SmartZone 4.x and SmartZone Astro P25

[maus92]

Can someone enlighten me on the differences between these systems? Can anyone point me to some in depth info about how these systems are designed, i.e. a design guide of some kind?

Thanks,

CA
Annapolis

 

[greenthumb]

In a nutshell, SmartZone 4.x is Motorola's proprietary wide area trunking system. It will support APCO Project 25 digital modulation on the system with the right user and backbone equipment, but the 3600 bps control channel is not APCO Project 25 compliant, and an APCO Project 25 control channel operates at 9600 bps. Analog transmissions are supported on SmartZone 4.x whereas they are not supported in ASTRO-25 ("SmartZone Astro P25"). SmartZone 4.x is a circuit-switched backbone and ASTRO-25 is a packet (IP) switched backbone. Aside from those high-level differences, the overall theory of operation for the systems is essentially the same.

What specific design questions do you have?

 

[maus92]

Thanks for the reply and the info. I was trying to clear up a debate in another forum

http://www.radioreference.com/forums/showthread.php?t=94126

because there was a gentleman who contended that a SZ 4.x system was incapable of P25 operations which is not totally correct. I think that semantics and stubborness was getting in the way of understanding....

You mentioned that the backbone is circuit switched on a SZ 4.x system, whereas an AstroP25 system is IP based. I'm curious exactly what is going on. I'm guessing that in a SZ4.x, analog audio is sent from the dispatch center (zone controller?) to the tower site, either over a telephone line or microwave. In a AstroP25 system, the voice/data is sent over a T1, fiber, or microwave link to the tower site. Could a SZ 4.x system use a more advanded backbone, i.e. fiber? Is there a logical upgrade path between a SZ 4.x system and AstroP25, or is it so different that you would be basically starting from scratch? Please correct any misassumptions that I have made.

I was looking for a reference about how systems are designed, specifically about what types of equipment are located where in the system, and what is their function. For example, in a SZ 4.x system, where there are P25 "subscribers" - where is the D/A conversion made? At the tower site, or is the P25 audio piped back to the dispatch center? Or someplace else?

I'm really trying to develop a strong understanding about how these systems work.

Thanks for any help you can provide.

CA
Annapolis

 

[WayneH]

I'm guessing that in a SZ4.x, analog audio is sent from the dispatch center (zone controller?) to the tower site, either over a telephone line or microwave. In a AstroP25 system, the voice/data is sent over a T1, fiber, or microwave link to the tower site. Could a SZ 4.x system use a more advanded backbone, i.e. fiber?

Going from a console involves various hardware (e.g., "CEB's") to send audio (when analog) to a Zone Controller. The ZC is connected to an audio switch. The ZC determines which sites need the audio and routes audio through the switch appropriately. Commonly the audio runs over a microwave link. To send over the M/W the audio has to be digitized through a C/DSU which puts it on to a DS-0 then multiplexed (to a T-1/DS-1 or larger) and transmitted over the M/W.

In an IP situation you don't have to deal with CSUs, as much multiplexing, etc, it all goes over ethernet connections. So the voice is put in to a digital form and transfered via IP just as how voice from a computer, IP Phone, or whatever is sent over the internet.

Motorola has some expensive manuals that explain the infrastructure equipment and how it's (roughly) assembled through block diagrams. Since most systems deployed are different from another you can't always say for sure how audio goes from point A to B in exact detail. Most of the actual Motorola infrastructure will be the same but how sites and dispatch consoles are connected can vary (typically microwave).

 

[greenthumb]

You mentioned that the backbone is circuit switched on a SZ 4.x system, whereas an AstroP25 system is IP based. I'm curious exactly what is going on. I'm guessing that in a SZ4.x, analog audio is sent from the dispatch center (zone controller?) to the tower site, either over a telephone line or microwave. In a AstroP25 system, the voice/data is sent over a T1, fiber, or microwave link to the tower site. Could a SZ 4.x system use a more advanded backbone, i.e. fiber?

As far as console audio, that depends on what the console type is. With the current consoles (Centracom Gold Elite), the audio originates at the console and is routed to the CEB and AEB, then out to the MGEG where it is converted from analog audio to IP packets and routed over the IP network to the appropriate site(s). Management of where the IP packets need to go (sites, consoles, logging recorders, interzone links, etc.) is done by the zone controller using IP multicast.

Audio from subscribers into the sites comes in as RF through the RF distribution system, then into the repeaters (Quantar, STR-3000, or GTR-8000 stations) where the packets are placed onto the IP network. Again, the zone controller will direct where the IP packets are to be distributed.

As far as the medium by which the analog audio, V.25 data, or IP packets is sent - it really matters more what the capacity of the medium is over what the actual medium is. There needs to be enough capacity over the medium to support the number of channels in use at the site. Analog audio can go over pretty much any medium (POTS, T-1, DSx microwave, fiber, etc. - the multiplexer on the end is what makes the difference on how the capacity is broken out). IP packets on an ASTRO-25 network cannot use a POTS line.

Is there a logical upgrade path between a SZ 4.x system and AstroP25, or is it so different that you would be basically starting from scratch? Please correct any misassumptions that I have made.

It is pretty much a forklift upgrade from 4.x to ASTRO-25. Quantars can be upgraded, and some Centracom Gold Elite console equipment can be used, but the zone controller, routers, switches, and network management systems required will be different. Subscribers must be an XTS-3000 or newer radio and must be flash-upgraded, so it is pretty expensive just to upgrade subscriber equipment via FLASHport upgrades, and much more expensive if all new subscribers must be purchased.

For example, in a SZ 4.x system, where there are P25 "subscribers" - where is the D/A conversion made?

Subscribers are just the portable and mobile radios using the system. The encoding of the analog voice signal into the subscriber's microphone is done inside the subscriber radio, as is the decoding of the received (vocoded) audio from the RF system. For Centracom Gold Elite consoles, the encoding/decoding is done in the MGEG (Motorola Gold Elite Gateway). No decoding of the audio is done at the sites.

As Wayne mentioned, Motorola does have some very useful documentation to describe different system configurations. If you call Motorola at 1-800-422-4210 you should be able to order that documentation, but it is probably going to be pretty expensive (~$60-$100 per manual - they're a LOT of paper). They may give you access to it via Motorola Online, which would make it free of cost.