ProScan - how does it work?

[kyparamedic]

Currently we operate off of two towers. They are programmed in to our radios as 2 separate systems that we have to manually switch to depending on our location in the county. They are putting up a 3rd site at which time we will be adding ProScan so that we no longer have to switch. Will our radios still have 3 separate systems programmed in? From what I've been told, not all the talkgroups are on both the sites we have now as they're not needed in that part of the county. If for some reason we were to try to use one of these and were in the coverage area of the site that doesn't have it, what would happen?

What are the advantages/reasons for operating a multicast system like this as opposed to simulcast? It seems like it just ties up more frequencies. The only thing that came to the top of my head is that if one site went down, you would still have the others if in range.

One last thing. We have a few radios that will automatically pick up the strongest tower. It will go to CC SCAN for a second and then WA SCAN until it gets the other system. (I know this stands for control channel and wide area.) When we rebanded, some people asked the radio guy to program their radios to do this. He said that he didn't really feel comfortable because we could get in an area that had about equal reception and it would just switch back and forth continously and we wouldn't be able to call out. However, he would do it if they insisted. He said that for the radios to switch automatically and reliably, they needed to install a switch in dispatch which would run about $30k. Was he referring to ProScan?

Thanks.

 

[EDACSTECH]

Many reasons factor into why your system was not configured as Simulcast when first installed. Whitout knowing the history of requirements along with your budget, any response would only be a guess. Proscan is only the current M/A-COM way to allow the radio to change systems when the current system signal level falls below a pre-selected/ programmed amount. Your radio will have up to three systems programmed that you can manually switch or have Proscan switch.

EDACS has five configuration options, which can each be expanded
to meet changing requirements for coverage or functionality at any
time:
• Single Site
• Voted
• Simulcast
• Single Channel
• Multi-site
Single site EDACS systems are used to cover small geographical
areas, such as a small to medium-sized town. The system comprises
a single base station site with 3 to 24 channels and associated
antenna system.
Voted EDACS systems allow several receiver sites to be used in
conjunction with the transmitter site to improve signal reception from
portable radios.
Simulcast EDACS systems use the simultaneous transmission and
reception of identical audio and data information over two or more
base stations with the same RF carrier frequency. Simulcast is used
in situations where the number of frequencies available is limited, but
the coverage area is too large for a single site, or where there is a
need for consistent RF coverage in built-up areas.
Single Channel EDACS systems are primarily used in conjunction
with single site, voted or simulcast systems to provide coverage in
specific areas not covered by the main system (remote areas) and
where there is a shortage of frequencies.
Multi-site EDACS systems can be created by adding a radio switch,
called an Integrated Multi-site and Console Controller (IMC),
between two or more single site, voted, simulcast or single channel
- 5 -
systems. The IMC monitors activity at each of the connected sites
and passes calls from one site to another. It is able to control traffic
between sites in an intelligent way so that each site only assigns a
working channel to a call when it has users who need to be involved.
The IMC does this by keeping track of the users and their selected
groups in the system. Several multi-site systems can be connected
together to form an extended network. This capability makes EDACS
an ideal communications solution for large geographical areas, such
as a region, state or an entire country

 

[kyparamedic]

What happens if you have more than 3 sites/repeaters that you use? I wouldn't think this would be enough to cover some larger geographic areas.

Also, can you explain what the radio tech was trying to tell me about not wanting to set the individual radios to switch between the sites on their own, without having ProScan installed?

He mentioned how it was silly that the local PD wanted their channels broadcast over our other site that covered an area outside their working area. They would never need to use their channels in that area and if they did, they could use another law enforcement talkgroup that was. However, from what you have said and what I understand, if no other subscriber from this particular talkgroup is on the other site, then it won't be broadcast, correct? Or is this an independent feature for each system?

One last question. On a single channel system like you mentioned, is this actually two channels, or frequencies I should say? A control channel and voice channel? Would this be used in a building or other similar site that has been identified as limited coverage?

Thanks a bunch.

 

[EDACSTECH]

What happens if you have more than 3 sites/repeaters that you use? I wouldn't think this would be enough to cover some larger geographic areas.

Also, can you explain what the radio tech was trying to tell me about not wanting to set the individual radios to switch between the sites on their own, without having ProScan installed?

He mentioned how it was silly that the local PD wanted their channels broadcast over our other site that covered an area outside their working area. They would never need to use their channels in that area and if they did, they could use another law enforcement talkgroup that was. However, from what you have said and what I understand, if no other subscriber from this particular talkgroup is on the other site, then it won't be broadcast, correct? Or is this an independent feature for each system?

One last question. On a single channel system like you mentioned, is this actually two channels, or frequencies I should say? A control channel and voice channel? Would this be used in a building or other similar site that has been identified as limited coverage?

Thanks a bunch.

A site is a transmitter location, such as a tower or building top etc. It will have at least two repeaters / channels. I don't know why this Ericsson written article listed 3 -24 repeaters / channels other than a two channel site will only allow one user at a time and this is not much of a trunked system. You can have many many sites to cover a large area as long as you have the frequencies & $$$ to build and operate such a system.

The radio tech was telling you that any time you set up system scan, such as "wide-area scan" or even Proscan, the radio will scan to a different system (Site) without your intervention. This could result in confusion or problems depending on many factors. No EDACS system scan method works perfect like a cellular hand-off. Much design consideration and configuration is needed in many cases to use system scan. Proscan is just athe newest version of system scan.

With a IMC Switch & CSD Server, you can configure sites to assign a repeater to a call if there is a user logged into that site or you can force the call to go out all of the time. There is a lot of options and choices that play into the design and configuration of an EDACS system, "IF" you have the equipment required and someone take the time to configure it to the requirements of the user(s).

A single channel "SCAT" site is one repeater / channel that act as the control channel and then assignes the call to itself as a working channel. This is used to fill in a dead area when very little traffic will be required.

 

[ocguard]

Very well explained.

However, from what you have said and what I understand, if no other subscriber from this particular talkgroup is on the other site, then it won't be broadcast, correct? Or is this an independent feature for each system?

Clarification on this. It depends on how the system is configured. What you've said may be true if the system is designed in such a way that a site will only carry a talk group if there is a specific user affiliated with the site requiring that talk group. HOWEVER, talk groups can also be configured as wide area, in which case they would be forced across a particular site regardless of the need from a specific radio on that site.

The two most common reasons for setting up a system as multi-cast (sometimes know as zoned) versus simulcast are...
1. frequency availability: A specific frequency may be available for licensing in only one area of your desired coverage area, typically due to a co-channel licensee nearby, too close to one side of your region, but far enough from another side to allow that frequency to be licensed to only that specific area...
2. different system capacities/users isolated to different areas: An example would be a county with two significant population centers. Town A may need a system with a capacity of 5 channels, while Town B may need a system with a capacity of 10, unrelated to Town A's users. The needed capacity for wide-area calls may be only 3 channels. Instead of building a simulcast system with 18 channels to cover the entire area, a system of two sub-systems is created. Calls isolated to the respective towns are carried on only their respective sub-systems, while county-wide (wide area) calls are carried on both systems. User radios may (should) be programmed with both sub-systems in the event that users may travel between system coverage areas.

And remember, because there are two sub-systems doesn't mean there are only two tower sites. The individual sub-systems can be set up in simulcast if their required coverage areas extends beyond the capability of one tower site.

 

[kyparamedic]

A neighboring county uses a multi-cast EDACS system like ours so we share some talkgroups for mutual aid and for talking to hospitals that we transport to. We get to them by selecting a different system on our radio, just like we do to change sites in ours. I'm almost positive they use ProScan on their system. So when we select their system and talk to them, do we just have one particular site programmed into our radios or is it actually selecting the best one based on signal strength? I'm assuming we just have the primary site that covers the area where the majority of their hospitals are located. I'm pretty sure they operate 3 sites, based on the database. Here's the link if you want to see it: http://www.radioreference.com/apps/db/?sid=5241
It mentions virtual sites and I don't really know what that is.

Thanks.

 

[kyparamedic]

Another question. Sorry, I know I have a lot but can never find the answers through searches on this site or on Google. In the part of the county where I'm stationed, we operate off a different site from most others. I've noticed that whenever somebody transmits from the other site, the ID is the alias for dispatch. There are like 10 or 15 group numbers that have this alias assigned to them. The same thing occurs in the reverse situation, where we're at the main site and someone transmits from the other one. If both users are on the same site though, their actual ID shows up. Is this because the two systems are bridged somehow (see next question)? Does it always work this way on multi-cast systems or is it just the way ours is setup?

During my last shift, one of the units called out, dispatch answered, and then we never heard anything else from them. While we were out, we kept hearing dispatch answer other units and give them times, but we couldn't hear them. Dispatch could still hear us though. I told one of the deputies that was out with us and he said our bridge must be down and to call dispatch. Once we were through with the run I did, and the dispatcher said the patch must be down and she would fix it. A little while later it started working again so she must have. I tried going to our 2 other talkgroups to see if they went across both sites and they didn't. I don't remember if they had before or not. Do most multi-cast/multi-site systems operate like this, using a bridge or patch? Is it an independent thing for each talkgroup? The deputy didn't seem to think anything was wrong on his talkgroup so I'm assuming it's independent. I also take it that it's sometype of software type patch?

I'm beginning to think that they went cheap when building/setting up our system.

 

[ocguard]

As for the question regarding use of your neighboring county's EDACS, it's hard to answer. It depends on how your radios are set up to operate on their system... It would make the most sense to have your radios programmed to operate on their entire system, in the event that you may need to respond anywhere in their county. However, it's likely that, for the sake of simplicity, you are only programmed for the site nearest where you would operate while enroute to that hospital.

With regards to your last post, I make from this that the two systems in your county are completely independant of one another, and are connected not by network, but by simple console patches. My conclusion comes from two pieces of information you've given:

First is the radio alias situation. When a console patch is established, the the console does not carry over the incoming caller's ID. It replaces it with the console's ID for the talk group module.

Second is you only hearing the dispatcher's side of the calls. When a patched medium is being used by a dispatcher, it is usually also necessary to multi-select both patched mediums for talk-out purposes. This allows the dispatcher to transmit on both patched talk groups. Often times, when the system momentarily fails or 'burps' the patches that were in place may be lost, but typically, the multi-selects are held. Therefore, until the patches are re-established, the dispatcher will continue to transmit on both groups, but incoming calls from one group are not carried over to the other group, and visa versa.

 

[LS1_TA]

Other considerations when provisioning Proscan are the parameters that make it switch like time and RSSI. Do not forget the adjacency tables either. These parameters should be available in your Programmer or RPM help. I prefer Dynamic Proscan as well.