| Basics of phisiscs OK: 850 MHz - bigger foot print / 1900 MHz - smaller foot print.
Now, you would ask, why are they doing it? are they mad ?!
Nope...is just capacity.
OK - recap: if I give you a footprint of say 8 miles radius, the user x, at the fringe of the foot print can grab channels and use up a lot of capacity - internet voice, etc. - ( I will not enter here in EDGE / GPRS channel and resources allocation). You, user y closer to the tower, at times, you will not be able to connect, due to lack of resources, because of user(s) x. Enters 1900 MHz. In order to provide coverage for the licensed area of AT&T there are needed more 1900 MHz cells - so is no brainer that is not a good deal for AT&T to switch and move users to 1900. Still, why are they doing it??? Reason - more cells, more users. Now is true that the indoor penetration is not that great like 850, but between having blocked calls and no service for users, and having lower speeds, guess who wins ?!
So, here you have it. |
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| I really don't understand what you are trying to say. ATT is moving 3G users to 850MHZ in some areas because they have more 850MHZ bandwidth in those areas. In most cases(not all), 850MHZ is the best spectrum to use for voice and data. It makes sense that ATT is moving the majority of their users to the most reliable spectrum where necessary. |
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| You don't get it....that's why I didn't entered the GSM / UMTS specs (read David Lee's books). One other thing, in some states they have sufficient 850, in some they don't.
850 is good for propagation. Capacity wise may not be the best in urban areas. "Voice and data" ....is all radio !!!! never mind, you won't get it any way. |
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| reply to forefun
Even more basic..
You have one tower in the middle of a heavily populated town (obviously not the norm, but for this purpose assume)
They would use the 850Mhz band for the far away customers. And then use the 1.9Ghz band for the close-in customers.
If you only use one band you can only have so many overlapping channels with an antenna array. Say 100 customers per antenna with 4-5 antennas per band/Tower (I have no idea about cell spacing or capacity) So that's 400-500 customers that can use that tower so to speak.
Now add the 1.9Ghz to that same tower. It doesn't go as far (i.e. customers in buildings around tower), but adds capacity for more customers/tower. Now you have a single tower capacity of 800-1000 customers. Get it??
#### Numbers are BS and not for argument, just illustration. |
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