Vivo is the largest mobile phone

Mobile phone

A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

 service provider in Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 and in South America with over 60 million users. It originated from the merger of several Brazilian mobile phone operations under a joint-venture owned equally by Portugal Telecom

Portugal Telecom

Portugal Telecom is the largest telecommunications service provider in Portugal. Although it operates mainly in Portugal and Brazil, it has also a significant presence in Guinea-Bissau, Cape Verde, Mozambique, Timor-Leste, Angola, Kenya, the People's Republic of China, and São Tomé and...

 (PT) and Spain's Telefónica

Telefónica

Telefónica, S.A. is a Spanish broadband and telecommunications provider in Europe and Latin America. Operating globally, it is the third largest provider in the world...

; however, Telefónica is now its owner, after having bought PT's shares in July 2010.
Most of its network was initially IS-95

IS-95

Interim Standard 95 is the first CDMA-based digital cellular standard by Qualcomm. The brand name for IS-95 is cdmaOne. IS-95 is also known as TIA-EIA-95....

/cdmaOne based, although there were parts of it that were still analog AMPS

Advanced Mobile Phone System

Advanced Mobile Phone System was an analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983, Israel in 1986, and Australia in 1987. It was the primary analog mobile phone system in North America through the 1980s and into the 2000s...

 and parts (resulting from acquisition of other companies) using TDMA

Digital AMPS

IS-54 and IS-136 are second-generation mobile phone systems, known as Digital AMPS . It was once prevalent throughout the Americas, particularly in the United States and Canada. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000...

 (IS-136).