Question 1)
Their has been 5 generations 0G , 1G , 2G , 3G ,4G plus some in between generations ,...etc

I am wondering how backwards compatibly or forward compatibly the generations are for different phone providers?


Question 2)
Are AT&T , Verizon , T-mobile , Sprint the only major cell networks/providers in the United States?

Question 3)
How compatibly is their hardware / modulation ,...etc what networks in theory could you interchange your service with (forgetting for a moment the legal issues of breaking a contract etc..)
Like a phone made for At&t networks could it be switch to a Verizon or other network..... without changing the hardware or is the modulation schemes and hardware to transmit totally not compatible?

 

Q1 - Most, if not all, 3G phones will be 2G (GSM) compatable as not everywhere has 3G coverage but most places have 2G coverage.

Q2 - Hmm, don't know as I'm not in the US. Try here http://en.wikipedia.org/wiki/List_of_United_States_wireless_communications_service_providers

To answer Q3, assuming your phone is not locked to a provider by a sim lock then you should be able to take your sim for operator 'A' or operator 'B' and use it in the phone. A lot of phones will be "branded" so the software will be configured to suit a particular operators services (i.e. logo wallpaper etc) but this is at the user/GUI level and not the OS/Engine level.

There are a large number of functional requirements that the phone hardware/software must meet - I'm not talking at the GUI level but at the 'engine' level. Have a look at http://www.3gpp.org/specifications if you want to see some of the specs (there's 1,000's of pages of technical requirements so I'll give you a few days to read them all ).

 

ok , for question 2
I googled and found that at&t, t-mobile , verizion , sprint are the biggest cell phone providers / main ones in the US.

However I would like to know the percentage of which provider has what (customer wise) and how much the other providers have something like a pie chart . i.e at&t has 30% of customers that use cell phones , verizion 20% ,...etc
others 5% ...etc

Also what cell provider companies have /own the cell phone towers and equipment ?

 

Cell phones keep you connected, always, to best friends and also the latest news update. cellular phone suppliers vary the maximum amount as your cell phones, providing everything from unlimited minutes to video calls to web access plans.Nowadays there are large set of applications and plans are supported to the mobile phones.As well as they have the large set of mobile phone providers like android application, 3G etc..