Edacs multi sites and channel layouts.

[Pro-95]

Ok sorry guys for treading into deep waters with my life vest on but I have a design question that you guys can answer that may help me figure out our statewide system.

First off it's Nevada Shared Radio System. There are 70+ sites around the state all using a small amount of actual frequencies with Las Vegas having the largest per tower(site) at 15.

From a design aspect with a lot of small sites with 3 to 6 frequencies that are significantly geographically seperated, wouldn't it make the most sense to keep the same LCN? Wouldn't this make travel across the state easier? I give the following as an example:

009 Beatty          855.7375	856.7375	857.7375	
017 S. Lake Tahoe	855.7375	856.7375	857.7375

So now why then upset the apple cart with this series?

022 Nixon	          855.7375	856.7375	860.4375	
029 Fallon/Fairview	855.7375	856.9375	859.2125

Any input would be greatly appreciated.

 

[crayon]

Wouldn't this make travel across the state easier?

This is a very good question, as I have wondered the same because of the huge AEP EDACS system here in Oklahoma.

I am not an EDACS fan so hopefully some can enlighten us.

 

[DaveNF2G]

I'd look for other licensees on those frequencies, especially in adjacent states. It's probably a coordination issue.

 

[greenthumb]

Well, if the radio has 3 sites in it that have the exact same frequencies, LCN, and site number, it won't matter where the user is - the radio will affiliate with that site. As such the situation may occur where the user appears to be affiliated with a site in the north part of the state (based on what is shown on the radio's display) when he/she is in the south part of the state. Therefore, if they mix up the LCN, the sites are different and the problem is solved

 

[senss]

Here in Quebec, we have exactly the same situation.

Site 1 : Freq, A,B,C,D,E
Site 2 : Freq, A,B,C,G,H

That's a coordination issues because the frequencies is already assigned to other users.

So, they create a new sys id with most of the same frequencies but not at all.

Alain

 

[Pro-95]

Well, if the radio has 3 sites in it that have the exact same frequencies, LCN, and site number, it won't matter where the user is - the radio will affiliate with that site. As such the situation may occur where the user appears to be affiliated with a site in the north part of the state (based on what is shown on the radio's display) when he/she is in the south part of the state. Therefore, if they mix up the LCN, the sites are different and the problem is solved

Ok now I'm a little confused. I can understand the nearby or adjacent neighboring entities that are not supposed to be affiliated for reasoning (except in my example there is no nearby or adjacent entities ). But my understanding (and this could be wrong) of EDACS is that no matter what site/tower a person is on, the assignment of "dispatch/home" was based on talkgroup not tower/site. To further illustrate my understanding (or lack thereof) is that a radio could travel the entire state yet still be in contact with the same dispatcher no matter what site/tower they are using. And dispatch could release them to a different dispatch center. Also on my scanner which is obviously not the same as a radio, with TX/RX and built around a specific application, I can know which tower or site I'm listening to simply by displaying a short line of text associated with a frequency stating "Reno Met 09" and the next line with talkgroup. In this case Reno Met 09 is a tower in Reno Metro using frequency 09 in LCN. I "assume" a TX/RX radio has the same capabilities??? What you are saying (what I'm hearing) is that someone travelling across the state must somehow manually switch or indicate which site they are going to be using? It would seem to me that the average operator doesn't need to know or care which site/tower they are using. I would also think that requiring operator intervention would create a lot more problems than it would solve.

Are radios(TX/RX) that much smarter than a scanner? Can a radio be travelling across the state and automatically adjust for LCN changes of the same frequencies? From those who use radios that I sell scanners to they indicate that for the most part their interaction with the radio other than keying and adjusting the volume is that they can switch to "Red", "White", "Tac 1" etc etc etc.

Now regarding a scanner, This seemingly creates a nightmare of channel posibilities (you'need many, many banks of several LCN's and not scan banks that have similar freqs) because if I programmed a bank with those frequencies in my scanner, the scanner would become confused because there would be 3 (example above) entries of the same frequency followed by two different frequencies but I'd need to program all 3 series for my scanner to decipher the communications. And if the scanner picked up on one of the freqs out of a different series LCN the scanner would loose the control becuase on an EDACS system the freqs MUST be in LCN whereas (my understanding) on a Motorola system you could just program all the frequencies the wide area has, yes????

Please tell me this is (or I am) wrong. Because if I am understanding this correctly, why on gods green earth would anyone buy an EDACS system for use in a wide area network. Surely I am missing something here or the radios are that much significantly smarter than a scanner.

*Radio = a device capable of TX/RX and designed for a specific application
*Scanner = a device for listening in not designed for the application

 

[Pro-95]

This is what I don't understand why a cell styled network isn't deployed. Here is an example utliizing only 30 frequencies and breaking them up into 10 "sets" of 3 frequencies and keeping the same LCN throughout. Also utilizing the sets to build a superset for major metropolitan areas such as Las Vegas which is only currently using 15 freqs. This would, from a scanner aspect, allow you to have banks set up based upon the amount of sets in a cell. Geopgraphy would determine what tower you are picking up without requiring any intervention. Wouldn't this also apply to the radios?

EDIT: Yes I realize a scanner would have to be reset to pick up the new control channel if you passed between the single sets cells if the single sets cells were in one bank. But if I understand the radios correctly this wouldn't be a problem for them and after all they are designing for the radio use not for simplicity of the scanner operator.

EDIT2: Actually you could program using only 2 banks with the entire series in each bank (A,B,C,D,E,F,G,H,I,J) and the radio would pick up the control channel depending on where you are and how many sets in the cell you are in. Possibly alleviating the need to reset.

Ok, now my head hurts.

 

[iceman47]

The radios used in an EDACS system are far smarter than a scanner.
A radio can travel throughout the State and as it does it will lose signal on the previous CC of the last site and scan for a new control Channel and affiliate with that site. This function of site affilation is automatic thru programming.
Once it picks up a new CC, and affiliates with the new site, it can only be assigned Voice or Working Channels, assigned to that site.
Remember that all the radio's in an EDACS system, as well as scanners, monitor the control channel data for assignment of the "voice channel".
The 03 site in Las Vegas is at the NHP control point on Flamingo Road.
There are several sites in the L.V. area:
010: S/ Clark County
013: N/W Clark County
042: N/L.V. Apex
062: Overton Glendale
All in the greater L.V. Clark County area.

As to the question as to why anyone would pick EDACS for statewide coverage, That question will be on the minds of those who bought it for years.
Perhaps, a slick talking salesman??????
The best question of all is why did they use 800 Mhz in a system that has tower spacing in excess of EDACS specs???????? (7.8 miles)
The original EDACS was for NDOT road crews only, and NHP went on the system due to the lack of FCC licensing for the 150 Mhz frequencies.
The previous Motorola System worked far better in the 150 Mhz. range.
They just chose the wrong tool for the job!
Maybe they should have just improved the original 40 Mhz. system they had for 40 years.
Sometimes new technology is not the answer.

 

[crayon]

Remember that all the radio's in an EDACS system, as well as scanners, monitor the control channel data for assignment of the "voice channel".

This is the crux of the problem.

As I understand it, EDACS radios are hard coded or programmed with the channel number/frequency assignments in the radio itself. All the control channel does is spew out the LCN channel numbers and the radio references its internal list to find the correct frequency.


If this is the case, I think that the real question(s) here are:

1. What is the limitations of a real EDACS user (not a scanner) on a statewide system?
2. If there are 23 sites, each with its own LCN, does one program all 23 LCN's into the radio?
3. If so, how does the radio know which list to use after affliation?

I have others, but will save them for later ..

 

[Pro-95]

The radios used in an EDACS system are far smarter than a scanner.

This is a good thing, I'd hate to see a trooper chasing some guy at 100+ mph have to be fiddleing with the radio as he passes from one tower coverage to another.

A radio can travel throughout the State and as it does it will lose signal on the previous CC of the last site and scan for a new control Channel and affiliate with that site. This function of site affilation is automatic thru programming.

I figured this :?: worked :?: somehow otherwise we got gyped. But in actuality there really isn't a definitive break in coverage and theoretically you could be receiveng 2 different control channels at the same time, right ??? I mean otherwise there is dead-zones of no coverage to allow the radio to drop then pick up another control channel. :shock:

As to the question as to why anyone would pick EDACS for statewide coverage, That question will be on the minds of those who bought it for years.
Perhaps, a slick talking salesman??????

:lol:

The best question of all is why did they use 800 Mhz in a system that has tower spacing in excess of EDACS specs???????? (7.8 miles)

No that's some overlap!

Sometimes new technology is not the answer.

Change for the sake of change.
Thanks!

 

[Pro-95]

As I understand it, EDACS radios are hard coded or programmed with the channel number/frequency assignments in the radio itself. All the control channel does is spew out the LCN channel numbers and the radio references its internal list to find the correct frequency.

If this is true then a radio that travels across the state would have to have "hard coded" ALL the different possibilities of LCN's it could run across. :shock: Yikes! I wouldn't want to have to maintain the radios. Imagine the impact of adding another site with a different set of LCN's, there would be a huge line of radios to upgrade.

And I apologize for going from radio to scanner and back it's not my intention to belittle the conversation of EDACS design and operation for the convience of scanning. I just figured that even if the radio is that much smarter then the scanner both should have some common functionality, even if it is only in the most basic of roots.

 

[iceman47]

The mobile radio is only programmed with the mobile frequencies. In this case 821 Mhz area.
As the radio monitors the control channel, the mike is keyed and a digital message is sent to the site controller, requesting a working channel.
the site controller then assigns a a vacant working channel.
both the site and the mobile radio then set transmit and receive to the correct frequencies.
By using this method a mobile radio can effectively "roam" throughout the network and be able to affiliate with any site in that network.
All control functions and channel assignment take place on the control channel only. The site controller assigns the frequencies to be used, not the mobile radio.
The original site control channel will not change until a new control channel of sufficient signal level is acquired.
In the Nevada system the tower spacing is too far apart, causing the mobile radio to stay on a weak control channel. This is true in the outlying areas and not so much in Reno or L.V. proper. In these areas towers are closer so signal levels are greater.
This causes static and poor transmission due to low signal strength both on the control channel and the working channels.

 

[Pro-95]

Ok so as a radio communicates to a new site. The new site then tells the radio (in simple terms) what the LCN is for this site and then the radio re-programs for the new LCN?

 

[iceman47]

simply stated, yes.

 

[Pro-95]

simply stated, yes.

Ok, that explains why LCN's can vary from site to site. Thanks!

I will say though that, and I re-iterate and expand on your sentiment... tech for tech sakes. And that if I was a builder/buyer I'd want the least amount of technology in the most amount of equipment. That way maintenance and upkeep would be easier and therefore cheaper. Plus the use/abuse a field piece of equipment gets is far greater than that of a controlled environment such as a tower or dispatch center.

Thanks again although now I'm bummed because there seems to be no way to program even a 10 bank scanner to travel around the state without reloading configurations or reprogramming on the fly. Oh well I'll focus on what I need for the trip across 80 and tell the customer no-dice on a statewide config.

 

[iceman47]

What if you program several tower sites into one bank and lock out the ones you are not listening to at the time.
I don't know if that would work; would it?
That would mean that you would have to fiddle to lock and unlock different sites on the road.
Or, how about 10 sites in 10 separate banks and then you would only have to open and close banks as you go????
Just a pop thought I had.

 

[Pro-95]

What if you program several tower sites into one bank and lock out the ones you are not listening to at the time.
I don't know if that would work; would it?
That would mean that you would have to fiddle to lock and unlock different sites on the road.
Or, how about 10 sites in 10 separate banks and then you would only have to open and close banks as you go????
Just a pop thought I had.

Too bad there wasn't macros built into scanners, that would make it much easier. (I don't want a royalty for the idea but a free new scanner a year for life would be ok) But I'm on your same wavelength. I figure I could fill/lock out freqs in a bank based upon expected/planned stops like lunch/gas etc, that way planning on two stops I *could* program ahead for 30 sites. Unless of course the sites I'll be running by are by luck the same LCN. Now I get to finish my site mapping project just to make sure I get all the sites along the way.

BTW, What portion of NSRS are you picking up in Fallon? Just the 3 freqs on 029? No I won't be going by just curious.

855.7375, 856.9375, 859.2125

I ask because you mentioned 820???

 

[crayon]

All control functions and channel assignment take place on the control channel only. The site controller assigns the frequencies to be used, not the mobile radio.

I think that our thought processes are running parallel on this.

The site controller does assign frequencies, but only as LCN's. AFAIK, there is nothing in the EDACS control channel data stream that tells an affilated radio to tune based upon frequency. The LCN to frequency mapping can only be stored in a radio. That is why when you are running eTrunker you get an 0x001 entry instead of a frequency as you do on a moto system.

To support that, I'll quote from: http://www.signalharbor.com/ttt/00apr/

EDACS, however, assigns each radio frequency a Logical Channel Number (LCN). These LCNs are programmed into each radio in the system, and the control channel uses the LCN to instruct a radio to tune to the corresponding frequency.

It would follow that if, in fact, LCN to frequencies assignments were being transmitted in the control channel then eTrunker should be able to pick up these messages and display the correct LCN to frequency as radios affilate. But I have not seen that happen.



Therefore, we are still left with the unanswered question as to how an EDACS user is able to move within a huge multi-site system. How does the radio know all of the LCN's for every site?

 

[iceman47]

The mobile radio transmits on any one of a group of frequencies programmed in to it.
The control Channel, through the handshake of the mobile and site location, tells the mobile radio which channel to transmit and receive on.
The logical channel numbering refers to the order the frequencies are assigned to a user.
The entire process is based on the instructions that are given to the mobile on the CC. It is all acomplished thru digital I.D.s transmitted on the control channel.
Believe me when I tell you that the total control of the system is based on information sent by the control channel.
The LCN applies to the site and not the mobile radio.
As the unit moves from site to site and affiliates with a new C.C at a site, the mobile can only be assigned a channel for the site it is now affiliated with. The mobile radio is told this by information it receives on the control channel.

I also stated the mobile frequencies were in the 820 range. I was in error, they are in the 810-812 range. Must have had a senior moment! LOL

In Fallon I can only monitor the Eagle Ridge site near Fernley since the Fairview/Fallon site is not readable. I can hear the control channel but no V.C. from that site. Hence my comment on tower spacing.

I'm sorry if I am making this complicated, but I seem to have problems putting my thoughts into type.
If we were talking face to face I think I could explain a bit better.

I'll think on it and see if I can somehow simplify my explination.
I hope!!!!!!!!
It took me a long time to figure out what EDACS was actually doing since I started out as a simplex/duplex conventional person and EDACS is by no means a simple system.
I do try!!!

 

[Pro-95]

If we were talking face to face I think I could explain a bit better.

Next time I go to the Fallon store to fix something, I'll give you a PM and I'll buy you a cup of coffee or three.