So Africom, Powertel, ZOL and Liquid are now all on VoIP and you can actually call using their lines and a standard size cellphone for very low rates, while amazingly, they have very few subscribers compared to our Mobile Network Operators (MNO) Econet, Netone and Telecel why?
This is simply because MNO use a different technology called GSM to make calls while these are on a separate technology called CDMA.
The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.
CDMA employs analog-to-digital conversion (ADC) in combination with spread spectrum technology. Audio input is first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency.
There are trillions of possible frequency-sequencing codes, which enhance privacy and makes cloning difficult.
CDMA allows several transmitters to send information simultaneously over a single communication channel; thus allowing several users to share a band of frequencies (see bandwidth).
To permit this without undue interference between the users, CDMA employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code).
CDMA is used as the access method in many mobile phone standards such as cdmaOne, CDMA2000 (the 3G evolution of cdmaOne), and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA.
In Zimbabwe, the technology has been rolled out but with much resistance. Companies like Powertel and Africom have since introduced the technology in the local market. Though the technology has not been received with much aplomb, CDMA technology provides better capacity for voice and data communications than any other commercial mobile technologies, allowing more subscribers to connect at any given time, and it is the common platform on which 3G technologies are built.
CDMA was first used during World War II by English allies to foil German attempts at jamming transmissions. The allies decided to transmit over several frequencies, instead of one, making it difficult for the Germans to pick up the complete signal.