GSM And CDMA Sites

Jim1348 · Post by **Jim1348** » Sun Jul 22, 2012 7:20 am

I realize that this isn't a cell phone forum, but can anybody here pass along any good URLs for sites that will help me learn more about the technical details of GSM vs. CDMA systems, etc. I have tried Googling this as well as Howard Forums, but I am still not quite finding what I want. I want to find out in rural area what sort of coverage an average GSM and CDMA site have. (Well whatever "typical" or "average" is.) Anyway, among other things, do the sites consider a maximum radius of 10 miles from either type of site or am I way off?

Bill_G · Post by **Bill_G** » Sun Jul 22, 2012 7:59 am

There is no typical or average. The whole point of cellular is to size the footprint exactly where you need it so you can reuse the channels elsewhere without self interference. The real limitation is the subscriber unit uplink with it's inherent low power and poor antenna.

Jim1348 · Post by **Jim1348** » Sun Jul 22, 2012 10:49 am

Thank you very much for the reply. I was aware of what you posted, but I am looking for a range of "footprint" if you will. For example, are some CDMA sites so small that handsets only work about a 2 mile radius from them? Conversely, are some so large (rural) that handsets 10 miles away are affiliating with them? Again, I understand that there is no typical site, but what is a range of footprint size?

Post by **escomm** » Sun Jul 22, 2012 11:44 am

There is no typical size. That's what Bill is saying. Each site is constructed with the neighboring sites taken into consideration. As well as the capacity requirements. As you have alluded to, sites in urban areas will be more densely packed in. Sites in rural areas will be much further spread out.

AEC · Post by **AEC** » Sun Jul 22, 2012 2:38 pm

Cell sites deal with frequency reuse, meaning the same channels at one site, 25 miles away, is 'reused' at this site. It is also in their licensing, as well as market area, or MSA for metro, and RSA for rural.
In analog AMPS days, we used to run a dead channel into another competitor's area with no data, just a carrier, and the receiver wasn't tied into that panel either.
This was to prevent roaming and access to 'our' sites when users are near our towers, this used to cause that pesky 'roam' indicator to light up in the competitor's service area, the real reason we did what we did. Also, we did not have a roaming agreement with that carrier, so billing issues would always pop ut at the switch.
Expect a typical cell site to have a 10 to 15 mile coverage radius, given terrain and line of sight issues not withstanding of course.

I still chuckle about the comments I heard years ago regarding utility poles, and how the signals used to ravel these..HA HA.
Some people just can NOT be shown proof, they made up their minds and that is how it is...

fineshot1 · Post by **fineshot1** » Tue Jul 24, 2012 3:24 pm

Jim1348 wrote:Thank you very much for the reply. I was aware of what you posted, but I am looking for a range of "footprint" if you will. For example, are some CDMA sites so small that handsets only work about a 2 mile radius from them? Conversely, are some so large (rural) that handsets 10 miles away are affiliating with them? Again, I understand that there is no typical site, but what is a range of footprint size?

Jim as everyone else has said the cell sites coverage is tailored so as to be able to accurately
handoff calls to other cells so there is no average coverage of a cell sites coverage. This is done
by various parameters in the cell sites to tailor each and every cell sites coverage to fit into the
handoff canidates for each cell.

mr.syntrx · Post by **mr.syntrx** » Thu Sep 20, 2012 7:52 pm

GSM has a maximum range of about 35km. This page does a great job of explaining the details of why:

http://gsmfordummies.com/timing/timing.shtml

Bill_G · Post by **Bill_G** » Fri Sep 21, 2012 6:03 am

mr.syntrx wrote:GSM has a maximum range of about 35km. This page does a great job of explaining the details of why:

http://gsmfordummies.com/timing/timing.shtml

That was good info. Excellent explanation. Thx.

cleb · Post by **cleb** » Fri Sep 21, 2012 2:05 pm

Jim,

If you are interested in the inner workings of GSM, take a look here: http://openbsc.osmocom.org/trac/wiki/OpenBSC
A group of developers have written an open source version of the GSM core network. The OpenBSC software does not strictly conform to all of the standards, but if you want to learn about and have a working GSM base station/network, its the way to go. If after reading the wiki you are interested in locating hardware (NanoBTS, Nokia inSite BTS), PM me.

c

MikeOxlong · Post by **MikeOxlong** » Sat Sep 22, 2012 5:42 am

mr.syntrx wrote:GSM has a maximum range of about 35km. This page does a great job of explaining the details of why:

http://gsmfordummies.com/timing/timing.shtml

GSM has a maximum range of 70kms if you use extended range mode.

It robs every other timeslot so the timing advance can be increased.

Jim202 · Post by **Jim202** » Sun Sep 23, 2012 3:22 am

There are many things to keep in mind when a cell site is designed. As others have said the density of the cell sites will be controlled by the user volume. More users, more cell sites. You also have to factor in the ground clutter. What I mean by this is the type of trees or lack of them. If you have 120 to 150 foot pine trees all around, you might expect to see the cell sites on tall towers and spaced about 4 or 5 miles apart. They will also use down tilt antennas. If your out in the open rolling plains area, again you will see tall towers and they will be spaced out maybe 10 to 20 miles or so. These open plains sites will follow along the main Interstates and or main highways. You get off the beaten path, your SOL.

On the other hand, if your in the city, you can expect to see a cell site with the antennas down low, using down tilt antennas and spaced maybe 0.5 miles apart. The capacity required in the city means more sites closely spaced. It also means that in order to reuse the frequencies, the antennas need to limit the coverage.

So you can see that there is no simple answer as to how far apart the cell sites will be spaced.

Jim