHz system in Cuyahoga County will primarily support agencies in the County using MARCS that don't have a need to roam outside the county (RTA, Eastcom, etc.). Users on the 700 MHz system will not be able to automatically roam out of the county to any 800 MHz MARCS sites, the radios will still have the statewide MARCS system in a different zone, but users will have to manually change channels if they leave the county.

The 700 Mhz system is the start of a broader initiative to migrate MARCS from Smartzone to P25, in the future as more sites are built the 700 Mhz system could be the only MARCS network in the county but that's years away.

Will psr800 monitor marcs tdma?

The PSR800 has reportedly been working on Motorola X2 TDMA systems. X2 is a Motorola specific protocol that's based on the draft standard for P25 TDMA. Since X2 should be close to the final P25 TDMA standard there's a good chance it will work fine, but until an official P25 compliant TDMA system goes live & the PSR800 is tried I can't say for sure.

Once marcs goes tdma, starting w/ given regions, then the whole system, will marcs datanet freq also go away? Ie. Will the data currently going out through seperate 800 mhz datanet frequencies start going out w/ the datastream of the tdma transmission?

The 700 MHz system is voice only, nothing with the 700 MHz system or TDMA will affect the data network. Motorola offers a system called IV&D to allow data to be carried on either FDMA or TDMA voice networks, but it only runs 9600 bps.