Cellular Geekfest!

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AmpedNow
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Cellular Geekfest!

Post by AmpedNow » Mon Apr 05, 2010 1:54 am

All this talk about cell phones has me curious about how they work with the towers.

1. When you look at a cell tower, it's obvious that the cells can be designed in highly directional arrays. When connecting to a call or data, do the cells "broadcast" out to the phone in all directions? Or just from a single cell in whatever direction the phone is from the tower?

2. Some cells are more short and square, while some are more long and rectangular. Which is for voice? Which is for data? Or is it a GSM/CDMA thing?

3. Anyone know what the 4G/WiMax/LTE cells look like, so I can spot them when they begin rolling out?

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Big Media
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Re: Cellular Geekfest!

Post by Big Media » Mon Apr 05, 2010 1:21 pm

Years ago, I came across a web site with excellent pictures explaining all this shit. I haven't been able to find it since. Great topic. I am interested, too, if anyone knows.

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Re: Cellular Geekfest!

Post by TimeEnuf » Tue Apr 06, 2010 10:36 pm

Ok, I am being a bit lazy here, but here is one( of many links) to be found using Google.

http://en.wikipedia.org/wiki/History_of_mobile_phones

Generally speaking most cellular phones operate on 850,900,1800,1900 MHz. The two major technology used since analog cell service went away, are TDMA,time division multiple access, (AT&T) and CDMA, code division multiple access(everyone else).
You may ask yourself.......what about GSM? GSM is the European standard that at it core uses CDMA technology.
Beyond this you have 1st, 2nd, 3rd, and so on generations of technology that has more to do with the speed of the digital network than anything else.
One other general rule, is that as the RF frequency of the service goes up, there is a need for more towers, also the higher the frequency the smaller the antennas
This is also why you have great ntelos service up I-79, but you see a cell tower around every curve, since their service is in the PCS band.(and don't venture more than a mile off of the Interstate, if you need cell service).
I am about 3+ years out of the loop on most of this stuff, since I decided to get a job in broadcast radio. If I missed something, or some of my info is wrong or incomplete............ to quote John McKinney, "Bite Me!"

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Re: Cellular Geekfest!

Post by AmpedNow » Wed Apr 07, 2010 12:08 am

AT&T uses 1900 Mhz for voice and EDGE, 850 Mhz for 3G in many (but not all) areas.

As a result, they have many more towers than Verizon, which currently uses 850 and 900 for pretty much everything.

Because of having more towers, it appears that AT&T will have better coverage overall after they upgrade all of their cell cites to 7.2 Mb/s 3G. Esp using 850. This should be complete by 2012. Supposedly.

After that, the 4G race will be in full swing.

I assume that much 4G will be in the 750 Mhz block of spectrum that the FCC auctioned off in 2007. Verizon got the lion's share of it, but AT&T and others got some of it, too.

This will be great because in addition to blazing 4G speeds, the signal will also be more reliable than the higher bands in heavy use now.

As anyone with AT&T can attest, 1900 is very fickle. You can watch the bars swing back and forth even when the phone is stationary.

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