daman88:
Most of the countries are now adopting W850 network or 850 MHZ frequency because it has better coverage and better voice quality.
You couldn't be more wrong - Telcos around the world aren't "choosing" to adopt a frequency, they are using what they already have - in NZ Telecom have used 800/850 so they had no choice but to move to UMTS850. LIkewise, it made sense for Vodafone to run with UMTS900.
900 is the dominant frequency worldwide and will be for quite a while to come - 850 was never widely adopted outside of the Americas and AU/NZ.

